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SDLRC - Scientific Articles all years by Author - Pe-Pn


The Sheahan Diamond Literature Reference Compilation
The Sheahan Diamond Literature Reference Compilation is compiled by Patricia Sheahan who publishes on a monthly basis a list of new scientific articles related to diamonds as well as media coverage and corporate announcementscalled the Sheahan Diamond Literature Service that is distributed as a free pdf to a list of followers. Pat has kindly agreed to allow her work to be made available as an online digital resource at Kaiser Research Online so that a broader community interested in diamonds and related geology can benefit. The references are for personal use information purposes only; when available a link is provided to an online location where the full article can be accessed or purchased directly. Reproduction of this compilation in part or in whole without permission from the Sheahan Diamond Literature Service is strictly prohibited. Return to Diamond Resource Center
Sheahan Diamond Literature Reference Compilation - Scientific Articles by Author for all years
A-An Ao+ B-Bd Be-Bk Bl-Bq Br+ C-Cg Ch-Ck Cl+ D-Dd De-Dn Do+ E F-Fn Fo+ G-Gh Gi-Gq Gr+ H-Hd He-Hn Ho+ I J K-Kg Kh-Kn Ko-Kq Kr+ L-Lh
Li+ M-Maq Mar-Mc Md-Mn Mo+ N O P-Pd Pe-Pn Po+ Q R-Rh Ri-Rn Ro+ S-Sd Se-Sh Si-Sm Sn-Ss St+ T-Th Ti+ U V W-Wg Wh+ X Y Z
Sheahan Diamond Literature Reference Compilation - Media/Corporate References by Name for all years
A B C D-Diam Diamonds Diamr+ E F G H I J K L M N O P Q R S T U V W X Y Z
Tips for Users
Posted/Published Reference CodesThe SDLRC provides 3 types of references identified in the reference code. DS for scientific article, DM for a media article, and DC for a corporate announcement. Consider DS0512-0001. The DS stands for "diamond scientific". 05 stands for 2005, the year the reference was posted. 12 represents the month the reference was posted. For all years prior to 2015 the default month is 12. -0001 is the reference's identifier and it does not mean anything. The number below the refence code, ie 2015, is the year the article was published. Note that the posted year may sometimes be later than the published year.
Sort OrderReferences are sorted by the "author" name and when the reference was posted to the compilation.
Most RecentIf the reference code is highlighted yellow, the reference was made available through the most recent monthly compilation of new literature. Use this to check out new references. When new references are posted, we make it our priority to track down an online link and obtain an abstract. With regard to older references, tracking down an abstract and an online link is a work in progress.
Link to external location of article: If the title has a link, it means we have found a location online where you can either retrieve the full article free, or purchase access to it. The Sheahan Diamond Literature Service is not a technical article procurement service; if you want a restricted article, you must deal directly with the vendor who controls the copyright to the article.
Searching this page for a specific term or authorIn your Firefox browser click Edit in the menu bar and then Find. In the Find box that shows up at the bottom of the web page enter your search term. Firefox will highlight all occurrences. This is particularly helpful when the author you are seeking was not the lead author by whom the compilation is sorted.
Sending or sharing a referenceThe left column (Posted/Published) has an embedded hyperlink for each reference. In Firefox, if you right click on it, you can obtain the link url for that reference's location within the page, which you can copy and paste into an email or any other document. You can also use the "share this link" option to tweet, facebook etc the link.
Author Index
A-An Ao+ B-Bd Be-Bk Bl-Bq Br+ C-Cg Ch-Ck Cl+ D-Dd De-Dn Do+ E F-Fn Fo+ G-Gh Gi-Gq Gr+ H-Hd He-Hn Ho+ I J K-Kg Kh-Kn Ko-Kq Kr+ L-Lh
Li+ M-Maq Mar-Mc Md-Mn Mo+ N O P-Pd Pe-Pn Po+ Q R-Rh Ri-Rn Ro+ S-Sd Se-Sh Si-Sm Sn-Ss St+ T-Th Ti+ U V W-Wg Wh+ X Y Z
Sheahan Diamond Literature Reference Compilation - Scientific Articles by Author for all years - Pe-Pn
Posted/
Published
AuthorTitleSourceRegionKeywords
DS1993-1134
1993
Peach, C.L.Nilsson, K., Peach, C.L.Sulfur speciation, oxidation state and sulfur concentration in backarcmagmasGeochimica et Cosmochimica Acta, Vol. 57, pp. 3807-3813GlobalSilicate melts, MORBS
DS1990-1163
1990
Peachpit PressPeachpit Press, Berkley CaliforniaWordPerfect: desktop publishing in stylePeachpit Press, Berkley California, 645pGlobalWill-Harris, D., Wordperfect
DS201610-1895
2016
Peacock, J.R.Peacock, J.R., Denton, K.M., Ponce, D.A.Magnetotelluric imaging of a carbonatite terrane in the southeast Mojave desert, California and Nevada.ASEG-PESA-AIG 2016 25th Geophysical Conference, abstract 5p.United States, California, NevadaCarbonatite

Abstract: The southeast Mojave Desert hosts one of the world’s largest rare earth element (REE) deposits at Mountain Pass, California. Although surface geology has been studied, a full understanding of the carbonatite and associated intrusive suite complex requires subsurface geophysical characterization. In this study, a combination of geophysical methods, including magnetotelluric (MT), magnetics, and gravity are used to create a two-dimensional (2D) geophysical model to a depth of about 10 km. An electrically conductive body is found 2-3 km below and west of the deposit that is associated with a magnetic high that could be connected to a deeper (10 km) conductive body related to possible intrusions or hydrothermal systems. The carbonatite body coincides with a steep magnetic gradient and a bench or terrace in the gravity data that may reflect relative lower-density intrusive rocks. Although carbonatite rocks are typically magnetic, the carbonatite rocks, associated intrusive suite, and host rocks in this area are essentially non-magnetic. Combined geophysical data indicate that the enriched REE deposit may be related to a regional extensive hydrothermal alteration event.
DS1990-1164
1990
Peacock, S.M.Peacock, S.M.Fluid processes in subduction zonesScience, Vol. 248, No. 4953, April 20, pp. 329-337GlobalMantle-crust, Tectonics
DS1991-1308
1991
Peacock, S.M.Peacock, S.M.Metamorphic geologyInternational Union of Geodesy and Geophysics, 20th. meeting held Vienna August, pp. 486-499GlobalMetamorphic geology, Overview -review paper
DS1991-1645
1991
Peacock, S.M.Spear, F.S., Peacock, S.M., Kohn, M.J., Florence, F.P., Menard, T.Computer programs for petrologic P-T-t path calculationsAmerican Mineralogist, Vol. 76, No. 11, 12 November-December pp. 2009-2012GlobalComputer, Program -petrologic P-T-t
DS1993-1202
1993
Peacock, S.M.Peacock, S.M.The importance of blueschist - eclogite dehydration reactions in subducting oceanic crustGeological Society of America Bulletin, Vol. 105, No. 5, May pp. 684-694Globalmetamorphism, Crust, Subduction
DS1993-1203
1993
Peacock, S.M.Peacock, S.M.Large scale hydration of the lithosphere above subducting slabsChemical Geology, Vol. 108, No. 1-4, August 5, pp. 49-60GlobalSubduction, Mantle, Tectonics
DS1993-1204
1993
Peacock, S.M.Peacock, S.M.Large scale hydration of the lithosphere above subducting slabsChemical Geology, Vol. 108, No. 1-4, August 5, pp. 49-60.MantleSubduction, Tectonics
DS1994-1345
1994
Peacock, S.M.Peacock, S.M., Rushmer, T., Thompson, A.B.Partial melting of subducting oceanic crustEarth and Planetary Science Letters, Vol. 121, No. 1/2, January pp. 227-244.MantleSubduction, Tectonics, Oceanic Crust
DS1994-1346
1994
Peacock, S.M.Peacock, S.M., Rushmer, T., Thompson, A.B.Partial melting of subducting oceanic crustEarth and Planetary Science Letters, Vol. 121, pp. 227-244MantleTectonics, Subduction
DS1995-1452
1995
Peacock, S.M.Peacock, S.M., Goodge, J.W.Eclogite facies metamorphism preserved in tectonic blocks from a lower crustal shear zone, TransantarcticLithos, Vol. 36, No. 1, Aug. 1, pp. 1-14.Antarcticametamorphism, Eclogite
DS1999-0537
1999
Peacock, S.M.Peacock, S.M., Hervig, R.L.Boron isotopic composition of subduction zone rocksChemical Geology, Vol. 160, No. 4, Sept. 2, pp. 281-90.MantleGeochronology, Subduction
DS1999-0538
1999
Peacock, S.M.Peacock, S.M., Hyndman, R.D.Hydrous minerals in the mantle wedge and the maximum depth of subduction thrust earthquakes.Geophysical Research. Lett., Vol. 26, No. 16, Aug. 15, pp. 2517-20.MantleSubduction, Mineralogy
DS2001-0894
2001
Peacock, S.M.Peacock, S.M.Are the lower planes of double seismic zones caused by serpentine dehydration in subducting oceanic mantle?Geology, Vol. 29, No. 4, Apr. pp.299-302.Mantlemetamorphism, Subduction
DS2002-0192
2002
Peacock, S.M.Bostock, M.G., Hyndman, R.D., Rondenay, S., Peacock, S.M.An inverted continental MOHO and serpentinization of the forearc mantleNature, No. 6888, May 3o, pp.536-7.MantleBoundary
DS2003-0614
2003
Peacock, S.M.Hyndman, R.D., Peacock, S.M.Serpentinization of the forearc mantleEarth and Planetary Science Letters, Vol. 212, 3/4, pp. 417-432.MantleMetasomatism
DS200412-0863
2003
Peacock, S.M.Hyndman, R.D., Peacock, S.M.Serpentinization of the forearc mantle.Earth and Planetary Science Letters, Vol. 212, 3/4, pp. 417-432.MantleMetasomatism
DS202009-1653
2020
Peacock, S.M.Peacock, S.M.Advances in the thermal and petrologic modeling of subduction zones.Geosphere, Vol. 16, 4, 17p. PdfMantlegeothermometry

Abstract: In the two decades since Subduction: Top to Bottom was published in 1996, improved analytical and numerical thermal-petrologic models of subduction zones have been constructed and evaluated against new seismological and geological observations. Advances in thermal modeling include a range of new approaches to incorporating shear (frictional, viscous) heating along the subduction interface and to simulating induced flow in the mantle wedge. Forearc heat-flux measurements constrain the apparent coefficient of friction (µ') along the plate interface to <~0.1, but the extent to which µ' may vary between subduction zones remains challenging to discern owing to scatter in the heat-flux measurements and uncertainties in the magnitude and distribution of radiogenic heat production in the overriding crust. Flow in the mantle wedge and the resulting thermal structure depend on the rheology of variably hydrated mantle rocks and the depth at which the subducting slab becomes coupled to the overlying mantle wedge. Advances in petrologic modeling include the incorporation of sophisticated thermodynamic software packages into thermal models and the prediction of seismic velocities from mineralogic and petrologic models. Current thermal-petrologic models show very good agreement between the predicted location of metamorphic dehydration reactions and observed intermediate-depth earthquakes, and between the predicted location of the basalt-to-eclogite transition in subducting oceanic crust and observed landward-dipping, low-seismic-velocity layers. Exhumed high-pressure, low-temperature metamorphic rocks provide insight into subduction-zone temperatures, but important thermal parameters (e.g., convergence rate) are not well constrained, and metamorphic rocks exposed at the surface today may reflect relatively warm conditions in the past associated with subduction initiation or ridge subduction. We can anticipate additional advances in our understanding of subduction zones as a result of further testing of model predictions against geologic and geophysical observations, and of evaluating the importance of advective processes, such as diapirism and subduction-channel flow, that are not captured in hybrid kinematic-dynamic models of subduction zones but are observed in fully dynamical models under certain conditions.
DS1989-0762
1989
Peacor, D.R.Kersting, A.B., Peacor, D.R., Arculus, R.J.STEM study of preserved diffusion gradients in lower crustal Upper Mantle spinel megacrysts, KilbourneHole, New MexicoEos, Vol. 70, No. 43, October 24, p. 1393. AbstractNew MexicoMegacrysts, STEM.
DS1993-1799
1993
Peacor, D.R.Yen-Hong Shau, Peacor, D.R., Essene, E.J.Formation of magnetic single-domain magnetite in ocean ridge basalts with implications for sea floor magnetismScience, Vol. 261, July 16, pp. 343-345Sea floorRifting, Tectonics
DS202004-0497
2020
Peaker, C.V.Ashfold, M.N.R., Goss, J.P., Green, B., May, P.W., Newton, M.E., Peaker, C.V.Nitrogen in diamond.Chemical Reviews, Vol. 120, 4, 10.1021/ acs.chemrev.9b00578 50p. PdfGlobalHPHT, CVD, synthetics

Abstract: Nitrogen is ubiquitous in both natural and laboratory-grown diamond, but the number and nature of the nitrogen-containing defects can have a profound effect on the diamond material and its properties. An ever-growing fraction of the supply of diamond appearing on the world market is now lab-grown. Here, we survey recent progress in two complementary diamond synthesis methods: high pressure high temperature (HPHT) growth and chemical vapor deposition (CVD), how each is allowing ever more precise control of nitrogen incorporation in the resulting diamond, and how the diamond produced by either method can be further processed (e.g., by implantation or annealing) to achieve a particular outcome or property. The burgeoning availability of diamond samples grown under well-defined conditions has also enabled huge advances in the characterization and understanding of nitrogen-containing defects in diamond alone and in association with vacancies, hydrogen, and transition metal atoms. Among these, the negatively charged nitrogen-vacancy (NV-) defect in diamond is attracting particular current interest in account of the many new and exciting opportunities it offers for, for example, quantum technologies, nanoscale magnetometry, and biosensing.
DS2003-0307
2003
Peakman, T.M.Dahl, J.E.P., Moldowan, J.M., Peakman, T.M., Clardy, J.C., Lobkovsky, E.Isolation and structural proof of the large diamond molecule, cycloheamantane (Angewandte Chemie, Vol. 42, 18, pp. 2040-44.GlobalMineral chemistry
DS200412-0398
2003
Peakman, T.M.Dahl, J.E.P., Moldowan, J.M., Peakman, T.M., Clardy, J.C., Lobkovsky, E., Olmstead, M.M., May, P.W., Davis, T.Isolation and structural proof of the large diamond molecule, cycloheamantane ( C26H30).Angewandte Chemie, Vol. 42, 18, pp. 2040-44.TechnologyMineral chemistry
DS201012-0075
2010
Peale, R.E.Brusentsova, T.N., Peale, R.E., Maukonen, D., Harlow, G.E., Boesenberg, J.S., Ebel, D.Far infrared spectroscopy of carbonate minerals.American Mineralogist, Vol. 95, pp. 1515-1522.TechnologyIR - not specific to diamonds
DS2002-0928
2002
PearceLe Roux, P.J., Le Roex, A.P., Schilling, J.G., Shimizu, N., Perkins, W.W., PearceMantle heterogeneity beneath the southern Mid-Atlantic Ridge: trace element evidenceEarth and Planetary Science Letters, Vol. 203, 1, pp. 479-98.MantleGeochemistry
DS201809-2113
2018
Pearce, A.Welford, K., Pearce, A., Geng, M., Dehler, S.A., Dickie, K.Crustal structure of Baffin Bay from constrained 3-D gravity inversion and deformable plate tectonic models. Geophysical Journal International, Vol. 214, 2, pp. 1281-1300. doi:1093/gji/ggy193Canada, NunavutGeophysics - gravity

Abstract: Mesozoic to Cenozoic continental rifting, breakup and spreading between North America and Greenland led to the opening, from south to north, of the Labrador Sea and eventually Baffin Bay between Baffin Island, northeast Canada and northwest Greenland. Baffin Bay lies at the northern limit of this extinct rift, transform and spreading system and remains largely underexplored. With the sparsity of existing crustal-scale geophysical investigations of Baffin Bay, regional potential field methods and quantitative deformation assessments based on plate reconstructions provide two means of examining Baffin Bay at the regional scale and drawing conclusions about its crustal structure, its rifting history and the role of pre-existing structures in its evolution. Despite the identification of extinct spreading axes and fracture zones based on gravity data, insights into the nature and structure of the underlying crust have only been gleaned from limited deep seismic experiments, mostly concentrated in the north and east where the continental shelf is shallower and wider. Baffin Bay is partially underlain by oceanic crust with zones of variable width of extended continental crust along its margins. 3-D gravity inversions, constrained by bathymetric and depth to basement constraints, have generated a range of 3-D crustal density models that collectively reveal an asymmetric distribution of extended continental crust, approximately 25-30?km thick, along the margins of Baffin Bay, with a wider zone on the Greenland margin. A zone of 5-13?km thick crust lies at the centre of Baffin Bay, with the thinnest crust (5?km thick) clearly aligning with Eocene spreading centres. The resolved crustal thicknesses are generally in agreement with available seismic constraints, with discrepancies mostly corresponding to zones of higher density lower crust along the Greenland margin and Nares Strait. Deformation modelling from independent plate reconstructions using GPlates of the rifted margins of Baffin Bay was performed to gauge the influence of original crustal thickness and the width of the deformation zone on the crustal thicknesses obtained from the gravity inversions. These results show the best match with the results from the gravity inversions for an original unstretched crustal thickness of 34-36?km, consistent with present-day crustal thicknesses derived from teleseismic studies beyond the likely continentward limits of rifting around the margins of Baffin Bay. The width of the deformation zone has only a minimal influence on the modelled crustal thicknesses if the zone is of sufficient width that edge effects do not interfere with the main modelled domain.
DS201901-0058
2018
Pearce, C.R.Prikryl, J., Stefansson, A., Pearce, C.R.Tracing olivine carbonation and serpentinization in CO2 rich fluids via magnesium exchange and isotopic fractionation.Geochimica et Cosmochimica Acta, Vol. 243, pp. 133-148.Mantleolivine

Abstract: Chemical exchange between seawater and the oceanic crust is thought to play a significant role in the regulation of the global magnesium (Mg) cycle, yet relatively little is known about the rates and mechanisms of Mg exchange in these crustal environments. In this study we experimentally characterize the extent, and nature, of Mg isotope fractionation during the carbonation and serpentinization of olivine (one of the principal minerals found in ultramafic rocks) under hydrothermal conditions. Olivine alteration was found to be incongruent, with the reactant fluid composition varying according to the extent of olivine dissolution and the precipitation of secondary minerals. In mildly acid water (pH?~?6.5), olivine dissolved to form Mg-Fe carbonate solid solutions and minor chrysotile. Upon carbonation and a decrease of CO2 in the water, the pH increased to >8, with chrysotile and brucite becoming the dominant alteration minerals. The Mg-rich carbonates preferentially incorporated lighter Mg isotopes, resulting in a ~0.5‰ increase of the d26Mg composition of the fluid relative to olivine during the initial carbonation and serpentinization reactions. This was followed by a decrease in d26Mg under higher pH conditions associated with the formation of brucite. Our experimental and modeling results therefore demonstrate that the d26Mg composition of fluids involved in olivine alteration reflect the type and quantity of secondary Mg minerals formed, which in turn depend on the pH and CO2 concentration of the water. Comparison of these results with natural groundwaters and geothermal waters from basaltic terrains indicate that the d26Mg composition of natural waters are likely to also be controlled by mafic rock dissolution and the preferential incorporation of isotopically light Mg into carbonates and isotopically heavy Mg into Mg-Si minerals. Together, these findings improve our understanding of Mg isotope systematics during water-rock interaction, and suggest that d26Mg may be a useful tool for tracing reactions that are critical to geological CO2 sequestration.
DS1992-1174
1992
Pearce, J.Pearce, J.An element of recyclingNature, Vol. 360, No. 6405, December 17, p. 629-630GlobalGeochemistry, Mantle
DS1992-1175
1992
Pearce, J.Pearce, J.An element of recyclingNature, Vol. 360, Dec. 17, pp. 629-30.MantleXenoliths, Subduction
DS200612-1387
2006
Pearce, J.Straub, S., Pearce, J.Subduction zone evolution in 4-D.Goldschmidt Conference 16th. Annual, S6-06 theme abstract 1/8p. goldschmidt2006.orgMantleGeochemistry
DS201607-1387
2016
Pearce, J.Yang, J., Dilek, Y., Pearce, J., Schertl, H-P., Zhang, C.Diamonds and crustal recycling into deep mantle.IGC 35th., Session The Deep Earth 1 p. abstractMantleSubduction
DS1995-1453
1995
Pearce, J.A.Pearce, J.A., Peate, D.W.Tectonic implications of the composition of volcanic arc magmasAnnual Review of Earth Planetary Sciences, Vol. 23, pp. 251-286MantleTectonics, Magmas - arc
DS1998-1123
1998
Pearce, J.A.Parkinson, I.J., Pearce, J.A.Peridotites from the Izu Bonin Mariana Forearc: evidence for mantle melting and melt mantle interactionJournal of Petrology, Vol. 39, No. 9, pp. 1577-1618.MantlePeridotites - melting, Subduction
DS2003-1018
2003
Pearce, J.A.Niu, Y., O'Hara, M.J., Pearce, J.A.Initiation of subduction zones as a consequence of lateral compositional buoyancy:Journal of Petrology, Vol. 44, 5, pp. 851-66.MantleSubduction
DS200412-1441
2003
Pearce, J.A.Niu, Y., O'Hara, M.J., Pearce, J.A.Initiation of subduction zones as a consequence of lateral compositional buoyancy: contrast within the lithosphere: a petrologicJournal of Petrology, Vol. 44, 5, pp. 851-66.MantleSubduction
DS200512-0831
2005
Pearce, J.A.Pearce, J.A.Mantle preconditioning by melt extraction during flow: theory and petrogenetic implications.Journal of Petrology, Vol. 46, 5, pp. 973-997.MantleMelting
DS200612-1058
2006
Pearce, J.A.Pearce, J.A.When did subduction start - and how did it evolve?Geochimica et Cosmochimica Acta, Vol. 70, 18, p. 12. abstract only.MantleSubduction
DS200912-0151
2009
Pearce, J.A.Dare, S.A.S., Pearce, J.A., McDonald, I.,Styles, M.T.Tectonic discrimination of peridotites using fO2 Cr# and Ga Ti Fe111 systematics in chrome spinel.Chemical Geology, Vol. 261, 3-4, April 30, pp. 199-216.TechnologyMineral chemistry database
DS1991-0593
1991
Pearce, K.Gould, C.C., Pearce, K.Informatiuon needs in the sciences: an assessmentResearch Libraries, Mountain View, 79p. Cost?GlobalInformation, Sciences
DS201711-2531
2017
Pearce, M.A.Timms, N.E., Erickson, T.M., Zanetti, M.R., Pearce, M.A., Cayron, C., Cavosie, A.J., Reddy, S.M., Wittman, A., Carpenter, P.K.Cubic zirconia in >2370 C impact melt records Earth's hottest crust.Earth and Planetary Science Letters, Vol. 478, pp. 52-58.Canada, QuebecMistastin crater

Abstract: Bolide impacts influence primordial evolution of planetary bodies because they can cause instantaneous melting and vaporization of both crust and impactors. Temperatures reached by impact-generated silicate melts are unknown because meteorite impacts are ephemeral, and established mineral and rock thermometers have limited temperature ranges. Consequently, impact melt temperatures in global bombardment models of the early Earth and Moon are poorly constrained, and may not accurately predict the survival, stabilization, geochemical evolution and cooling of early crustal materials. Here we show geological evidence for the transformation of zircon to cubic zirconia plus silica in impact melt from the 28 km diameter Mistastin Lake crater, Canada, which requires super-heating in excess of 2370?°C. This new temperature determination is the highest recorded from any crustal rock. Our phase heritage approach extends the thermometry range for impact melts by several hundred degrees, more closely bridging the gap between nature and theory. Profusion of >2370?°C superheated impact melt during high intensity bombardment of Hadean Earth likely facilitated consumption of early-formed crustal rocks and minerals, widespread volatilization of various species, including hydrates, and formation of dry, rigid, refractory crust.
DS1996-1084
1996
Pearce, N.J.G.Pearce, N.J.G., Leng, M.J.The origin of carbonatites and related rocks from the Igaliko dyke swarm, Gardar Province, South Greenland.Lithos, Vol. 39, pp. 21-40.GreenlandCarbonatite, Geochemistry, geochronology
DS1997-0894
1997
Pearce, N.J.G.Pearce, N.J.G., Leng, M.J., Emeleus, C.H., Bedford, C.M.The origins of carbonatites and related rocks from the Gronnedal Ikanepheline syenite complex. C-O-Sr evid.Mineralogical Magazine, No. 407, August pp. 515-530.Greenland, south GreenlandCarbonatite
DS2003-0290
2003
Pearce, N.J.G.Coulson, I.M., Goodenough, K.M., Pearce, N.J.G., Leng, M.J.Carbonatites and lamprophyres of the Gardar Province - a window to the sub-GardarMineralogical Magazine, Vol. 67, 5, pp. 855-872.GreenlandCarbonatite
DS200412-0377
2003
Pearce, N.J.G.Coulson, I.M., Goodenough, K.M., Pearce, N.J.G., Leng, M.J.Carbonatites and lamprophyres of the Gardar Province - a window to the sub-Gardar mantle?Mineralogical Magazine, Vol. 67, 5, pp. 855-72.Europe, GreenlandCarbonatite
DS1986-0634
1986
Pearce, T.H.Pearce, T.H.Friends of the igneous rocks: first meetingGeoscience Canada, Vol. 14, No.1, March pp. 60-61GlobalConference Review
DS1990-1281
1990
Pearce, T.H.Russell, J.K., Nicholls, J., Stanley, C.R., Pearce, T.H.Pearce element ratiosEos, Vol. 71, No. 5, January 30, pp. 234, 235, 236, 246, 247GlobalIgneous rocks, Chemical variations -Pearce element ratios
DS1993-1205
1993
Pearce, T.H.Pearce, T.H.Analcime phenocrysts in igneous rocks: primary or secondary? DiscussionAmerican Mineralogist, Vol. 78, pp. 225-9.GlobalLeucite
DS1992-1176
1992
Pearse, P.H.Pearse, P.H.Natural resources in tomorrow's high tech economy: the search for sustainable development strategiesCentre for Resource Perspectives, No. 38, February pp. 15-23CanadaMining, Economics
DS1970-0173
1970
Pearse, T.D.Pearse, T.D.The Trapping Creek Ultramafic IntrusiveBsc. Thesis, Univ of British Columbia, 30pBritish ColumbiaAlkaline Rocks, Carbonatite
DS1991-1257
1991
PearsonOliver, N.H.S., Holcombe, Hill, PearsonTectono-metamorphic evolution of the Mary Kathleen fold belt: a reflection of mantle plume processes?Australian Journal of Earth Sciences, Vol. 38, No. 4, pp. 425-55.AustraliaCrustal evolution - not specific to diamond
DS1998-0535
1998
PearsonGriffin, W.L., Doyle, B.J., Ryan, Pearson, O'ReillyLithosphere structure and mantle terranes: Slave Craton, Canada7th International Kimberlite Conference Abstract, pp. 271-273.Northwest TerritoriesTerranes, xenoliths, Deposit - Ranch Lake, Jericho, Cross Lake
DS1999-0545
1999
PearsonPearson, Griffin, Doyle, O'Reilly, Van Acterbergh, KiviXenoliths from kimberlite pipes of the Lac de Gras area, Slave Craton, Canada. (DO18, 27, A154S)7th International Kimberlite Conference Nixon, Vol. 2, pp. 644-58.Northwest TerritoriesPetrography, mineral chemistry, analyses, thermometry
DS2000-0139
2000
PearsonCarlson, R.W., Janney, Shirey, Boyd, Pearson, IrvineChemical and age structure of the southern African lithospheric mantle: implications continent formationGeological Society of America (GSA) Abstracts, Vol. 32, No. 7, p.A-163.South AfricaMantle xenoliths - Kaapvaal Craton, Geophysics - seismics
DS2001-0062
2001
PearsonAulbach, S., Griffin, Pearson, O'Reilly, Doyle, KiviRe Os isotope evidence for Meso-Archean mantle beneath 2.7 Ga Contwoyto Terrane, implications tectonic historySlave-Kaapvaal Workshop, Sept. Ottawa, 5p. abstractMantleGeochemistry - major, trace elements, Slave Craton - tectonics
DS2001-0266
2001
PearsonDowall, D.P., Nowell, G.M., Pearson, Kjarsgaard, et al.Geochemistry of Slave and Somerset Island kimberlites29th. Yellowknife Geoscience Forum, Nov. 21-23, abstract p. 13-14.Northwest Territories, Somerset IslandGeochemistry - mantle lithosphere, Deposit - Jericho, Somerset Island
DS2001-0267
2001
PearsonDowall, D.P., Nowell, Pearson, Kjarsgaard, KopylovaComparative geochemistry of the source regions of southern African and Slave kimberlites.Slave-Kaapvaal Workshop, Sept. Ottawa, 6p. abstractNorthwest Territories, South AfricaGeochemistry, Geochronology - Lac de Gras, Contwyoto, Somerset
DS2001-0512
2001
PearsonIrvine, G.J., Pearson, Kopylova, Carlson, KjarsgaardThe age of two cratons: a platinum group elements (PGE) and Os isotopic study of peridotite c xenoliths from the Jericho, Somerset Isl.Slave-Kaapvaal Workshop, Sept. Ottawa, 5p. abstractNorthwest Territories, Nunavut, Somerset IslandGeochronology, Churchill Province, Slave Craton, Deposit - Jericho
DS2001-0706
2001
PearsonLuguet, A., Alard, O., Lorand, Pearson, Ryan, O'ReillyLaser ablation microprobe LAM ICPMS unravels the highly siderophile element geochemistry of oceanic mantle.Earth and Planetary Science Letters, Vol. 189, No. 3-4, July 15, pp. 285-94.MantleGeochemistry
DS2001-0869
2001
PearsonO'Reilly, S. Griffin, Djomani, Natapov, Pearson, DaviesThe mantle beneath the Slave Craton: composition and architectureSlave-Kaapvaal Workshop, Sept. Ottawa, 5p. abstractNorthwest TerritoriesPetrology, Tectonics - geochemistry, geophysics, plume
DS2001-0999
2001
PearsonRyan, C.G., Can Achterberg, Griffin, Pearson, O'ReillyNuclear microprobe analysis of melt inclusions in minerals: windows on metasomatic processes in mantleNuclear Instruments and Methods, Phys. Res. B., Vo.l81, pp. 578-85.MantleMetasomatism
DS2001-1178
2001
PearsonVan Achterbergh, A.E., Griffin, Kivi, Pearson, O'ReillyCarbonatites at 200 km: quenched melt inclusions in megacrystalline lherzolite xenoliths Slave Craton.Journal of South African Earth Sciences, Vol. 32, No. 1, p. A 35.(abs)Northwest TerritoriesCarbonatite, A 154 kimberlite
DS2002-0614
2002
PearsonGriffin, W.L., Wang, X., Jackson, Pearson, O'Reilly, XuZircon chemistry and magma mixing, SE China: in situ analysis of Hf isotopes, Tonglu and Pingtan complexes.Lithos, Vol.61, No.1-4, pp. 237-69., Vol.61, No.1-4, pp. 237-69.China, SoutheastGeochemistry - magma mixing, Geochronology
DS2002-0615
2002
PearsonGriffin, W.L., Wang, X., Jackson, Pearson, O'Reilly, XuZircon chemistry and magma mixing, SE China: in situ analysis of Hf isotopes, Tonglu and Pingtan complexes.Lithos, Vol.61, No.1-4, pp. 237-69., Vol.61, No.1-4, pp. 237-69.China, SoutheastGeochemistry - magma mixing, Geochronology
DS2002-1127
2002
PearsonNeumann, E.R., WulffPedersen, E., Pearson, SpencerMantle xenoliths from Tenerife: evidence for reactions between mantle peridotites and silicic carbonatite ..Journal of Petrology, Vol.43,5,pp.825-8., Vol.43,5,pp.825-8.Canary IslandsXenoliths, Melting
DS2002-1128
2002
PearsonNeumann, E.R., WulffPedersen, E., Pearson, SpencerMantle xenoliths from Tenerife: evidence for reactions between mantle peridotites and silicic carbonatite ..Journal of Petrology, Vol.43,5,pp.825-8., Vol.43,5,pp.825-8.Canary IslandsXenoliths, Melting
DS2002-1531
2002
PearsonSpetius, Z.V., Belousova, Griffin, O'Reilly, PearsonArchean sulphide inclusions in Paleozoic zircon megacrysts from the Mir kimberlite: implications datingEarth and Planetary Science Letters, Vol.199,1-2,pp.111-26., Vol.199,1-2,pp.111-26.Russia, YakutiaGeochronology - dating of diamonds, Deposit - Mir
DS2002-1532
2002
PearsonSpetius, Z.V., Belousova, Griffin, O'Reilly, PearsonArchean sulphide inclusions in Paleozoic zircon megacrysts from the Mir kimberlite: implications datingEarth and Planetary Science Letters, Vol.199,1-2,pp.111-26., Vol.199,1-2,pp.111-26.Russia, YakutiaGeochronology - dating of diamonds, Deposit - Mir
DS2002-1685
2002
PearsonWang, X., Griffin, O'Reilly, Zhou, Xu, Jackson, PearsonMorphology and geochemistry of zircons from late Mesozoic igneous complexes in coastal SE China:Mineralogical Magazine, Vol.66,2,pp. 235-52., Vol.66,2,pp. 235-52.China, southeastPetrogenesis
DS2002-1686
2002
PearsonWang, X., Griffin, O'Reilly, Zhou, Xu, Jackson, PearsonMorphology and geochemistry of zircons from late Mesozoic igneous complexes in coastal SE China:Mineralogical Magazine, Vol.66,2,pp. 235-52., Vol.66,2,pp. 235-52.China, southeastPetrogenesis
DS200712-0220
2007
PearsonDavies, G.R., Wasch, L., Van der Zwan, F., Morel, M.L.A., Nebel, Van Westrenen, Pearson, HellebrandThe origin of silica rich Kaapvaal lithospheric mantle.Plates, Plumes, and Paradigms, 1p. abstract p. A205.Africa, South AfricaDeposit - Kimberley
DS200812-1196
2008
PearsonUshkov, V.V., Ustinov, V.N., Smith, C.B., Bulanova, G.P., Lukyanova, L.I., Wiggers de Vries, D., PearsonKimozero, Karelia: a Diamondiferous paleoproterozoic metamorphosed volcaniclastic kimberlite.9IKC.com, 3p. extended abstractRussia, KareliaDeposit - Kimozero
DS200812-1321
2008
PearsonZheng, J.P., Griffin, W.L., O'Reilly, S.Y., Hu, Zhang, Tang, Su, Zhang, Pearson, Wamg, Lu.Continental collision and accretion recorded in the deep lithosphere of central China.Earth and Planetary Science Letters, Vol. 269, 3-4 May 30, pp. 496-506.ChinaBasaltic diatremes, geochronology, craton, tectonics
DS200912-0861
2009
PearsonZheng, J.P., Griffin, W.L., O'Reilly, S.Y., Zhao, J.H., Wu, Liu, Pearson, Zhang, Ma, Zhang, Yu, Su, TangNeoarchean ( 2.7-2.8 Ga) accretion beneath the North Chin a Craton: U Pb age, trace elements and Hf isotopes of zircons in Diamondiferous kimberlites.Lithos, Vol. 117, pp. 188-202.ChinaGeochronology
DS201112-0639
2011
PearsonMalkovets, V.G., Griffin, Pearson, Rezvukhin, O'Reilly, Pokhilenko, Garanin, Spetsius, LitasovLate metasomatic addition of garnet to the SCLM: Os-isotope evidence.Goldschmidt Conference 2011, abstract p.1395.RussiaUdachnaya, Daldyn
DS201012-0617
2010
Pearson, A.J.Rege, S., Griffin, W.L., Pearson, A.J., Araujo, D., Zedgenizov, D., O'Reilly, S.Y.Trace element patterns of fibrous and monocrystalline diamonds: insights into mantle fluids.Lithos, Vol. 118, pp. 313-337.TechnologyDiamond genesis, morphology
DS1991-1309
1991
Pearson, C.Pearson, C.The world diamond marketInternational Gemological Symposium, June 20-24, 1991 Los Angeles, Gems and Gemology, Vol. 27, Spring, Program p. 10GlobalDiamond market
DS1993-1206
1993
Pearson, C.Pearson, C., et al.De Beers and the war... Brief overview of background of de Beers during Second World War. Critique of recent film/video on de Beers and the CSO.Preprint, 12p.South Africa, GlobalDe Beers film/video
DS1995-1454
1995
Pearson, C.Pearson, C.Diamond to the year 2000Address to the Gem Fest Europa 1995, Vicenza Italy June 12, 16p.GlobalDiamond outlook, CSO Marketing
DS1997-0895
1997
Pearson, C.Pearson, C.Diamonds - a global perspectiveWorld Diamond Conference, held Oct 7-8, 8p.GlobalDiamond market
DS1999-0539
1999
Pearson, C.Pearson, C.Diamonds: a global businessGemological Institute of America (GIA) International Gem. Symposium June 21-24, 7p.GlobalDiamond production, Overview
DS1999-0540
1999
Pearson, C.Pearson, C.Diamonds - a global businessGemological Institute of America (GIA) Symposium Handout, 7p.GlobalEconomics, Diamond markets
DS200512-0832
2005
Pearson, C.Pearson, C.Market changes and the outlook, paradigm shift the 1990's and the 21st century. Outlook express and synthetics.World Diamond Conference Nov. 23, Perth, 5p. textNews item - production, markets
DS1900-0362
1905
Pearson, C.A.Williams, A., Pearson, C.A.The Romance of Mining Containing Interesting Descriptions Of the Methods of Mining for Minerals in All Parts of the World.London: C.a. Pearson., 401P.Africa, South Africa, India, MyanmarMining, History, Kimberley
DS1998-1340
1998
Pearson, D.Shimizu, N., Pokhilenko, N.P., Boyd, F.R., Pearson, D.Trace element characteristics of garnet dunites/harzburgites, host rocks for peridotite diamond7th International Kimberlite Conference Abstract, pp. 803-4.Russia, SiberiaMineral chemistry, Peridotite diamonds
DS1999-0664
1999
Pearson, D.Shimizu, N., Pokhilenko, N.P., Boyd, F.R., Pearson, D.Trace element characteristics of garnet dunites /harzburgites. Host rocks for Siberian peridotitic ..7th International Kimberlite Conference Nixon, Vol. 2, pp. 773-82.Russia, Siberia, YakutiaPeridotite - diamond, geochemistry, Deposit - Udachnaya
DS1987-0571
1987
Pearson, D.G.Pearson, D.G., Davies, G.R., Nixon, P.H.Diamond facies garnet pyroxenites of Beni Bousera Morocco:recycled oceanic lithosphereTerra Cognita, Conference abstracts Oceanic and Continental Lithosphere:, Vol. 7, No. 4, Autumn, abstract only p. 622MoroccoBlank
DS1989-1185
1989
Pearson, D.G.Pearson, D.G., Davies, G.R., Nixon, D.H.Graphite-bearing pyroxenites from Morocco:evidence of recycled oceanic lithosphere And the origin of E type diamondsDiamond Workshop, International Geological Congress, July 15-16th. editors, pp. 83-86. AbstractMoroccoE type diamond Beni Bousera, Diamond morphology
DS1989-1186
1989
Pearson, D.G.Pearson, D.G., Davies, G.R., Nixon, P.H., Milledge, H.J.Graphitized diamonds from a peridotite massif in Morocco and Implications for anomalous diamondoccurrencesNature, Vol. 338, No. 6210, March 2, pp. 60-62MoroccoDiamond morphology, Diamond genesis
DS1990-1165
1990
Pearson, D.G.Pearson, D.G., Boyd, F.R., Nixon, P.H.Graphite-bearing mantle xenoliths from the Kaapvaal Craton: Implications for graphite and diamond genesisCarnegie Institution Geophysical Laboratory Annual Report of the Director, No. 2200, pp. 11-19Southern Africa, LesothoGraphite, Diamond genesis
DS1991-1310
1991
Pearson, D.G.Pearson, D.G., Boyd, F.R., Field, S.W., Pasteris, J.D., HaggertyGraphite bearing peridotites from the Kaapvaal craton: their carbon isotopic compositions and implications for peridotite thermobarometryProceedings of Fifth International Kimberlite Conference held Araxa June 1991, Servico Geologico do Brasil (CPRM) Special, pp. 323-325South Africa, LesothoKimberley, Jagersfontein, spectrometry, Carbon composition -table
DS1991-1311
1991
Pearson, D.G.Pearson, D.G., Davies, G.R., Nixon, P.H.Diamond facies pyroxenites from the Beni Bousera peridotite massif And implications for the origin of eclogite xenolithsProceedings of Fifth International Kimberlite Conference held Araxa June 1991, Servico Geologico do Brasil (CPRM) Special, pp. 326-328MoroccoGeochronology -oxygen isotope, Mineral chemistry
DS1991-1312
1991
Pearson, D.G.Pearson, D.G., Davies, G.R., Nixon, P.H., Greenwood, P.B.Oxygen isotope evidence for the origin of pyroxenites in the Beni Bousera peridotite massif, North Morocco: derivation from subducted oceaniclithosphereEarth and Planetary Science Letters, Vol. 102, No. 3/4, March pp. 289-301MoroccoGeochemistry, Ophiolite - Beni Bousera
DS1991-1313
1991
Pearson, D.G.Pearson, D.G., O'Reilly, S.Y., Griffin, W.L.The thermal evolution of cratonic lower crust/upper mantle: examples from eastern Australia and southern AfricaProceedings of Fifth International Kimberlite Conference held Araxa June 1991, Servico Geologico do Brasil (CPRM) Special, pp. 332-333Australia, Southern AfricaKaapvaal craton, Geothermobarometry
DS1991-1314
1991
Pearson, D.G.Pearson, D.G., Shirey, S.B., Carlson, R.W., Boyd, F.R., Nixon, P.H.Rhenium-osmium isotope systematics in southern African and SiberanProceedings of Fifth International Kimberlite Conference held Araxa June 1991, Servico Geologico do Brasil (CPRM) Special, pp. 329-331Southern Africa, RussiaGeochronology -Re/Os isotope, Kaapvaal xenoliths
DS1991-1360
1991
Pearson, D.G.Pokhilenko, N.P., Pearson, D.G., Boyd, F.R., Sobolev, N.V.Megacrystalline dunites and peridotites: hosts for Siberian diamondsCarnegie Institute Annual Report of the Director Geophysical Laboratory, No. 2250, pp. 11-18Russia, SiberiaDunites, Peridotites
DS1992-1177
1992
Pearson, D.G.Pearson, D.G., Taylor, L.A.On isotope constraints on the petrogenesis of eclogite xenolithsEos Transactions, Vol. 73, No. 14, April 7, supplement abstracts p.376South AfricaBellsbank, Geochronology
DS1993-0150
1993
Pearson, D.G.Boyd, F.R., Pearson, D.G., Nixon, P.H., Mertzman, S.A.Low calcium garnet harzburgites from southern Africa: their relations to craton structure and diamond crystallizationContribution to Mineralogy and Petrology, Vol. 113, pp. 352-366South AfricaGarnet, Mineralogy
DS1993-0151
1993
Pearson, D.G.Boyd, F.R., Pearson, D.G., Pokhilenko, N.P., Mertzman, S.A.Cratonic mantle composition: evidence from Siberian xenolithsEos, Transactions, American Geophysical Union, Vol. 74, No. 16, April 20, supplement abstract p. 321Russia, SiberiaBulk composition, Mineral chemistry
DS1993-0320
1993
Pearson, D.G.Davies, G.R., Nixon, P.H., Pearson, D.G., Obata, M.Tectonic implications of graphitized diamonds from the Ronda peridotitemassif, southern SpainGeology, Vol. 21, No. 5, May pp. 471-474GlobalTectonics, Graphite morphology, Pyroxene
DS1993-1207
1993
Pearson, D.G.Pearson, D.G., Davies, G.R., Nixon, P.H.Geochemical constraints on the petrogenesis of diamond facies pyroxenites from the Beni Boussera peridotite Massif, North Morocco.Journal of Petrology, Vol. 34, No. 1, February pp. 125-172.MoroccoDiamond, geochemistry, Pyroxenite
DS1993-1247
1993
Pearson, D.G.Pokhilenko, N.P., Sobolev N.V., Boyd, F.R., Pearson, D.G., Shimizum N.Megacrystalline pyrope peridotites in the lithosphere of the Siberianplatform: mineralogy, geochemical pecularities and the problem of their origin.Russian Geology and Geophysics, Vol. 34, No. 1, pp. 1-12.Russia, Commonwealth of Independent States (CIS), SiberiaPyrope peridotites, Siberian Platform, Geochemistry
DS1994-0201
1994
Pearson, D.G.Boyd, F.R., Pearson, D.G., Olson Hoal, K.E., Hoal, B.G.Composition and age of Namibian peridotite xenolith: a comparison of cratonic and non cratonic lithosphere.Eos, Vol. 75, No. 16, April 19, p. 192.NamibiaXenoliths, Peridotites
DS1994-0256
1994
Pearson, D.G.Canil, D., O'Neill, H.S., Pearson, D.G., Rudnick, R.L.Ferric ion in peridotites and mantle oxidation statesEarth Planet. Sci. Letters, Vol. 123, No. 1-2, May pp. 205-220.MantlePeridotites
DS1994-1347
1994
Pearson, D.G.Pearson, D.G., Boyd, F.R., Haggerty, S.E., Pasteris, J.D.The characterization and origin of graphite in cratonic lithosphericmantle: a petrological carbon isotope and Raman spectroscopic study.Contr. Mineralogy and Petrology, Vol. 116, No. 3, pp. 449-466.MantleGeochronology, Graphite
DS1994-1348
1994
Pearson, D.G.Pearson, D.G., Snyder, G.A., Shirley, S.B., Taylor, L.A.Rhenium- Osmium (Re-Os) isotope evidence for a mid-Archean age of Diamondiferous eclogite xenoliths -Udachnaya.Mineralogical Magazine, Vol. 58A, pp. 705-706. AbstractRussia, YakutiaGeochronology, Deposit -Udachnaya
DS1995-0192
1995
Pearson, D.G.Boyd, F.R., Pokhilenko, N.P., Pearson, D.G., Sobolev, N.V.Peridotite xenoliths from the Udachnaya kimberlite pipeProceedings of the Sixth International Kimberlite Conference Extended Abstracts, p. 57-59.Russia, YakutiaXenoliths, Deposit -Udachnaya
DS1995-0270
1995
Pearson, D.G.Carlson, R.W, Shirey, S.B., Pearson, D.G., Boyd, F.R.The mantle beneath continentsCarnegie Institution Yearbook 93 for 1993-1994., pp. 109-119.South Africa, Russia, SiberiaMantle, Plumes, keels
DS1995-0804
1995
Pearson, D.G.Hoal, B.G., Hoal, K.E.O., Boyd, F.R., Pearson, D.G.Tectonic setting and mantle composition inferred from peridotite Gibeon kimberlite field, Namibia.Proceedings of the Sixth International Kimberlite Conference Abstracts, pp. 239-241.NamibiaTectonics, Deposit -Gibeon area
DS1995-0805
1995
Pearson, D.G.Hoal, B.G., Hoal, R.E.O., Boyd, F.R., Pearson, D.G.Age constraints on crustal and mantle lithosphere beneath the Gibean kimberlite field, Namibia.South. African Journal of Geology, Vol. 98, No. 2, June pp. 112-118.NamibiaGeochronology, Deposit -Gibeon field
DS1995-1455
1995
Pearson, D.G.Pearson, D.G., Carlson, R.W., Nixon, P.H.Stabilizaton of Archean lithospheric mantle: a Re:Os isotope study of peridotite xenoliths Kaapvaal CratonEarth and Planetary Science Letters, Vol. 134, No. 3-4, Sept. 1, pp. 341-358South AfricaXenoliths, Kaapvaal Craton
DS1995-1456
1995
Pearson, D.G.Pearson, D.G., Carlson, R.W., Nixon, P.H.Stabilization of Archean lithospheric mantle: a RE; OS isotope study of peridotite xenoliths Kaapvaal Craton.Earth and Planetary Science Letters, Vol. 134, No. 3-4, Sept. 1, pp. 341-358.South AfricaXenoliths, Craton -Kaapvaal
DS1995-1457
1995
Pearson, D.G.Pearson, D.G., Davies, G.R., Nixon, P.H.Orogenic ultramafic rocks of ultra high pressure (UHP) (diamond facies) originCambridge University of Press, pp. 456-510.Morocco, Spain, British Columbia, Russia, Tibet, Burkina FasoPeridotite - Beni Bousera, Ronda, Ophiolites - diamondiferous
DS1995-1458
1995
Pearson, D.G.Pearson, D.G., Kelley, S.P., Pokhilenko, N.P., Boyd, F.R.Laser 40 Ar-39 Ar analyses of phlogopites from kimberlites and theirxenoliths: constraints eruptionProceedings of the Sixth International Kimberlite Conference Abstracts, pp. 424-426.Russia, Yakutia, South AfricaGeochronology -eruption ages, Argon, Deposit -Mir, Udachnaya, Leningrad, Letseng, Kampfersda
DS1995-1459
1995
Pearson, D.G.Pearson, D.G., Meyer, H.O.A., Boyd, F.R., Shirey, S.B.Rhenium- Osmium (Re-Os) isotope evidence for late Archean stabilization of thick lithosphere mantle keel beneath Kirkland LakeProceedings of the Sixth International Kimberlite Conference Abstracts, pp. 427-429.Ontario, Kirkland LakeGeochronology, Mantle keel
DS1995-1460
1995
Pearson, D.G.Pearson, D.G., Rogers, N.W., Irving, A.J., Smith, C.B.Source regions of kimberlites and lamproites: constraints from Rhenium- Osmium (Rhenium- Osmium (Re-Os))isotopes.Proceedings of the Sixth International Kimberlite Conference Abstracts, pp. 430-432.South AfricaGeochronology, Lamproites
DS1995-1461
1995
Pearson, D.G.Pearson, D.G., Shirey, S.B., Carlson, R.W, Boyd, F.R.Rhenium- Osmium (Re-Os),samarium-neodymium (Sm-Nd) Rubidium-Strontium isotope evidence for thick Archean lithospheric mantle beneath the Siberian craton ....Geochimica et Cosmochimica Acta, Vol. 59, No. 3, pp. 959-977.Russia, SiberiaMantle geochemistry, geochronology, Metasomatism -multistage
DS1995-1462
1995
Pearson, D.G.Pearson, D.G., Snyder, G.A., Shirey, S.B., Taylor, L.A.Archean Rhenium- Osmium (Re-Os) age for Siberian eclogites and constraints on Archeantectonics.Nature, Vol. 374, No. 6524, April 20, pp. 711-713.Russia, Siberia, RussiaGeochronology, Eclogites
DS1995-1736
1995
Pearson, D.G.Shimizu, N., Pokhilenko, N.P., Biyd, F.R., Pearson, D.G.Geochemical characteristics of mantle xenoliths from the Udachnaya kimberlite pipe.Proceedings of the Sixth International Kimberlite Conference Abstracts, pp. 524-525.Russia, YakutiaGeochemistry, Deposit -Udachnaya
DS1996-1085
1996
Pearson, D.G.Pearson, D.G., Nixon, P.H.Diamonds in young orogenic belts: graphitised diamonds from Beni Bousera: acomparison with kimberlite derivedAfrica Geoscience Review, Vol. 3, No. 2, pp. 295-316.MoroccoGraphite aggregates, diamond genesis, exploration, Diamond facies pyroxenites
DS1998-0215
1998
Pearson, D.G.Carlson, R.W., Pearson, D.G., Boyd, F.R., Shirey, IrvineRegional age variation of the southern African mantle: significance for model lithospheric mantle formation..7th International Kimberlite Conference Abstract, pp. 135-137.South AfricaGeochronology, Craton - on and off ages
DS1998-0566
1998
Pearson, D.G.Hamilton, M.A., Pearson, D.G., Stern R.A., Boyd, F.R.Constraints on MARID petrogenesis: SHRIMP II uranium-lead (U-Pb) zircon evidence for pre-eruption Metasomatism..7th International Kimberlite Conference Abstract, pp. 296-8.South AfricaGeochronology, Deposit - KampfersdaM.
DS1998-0596
1998
Pearson, D.G.Hauri, E.H., Pearson, D.G., Bulanova, G.P., Milledge, H.Microscale variations in Carbon and Nitrogen isotopes within mantle diamonds revealed by SIMS.7th International Kimberlite Conference Abstract, pp. 317-9.Russia, Siberia, southern AfricaDiamond morphology, Geochronology
DS1998-0660
1998
Pearson, D.G.Irvine, G.J., Pearson, D.G., Carlson, R.W., Boyd, F.R.Platinum group element constraints on the origin of cratonic peridotites: a study of Kimberley xenoliths..7th International Kimberlite Conference Abstract, pp. 346-8.South AfricaXenoliths - platinum group elements (PGE), Deposit - Kimberley
DS1998-1078
1998
Pearson, D.G.Nixon, P.H., Pearson, D.G.Ultra-magmatism komatiites of Phanerozoic age from southeast Spain7th International Kimberlite Conference Abstract, pp. 625-7.GlobalStructure - spinifex textured harzburgites, Geochemistry
DS1998-1080
1998
Pearson, D.G.Nowell, G.M., Kempton, P.D., Pearson, D.G.Hafnium - neodymium isotope systematics of kimberlites: relevance to terrestrial Hafnium - neodymium systematics.7th International Kimberlite Conference Abstract, pp. 628-30.MantleChondrites - bulk silicate earth, Geochronology
DS1998-1081
1998
Pearson, D.G.Nowell, G.M., Kempton, P.D., Pearson, D.G.Trace element and isotope geochemistry of Siberian kimberlites7th International Kimberlite Conference Abstract, pp. 631-3.Russia, YakutiaGeochemistry, Group I kimberlites
DS1998-1082
1998
Pearson, D.G.Nowell, G.M., Pearson, D.G.Hafnium isotope constraints on the genesis of kimberlitic megacrysts : evidence for a deep mantle component.7th International Kimberlite Conference Abstract, pp. 634-6.South AfricaKimberlite magmatism, Deposit - Frank Smith, Monastery
DS1998-1083
1998
Pearson, D.G.Nowell, G.M., Pearson, D.G., Kempton, irving, TurnerA Hafnium isotope study of lamproites: implications for their origins and relationships to kimberlite.7th International Kimberlite Conference Abstract, pp. 637-9.Montana, Australia, SpainGeochronology, Lamproites
DS1998-1084
1998
Pearson, D.G.Nowell, G.M., Pearson, D.G., Kempton, Noble, SmithThe source regions/components of kimberlites: constraints from Hafnium - neodymium isotope systematics.7th. Kimberlite Conference abstract, pp. 640-2.South AfricaGeochronology, Group I, II
DS1998-1133
1998
Pearson, D.G.Pearson, D.G., Carlson, R.W., Boyd, F.R., Shiry, NixonLithospheric mantle growth around cratons: a Rhenium- Osmium (Re-Os) isotope study of peridotite xenoliths East Griqualand.7th. Kimberlite Conference abstract, pp. 658-60.South AfricaCraton, Geochronology - xenoliths
DS1998-1134
1998
Pearson, D.G.Pearson, D.G., Davies, R., Shirey, Carlson, R., Griffin.The age and origin of eastern Australian diamonds: Rhenium- Osmium (Re-Os) isotope evidence from sulfide inclusions...7th. Kimberlite Conference abstract, pp. 664-6.Australia, New South WalesDiamond inclusions, geochronology, Deposit - Copeton, Bingara
DS1998-1135
1998
Pearson, D.G.Pearson, D.G., Ionov, D., Carlson, ShireyLithospheric evolution in circum cratonic settings: a Re- Os isotope studyof peridotite xenoliths Vitim ...Mineralogical Magazine, Goldschmidt abstract, Vol. 62A, p. 1147-8.Russia, VitiM.Geochemistry - whole rock, Spinels
DS1998-1136
1998
Pearson, D.G.Pearson, D.G., Milledge, H.J.Diamond growth conditions and preservation: inferences from trace elements in a large garnet inclusion...7th. Kimberlite Conference abstract, pp. 667-9.Russia, SiberiaDiamond morphology, diamond inclusions, Deposit - Udachnaya
DS1998-1137
1998
Pearson, D.G.Pearson, D.G., Shirey, S., Bulanova, Carlson, MilledgeDating diamonds using Rhenium- Osmium (Re-Os) isotope technique: a study of sulfide inclusions in Siberian diamonds.7th. Kimberlite Conference abstract, pp. 661-3.Russia, SiberiaGeochronology, Deposit - Udachnaya
DS1998-1138
1998
Pearson, D.G.Pearson, D.G., Shirey, S.B., Carlson, R.W.Sulphide inclusions in diamonds from the Koffiefontein kimberlite:constraints on diamond ages and mantle R-OsEarth and Planetary Science Letters, Vol. 160, No. 3-4, Aug. 1, pp. 311-326.South AfricaGeochronology, diamond inclusions, Deposit - Koffiefontein
DS1999-0512
1999
Pearson, D.G.Nixon, P.H., Pearson, D.G., Condliffem E.Harzburgites with spinifex texture from southeast Spain - petrological and geochemical constraints on origin.7th International Kimberlite Conference Nixon, Vol. 2, pp. 605-15.GlobalHarzburgites, mineralogy, regional tectonics, Cerro del Almirez, Montenegro
DS1999-0516
1999
Pearson, D.G.Nowell, G.M., Pearson, D.G., Kempton, Noble, SmithOrigins of kimberlites: a Hafnium isotope perspective7th International Kimberlite Conference Nixon, Vol. 2, pp. 616-24.South AfricaGeochronology, Group I, II, model, subduction
DS1999-0541
1999
Pearson, D.G.Pearson, D.G.The age of continental rootsLithos, Vol. 48, No. 1-4, Sept. pp. 171-94.MantleGeochronology, Craton
DS1999-0542
1999
Pearson, D.G.Pearson, D.G., Shirey, Bulanova, Carlson, MilledgeDating and paragenetic distinction of diamonds using Re- Os isotope system: application Siberian diamonds.7th International Kimberlite Conference Nixon, Vol. 2, pp. 637-43.Russia, SiberiaGeochronology, sulphide inclusions, age determination, Udachnaya, Mir
DS1999-0543
1999
Pearson, D.G.Pearson, D.G., Shirey, S.B.Isotopic dating of diamondsSeg Reviews In Economic Geology, Vol. 12, Chapter 6, pp. 143-72.GlobalDiamond - inclusions, isotopic, Age determinations - silicate, sulphide
DS1999-0544
1999
Pearson, D.G.Pearson, D.G., Shirey, S.B., Milledge, H.J.Re Os isotope measurements of single sulphide inclusions in a Siberian diamond and its nitrogen ...Geochimica et Cosmochimica Acta, Vol. 63, No. 5, Mar. 1, pp. 7-3-12.Russia, SiberiaGeochronology - diamond inclusions, Nitrogen aggregation systematics
DS2001-0511
2001
Pearson, D.G.Irvine, G.J., Pearson, D.G., Carlson, R.W.Lithospheric mantle evolution of the Kaapvaal Craton : a Rhenium- Osmium (Re-Os) isotope study of peridotite nodules kimberlitesGeophysical Research Letters, Vol. 28, No. 13, July 1, pp. 2505-08.LesothoGeochronology
DS2001-0895
2001
Pearson, D.G.Pearson, D.G.New isotopic techniques for dating diamonds: examples from the Siberian Craton29th. Yellowknife Geoscience Forum, Nov. 21-23, abstract p. 64-5.RussiaGeochronology
DS2001-0896
2001
Pearson, D.G.Pearson, D.G., Biyd, F.R., Simon, N.S.C.Modal mineralogy and geochemistry of Kaapvaal peridotites: the origin of garnet diopside - stabilitySlave-Kaapvaal Workshop, Sept. Ottawa, 7p. abstractSouth AfricaCraton - stability
DS2002-0221
2002
Pearson, D.G.Bulanova, G.P., Pearson, D.G., Hauri, E.H., Griffin, B.J.Carbon and nitrogen isotope systematics within a sector growth diamond from the Mir kimberlite, Yakutia.Chemical Geology, Vol. 188, No. 1-2, pp. 105-123.Russia, YakutiaGeochronology, Deposit - Mir
DS2002-0681
2002
Pearson, D.G.Hauri, E.H., Wang, J., Pearson, D.G., Bulanova, G.P.Microanalysis of 13C 15 N and N abundances in diamonds by secondary ion mass spectrometry.Chemical Geology, Vol.145, 1-2, Apr.15, pp. 149-63.Russia, SiberiaDiamond - inclusions, carbon, nitrogen isotopes
DS2002-1235
2002
Pearson, D.G.Pearson, D.G., Nowell, G.M.The continental lithospheric mantle characteristics and significance as a mantle reservoirPhilosophical Transactions, Royal Society of London Series A Mathematical, Vol.1800, pp. 2383-2410.MantleTectonics, geochemistry
DS2003-0146
2003
Pearson, D.G.Boyd, F.R., Hoal, K.O., Hoal, B.G., Nicox, P.H., Pearson, D.G., Kingston, M.J.Garnet lherzolites from Louwrencia, Namibia: bulk sample compositions and P/T8 Ikc Www.venuewest.com/8ikc/program.htm, Session 6, AbstractNamibiaMantle petrology
DS2003-0182
2003
Pearson, D.G.Bulanova, G.P., Muchemwa, E., Pearson, D.G., Griffin, B.J., Kelly, S., KlemmeSyngenetic inclusions of yeminite in diamond from Sese kimberlite ( Zimbabwe) -8ikc, Www.venuewest.com/8ikc/program.htm, Session 3, POSTER abstractZimbabweDiamonds - inclusions, Deposit - Sese
DS2003-0183
2003
Pearson, D.G.Bulanova, G.P., Pearson, D.G., Hauri, E.H., Milledge, H.J., Barashkov, Yu.P.Dynamics of diamond growth: evidence from isotope and FTIR trends8ikc, Www.venuewest.com/8ikc/program.htm, Session 3, POSTER abstractRussiaDiamonds - inclusions, Geochronology, morphology
DS2003-0313
2003
Pearson, D.G.Davies, G.R., Stolz, A.J., Mahotkin, I.L., Nowell, G.M., Pearson, D.G.Trace element and Sr Pb Nd Hf isotope evidence for ancient fluid related enrichment in8 Ikc Www.venuewest.com/8ikc/program.htm, Session 7, POSTER abstractRussia, Aldan ShieldGeochronology
DS2003-0347
2003
Pearson, D.G.Dowall, D.P., Pearson, D.G., Nowell, G.M., Kjarsgaard, B.A., Armstrong, J.Comparative geochemistry of kimberlites from the Lac de Gras field, NWT - an8 Ikc Www.venuewest.com/8ikc/program.htm, Session 7, AbstractNorthwest TerritoriesKimberlite petrogenesis, Geochronology, database 98
DS2003-0540
2003
Pearson, D.G.Hamilton, M.A., Sobolev, N.V., Stern, R.A., Pearson, D.G.SHRIMP U Pb dating of a perovskite inclusion in diamond: evidence for a syneruption8ikc, Www.venuewest.com/8ikc/program.htm, Session 3, POSTER abstractRussia, Siberia, YakutiaDiamonds - inclusions, geochronology, Deposit - Sytykanskaya
DS2003-0622
2003
Pearson, D.G.Irvine, G.J., Pearson, D.G., Kjarsgaard, B.A., Carlson, R.W., Kopylova, M.G.A Re Os isotope and PGE study of kimberlite derived peridotite xenoliths fromLithos, Vol. 71, 2-4, pp. 461-488.South Africa, Northwest Territories, NunavutGeochronology
DS2003-0631
2003
Pearson, D.G.Jacob, D.E., Fung, A., Jagoutz, E., Pearson, D.G.Petrology and geochemistry of eclogite xenoliths from the Ekati kimberlite area8ikc, Www.venuewest.com/8ikc/program.htm, Session 2, POSTER abstractNorthwest TerritoriesEclogites and Diamonds, Deposit - Ekati
DS2003-1020
2003
Pearson, D.G.Nowell, G.M., Pearson, D.G., Jacob, D.E., Spetsius, S., Nixon, P.H., HaggertyThe origin of alkremites and related rocks: a Lu Hf Rb Sr and Sm Nd isotope study8ikc, Www.venuewest.com/8ikc/program.htm, Session 4, POSTER abstractRussia, YakutiaMantle geochemistry, Deposit - Udachnaya
DS2003-1050
2003
Pearson, D.G.Pearson, D.G., Nowell, G.M., Dowall, D.P., Kjarsgaard, B.A., Kopylova, M.G.The relative roles of lithosphere and convecting mantle in kimberlites from the Slave8 Ikc Www.venuewest.com/8ikc/program.htm, Session 7, AbstractNorthwest TerritoriesKimberlite petrogenesis, Geochronology
DS2003-1278
2003
Pearson, D.G.Simon, N.S., Irvine, G.J., Davies, G.R., Pearson, D.G., Carlson, R.W.The origin of garnet and clinopyroxene in 'depleted' Kaapvaal peridotitesLithos, Vol. 71, 2-4, pp. 289-322.South AfricaMineral chemistry
DS2003-1279
2003
Pearson, D.G.Simon, N.S.C., Carlosn, R.W., Davies, D.R., Nowell, G.M., Pearson, D.G.OS SR ND HF isotope evidence for the ancient depletion and subsequent multi stage8ikc, Www.venuewest.com/8ikc/program.htm, Session 4, POSTER abstractSouth AfricaMantle geochemistry, Geochronology
DS200412-0193
2003
Pearson, D.G.Boyd, F.R., Hoal, K.O., Hoal, B.G., Nicox, P.H., Pearson, D.G., Kingston, M.J.Garnet lherzolites from Louwrencia, Namibia: bulk sample compositions and P/T relations.8 IKC Program, Session 6, AbstractAfrica, NamibiaMantle petrology
DS200412-0197
2004
Pearson, D.G.Boyd, S.R., Pearson, D.G., Hoal, K.O., Hoal, B.G., Nixon, P.H., Kingston, M.J., Mertzman, S.A.Garnet lherzolites from Louwrensia, Namibia: bulk composition and P/T relations.Lithos, Vol. 77, 1-4, Sept. pp. 573-592.Africa, NamibiaGeothermometry, peridotite, Kaapvaal, mantle, lithosphe
DS200412-0239
2004
Pearson, D.G.Bulanova, G.P., Muchemwa, E., Pearson, D.G., Griffin, B.J., Kelley, S.P., Klemme, S., Smith, C.B.Syngenetic inclusions of yimengite in diamond from Sese kimberlite - evidence for metasomatic conditions of growth.Lithos, Vol. 77, 1-4, Sept. pp. 181-192.Africa, ZimbabweMagnetoplumbite, grochronology argon, mantle, metasomat
DS200412-0413
2003
Pearson, D.G.Davies, G.R., Stolz, A.J., Mahotkin, I.L., Nowell, G.M., Pearson, D.G.Trace element and Sr Pb Nd Hf isotope evidence for ancient fluid related enrichment in the source region of Aldan Shield lamproi8 IKC Program, Session 7, POSTER abstractRussia, Aldan ShieldKimberlite petrogenesis, geochronology
DS200412-0474
2003
Pearson, D.G.Dowall, D.P., Pearson, D.G., Nowell, G.M., Kjarsgaard, B.A., Armstrong, J., Hortswood, M.S.A.Comparative geochemistry of kimberlites from the Lac de Gras field, NWT - an integrated isotopic and elemental study.8 IKC Program, Session 7, AbstractCanada, Northwest TerritoriesKimberlite petrogenesis, Database 98
DS200412-0874
2003
Pearson, D.G.Irvine, G.J., Pearson, D.G., Kjarsgaard, B.A., Carlson, R.W., Kopylova, M.G., Dreibus, G.A Re Os isotope and PGE study of kimberlite derived peridotite xenoliths from Somerset Island and a comparison to the Slave andLithos, Vol. 71, 2-4, pp. 461-488.Africa, South Africa, Northwest Territories, NunavutGeochronology
DS200412-1448
2004
Pearson, D.G.Nowell, G.M., Pearson, D.G., Bell, D.R., Carlson, R.W., Smith, C.B., Kempton, P.D., Noble, S.R.Hf isotope systematics of kimberlites and their megacrysts: new constraints on their source regions.Journal of Petrology, Vol. 45, 8, pp. 1583-1612.Africa, South AfricaGeochronology
DS200412-1508
2004
Pearson, D.G.Pearson, D.G., irvine, G.J., Ionov, D.A., Boyd, F.R., Dreibus, G.E.The Re Os systematics and platinum group element fractionation during mantle melt extraction: a study of massif and xenolith perChemical Geology, Vol. 208, 1-4, pp. 29-59.Africa, Lesotho, Namibia, MoroccoGeochronology, mantle melt extraction
DS200412-1509
2003
Pearson, D.G.Pearson, D.G., Nowell, G.M., Dowall, D.P., Kjarsgaard, B.A., Kopylova, M.G., Armstrong, J.A.The relative roles of lithosphere and convecting mantle in kimberlites from the Slave Province NWT: constraints from Re Os isoto8 IKC Program, Session 7, AbstractCanada, Northwest TerritoriesKimberlite petrogenesis Geochronology
DS200412-1831
2003
Pearson, D.G.Simon, N.S., Irvine, G.J., Davies, G.R., Pearson, D.G., Carlson, R.W.The origin of garnet and clinopyroxene in 'depleted' Kaapvaal peridotites.Lithos, Vol. 71, 2-4, pp. 289-322.Africa, South AfricaMineral chemistry
DS200512-0140
2005
Pearson, D.G.Carlson, R.W., Pearson, D.G., James, D.E.Physical, chemical and chronological characteristics of continental mantle.Reviews of Geophysics, Vol. 43, 1, RG1001 10.1029/2004 TG000156MantleGeochemistry
DS200512-0220
2005
Pearson, D.G.Day, J.M.D., Hilton, D.R., Pearson, D.G., MacPherson, C.G., Kjarsgaard, B.A., Janney, P.E.Absence of a high time integrated 3He (U-Th) source in the mantle beneath continents.Geology, Vol. 33, 9, Sept. pp. 733-736.Mantle, Canada, Africa, South Africa, UgandaGeochronology - helium isotopes
DS200512-1072
2003
Pearson, D.G.Tappe, S., Foley, S.F., Pearson, D.G.African type kamafugites: a mineralogical and geochemical comparison with their Italian and Brazilian analogues.Periodico di Mineralogia, (in english), Vol. LXX11, 1. April, pp. 51-77.South America, Brazil, Africa, UgandaMelilite, katsilite, Toro Ankole Rift
DS200512-1084
2005
Pearson, D.G.Thompson, R.N., Ottley, C.J., Smith, P.M., Pearson, D.G., Dickin, A.P., Morrison, M.A., Leat, P.T., Gibson, S.A.Source of the Quaternary alkalic basalts, picrites and basanites of the Potrillo volcanic field, New Mexico, USA: lithosphere or convecting mantle?Journal of Petrology, Vol. 46, 8, pp. 1603-1643.United States, New Mexico, Colorado PlateauConvection
DS200512-1085
2005
Pearson, D.G.Thompson, R.N., Ottley, C.J., Smith, P.M., Pearson, D.G., Dickin, A.P., Morrison, M.A., Leat, P.T., Gibson, S.A.Source of the Quaternary alkaline basalts, picrites and basanites of the Potrillo volcanic field, New Mexico, USA: lithosphere or convecting mantle?Journal of Petrology, Vol. 46, 8, pp. 1603-1643.United States, New Mexico, Colorado PlateauPicrite, basanites
DS200612-0315
2006
Pearson, D.G.Davies, G.R., Stolz, A.J., Mahotkin, I.L., Nowell, G.M., Pearson, D.G.Trace element and Sr Pb Nd Hf isotope evidence for ancient fluid dominated enrichment of the source of the Aldan Shield, lamproites.Journal of Petrology, Vol. 47, 6, pp. 1119-1146.RussiaGeochronology, geochemistry lamproites
DS200612-0534
2006
Pearson, D.G.Harlou, R., Pearson, D.G., Davidson, J.P., Kamenetsky, V.S., Yaxley, G.M.Source variability and crustal contamination of the Baffin Island picrites - coupled Sr isotope and trace element study of individual melt inclusions.Geochimica et Cosmochimica Acta, Vol. 70, 18, 1, p. 11, abstract only.Canada, Nunavut, Baffin IslandPicrite
DS200612-0840
2006
Pearson, D.G.Luguet, A., Nowell, G.M., Pearson, D.G., Dreher, S.T.186 Os and 187 Os signatures of pyroxenites and the core mantle interaction debate.Geochimica et Cosmochimica Acta, Vol. 70, 18, p. 35, abstract only.MantleGeochronology
DS200612-1059
2006
Pearson, D.G.Pearson, D.G., Harris, J.W.Diamond geochronology - a record of continental lithosphere evolution.Geochimica et Cosmochimica Acta, Vol. 70, 18, p. 13. abstract only.MantleGeochronology
DS200712-0550
2007
Pearson, D.G.Klein Ben-David, O., Pearson, D.G.Sr isotopes and trace element pattern in sub-calcic garnets: a perspective on diamond bearing fluids.Plates, Plumes, and Paradigms, 1p. abstract p. A490.Canada, Northwest TerritoriesEkati
DS200712-0749
2007
Pearson, D.G.Morel, M.L.A., Pearson, D.G., Luguiet, A., Davies, G.R.Os isotopic and PGE evidence for major disruption and addition to the lithospheric mantle: a study of peridotites from the Premier Mine, Kaapvaal Craton. SAPlates, Plumes, and Paradigms, 1p. abstract p. A687.Africa, South AfricaPremier
DS200712-0806
2007
Pearson, D.G.Parman, S.W., Pearson, D.G., Nowell, G.M.The hidden history of mantle depletion: Os isotopes reveal a link between mantle depletion and crustal growth.Plates, Plumes, and Paradigms, 1p. abstract p. A757.MantlePulsed growth
DS200712-0821
2007
Pearson, D.G.Pearson, D.G., Harlou, R., Hayman, P., Cartigny, P., Kopylova, M.Sr isotopic compositions of ultra deep inclusions in diamonds: implications for mantle chemical structure and evolution.Plates, Plumes, and Paradigms, 1p. abstract p. A769.MantleUHP
DS200712-0822
2007
Pearson, D.G.Pearson, D.G., Parman, S.W., Nowell, G.M.A link between large mantle melting events and continent growth seen in osmium isotopes.Nature, Vol. 449, Sept. 13, ppp. 202-205.MantleGeochronology, melting
DS200712-0990
2007
Pearson, D.G.Simon, N.S.C., Carlson, R.W., Pearson, D.G., Davies, G.R.The origin and evolution of the Kaapvaal Cratonic lithospheric mantle.Journal of Petrology, Vol. 48, 3, pp. 589-625.Africa, South AfricaTectonics
DS200812-0225
2008
Pearson, D.G.Coe, N., Le Roex, A., Gurney, J., Pearson, D.G., Nowell, G.Petrogenesis of the Swartruggens and Star Group II kimberlite dyke swarms, South Africa: constraints from whole rock geochemistry.Contributions to Mineralogy and Petrology, Vol. 156, pp. 627-652.Africa, South AfricaKaapvaal Craton, petrogenesis
DS200812-0226
2008
Pearson, D.G.Coe, N., Roex, A., Gurney, J., Pearson, D.G., Nowell, G.Petrogenesis of the Swartuggens and Star Group II kimberlite dyke swarms, South Africa: constraints from whole rock geochemistry.Contributions to Mineralogy and Petrology, Vol. 156, 5, pp. 627-652.Africa, South AfricaDeposit - Swartruggens and Star
DS200812-0577
2008
Pearson, D.G.Kjarsgaard, B.A., Pearson, D.G., Tappe, S., Nowell, G.M., Dowall, D.P.Kimberlites: high H2O/CO2, MgO rich and K poor silica undersaturated magmas. Lac de Gras9IKC.com, 3p. extended abstractAfrica, South Africa, Canada, Northwest TerritoriesGroup 1 kimberlites
DS200812-0580
2008
Pearson, D.G.Klein-Ben David, O., Pearson, D.G., Nowell, G.M., Ottley, C., Cantigny, P.Origins of diamond forming fluids - constraints from a coupled Sr Nd Pb isotope and trace element approach.Goldschmidt Conference 2008, Abstract p.A479.TechnologyMicro-inclusions
DS200812-0589
2008
Pearson, D.G.Kopylova, M.G., Nowell, G.M., Pearson, D.G., Markovic, G.Crystallization of megacrysts from kimberlites: geochemical evidence from high Cr megacrysts in the Jericho kimberlite.9IKC.com, 3p. extended abstractCanada, NunavutDeposit - Jericho
DS200812-0639
2008
Pearson, D.G.Le Roex, A., Coe, N., Gurney, J., Pearson, D.G., Nowell, G.Petrogenesis of Group II kimberlites: a case study from southern Africa.9IKC.com, 3p. extended abstractAfrica, South Africa, BotswanaDeposit - Swartruggens, Star
DS200812-0704
2008
Pearson, D.G.Malarkey, J., Pearson, D.G., Davidson, J.P., Wiitig, N.Origins of Cr diopside in peridotite xenoliths.Goldschmidt Conference 2008, Abstract p.A588.Europe, Greenland, Africa, South AfricaDeposit - Kimberley
DS200812-0804
2008
Pearson, D.G.Nowell, G.M., Pearson, D.G., Irving, A.J.Lu Hf and Re Os isotope studies of lamproite genesis.9IKC.com, 3p. extended abstractUnited States, Australia, CanadaLamproite - geochronology
DS200812-0867
2008
Pearson, D.G.Pearson, D.G., Kjarsgaard, B.A., Garrido, C., Nixon, P.H.The Ronda peridotite and lamproites in Spain. Salmeron, Jumill, Cerro Canbezo Maria. Chemical analyses of lamproite/ Isotopic systematics of lamproites.9th. IKC Field Trip Guidebook, CD 38p.Europe, SpainGuidebook - lamproites
DS200812-0868
2008
Pearson, D.G.Pearson, D.G., Nowell, G.M., Kjarsgaard, B.A., Dowall, D.P.The genesis of kimberlite: geochemical constraints.9IKC.com, 3p. extended abstractCanada, Northwest TerritoriesDeposit - Lac de Gras geochemistry
DS200812-0869
2008
Pearson, D.G.Pearson, D.G., Nowell, G.M., Klein Ben-David, O., Kjarsgaard, B.A.,Irving, A.J.Isotopic constraints on the source regions of alkaline volcanics.Goldschmidt Conference 2008, Abstract p.A731.MantleLamproite, Group I kimberlites, geochronology
DS200812-0870
2008
Pearson, D.G.Pearson, D.G., Wittig, N.Formation of Archean continental lithosphere and its diamonds: the root of the problem.Journal of the Geological Society, Vol. 165, pp. 895-914.MantleDiamond genesis - review
DS200812-0971
2008
Pearson, D.G.Rosenthal, A., Foley, S.F., Pearson, D.G., Nowell, G.M., Tappe, S.Origin of kamafugite magmas in the East African Rift of western Uganda.9IKC.com, 3p. extended abstractAfrica, UgandaToro Ankole volcanic field
DS200812-1060
2008
Pearson, D.G.Shirey, S.B., Richardson, S.H., Pearson, D.G., Carlson, R.W., Harris, J.W.Eclogitic sulfide and silicate inclusions in diamonds and subcontinental geological processes.Goldschmidt Conference 2008, Abstract p.A862.Africa, Botswana, South AfricaDeposit - Jwaneng, Koffiefontein, Orapa, Premier,Venetia
DS200812-1179
2008
Pearson, D.G.Tomlinson, E.I., Muller, W., Hinton, R.W., Klein Ben-David, O., Pearson, D.G., Harris, J.W.Metasomatic processes recorded in fibrous diamonds.Goldschmidt Conference 2008, Abstract p.A950.Canada, Northwest TerritoriesDeposit - Panda
DS200812-1259
2008
Pearson, D.G.Wittig, N., Pearson, D.G., Webb, M., Ottley, C.J., Irvine, G.J., Kopylova, M., Jensen, S.M., Nowell, G.M.Origin of cratonic lithospheric mantle roots: a geochemical study of peridotites from the North Atlantic Craton, West Greenland.Earth and Planetary Science Letters, In press available, 83p.Europe, GreenlandGeochemistry
DS200812-1260
2008
Pearson, D.G.Wittig, N., Pearson, D.G., Webb, M., Ottley, C.J., Irvine, G.J., Kopylova, M., Jensen, S.M., Nowell, G.M.Origin of cratonic lithospheric mantle roots: a geochemical study of peridotites from the North Atlantic craton, West Greenland.Earth and Planetary Science Letters, Vol. 274, 1-2, pp. 24-33.Europe, GreenlandGeochemistry
DS200812-1261
2008
Pearson, D.G.Wittig, N., Webb, M.,Pearson, D.G., Dale, C.W., Ottley, C.J., Luguet, A., Jensen, S.M.Lithosphere stabilization ages beneath sw Greenland.Goldschmidt Conference 2008, Abstract p.A1030.Europe, GreenlandNorth Atlantic Craton, kimberlites
DS200912-0143
2009
Pearson, D.G.Dale, C.W., Pearson, D.G., Starkey, N.A., Stuart, F.M., Ellam, Larsen, Fitton, MacPhersonOsmium isotope insights into high 3He4He mantle and convecting mantle in the North Atlantic.Goldschmidt Conference 2009, p. A260 Abstract.Canada, Nunavut, Baffin Island, Europe, GreenlandPicrite
DS200912-0144
2009
Pearson, D.G.Dale, C.W., Pearson, D.G., Starkey, N.A., Stuart, F.M., Ellam, R.M., Larsen, L.M., Fitton, J.G., Grousset, F.E.Osmium isotopes in Baffin Island and West Greenland picrites: implications for the 187 Os and 188 Os composition of the convection mantle and nature 3He/4heEarth and Planetary Interiors, Vol. 278, 3-4, pp. 267-277.MantleConvection
DS200912-0161
2009
Pearson, D.G.Day, J.M.D., Pearson, D.G., Macpherson, C.G., Lowry, D., Carracedo, J-C.Pyroxenite rich mantle formed by recycled oceanic lithosphere: oxygen osmium isotope evidence from Canary Island lavas.Geology, Vol. 37, 6, pp. 555-558.Mantle, Canary IslandsGeochronology
DS200912-0281
2009
Pearson, D.G.Harlou, R., Pearson, D.G., Nowell, G.M., Ottley, C.J., Davidson, J.P.Combined Sr isotope and trace element analysis of melt inclusions at sub-ng levels using micro-milling, TIMS and ICPMS.Chemical Geology, Vol. 260, 3-4, pp. 254-268.TechnologyGeochronology
DS200912-0330
2009
Pearson, D.G.Ishikawa, A., Pearson, D.G., Dale, C.W.Re Os isotopes and platinum group elements in a peridotite pyroxenite hydrid mantle.Goldschmidt Conference 2009, p. A572 Abstract.MantleMagmatism
DS200912-0385
2009
Pearson, D.G.Kjarsgaard, B.A., Pearson, D.G., Tappe, S., Nowell, G.M., Dowall, D.P.Geochemistry of hypabyssal kimberlites from Lac de Gras Canada: comparisons to global database and implications to the parent magma problem.Lithos, In press available, 49p.Canada, Northwest TerritoriesGeochemical - whole rock database
DS200912-0388
2009
Pearson, D.G.Klein-BenDavid, O., Pearson, D.G.Origins of subcalcic garnets and their relation to diamond forming fluids - case studies from Ekati (NWT-Canada) and Murowa ( Zimbabwe).Geochimica et Cosmochimica Acta, Vol. 73, pp. 837-855.Canada, Northwest Territories, Africa, ZimbabweDeposit - Ekati, Murowa
DS200912-0405
2009
Pearson, D.G.Kopylova, M.G., Nowell, G.M., Pearson, D.G., Markovic, G.Crystallization of megacrysts from protokimberlitic fluids: geochemical evidence from high - Cr megacrysts in the Jericho kimberlite.Lithos, In press - available 51p.Canada, NunavutDeposit - Jericho
DS200912-0422
2009
Pearson, D.G.Laiginhas, F., Pearson, D.G., Phillips, D., Burgess, R., Harris, J.W.Re Os and 40Ar 39Ar isotope measurements of inclusions in alluvial diamonds from the Ural Mountains: constraints on diamond genesis and eruption ages.Lithos, in press availableRussia, UralsGeochronology
DS200912-0459
2009
Pearson, D.G.Luguet, A., Jaques, A.I., Pearson, D.G., Smith, C.B., Bulanova, G.P., Roffey, S.L., Rayner, M.J., Lorand, J.P.An integrated petrological, geochemical and Re-Os isotope study of peridotite xenoliths from the Argyle lamproite, western Australia and implications forLithos, In press available, 64p.AustraliaGeochronology - Cratonic diamond occurrences
DS200912-0467
2009
Pearson, D.G.Malarkey, J., Pearson, D.G., Davidson, J.P., Nowell, G.M., Kjarsgaard, B., Ottley, C.J.Geochemical dissection of a kimberlite: What makes up a whole rock analysis?Goldschmidt Conference 2009, p. A820 Abstract.Canada, Nunavut, Somerset IslandDeposit - Jos
DS200912-0468
2009
Pearson, D.G.Malarkey, J., Pearson, D.G., Davidson, J.P., Nowell, G.M., Kjarsgaard, B., Ottley, C.J.Geochemical discretion of a kimberlite: what makes a whole rock analysis?GAC/MAC/AGU Meeting held May 23-27 Toronto, Abstract onlyTechnologyGeochronology
DS200912-0481
2009
Pearson, D.G.Mather, K.A., Pearson, D.G., Kjarsgaard, B.A., Stachel, T.A new look at Slave lithosphere paleogeotherms and the 'diamond window'.37th. Annual Yellowknife Geoscience Forum, Abstracts p. 42-3.Canada, Northwest TerritoriesGeothermometry
DS200912-0491
2009
Pearson, D.G.McNeill, J.C., Klein-BenDavid, O., Pearson, D.G., Nowell, D.G., Ottley, C.J., Chinn, I., Malarkey, J.Quantitative analysis of trace element impurity levels in some gem-quality diamonds.GAC/MAC/AGU Meeting held May 23-27 Toronto, Abstract onlyTechnologyDiamond inclusions
DS200912-0661
2009
Pearson, D.G.Sand, K.K., Waight, T.E., Pearson, D.G., Nielsen, T.F.D., Makovicky, E., Hutchison, M.T.The lithospheric mantle below southern West Greenland: a geothermobarometric approach to diamond potential and mantle stratigraphy.Lithos, In press availableEurope, GreenlandDiamond prospectivity, geothermometry
DS200912-0702
2009
Pearson, D.G.Smith, C.B., Bulanova, G.P., Kohn, S.C., Milledge, H.J., Hall, A.E., Griffin, B.J., Pearson, D.G.Nature and genesis of Kalimantan diamonds.Lithos, In press available, 38p.Indonesia, KalimantanAlluvials, diamond morphology
DS200912-0703
2009
Pearson, D.G.Smith, C.B., Pearson, D.G., Bulanova, G.P., Beard, A.D., Carlson, R.W., Wittig, N., Sims, K., Chimuka, L., Muchemwa, E.Extremely depleted lithospheric mantle and diamonds beneath the southern Zimbabwe Craton.Lithos, In press available, 41p.Africa, ZimbabweDeposit - Murowa, Sese
DS200912-0807
2009
Pearson, D.G.Wasch, L.J., Van der Zwan, F.M., Nebel, O., Morel, M.L.A., Hellebrand, E.W.G., Pearson, D.G., Davies, G.R.An alternative model for silica enrichment in the Kaapvaal subcontinental lithospheric mantle.Geochimica et Cosmochimica Acta, Vol. 73, 22, pp. 6894-6917.MantleMelting
DS200912-0821
2009
Pearson, D.G.Wittig, N., Pearson, D.G., Downes, H., Baker, J.A.The U, Th and Pb elemental and isotope compositions of mantle clinopyroxenes and their grain boundary contamination derived from leaching and digestion experiments.Geochimica et Cosmochimica Acta, Vol. 73, 2, pp. 469-488.MantleGeochronology
DS201012-0088
2010
Pearson, D.G.Carlson, R., Pearson, D.G.The formation and evolution of continental lithospheric mantle. Keynote paperGoldschmidt 2010 abstracts, abstractMantleReview
DS201012-0274
2010
Pearson, D.G.Heaman, L.M., Pearson, D.G.Nature and evolution of the Slave Province subcontinental lithospheric mantle.Canadian Journal of Earth Sciences, Vol. 47, 4, pp. 369-388.Canada, Northwest TerritoriesGeophysics - seismic
DS201012-0322
2010
Pearson, D.G.Janney, P.E., Shirey, S.B., Carlson, R.W., Pearson, D.G., Bell, D.R., Le Roex, A., Ishikawa, Nixon, BoydAge, composition and thermal characteristics of South African off craton mantle lithosphere: evidence for a multi stage history.Journal of Petrology, Vol. 51, 9, pp. 1849-1890,Africa, South AfricaGeochronology, geothermometry
DS201012-0393
2010
Pearson, D.G.Klein Ben-David, O., Pearson, D.G., Nowell, G.M., Ottley, C., McNeill, J.C.R., Cartigny, P.Mixed fluid sources involved in diamond growth constrained by Sr-Nd-Pb-C-N- isotopes and trace elements.Earth and Planetary Science Letters, Vol. 289, pp. 123-133.MantleMagmatism, fibrous diamonds
DS201012-0469
2010
Pearson, D.G.Malarkey, J., Pearson, D.G., Kjarsgaard, B.A., Davidson, J.P., Nowell, G.M., Ottley, C.J., Stammer, J.From source to crust: tracing magmatic evolution in a kimberlite and a melilitite using microsample geochemistry.Earth and Planetary Science Letters, Vol. 299, 1-2, Oct. 15, pp. 80-90.Canada, Northwest Territories, Africa, South AfricaGeochemistry - JOS
DS201012-0476
2010
Pearson, D.G.Mather, K.A., Pearson, D.G., Kjarsgaard, B.A., Jackson, S.Understanding the lithosphere beneath Arctic Canada - an example from the N. Slave craton.38th. Geoscience Forum Northwest Territories, Abstract p. 65.Canada, Northwest TerritoriesDeposit - Artemisia
DS201012-0621
2010
Pearson, D.G.Rehfeldt, T., Foley, S.F., Jacob, D.E., Pearson, D.G.Trace elements in mantle olivine and orthopyroxene from the North Atlantic and Kaapvaal Cratons.Goldschmidt 2010 abstracts, abstractAfrica, South Africa, EuropeGeochemistry
DS201012-0779
2010
Pearson, D.G.Tappe, S., Pearson, D.G., Heaman, L., Nowell, G., Milstead, P.Relative roles of cratonic lithosphere and asthenosphere in controlling kimberlitic magma compositions: Sr Nd Hf isotope evidence fromGoldschmidt 2010 abstracts, abstractEurope, Greenland, Canada, LabradorGeochronology
DS201012-0848
2010
Pearson, D.G.Wiggers de Vries, D.F., Drury, M.R., De Winter, D.A.M., Bulanova, G.P., Pearson, D.G., Davies, G.R.Three dimensional cathodluminescence imaging and electron backscatter diffraction: tools for studying the genetic nature of diamond inclusions.Contributions to Mineralogy and Petrology, in press available, 15p.TechnologyDiamond inclusions
DS201012-0854
2010
Pearson, D.G.Wittig, N., Webb, M., Pearson, D.G., Dale, C.W., Ottley, C.J., Hutchison, M., Jensen, S.M., Luget, A.Formation of the North Atlantic craton: timing and mechanisms constrained from Re-Os isotope and PGE dat a of peridotite xenoliths from S.W. Greenland.Chemical Geology, Vol. 276, 3-4, pp. 166-187.Europe, GreenlandCraton
DS201012-0855
2010
Pearson, D.G.Wittig, N., Webb, M., Pearson, D.G., Dale, C.W., Ottley, C.J., Hutchison, M., Jensen, S.M., Luget, A.Formation of the North Atlantic craton: timing and mechanisms constrained from Re-Os isotope and PGE dat a of peridotite xenoliths from S.W. Greenland.Chemical Geology, Vol. 276, 3-4, pp. 166-187.Europe, GreenlandCraton
DS201112-0111
2011
Pearson, D.G.Brin, L.E., Pearson, D.G., Riches, A.J.V., Miskovic, A., Kjarsgaard, B.A., Kienlen, B., Reford, S.W.Evaluating the northerly extent of the Slave Craton in the Canadian Arctic.Yellowknife Geoscience Forum Abstracts for 2011, Poster abstract p. 95.Canada, Northwest Territories, Nunavut, Victoria Island, Parry PeninsulaKimberlite borne - xenoliths -
DS201112-0231
2011
Pearson, D.G.Wiggers de Vries, D.F., Drury, M.R., de Winter, D.A.M., Bulanova, G.P., Pearson, D.G., Davies, G.R.Three dimensional cathodluminescence imaging and electron backscatter diffraction: tools for studying the genetic nature of diamond inclusions.Contributions to Mineralogy and Petrology, Vol. 161, 4, pp. 565-579.RussiaDeposit - Udachnaya
DS201112-0625
2011
Pearson, D.G.Luget, A., Behrens, M., Herwartz, D., Pearson, D.G.Re-Os and Lu-Hf dating in Letlhakane peridotite xenoliths ( Botswana).Goldschmidt Conference 2011, abstract p.1365.Africa, BotswanaGeochronology, Magondi Belt
DS201112-0633
2011
Pearson, D.G.Malarkey, J., Wittig, N., Pearson, D.G., Davidson, J.P.Characterising modal metasomatic processes in young continental lithospheric mantle: a microsampling isotopic and trace element study on xenoliths from the Middle Atlas Mountains, Morocco.Contributions to Mineralogy and Petrology, Vol. 162, 2, pp. 289-302.Europe, Africa, MoroccoMetasomatism
DS201112-0634
2011
Pearson, D.G.Malarkey, J., Wittig, N., Pearson, D.G., Davidson, J.P.Characterising modal metasomatic processes in young continental lithospheric mantle: a microsampling isotopic and trace element study on xenoliths ...Contributions to Mineralogy and Petrology, in press, availableAfrica, MoroccoMetasomatism - Middle Atlas Mountains
DS201112-0654
2011
Pearson, D.G.Mather, K.A., Pearson, D.G., McKenzie, D., Kjarsgaard, B.A., Priestley, K.Constraints on the depth and thermal history of cratonic lithosphere from peridotite xenoliths, xenocrysts and seismology.Lithos, Vol. 125, pp. 729-742.Africa, South Africa, Canada, Somerset IslandGeothermometry, geophysics - seismics
DS201112-0684
2011
Pearson, D.G.Miskovic, A., Ickert, R.B., Pearson, D.G., Stern, R.A.Oxygen isotope survey of the Northern Canadian lithospheric mantle: implications for the evolution of cratonic roots.Yellowknife Geoscience Forum Abstracts for 2011, abstract p. 64-65.Canada, Northwest TerritoriesSCLM - geodynamics
DS201112-0773
2011
Pearson, D.G.Pearson, D.G., Kjarsgaard, B.A.Diamonds and the mantle lithosphere in northern Canada.PDAC 2011, 1/2p. abstractCanada, Northwest TerritoriesGeochronology
DS201112-0774
2011
Pearson, D.G.Pearson, D.G., Tappe, S., Smart, K.A., Mather, K.S., Dale, C.W., Kjarsgaard, B.A.Crust mantle links in cratons.Goldschmidt Conference 2011, abstract p.1610.MantleSlave, Kaapvaal, coupling -decoupling
DS201112-0862
2011
Pearson, D.G.Riches, A.J.V., Pearson, D.G., Kjarsgaard, B.A., Jackson, S.E., Stachel, T., Armstrong, J.P.Deep lithosphere beneath the Rae Craton: peridotite xenoliths from Repulse Bay, Nunavut.Yellowknife Geoscience Forum Abstracts for 2011, abstract p. 74-75.Canada, Nunavut, Victoria Island, Parry PeninsulaMineralogy
DS201112-1028
2011
Pearson, D.G.Tappe, S., Pearson, D.G., Nowell, G., Nielsen, T., Milstead, P., Muehlenbachs, K.A fresh isotopic look at Greenland kimberlites: craton mantle lithosphere imprint on deep source signal.Earth and Planetary Science Letters, Vol. 305, 1-2, pp. 235-248.Europe, GreenlandGeochronology - convection
DS201112-1029
2011
Pearson, D.G.Tappe, S., Smart, K.A., Pearson, D.G., Steenfelt, A., Simonetti, A.Craton formation in late Archean subduction zones revealed by first Greenland eclogites.Geology, Vol. 39, 12, pp. 1103-1106.Europe, GreenlandMelting , Nunatak-1390
DS201212-0097
2012
Pearson, D.G.Bulanova, G.P., Wiggers de Vries, D.F., Beard, A., Pearson, D.G., Mikhail, S.S., Smelov, A.P., Davies, G.R.Two stage origin of eclogitic diamonds recorded by a single crystal from the Mir pipe, Yakutia.10th. International Kimberlite Conference Held Bangalore India Feb. 6-11, Poster abstractRussia, YakutiaDeposit - Mir
DS201212-0318
2012
Pearson, D.G.Hunt, L.,Stachel, T., Pearson, D.G., Jackson, S., McLean, H., Kjarsgaard, B.The origin of websterites at Diavik diamondmine, Canada, and the realationship to diamond growth.10th. International Kimberlite Conference Feb. 6-11, Bangalore India, AbstractCanada, Northwest TerritoriesDeposit - Diavik
DS201212-0324
2012
Pearson, D.G.Hutchison, M.T., Dale, C.W., Nowell, G.M., Pearson, D.G.Age constraints on ultra deep mantle petrology shown by Juin a diamonds.10th. International Kimberlite Conference Held Bangalore India Feb. 6-11, Poster abstractSouth America, BrazilDeposit - Juina
DS201212-0463
2012
Pearson, D.G.Melton, G.L., McNeill, J., Stachel, T., Pearson, D.G., Harris, J.W.Trace elements in gem diamond from Akwatia, Ghana and De Beers Pool, South Africa.Chemical Geology, Vol. 314-317, pp. 1-8.Africa, South Africa, GhanaDeposit - Akwatia, DeBeers Pool - Inclusions
DS201212-0538
2012
Pearson, D.G.Palot, M., Pearson, D.G., Stern, R., Stachel, T., Harris, J.W.Multiple growth events, processes and fluid sources involved in the growth of diamonds from Finsch mine, RSA: a micro-analytical study.10th. International Kimberlite Conference Feb. 6-11, Bangalore India, AbstractAfrica, South AfricaDeposit - Finsch
DS201212-0546
2012
Pearson, D.G.Pearson, D.G., Mather, K.A., Ishikawa, A., Kjarsgaard, B.A.Origin and evolution of cratonic roots.10th. International Kimberlite Conference Feb. 6-11, Bangalore India, AbstractGlobalCraton
DS201212-0585
2012
Pearson, D.G.Riches, A.J.V., Pearson, D.G., Stern, R.A., Ickert, R.B., Kjarsgaard, B.A., Jackson, S.E., Ishikawa, A.Multi-stage metasomatism of a Roberts Victor eclogite linked to the formation and destruction of diamond.10th. International Kimberlite Conference Feb. 6-11, Bangalore India, AbstractAfrica, South AfricaDeposit - Roberts Victor
DS201212-0649
2012
Pearson, D.G.Shirey, S.B., Cartigny, P., Frost, D.J., Nestola, F., Nimis, P., Pearson, D.G., Sobolev, N.V., Walter, M.J.Diamonds and the geology of Earth mantle carbon.GSA Annual Meeting, Paper no. 211-5, abstractMantleSubduction
DS201212-0677
2012
Pearson, D.G.Smith, E.M., Kopylova, M.G., Nowell, G.M., Pearson, D.G., Ryder, J.Archean mantle fluids preserved in fibrous diamonds from Wawa, Superior Craton.Geology, Vol. 40, Dec. pp. 1071-74.Canada, OntarioDeposit - Wawa
DS201212-0678
2012
Pearson, D.G.Smith, E.M., Kopylova, M.G., Nowell, G.M., Pearson, D.G., Ryder, J., Afanasev, V.P.D., Beeby, A.The contrast in trace element chemistry and volatile composition between fluid inclusions n fibrous and octahedral diamonds.10th. International Kimberlite Conference Held Bangalore India Feb. 6-11, Poster abstractCanada, Ontario, WawaDiamond inclusions
DS201212-0679
2012
Pearson, D.G.Smith, E.M., Kopylova, M.G., Nowell, G.M., Pearson, D.G., Ryder, J., Afanasiev, V.P.The contrast in trace element chemistry and volatile composition between fluid inclusions in fibrous and octahedral diamonds.10th. International Kimberlite Conference Feb. 6-11, Bangalore India, AbstractCanada, Ontario, WawaDiamond - inclusions
DS201212-0778
2012
Pearson, D.G.Wiggers de Vries, D.F., Harris, J.W., Pearson, D.G., Davies, G.R.Re-Os isotope constraints on the ages of diamonds from Mwadui, Tanzania.10th. International Kimberlite Conference Held Bangalore India Feb. 6-11, Poster abstractAfrica, TanzaniaDeposit - Mwadui
DS201312-0093
2013
Pearson, D.G.Bragagni, A., Luguet, A., Pearson, D.G., Fonseca, R.O.C., Kjarsgaard, B.A.Insight on formation and evolution of cratonic mantle: Re-Os dating of single sulfides from Somerset mantle xenoliths ( Rae Craton) Canada.Goldschmidt 2013, AbstractCanada, NunavutGeochronolgy
DS201312-0410
2013
Pearson, D.G.Hunt, L., Stachel, T., Pearson, D.G., Stern, R., Muehlenbachs, K., McLean, H.Multi-stage evolution of non-gem diamonds at the Diavik diamond mine, Canada.GAC-MAC 2013 SS4: Diamond: from birth in the mantle to emplacement in kimberlite, abstract onlyCanada, Northwest TerritoriesDeposit - Diavik
DS201312-0411
2013
Pearson, D.G.Hunt, L., Stachel, T., Pearson, D.G., Stern, R., Muehlenbachs, K., McLean, H.The complex growth of non-gem diamonds at the Diavik diamond mine, Canada.Geoscience Forum 40 NWT, abstract only p. 19Canada, Northwest TerritoriesDiamond morphology
DS201312-0489
2013
Pearson, D.G.Klein-BenDavid, O., Pearson, D.G., Nowell, G.M., Ottley, C., McNeill, J.C.R., Logvinova, A., Sobolev, N.V.The sources and time integrated evolution of diamond forming fluid - trace elements and Sr isotopic evidence.Geochimica et Cosmochimica Acta, Vol. 125, pp. 146-169.Russia, Africa, Democratic Republic of Congo, Canada, Northwest TerritoriesFibrous diamonds, HDF, Diavik, Udachnaya
DS201312-0496
2014
Pearson, D.G.Konig, S., Lorand, J-P., Luguet, A., Pearson, D.G.A non primitive origin of near-chondritic S-Se-Te ratios in mantle peridotites; implications for the Earth's late accretionary history.Earth and Planetary Science Letters, Vol. 385, pp. 110-121.MantlePeridotite
DS201312-0516
2013
Pearson, D.G.Krebs, M.Y., Pearson, D.G., Stachel, T., Stern, R.A., Nowicki, T., Cairns, S.Variability in diamond population characteristics across the size range 0.2- 2-4 mm - a case study based on diamonds from Misery ( Ekati mine).2013 Yellowknife Geoscience Forum Abstracts, p. 34-35.Canada, Northwest TerritoriesDeposit - Misery
DS201312-0667
2013
Pearson, D.G.O'reilly, S., Griffin, W.L., Begg, G.C., Pearson, D.G., Hronsky, J.M.A.Archean lithospheric mantle: the fount of all ores?Goldschmidt 2013, AbstractMantleMagmatism
DS201312-0676
2013
Pearson, D.G.Palot, M., Pearson, D.G., Stachel, T.Multiple growth episodes or prolonged formation of diamonds? Inferences from infrared absorption data.Proceedings of the 10th. International Kimberlite Conference, Vol. 1, Special Issue of the Journal of the Geological Society of India,, Vol. 1, pp. 281-296.TechnologyDiamond morphology
DS201312-0677
2013
Pearson, D.G.Palot, M., Pearson, D.G., Stern, R.A., Stachel, T., Harris, J.W.Multiple growth events, processes and fluid sources involved in diamond genesis: a micro-analytical study of sulphide bearing diamonds from Finsch mine, RSA.Geochimica et Cosmochimica Acta, Vol. 106, pp. 51-70.Africa, South AfricaDeposit - Finsch
DS201312-0692
2013
Pearson, D.G.Pearson, D.G., Brin, L., Liu, J., Riches, A., Stachel, T., Mather, K.A., Kjarsgaard, B.A.Canada's Arctic cratons: how many, how old, how come?2013 Yellowknife Geoscience Forum Abstracts, p. 49-50.Canada, Northwest Territories, Nunavut, Victoria Island, Parry PeninsulaGeochronology - mantle peridotites
DS201312-0777
2013
Pearson, D.G.Sarkar, C., Heaman, L., Pearson, D.G.Detailed geochemical studies of Lac de Gras kimberlites - redefining the 'diamond age window'?Geoscience Forum 40 NWT, abstract only p. 43Canada, Northwest TerritoriesDeposit - Lac de gras ones
DS201312-0815
2012
Pearson, D.G.Shirey, S.B., Cartigny, P.,Frost, D.J., Nestola, F., Pearson, D.G., Sobolev, N.V., Walter, M.J.Diamonds and the geology of Earth mantle carbonGeological Society of America Annual Meeting abstract, Paper 211-5, 1/2p. AbstractMantleCarbon
DS201312-0816
2013
Pearson, D.G.Shirey, S.B., Cartigny, P., Frost, D.J., Keshav, S., Nestola, F., Nimis, P., Pearson, D.G., Sobolev, N.V., Walter, M.J.Diamonds and the geology of mantle carbon.Reviews in Mineralogy and Geochemistry, Vol. 75, pp. 355-421.MantleDiamond genesis
DS201312-0901
2013
Pearson, D.G.Tappe, S., Pearson, D.G., Kjarsgaard, B.A., Nowell, G., Dowall, D.Mantle transition zone input to kimberlite magmatism near a subduction zone: origin of anomalous Nd-Hf isotope systematics at Lac de Gras, Canada.Earth and Planetary Science Letters, Vol. 371-372, pp. 235-251.Canada, Northwest TerritoriesGeochronology, convection
DS201312-0903
2013
Pearson, D.G.Tappe, S., Pearson, D.G., Kjarsgaard, B.A., Nowell, G.M., Dowall, D.Linking kimberlite magmatism, transition zone diamonds, and subduction processes.Goldschmidt 2013, AbstractMantleSubduction
DS201312-0904
2013
Pearson, D.G.Tappe, S., Pearson, D.G., Prelevic, D.Kimberlite, carbonatite, and potassic magmatism as part of the geochemical cycle.Chemical Geology, Vol. 353, pp. 1-3 intro.MantleMelting, recyle
DS201312-0970
2013
Pearson, D.G.Wiggers de Vries, D.F., Pearson, D.G., Bulanova, G.P., Smelov, A.P., Pavlushin, A.D., Davies, G.R.Re-Os dating of sulphide inclusions zonally distributed in single Yakutian diamonds: evidence for multiple episodes of Proterozoic formation and protracted timescales of diamond growth.Geochimica et Cosmochimica Acta, Vol. 120, pp. 363-394.Russia, YakutiaDeposit - Mir, 23, Udachnaya
DS201412-0082
2014
Pearson, D.G.Bulanova, G.P., Wiggers de Vries, D.F., Pearson, D.G., Beard, A., Mikhail, S., Smelov, A.P., Davies, G.R.An eclogitic diamond from Mir pipe (Yakutia), recording two growth events from different isotopic sources.Chemical Geology, Vol. 381, pp. 40-54.Russia, YakutiaDeposit - Mir
DS201412-0086
2014
Pearson, D.G.Bussweiler, Y., Foley, S.F., Prelevic, D., Jacob, D.E., Pearson, D.G., Stachel, T.Olivine as a petrogenetic and exploration indicator in Lac de Gras kimberlites.2014 Yellowknife Geoscience Forum, p. 20, 21 abstractCanada, Northwest TerritoriesDeposit - Ekati
DS201412-0479
2014
Pearson, D.G.Krebs, M.Y., Pearson, D.G., Stachel, T., Stern, R.A., Nowicki, T., Cairns, S.Variability in diamond population characteristics across the size range 0.2-3.4 MM - a case study based on diamonds from Misery ( Ekati mine).Geological Society of America Conference Vancouver Oct. 19-22, 1p. AbstractCanada, Northwest TerritoriesDiavik mine - Misery
DS201412-0548
2014
Pearson, D.G.Marchesi, C., Dale, C.W., Garrdo, C.J., Pearson, D.G., Bosch, D., Bodinier, J-L., Gervilla, F., Hidas, K.Fractionation of highly siderophile elements in refertilized mantle: implications for the Os isotope composition of basalts.Earth and Planetary Science Letters, Vol. 400, pp. 33-44.MantleRonda peridotite
DS201412-0656
2014
Pearson, D.G.Palot, M., Pearson, D.G., Stern, R.A., Harris, J.W., Stachel, T.Fluid sources of ultradeep diamonds.2014 Yellowknife Geoscience Forum, p. 61, abstractAfrica, GuineaDeposit - Kankan
DS201412-0657
2014
Pearson, D.G.Palot, M., Pearson, D.G., Stern, R.A., Stachel, T., Harris, J.W.Isotopic constraints on the nature and circulation of deep mantle C-H-O-N fluids: Carbon and nitrogen systematics within ultra-deep diamonds from Kankan ( Guinea).Geochimica et Cosmochimica Acta, Vol. 139, pp. 26-46.Africa, GuineaDeposit - Kankan
DS201412-0667
1999
Pearson, D.G.Pearson, D.G.Evolution of cratonic lithospheric mantle: an isotopic perspective.Geochemical Society Special Publication No. 6, Mantle Petrology, No. 6, pp.MantleGeochronology
DS201412-0668
2014
Pearson, D.G.Pearson, D.G., Brenker, F., Nestola, F., McNeil, J., Nasdala, L., Hutchison, M., Mateev, S., Mather, K., Silversmit, G., Schmitz, S., Vekemans, B., Vinczw=e, L.A hydrous mantle transition zone indicated by ring woodite included within diamond.Goldschmidt Conference 2014, 1p. AbstractMantleDiamond inclusion
DS201412-0669
2014
Pearson, D.G.Pearson, D.G., Brenker, F.E., Nestola, F., McNeill, J., Nasdala, L., Hutchinson, M.T., Mateev, S., Mather, K., Silversmit, G., Schmitz, S., Vekemans, B., Vincze, L.Hydrous mantle transition zone indicated by ring woodite included in diamond.Nature, Vol. 507, March 13, pp. 221-224.Mantle, South America, Brazil, Mato GrossoDiamond inclusion - water storage capacity, magmatism
DS201412-0844
2014
Pearson, D.G.Smit, K.V., Pearson, D.G., Stachel, T., Seller, M.Peridotites from Attawapiskat, Canada: Mesoproterozoic reworking of Paleoarchean lithospheric mantle beneath the northern Superior Superterrane.Journal of Petrology, Vol. 55, 9, pp. 1829-1863.Canada, Ontario, AttawapiskatDeposit - Victor arena
DS201412-0959
2014
Pearson, D.G.Wang, H., Van Hunen, J., Pearson, D.G., Allen, M.B.Craton stability and longevity: the roles of composition- dependent rheology and buoyancy.Earth and Planetary Science Letters, Vol. 391, 1, pp. 224-233.MantleCraton
DS201504-0215
2015
Pearson, D.G.Sarkar, C., Heaman, L.M., Pearson, D.G.Duration and periodicity of kimberlite volcanic activity in the Lac de Gras kimberlite field, Canada and some recommendations for kimberlite geochronology.Lithos, Vol. 218-219, pp. 155-166.Canada, Northwest TerritoriesDeposit - Eddie
DS201507-0322
2015
Pearson, D.G.Liu, J., Scott, J.M., Martin, C.E., Pearson, D.G.The longevity of Archean mantle residues in the convecting upper mantle and their role in young continent formation.Earth and Planetary Science Letters, Vol. 424, pp. 109-118.MantleConvection
DS201508-0367
2015
Pearson, D.G.Luguet, A., Behrens, M., Pearson, D.G., Konig, S., Herwartz, D.Significance of the whole rock Re-Os ages in cryptically and modally metasomatized cratonic peridotites: constraints from HSE-Se-Te systematics.Geochimica et Cosmochimica Acta, Vol. 164, pp. 441-463.Africa, BotswanaDeposit - Letlhakane
DS201509-0435
2015
Pearson, D.G.Wainwright, A.N., Luguet, A., Fonsec, R.O.C., Pearson, D.G.Investigating metasomatic effects on the 187Os isotopic signature: a case study on the micrometric base metal sulphides in metasomatised peridotite from the Letlhakane kimberlite, (Botswana). Lithos, Vol. 232, pp. 35-48.Africa, BotswanaDeposit - Letlhakane

Abstract: The peridotite xenoliths of the Letlhakane kimberlite (Botswana), which intrude the Proterozoic Magondi Belt on the western margin of the Zimbabwe craton, represent highly depleted melting residues. These residues suffered subsequent variable metasomatic overprinting, evidenced by cryptic trace element enrichments in the spinel peridotites to modal addition of phlogopite, clinopyroxene and spinel within the garnet peridotites. In order to assess the robustness of the Re–Os chronometer in such highly metasomatised peridotites, detailed investigations of base metal sulphide (BMS) petrography and single-BMS grain 187Os/188Os analyses have been undertaken in three representative peridotites.
DS201509-0437
2015
Pearson, D.G.Weiss, Y., McNeill, J., Pearson, D.G., Ottley, C.J.Highly saline fluids from a subducting slab as the source for fluid-rich diamonds.Nature, Vol. 524, pp. 339-342.MantleSubduction

Abstract: The infiltration of fluids into continental lithospheric mantle is a key mechanism for controlling abrupt changes in the chemical and physical properties of the lithospheric root1, 2, as well as diamond formation3, yet the origin and composition of the fluids involved are still poorly constrained. Such fluids are trapped within diamonds when they form4, 5, 6, 7 and so diamonds provide a unique means of directly characterizing the fluids that percolate through the deep continental lithospheric mantle. Here we show a clear chemical evolutionary trend, identifying saline fluids as parental to silicic and carbonatitic deep mantle melts, in diamonds from the Northwest Territories, Canada. Fluid–rock interaction along with in situ melting cause compositional transitions, as the saline fluids traverse mixed peridotite–eclogite lithosphere. Moreover, the chemistry of the parental saline fluids—especially their strontium isotopic compositions—and the timing of host diamond formation suggest that a subducting Mesozoic plate under western North America is the source of the fluids. Our results imply a strong association between subduction, mantle metasomatism and fluid-rich diamond formation, emphasizing the importance of subduction-derived fluids in affecting the composition of the deep lithospheric mantle.
DS201512-1926
2015
Pearson, D.G.Hardman, M.F., Stachel, T., Pearson, D.G., Kinakin, Y.B., Bellinger, J.Improving the utility of eclogitic garnet in diamond exploration - examples from Lac de Gras and worldwide localities.43rd Annual Yellowknife Geoscience Forum Abstracts, abstract p. 47.Canada, Northwest TerritoriesGarnet chemistry

Abstract: In diamond exploration, the use of compositional data to identify diamond-related peridotitic xenocrysts has long been a widely used and powerful tool. In contrast, the application of similar methods to eclogitic garnet chemistry remains a challenge. The inability to unequivocally classify certain “eclogitic” garnet compositions as either mantle- or crust-derived implies that a high abundance of lower-crustal garnets will increase diamond-exploration expenditures by introducing a number of “false positives.” Revising existing classification schemes (e.g., Schulze, 2003) to reduce the abundance of “false positives” may, however, increase the number of “false negatives” through the misclassification of mantle-derived garnets as crustal. This study presents new geochemical and petrographical data for garnet and clinopyroxene from 724 kimberlite-hosted, crust- and mantle-derived xenoliths from localities worldwide, with a focus on samples whose lithology is constrained petrographically, rather than single mineral grains from concentrate. Mantle samples are primarily eclogitic and pyroxenitic, as constrained by mineral assemblage and garnet and clinopyroxene mineral chemistry, while crustal samples are dominantly plagioclase-bearing garnet-granulites. For those localities where an established geothermal gradient is available from literature resources, garnet-clinopyroxene pairs are employed in the estimation of pressure-temperature conditions of equilibration through the iterative coupling of the Krogh (1988) geothermometer and the relevant geothermal gradient. Our preliminary results suggest that closure temperatures for Fe-Mg exchange exceed the temperatures of residence of many lower-crustal samples, as geotherm-based calculated pressures of equilibration exceed the apparent stability of plagioclase (see Green and Ringwood, 1972). Comparison of equilibration pressures with sodium contents in garnet for mantle-derived samples (the diamond-facies criterion of Gurney, 1984) shows a positive correlation at localities for which an adequate range of pressures is observed (e.g., the Diavik mine). Other populations, such as mantle eclogitic garnets from Roberts Victor, plot at a much more restricted range of pressures and hence fail to demonstrate this correlation; instead, these samples may reflect the influence of a broader range of bulk-compositions, providing varying amounts of sodium to their constituent garnets. The results presented here demonstrate clearly that garnets from mantle- and crust-derived samples show significant overlap in geochemical character, for example in garnet Ca# vs. Mg# space (discrimination diagram of Schulze, 2003), where approximately 66% of our crust-derived garnet analyses plot in the “mantle” field. This percentage varies among locations. A selection of particularly high-Mg#, low-Ca# garnets derived from crustal, plagioclase-bearing lithologies in this study highlights the potential for crust-mantle confusion, as these garnets have Mg# in-excess of many mantle-derived eclogitic/pyroxenitic garnets. As a consequence, Fe-Mg-Ca-based classifications alone cannot reliably discriminate mantle and crustal garnets. The next step in this project will be to obtain trace element data for the entire sample suite. This will allow us to test the Li-geobarometer of Hanrahan et al. (2009) for eclogites and to search for trace element signatures that can be used as robust indicators of a diamond-facies origin of eclogitic garnets. Trace element data will also be employed in the refinement of the crust/mantle division discussed above.
DS201512-1986
2015
Pearson, D.G.Weiss, Y., Pearson, D.G., Mcneill, J., Nowell, G.M., Ottley, C.J.Salty fluids, subducted slabs and NWT diamonds.43rd Annual Yellowknife Geoscience Forum Abstracts, abstract p. 108.Canada, Northwest TerritoriesDiamond genesis

Abstract: Diamonds from the Ekati and Diavik mines have provided a wealth of information on diamond forming processes beneath the Slave craton. Fluid-rich “fibrous” diamonds trap some of the fluid from which the diamond is growing and hence provide a unique means to characterize directly the fluids that percolate through the deep continental lithospheric mantle. On a world-wide basis, Ekatic and Diavik fluid-rich diamonds trap an anomalously high proportion of fuids that are “salty” or high saline in composition, with high Na and Cl contents. The origin of these “salty” fluids has been something of a mystery. Here we show the first clear chemical evolutionary trend identifying saline fluids as parental to silicic and carbonatitic deep mantle melts, in diamonds from the Northwest Territories, Canada. Fluid-rock interaction along with in-situ melting cause compositional transitions, as the saline fluids traverse mixed peridotite-eclogite lithosphere. Moreover, the chemistry of the parental saline fluids - especially their Sr isotopic compositions - and the timing of host diamond formation suggest a subducting Mesozoic plate under western North America to be the source of the fluids. Our results imply a strong association between subduction, mantle metasomatism and fluid-rich diamond formation, emphasizing the importance of subduction-derived fluids in impacting the composition of the deep lithospheric mantle
DS201601-0028
2016
Pearson, D.G.Liu, J., Riches, A.J.V., Pearson, D.G., Luo, Y., Kienlen, B., Kjarsgaard, B.A., Stachel, T., Armstrong, J.P.Age and evolution of the deep continental root beneath the central Rae craton, northern Canada.Precambrian Research, Vol. 272, pp. 168-174.CanadaGeocronology, metasomatism, tectonics

Abstract: Canada is host to at least six separate cratons that comprise a significant proportion of its crustal extent. Of these cratons, we possess knowledge of the cratonic lithospheric roots beneath only the Slave craton and, to a lesser extent, the Superior craton, despite the discovery of many new diamond-bearing kimberlites in Canada's North. Here we present the first age, composition and geothermal information for kimberlite-borne peridotite xenoliths from two localities within the central Rae craton: Pelly Bay and Repulse Bay. Our aim is to investigate the nature and evolution of the deep lithosphere in these regions and to examine how events recorded in the mantle may or may not correlate with the complex history of crustal evolution across the craton. Peridotite xenoliths are commonly altered by secondary processes including serpentinization, silicification and carbonation, which have variably affected the major element compositions. These secondary processes, as well as mantle metasomatism recorded in pristine silicate minerals, however, did not significantly modify the relative compositions of platinum-group elements (PGE) and Os isotope ratios in the majority of our samples from Pelly Bay and Repulse Bay, as indicated by the generally high absolute PGE concentrations and mantle-like melt-depleted PGE patterns. The observed PGE signatures are consistent with the low bulk Al2O3 contents (mostly lower than 2.5%) of the peridotites, as well as the compositions of the silicate and oxide minerals. Based on PGE patterns and Os model ages, the peridotites from both localities can be categorized into three age groups: Archean (3.0-2.6 Ga overall; 2.8-2.6 Ga for Pelly Bay and 3.0-2.7 Ga for Repulse Bay), Paleoproterozoic (2.1-1.7 Ga), and "Recent" (<1 Ga, with model ages similar to the ca. 546 Ma kimberlite eruption age). The Archean group provides the first direct evidence of depleted Archean lithospheric mantle forming coevally with the overlying Archean crustal basement, indicating cratonization of the Rae during the Archean. The subtle difference in Os model ages between Pelly Bay and Repulse Bay coincides with the age difference between crustal basement rocks beneath these two areas, supporting the suggestion that the Rae craton was assembled by collision of separate two Archean blocks at 2.7-2.6 Ga. The Paleoproterozoic peridotites are interpreted to represent newly formed lithospheric mantle, most likely associated with regional-scale underplating during the 1.77-1.70 Ga Kivalliq-Nueltin event via removal of the lower portion of Archean lithospheric mantle followed by replacement with juvenile Paleoproterozoic lithospheric mantle. The existence of multiple age clusters in the lithosphere at each locality is consistent with the observation of present-day seismic lithospheric discontinuities (0540 and 0545) that indicate two or more layers of fossil lithospheric mantle fabric beneath this region. Our data define a shallow mantle lithosphere layer dominated by Archean depletion ages underlain by a layer of mixed Archean and Paleoproterozoic ages. This lithospheric mantle structure is probably a response to complex tectonic displacement of portions of the lithospheric mantle during Paleoproterozoic orogeny/underplating. The best equilibrated Archean and Paleoproterozoic peridotites at both Pelly Bay and Repulse Bay define a typical cratonic geotherm at the time of kimberlite eruption, with a ~200 km thick lithospheric root extending well into the diamond stability field, in keeping with the diamondiferous nature of the kimberlites. Such thick lithosphere remains in place to the present day as suggested by seismic and magnetotelluric studies (0540, 0545 and 0550). The metasomatically disturbed peridotites in the Rae lithospheric mantle, yielding model ages indistinguishable from kimberlite eruption, may represent parts of the Rae craton mantle root that show anomalous magnetotelluric signatures.
DS201601-0040
2015
Pearson, D.G.Riches, A.J.V., Ickert, R.B., Pearson, D.G., Stern, R.A., Jackson, S.E., Ishikawa, A.In situ oxygen isotope, major-, and trace element constraints on the metasomatic modification and crustal origin of a Diamondiferous eclogite from Roberts Victor, Kaapvaal Craton.Geochimica et Cosmochimica Acta, in press available, 45p.Africa, South AfricaDeposit - Roberts Victor
DS201602-0190
2016
Pearson, D.G.Aulbach, S., Mungall, J.E., Pearson, D.G.Distribution and processing of highly siderophile elements in cratonic mantle lithosphere.Reviews in Mineralogy and Geochemistry, Vol. 81, pp. 239-304.MantleMineralogy

Abstract: Cratonic lithospheric mantle is composed of predominantly refractory materials that formed at higher mantle potential temperatures (TP) than recorded in non-cratonic peridotites. It also shows stronger depletion and fractionation of Pd and Pt from Ru, Os and Ir than oceanic, supra-subduction zone or off-cratonic lithospheric mantle, as well as some of the lowest Se and Te contents. The varied response of the highly siderophile elements (HSE: Os, Ir, Ru, Rh, Pt, Pd, Re, Au), and their embedded radioactive decay systems, to changes in oxygen fugacity (fO2), sulfur fugacity (fS2) and pressure (P)-in particular through the impact of these parameters on the stability of the main HSE-bearing sulfide and alloy phases makes them potentially powerful tracers of their melting environment. Therefore, investigation of the HSE systematics of cratonic mantle peridotites, in combination with information from Re–Os isotopes on time-integrated enrichment or depletion, can help us to understand processes leading to mantle differentiation and continental lithosphere formation in the Archean, which are controversial subjects despite decades of research. The longevity of the cratonic lithosphere implies that there was ample opportunity for secondary overprint, obscuring our view of earlier processes. For example, destabilization of platinum-group element (PGE: Os, Ir, Ru, Rh, Pt, Pd) alloy leading to depletions in the compatible PGE, and perhaps Pt, in some cratonic mantle samples may occur in an oxidizing mantle wedge or through interaction with oxidizing small-volume, volatile-rich melts that typically invade cratonic roots. Such melts may eventually deposit S, Pd, Pt and Re and also capture remaining PGE alloys, consistent with the anomalous S-rich character of many kimberlite-borne xenoliths. Their basalt-borne counterparts show additional late effects of subaerial degassing that can deplete volatile elements (S, Re, Os). Basaltic melts can also scavenge PGE alloys at depth, while still sulfide-undersaturated. Such melts, may, on ascent, add sulfides when they become sulfur-saturated and, during the process, refertilize the mantle and modify major-element and modal compositions. The investigation of minor lithologies in the cratonic lithosphere, such as eclogites and pyroxenites, which are expressions of tectonothermal events ranging from subduction to melt infiltration, can enhance our understanding of the effects of these processes on HSE redistribution. Thus, three major topics will be discussed, using HSE systematics in cratonic mantle samples: (1) How did the HSE behave during the (in part) extreme degrees of partial melt extraction experienced by cratonic lithospheric mantle; (2) What were the effects of the secular metasomatic overprint of the cratonic mantle; (3) What was the composition of the Archean convecting mantle, for which cratonic mantle samples may afford better insight than modern samples, provided, of course, that we have an accurate grasp of how HSE are redistributed during partial melting and metasomatism. Models based on experiments done under controlled pressure (P), temperature (T), fO2 and fS2 conditions can help place the data in context and to distinguish between melt- and metasomatism-related processes. Disentangling the various primary and secondary effects is only possible when HSE are studied in combination with lithophile elements, with due attention to petrography and mineralogy. This adds many layers of complexity, but ultimately allows a more complete understanding of the variegated processes that have shaped the cratonic lithosphere through time. In this review, we commence by discussing the peculiarities and complexities of continental lithospheric mantle origin, evolution and current state. We then introduce the database used in this contribution, followed by a brief review of the mineral hosts of HSE in peridotite and of the diverse approaches to isolate the HSE for measurement. We examine the behavior of the HSE during the formation of cratonic lithospheric mantle under non-uniformitarian conditions, where the application of the Re–Os isotope system has afforded particularly useful information on the timing of initial melt depletion and the stabilization of cratonic roots. We then turn to the effects of mantle metasomatism, both during intra-plate and craton-margin processes (see also Gannoun et al. 2016, this volume), on HSE systematics in cratonic mantle. We also discuss the data in the context of melt extraction modelling that shed light on the primary versus secondary HSE signatures in cratonic mantle rocks. Finally, we evaluate the possibility that the HSE in cratonic mantle retain a memory of core formation and subsequent accretionary processes.
DS201602-0219
2016
Pearson, D.G.Liu, J., Riches, A.J.V., Pearson, D.G., Luo, Y., Kienlen, B., Kjarsgaard, B.A., Stachel, T., Armstrong, J.P.Age and evolution of the deep continental root beneath the central Rae craton, northern Canada.Precambrian Research, Vol. 272, pp. 168-184.Canada, Northwest TerritoriesGeochronology

Abstract: Canada is host to at least six separate cratons that comprise a significant proportion of its crustal extent. Of these cratons, we possess knowledge of the cratonic lithospheric roots beneath only the Slave craton and, to a lesser extent, the Superior craton, despite the discovery of many new diamond-bearing kimberlites in Canada's North. Here we present the first age, composition and geothermal information for kimberlite-borne peridotite xenoliths from two localities within the central Rae craton: Pelly Bay and Repulse Bay. Our aim is to investigate the nature and evolution of the deep lithosphere in these regions and to examine how events recorded in the mantle may or may not correlate with the complex history of crustal evolution across the craton. Peridotite xenoliths are commonly altered by secondary processes including serpentinization, silicification and carbonation, which have variably affected the major element compositions. These secondary processes, as well as mantle metasomatism recorded in pristine silicate minerals, however, did not significantly modify the relative compositions of platinum-group elements (PGE) and Os isotope ratios in the majority of our samples from Pelly Bay and Repulse Bay, as indicated by the generally high absolute PGE concentrations and mantle-like melt-depleted PGE patterns. The observed PGE signatures are consistent with the low bulk Al2O3 contents (mostly lower than 2.5%) of the peridotites, as well as the compositions of the silicate and oxide minerals. Based on PGE patterns and Os model ages, the peridotites from both localities can be categorized into three age groups: Archean (3.0-2.6 Ga overall; 2.8-2.6 Ga for Pelly Bay and 3.0-2.7 Ga for Repulse Bay), Paleoproterozoic (2.1-1.7 Ga), and “Recent” (<1 Ga, with model ages similar to the ca. 546 Ma kimberlite eruption age). The Archean group provides the first direct evidence of depleted Archean lithospheric mantle forming coevally with the overlying Archean crustal basement, indicating cratonization of the Rae during the Archean. The subtle difference in Os model ages between Pelly Bay and Repulse Bay coincides with the age difference between crustal basement rocks beneath these two areas, supporting the suggestion that the Rae craton was assembled by collision of separate two Archean blocks at 2.7-2.6 Ga. The Paleoproterozoic peridotites are interpreted to represent newly formed lithospheric mantle, most likely associated with regional-scale underplating during the 1.77-1.70 Ga Kivalliq-Nueltin event via removal of the lower portion of Archean lithospheric mantle followed by replacement with juvenile Paleoproterozoic lithospheric mantle. The existence of multiple age clusters in the lithosphere at each locality is consistent with the observation of present-day seismic lithospheric discontinuities (0540 and 0545) that indicate two or more layers of fossil lithospheric mantle fabric beneath this region. Our data define a shallow mantle lithosphere layer dominated by Archean depletion ages underlain by a layer of mixed Archean and Paleoproterozoic ages. This lithospheric mantle structure is probably a response to complex tectonic displacement of portions of the lithospheric mantle during Paleoproterozoic orogeny/underplating. The best equilibrated Archean and Paleoproterozoic peridotites at both Pelly Bay and Repulse Bay define a typical cratonic geotherm at the time of kimberlite eruption, with a ~200 km thick lithospheric root extending well into the diamond stability field, in keeping with the diamondiferous nature of the kimberlites. Such thick lithosphere remains in place to the present day as suggested by seismic and magnetotelluric studies (0540, 0545 and 0550). The metasomatically disturbed peridotites in the Rae lithospheric mantle, yielding model ages indistinguishable from kimberlite eruption, may represent parts of the Rae craton mantle root that show anomalous magnetotelluric signatures.
DS201603-0417
2016
Pearson, D.G.Riches, A.J.V., Ickert, R.B., Pearson, D.G., Stern, R.A., Jackson, S.E., Ishikawa, A., Kjarsgaard, B.A., Gurney, J.J.In situ oxygen-isotope, major, and trace element constraints on the metasomatic modification and crust origin of a Diamondiferous eclogite from Roberts Victor, Kaapvaal craton.Geochimica et Cosmochimica Acta, Vol. 174, pp. 345-359.Africa, South AfricaDeposit - Roberts Victor
DS201603-0420
2016
Pearson, D.G.Shu, Q., Brey, G.P., Hoefer, H.E., Zhao, Z., Pearson, D.G.Kyanite/corundum eclogites from the Kaapvaal craton: subducted troctolites and layered gabbros from the Mid- to Early Archean.Contributions to Mineralogy and Petrology, Vol. 171, 11, 24p.Africa, South AfricaDeposit - Bellsbank

Abstract: An oceanic crustal origin is the commonly accepted paradigm for mantle-derived eclogites. However, the significance of the aluminous members of the eclogite suite, containing kyanite and corundum, has long been underrated and their role neglected in genetic models of cratonic evolution. Here, we present a geochemical and petrological study of a suite of kyanite- and corundum-bearing eclogites from the Bellsbank kimberlite, S. Africa, which originate from depths between 150 and 200 km. Although clearly of high-pressure provenance, these rocks had a low-pressure cumulative origin with plagioclase and olivine as major cumulate phases. This is shown by the very pronounced positive Eu anomalies, low REE abundances, and d 18O values lower than the Earth’s mantle. Many chemical features are identical to modern-day troctolitic cumulates including a light REE depletion akin to MORB, but there are also distinguishing features in that the eclogites are richer in Na, Fe, and Ni. Two of the eclogites have a minimum age of ~3.2 Ga, defined by the extremely unradiogenic 87Sr/86Sr (0.7007) in clinopyroxene. Phase equilibria indicate that the parent melts were formed by partial melting below an Archean volcanic center that generated (alkali-)picritic to high-alumina tholeiitic melts from a mantle whose oxygen fugacity was lower than today. Fractional crystallization produced troctolites with immiscible sulfide melt droplets within the mafic crust. Instability of the mafic crust led to deep subduction and re-equilibration at 4 6 GPa. Phase relationships plus the presence of a sample with appreciable modal corundum but no Eu anomaly suggest that kyanite- and corundum-bearing eclogites may also originate as plagioclase-free, higher pressure cumulates of highly aluminous clinopyroxene, spinel, and olivine. This is consistent with the crystallizing phase assemblage from an olivine tholeiitic to picritic magma deeper in the Archean oceanic crust or uppermost mantle. We postulate that the magmatic and subduction processes driving modern plate tectonics already existed in the Meso- to Early Archean.
DS201604-0596
2016
Pearson, D.G.Bussweiler, Y., Pearson, D.G., Luth, R.W., Kjarsgaard, B.A., Stachel, T.The evolution of calcite-bearing kimberlite by rock-melt reaction during ascent - evidence from polymineralic inclusions within Cr- diopside and Cr-pyrope megacrysts from Lac de Gras kimberlites, Northwest Territories, Canada.GAC MAC Meeting Special Session SS11: Cratons, kimberlites and diamonds., abstract 1/4p.Canada, Northwest TerritoriesDeposit - Lac de Gras
DS201604-0616
2016
Pearson, D.G.Krebs, M.Y., Pearson, D.G., Stachel, T., Stern, R.A., Nowicki, T., Cairns, S.Using microdiamonds in kimberlite diamond grade prediction: a case study of the variability in diamond population characteristics across the size range 0.2 to 3.4 mm in Misery kimberlite, Ekati mine, NWT, Canada.Economic Geology, Vol. 111, 2, pp. 503-525.Canada, Northwest TerritoriesMicrodiamonds - Misery

Abstract: First predictions of the macrodiamond grade of newly discovered kimberlites are commonly obtained using size frequency distributions of microdiamonds. The success of this approach suggests a common origin of microdiamonds and macrodiamonds, an implication not yet conclusively established or disproved. In contrast to previous comparative studies on microdiamonds and macrodiamonds from single deposits, here all diamonds analyzed originate from the same microdiamond samples (558 diamonds, ranging from 0.212 to 3.35 mm). The diamonds were analyzed for their carbon isotope compositions and nitrogen characteristics, and, based on this dataset, statistical comparisons were conducted across the size range to assess cogenesis. As a whole, the Misery diamond suite shows high nitrogen contents (median = 850 at. ppm), a bimodal distribution in time-averaged mantle residence temperatures (two distinct subpopulations in mantle residence temperatures: =1,125° and =1,175°C), a high degree of platelet degradation, and d13C compositions that are isotopically slightly heavier (median = -4.4‰) than the global median. Statistical comparisons of the various size classes indicate the presence of subtly different subpopulations at Misery; however, the nature and magnitude of these geochemical differences are very small in the context of the global diamond database and are viewed as petrogenetically insignificant. The general geochemical similarity of diamonds from different size fractions at Misery reinforces the use of size-frequency analysis to predict diamond grade in kimberlite diamond deposits.
DS201604-0622
2016
Pearson, D.G.Poitras, S., Pearson, D.G., Stachel, T., Cairns, S., Day, S.A geochemical study of diamond indicator minerals from the NWT Interior Platform.GAC MAC Meeting Special Session SS11: Cratons, kimberlites and diamonds., abstract 1/4p.Canada, Northwest TerritoriesDiamond indicators

Abstract: The Central Mackenzie Valley (CMV) area of the Northwest Territories (NWT) comprises a Phanerozoic sedimentary basin that lies between the western margin of the Slave craton and the Cordillera. Although the region is considerably outside the bounds of the exposed Slave craton, both LITHOPROBE and more recent regional-scale surface wave studies (e.g., Priestley and McKenzie, 2006) indicate the likely presence of lithospheric mantle extending into the diamond stability field. Recent work conducted by Olivut Resources Ltd. led to the discovery of 29 kimberlites in the CMV. However, the indicator mineral chemistry of discovered kimberlites does not appear to be a good match (www.olivut.ca) with those during regional till and stream sediment sampling by the Geologic Survey of Canada (GSC) and Northwest Territories Geologic Survey (NTGS) in August 2003 and July 2005. We present new geochemical data on the regional indicator minerals with the aim of obtaining geotherm and depth of mantle sampling constraints on those indicator minerals discovered to date. A statistical evaluation of the data will compare the similarities to indicator mineral chemistry with parts of the Slave craton to evaluate whether the CMV indicators may ultimately be derived from that region. In total 3600 kimberlite indicator mineral grains were picked from the 0.25-2.0 mm size fractions. Peridotitic garnet grains dominate (46%), followed by magnesium ilmenite (26%), with decreasing individual proportions >15% of chromite, low-chrome diopside, olivine, chrome-diopside and eclogitic garnet. A sub-sample of these grains (3143) were analysed by EPMA. Garnet grains classify (after Grütter et al., 2004) as 1015 (62.1%) G9, 270 (16.5%) G11, 113 (6.9%) G10, 103 (6.3%) G12, 57 (3.5%) G1, 46 (2.8%) G10D, and the remaining 31 (1.9%) as G0, G3, G3D, G4, and G5. A sub-set of garnet grains (~700) were selected for LA-ICP-MS trace element analysis. Of the grains selected 74% G9, 14% G10 (and G10D), and 8% G11, with only 4% G12 and G0 (Grütter et al., 2004). Nickel concentrations from these grains range from 2.6-168.2 ppm, with the majority (>80%) between 20-100 ppm, yielding TNi (Canil, 1999) values ranging from 643-1348°C, with the majority between ~1000-1200°C. Using a central Slave craton geothermal gradient (Hasterok and Chapman, 2011), equilibration pressures for these garnet grains range from 20-80 kbars with the majority between 40-60 kbars (120-185 km). Preliminary analysis has 581 (81%) of the erupted peridotitic mantle garnet grains plotting within the diamond stability field (Kennedy and Kennedy, 1976). Of the 128 clinopyroxene grains analysed, only a few represent garnet peridotite (lherzolite) facies KIM clinopyroxene grains following compositional screening. Thermobarometry of these grains (Nimis and Taylor, 2000), assuming they were all derived from the same lithospheric section, yields P-T arrays identical to the central Slave geotherm that was 220 km thick at the time of eruption. These results are encouraging for diamond exploration. We thank Overburden Drilling Management Ltd. for grain picking and recovery of the small diamond, SGS Lakefield Research for mounting grains, and the GSC for probing of the grains.
DS201604-0628
2016
Pearson, D.G.Shirey, S.B., Pearson, D.G.Diamond ages: what do they mean?GAC MAC Meeting Special Session SS11: Cratons, kimberlites and diamonds., Keynote abstractTechnologyDiamond ages
DS201604-0631
2016
Pearson, D.G.Stachel, T., Stern, R.A., Luth, R.W., Pearson, D.G., Harris, J.W., DCO - Diamond ConsortiumModes of diamond precipitation through time.GAC MAC Meeting Special Session SS11: Cratons, kimberlites and diamonds., abstract 1/4p.TechnologyDiamond genesis
DS201604-0638
2016
Pearson, D.G.Weiss, Y., Pearson, D.G.Subduction-related Mesozoic metasomatism and diamond formation in the continental lithosphere under the Northwest Territories, Canada.GAC MAC Meeting Special Session SS11: Cratons, kimberlites and diamonds., abstract 1/4p.Canada, Northwest TerritoriesSubduction
DS201607-1288
2016
Pearson, D.G.Bussweiler, Y., Stone, R.S., Pearson, D.G., Luth, R.W., Stachel, T., Kjarsgaard, B.A., Menzies, A.The evolution of calcite bearing kimberlites by melt rock reaction: evidence from polymineralic inclusions within clinopyroxene and garnet megacrysts from Lac de Gras kimberlites, Canada.Contributions to Mineralogy and Petrology, Vol. 171, 7, 25p.Canada, Northwest TerritoriesDeposit - Lac de Gras arena

Abstract: Megacrystic (>1 cm) clinopyroxene (Cr-diopside) and garnet (Cr-pyrope) xenocrysts within kimberlites from Lac de Gras (Northwest Territories, Canada) contain fully crystallized melt inclusions. These ‘polymineralic inclusions’ have previously been interpreted to form by necking down of melts at mantle depths. We present a detailed petrographical and geochemical investigation of polymineralic inclusions and their host crystals to better understand how they form and what they reveal about the evolution of kimberlite melt. Genetically, the megacrysts are mantle xenocrysts with peridotitic chemical signatures indicating an origin within the lithospheric mantle (for the Cr-diopsides studied here ~4.6 GPa, 1015 °C). Textural evidence for disequilibrium between the host crystals and their polymineralic inclusions (spongy rims in Cr-diopside, kelyphite in Cr-pyrope) is consistent with measured Sr isotopic disequilibrium. The preservation of disequilibrium establishes a temporal link to kimberlite eruption. In Cr-diopsides, polymineralic inclusions contain phlogopite, olivine, chromite, serpentine, and calcite. Abundant fluid inclusion trails surround the inclusions. In Cr-pyropes, the inclusions additionally contain Al-spinel, clinopyroxene, and dolomite. The major and trace element compositions of the inclusion phases are generally consistent with the early stages of kimberlite differentiation trends. Extensive chemical exchange between the host phases and the inclusions is indicated by enrichment of the inclusions in major components of the host crystals, such as Cr2O3 and Al2O3. This chemical evidence, along with phase equilibria constraints, supports the proposal that the inclusions within Cr-diopside record the decarbonation reaction: dolomitic melt + diopside ? forsterite + calcite + CO2, yielding the observed inclusion mineralogy and producing associated (CO2-rich) fluid inclusions. Our study of polymineralic inclusions in megacrysts provides clear mineralogical and chemical evidence for an origin of kimberlite that involves the reaction of high-pressure dolomitic melt with diopside-bearing mantle assemblages producing a lower-pressure melt that crystallizes a calcite-dominated assemblage in the crust.
DS201608-1397
2016
Pearson, D.G.Bussweiler, Y., Stone, R.S., Pearson, D.G., Luth, R.W., Stachel, T., Kjarsgaard, B.A., Menzies, A.The evolution of calcite bearing kimberlites by melt rock reaction: evidence from polymineralic inclusions within clinopyroxene and garnet megacrysts from Lac de Gras kimberlites, Canada.Contributions to Mineralogy and Petrology, in press available 25p.Canada, Northwest TerritoriesDeposit - Lac de Gras

Abstract: Megacrystic (>1 cm) clinopyroxene (Cr-diopside) and garnet (Cr-pyrope) xenocrysts within kimberlites from Lac de Gras (Northwest Territories, Canada) contain fully crystallized melt inclusions. These ‘polymineralic inclusions’ have previously been interpreted to form by necking down of melts at mantle depths. We present a detailed petrographical and geochemical investigation of polymineralic inclusions and their host crystals to better understand how they form and what they reveal about the evolution of kimberlite melt. Genetically, the megacrysts are mantle xenocrysts with peridotitic chemical signatures indicating an origin within the lithospheric mantle (for the Cr-diopsides studied here ~4.6 GPa, 1015 °C). Textural evidence for disequilibrium between the host crystals and their polymineralic inclusions (spongy rims in Cr-diopside, kelyphite in Cr-pyrope) is consistent with measured Sr isotopic disequilibrium. The preservation of disequilibrium establishes a temporal link to kimberlite eruption. In Cr-diopsides, polymineralic inclusions contain phlogopite, olivine, chromite, serpentine, and calcite. Abundant fluid inclusion trails surround the inclusions. In Cr-pyropes, the inclusions additionally contain Al-spinel, clinopyroxene, and dolomite. The major and trace element compositions of the inclusion phases are generally consistent with the early stages of kimberlite differentiation trends. Extensive chemical exchange between the host phases and the inclusions is indicated by enrichment of the inclusions in major components of the host crystals, such as Cr2O3 and Al2O3. This chemical evidence, along with phase equilibria constraints, supports the proposal that the inclusions within Cr-diopside record the decarbonation reaction: dolomitic melt + diopside ? forsterite + calcite + CO2, yielding the observed inclusion mineralogy and producing associated (CO2-rich) fluid inclusions. Our study of polymineralic inclusions in megacrysts provides clear mineralogical and chemical evidence for an origin of kimberlite that involves the reaction of high-pressure dolomitic melt with diopside-bearing mantle assemblages producing a lower-pressure melt that crystallizes a calcite-dominated assemblage in the crust.
DS201608-1430
2016
Pearson, D.G.Palot, M., Jacobsen, S.D., Townsend, J.P., Nestols, F., Marquardt, K., Harris, J.W., Stachel, T., McCammon, C.A., Pearson, D.G.Evidence for H2O bearing fluids in the lower mantle from diamond inclusion.Lithos, in press available 27p.South America, BrazilSao Luis

Abstract: In this study, we report the first direct evidence for water-bearing fluids in the uppermost lower mantle from natural ferropericlase crystal contained within a diamond from São Luíz, Brazil. The ferropericlase exhibits exsolution of magnesioferrite, which places the origin of this assemblage in the uppermost part of the lower mantle. The presence of brucite-Mg(OH)2 precipitates in the ferropericlase crystal reflects the later-stage quenching of H2O-bearing fluid likely in the transition zone, which has been trapped during the inclusion process in the lower mantle. Dehydration melting may be one of the key processes involved in transporting water across the boundary between the upper and lower mantle.
DS201608-1432
2016
Pearson, D.G.Pearson, D.G., Weiss, Y.Diamond forming fluids - the importance of being salty.GSA Annual Meeting, Abstract, 1p.Canada, Northwest TerritoriesDeposit - Ekati, Diavik

Abstract: Fluids are now thought to be the growth medium for most diamonds sampled from the base of the lithosphere. Fluids trapped in fast-growing, fluid-rich diamonds provide the only direct view of this growth medium and provide valuable information on the geochemistry of deep mantle fluids in general. The most common fluids within fluid-rich diamonds are those belonging to the low- and high-Mg carbonatite affinity as well as more Si-rich variants. A sub-class of fluids that are very rich in alkalis and Cl, known as “saline” fluids, have been found but are generally scarce. At both Ekati and Diavik saline fluids appear much more common and provide a unique insight into their origin. We describe a novel sampling method that allows the analysis of the trace element and radiogenic isotope composition of diamonds (both gem and fluid-rich). Using these methods we analyzed 11 diamonds from the Fox kimberlite in the Ekati kimberlite cluster. The diamonds containing saline fluids are solely associated with peridotite on the basis of their micro-mineral inclusions. Silicic fluid compositions are related exclusively to eclogitic inclusions. Striking differences between the two fluid compositions are the positive Eu and Sr anomalies within saline fluids versus no anomalies in the silicic fluids. These characteristics are identical to previously studied fluids in fibrous diamonds from neighbouring kimberlites in Ekati and Diavik, which also contains diamonds carrying high- and low-Mg carbonatitic fluids. Combining the data, we show a clear chemical evolutionary trend, identifying for the first time saline fluids as parental to silicic and carbonatitic deep mantle melts, via fluid-rock interaction in the Slave CLM. Moreover, the trace-element and Sr isotopic fingerprints of subducting slabs and the timing of host diamond formation suggest that a subducting plate under western North America is the source of the saline fluids, which controlled metasomatism in the Slave lithosphere prior to Mesozoic kimberlite eruption. Saline fluids can be documented as a metasomatic product interacting with the lithosphere above shallow-subducting slabs such as the Farallon slab. As such they appear to be key players in the enrichment of the base of the lithosphere and the formation of diamonds.
DS201610-1896
2016
Pearson, D.G.Pearson, D.G., Weiss, Y.Diamond-forming fluids - the importance of being salty. Ekati and DiavikGSA Annual Meeting, 1/2p. abstractCanada, Northwest TerritoriesSaline fluids

Abstract: Fluids are now thought to be the growth medium for most diamonds sampled from the base of the lithosphere. Fluids trapped in fast-growing, fluid-rich diamonds provide the only direct view of this growth medium and provide valuable information on the geochemistry of deep mantle fluids in general. The most common fluids within fluid-rich diamonds are those belonging to the low- and high-Mg carbonatite affinity as well as more Si-rich variants. A sub-class of fluids that are very rich in alkalis and Cl, known as “saline” fluids, have been found but are generally scarce. At both Ekati and Diavik saline fluids appear much more common and provide a unique insight into their origin. We describe a novel sampling method that allows the analysis of the trace element and radiogenic isotope composition of diamonds (both gem and fluid-rich). Using these methods we analyzed 11 diamonds from the Fox kimberlite in the Ekati kimberlite cluster. The diamonds containing saline fluids are solely associated with peridotite on the basis of their micro-mineral inclusions. Silicic fluid compositions are related exclusively to eclogitic inclusions. Striking differences between the two fluid compositions are the positive Eu and Sr anomalies within saline fluids versus no anomalies in the silicic fluids. These characteristics are identical to previously studied fluids in fibrous diamonds from neighbouring kimberlites in Ekati and Diavik, which also contains diamonds carrying high- and low-Mg carbonatitic fluids. Combining the data, we show a clear chemical evolutionary trend, identifying for the first time saline fluids as parental to silicic and carbonatitic deep mantle melts, via fluid-rock interaction in the Slave CLM. Moreover, the trace-element and Sr isotopic fingerprints of subducting slabs and the timing of host diamond formation suggest that a subducting plate under western North America is the source of the saline fluids, which controlled metasomatism in the Slave lithosphere prior to Mesozoic kimberlite eruption. Saline fluids can be documented as a metasomatic product interacting with the lithosphere above shallow-subducting slabs such as the Farallon slab. As such they appear to be key players in the enrichment of the base of the lithosphere and the formation of diamonds.
DS201610-1903
2016
Pearson, D.G.Reimink, J.R., Davies, J.H.F.L., Chacko, T., Stern, R.A., Heaman, L.M., Sarkar, C., Schaltegger, U., Creaser, R.A., Pearson, D.G.No evidence for Hadean continental crust within Earth's oldest evolved rock unit. (Acasta Gneiss Complex)Nature Geoscience, Vol. 9, pp. 777-780.CanadaHadean crust

Abstract: Due to the acute scarcity of very ancient rocks, the composition of Earth’s embryonic crust during the Hadean eon (>4.0 billion years ago) is a critical unknown in our search to understand how the earliest continents evolved. Whether the Hadean Earth was dominated by mafic-composition crust, similar to today’s oceanic crust1, 2, 3, 4, or included significant amounts of continental crust5, 6, 7, 8 remains an unsolved question that carries major implications for the earliest atmosphere, the origin of life, and the geochemical evolution of the crust-mantle system. Here we present new U-Pb and Hf isotope data on zircons from the only precisely dated Hadean rock unit on Earth—a 4,019.6 ± 1.8?Myr tonalitic gneiss unit in the Acasta Gneiss Complex, Canada. Combined zircon and whole-rock geochemical data from this ancient unit shows no indication of derivation from, or interaction with, older Hadean continental crust. Instead, the data provide the first direct evidence that the oldest known evolved crust on Earth was generated from an older ultramafic or mafic reservoir that probably surfaced the early Earth.
DS201610-1904
2016
Pearson, D.G.Scott, J.M., Liu, J., Pearson, D.G., Waight, T.E.Mantle depletion and metasomatism recorded in orthopyroxene in highly depleted peridotites.Chemical Geology, Vol. 441, pp. 280-291.MantleMetasomatism

Abstract: Although trace element concentrations in clinopyroxene serve as a useful tool for assessing the depletion and enrichment history of mantle peridotites, this is not applicable for peridotites in which the clinopyroxene component has been consumed (~ 25% partial melting). Orthopyroxene persists in mantle residues until ~ 40% melting and it is therefore this mineral that offers petrological insights into the evolution of refractory peridotites. Major and trace element concentrations in orthopyroxene ± clinopyroxene from two spinel facies harzburgitic xenolith suites from New Zealand are examined. Samples from Cape L'Evique (CLEV) on Chatham Island contain traces of clinopyroxene (< 2 modal %) but a suite from Lake Moana (MOA) in the South Island is devoid of this mineral. When compared with modelled orthopyroxene trace element budgets, which are constructed from a review of published source modes, melting modes and element/melt partition co-efficients, the measured orthopyroxene rare earth element data in both suites generally indicate minimums of 25-30% partial melting. These results are consistent with co-existing elevated Mg# in olivine (mostly 91.4 to 93.0) and orthopyroxene (mostly 91.3 to 93.6), high spinel Cr# (commonly > 45) and low orthopyroxene Al2O3 (generally < 3.1 wt%). However, comparison of modelled and measured orthopyroxene compositions shows that all samples, even the most refractory, have undergone metasomatism by small volume light rare earth element-bearing agents. Measured orthopyroxene Ti concentrations show that the metasomatic agent that affected the CLEV suite carried Ti, but that the MOA suite metasomatiser was Ti-poor. Orthopyroxene trace elements in the inspected rocks are therefore partly decoupled from the major element abundances, with the results demonstrating that even highly refractory peridotites can record evidence for mantle metasomatism.
DS201612-2329
2016
Pearson, D.G.Reimink, J.R., Davies, J.H.F.L., Chacko, T., Stern, R.A., Heaman, L.M., Sarkar, C., Schaltegger, U., Creaser, R.A., Pearson, D.G.No evidence for Hadean continental crust within Earth's oldest evolved rock unit.Nature Geoscience, Vol. 9, pp. 777-780.CanadaAcasta Gneiss

Abstract: Due to the acute scarcity of very ancient rocks, the composition of Earth’s embryonic crust during the Hadean eon (>4.0 billion years ago) is a critical unknown in our search to understand how the earliest continents evolved. Whether the Hadean Earth was dominated by mafic-composition crust, similar to today’s oceanic crust1, 2, 3, 4, or included significant amounts of continental crust5, 6, 7, 8 remains an unsolved question that carries major implications for the earliest atmosphere, the origin of life, and the geochemical evolution of the crust-mantle system. Here we present new U-Pb and Hf isotope data on zircons from the only precisely dated Hadean rock unit on Earth—a 4,019.6 ± 1.8?Myr tonalitic gneiss unit in the Acasta Gneiss Complex, Canada. Combined zircon and whole-rock geochemical data from this ancient unit shows no indication of derivation from, or interaction with, older Hadean continental crust. Instead, the data provide the first direct evidence that the oldest known evolved crust on Earth was generated from an older ultramafic or mafic reservoir that probably surfaced the early Earth.
DS201701-0033
2017
Pearson, D.G.Snyder, D.B., Humphreys, E., Pearson, D.G.Construction and destruction of some North American cratons. Rae, Slave, WyomingTectonophysics, Vol. 694, pp. 464-486.United States, CanadaMetasomatism

Abstract: Construction histories of Archean cratons remain poorly understood; their destruction is even less clear because of its rarity, but metasomatic weakening is an essential precursor. By assembling geophysical and geochemical data in 3-D lithosphere models, a clearer understanding of the geometry of major structures within the Rae, Slave and Wyoming cratons of central North America is now possible. Little evidence exists of subducted slab-like geometries similar to modern oceanic lithosphere in these construction histories. Underthrusting and wedging of proto-continental lithosphere is inferred from multiple dipping discontinuities, emphasizing the role of lateral accretion. Archean continental building blocks may resemble the modern lithosphere of oceanic plateau, but they better match the sort of refractory crust expected to have formed at Archean ocean spreading centres. Radiometric dating of mantle xenoliths provides estimates of rock types and ages at depth beneath sparse kimberlite occurrences, and these ages can be correlated to surface rocks. The 3.6-2.6 Ga Rae, Slave and Wyoming cratons stabilized during a granitic bloom at 2.61-2.55 Ga. This stabilization probably represents the final differentiation of early crust into a relatively homogeneous, uniformly thin (35-42 km), tonalite-trondhjemite-granodiorite crust with pyroxenite layers near the Moho atop depleted lithospheric mantle. Peak thermo-tectonic events at 1.86-1.7 Ga broadly metasomatized, mineralized and recrystallized mantle and lower crustal rocks, apparently making mantle peridotite more ‘fertile’ and more conductive by introducing or concentrating sulfides or graphite at 80-120 km depths. This metasomatism may have also weakened the lithosphere or made it more susceptible to tectonic or chemical erosion. Late Cretaceous flattening of Farallon lithosphere that included the Shatsky Rise conjugate appears to have weakened, eroded and displaced the base of the Wyoming craton below 140-160 km. This process replaced the old re-fertilized continental mantle with relatively young depleted oceanic mantle.
DS201702-0251
2017
Pearson, D.G.Wang, H., van Hunen, J., Pearson, D.G.Making Archean cratonic roots by lateral compression: a two stage thickening and stabilization model.Tectonophysics, in press available, 10p.MantleCraton, tectonics

Abstract: Archean tectonics was capable of producing virtually indestructible cratonic mantle lithosphere, but the dominant mechanism of this process remains a topic of considerable discussion. Recent geophysical and petrological studies have refuelled the debate by suggesting that thickening and associated vertical movement of the cratonic mantle lithosphere after its formation are essential ingredients of the cratonization process. Here we present a geodynamical study that focuses on how the thick stable cratonic lithospheric roots can be made in a thermally evolving mantle. Our numerical experiments explore the viability of a cratonization process in which depleted mantle lithosphere grows via lateral compression into a > 200-km thick, stable cratonic root and on what timescales this may happen. Successful scenarios for craton formation, within the bounds of our models, are found to be composed of two stages: an initial phase of tectonic shortening and a later phase of gravitational self-thickening. The initial tectonic shortening of previously depleted mantle material is essential to initiate the cratonization process, while the subsequent gravitational self-thickening contributes to a second thickening phase that is comparable in magnitude to the initial tectonic phase. Our results show that a combination of intrinsic compositional buoyancy of the cratonic root, rapid cooling of the root after shortening, and the long-term secular cooling of the mantle prevents a Rayleigh-Taylor type collapse, and will stabilize the thick cratonic root for future preservation. This two-stage thickening model provides a geodynamically viable cratonization scenario that is consistent with petrological and geophysical constraints.
DS201703-0436
2017
Pearson, D.G.Van Acken, D., Luguet, A., Pearson, D.G., Nowell, G.M., Fonseca, R.O.C., Nagel, T.J., Schulz, T.Mesoarchean melting and Neoarchean ro Paleoproterozoic metasomatism during the formation of the cratonic mantle keel beneath West Greenland.Geochimica et Cosmochimica Acta, Vol. 203, pp. 37-53.Europe, GreenlandCraton
DS201705-0833
2017
Pearson, D.G.Gress, M.U., Pearson, D.G., Timmerman, S., Chinn, I.L., Koornneef, J., Davies, G.R.Diamond growth beneath Letlhakane established by Re-Os and Sm-Nd systematics of individual eclogitic sulphide, garnet and clinopyroxene inclusions.European Geosciences Union General Assembly 2017, Vienna April 23-28, 1p. 5540 AbstractAfrica, BotswanaDeposit - Letlhakane

Abstract: The diamondiferous Letlhakane kimberlites are part of the Orapa kimberlite cluster (˜ 93.1 Ma) in north-eastern Botswana, located on the edge of the Zimbabwe Craton, close to the Proterozoic Magondi Mobile Belt. Here we report the first Re-Os ages of six individual eclogitic sulphide inclusions (3.0 to 35.7µg) from Letlhakane diamonds along with their rhenium, osmium, iridium and platinum concentrations, and carbon isotope, nitrogen content and N-aggregation data from the corresponding growth zones of the host diamonds. For the first time, Re-Os data will be compared to Sm-Nd ages of individual eclogitic silicate inclusions recovered from the same diamonds using a Triton Plus equipped with four 1013O amplifiers. The analysed inclusion set currently encompasses pairs of individual sulphides from two diamonds (LK040 sf4 & 5, LK113 sf1 & 2) and two sulphide inclusions from separate diamonds (LK048, LK362). Ongoing work will determine the Sm-Nd ages and element composition of multiple individual eclogitic garnets (LK113/LK362, n=4) and an eclogitic clinopyroxene (LK040) inclusion. TMA ages of the six sulphides range from 1.06 to 2.38 Ga (± 0.1 to 0.54 Ga) with Re and Os contents between 7 and 68 ppb and 0.03 and 0.3 ppb, respectively. The host diamond growth zones have low nitrogen abundances (21 to 43 ppm N) and high N-aggregation (53 to 90% IaB). Carbon isotope data suggests the involvement of crustal carbon (d13C between -19.3 to -22.7 ± 0.2 per mill) during diamond precipitation. Cathodoluminescence imaging of central plates from LK040 and LK113 displays homogenous internal structure with no distinct zonation. The two sulphide inclusions from LK040 define an 'isochron' of 0.92 ± 0.23 Ga (2SD) with initial 187Os/188Os = 1.31 ± 0.24. Sulphides from LK113 have clear imposed diamond morphology and indicate diamond formation at 0.93 ± 0.36 Ga (2SD) with initial 187Os/188Os = 0.69 ± 0.44. The variation in the initial 187Os/188Os does not justify including these inclusions (or any from other diamonds) on the same isochron and implies an extremely heterogeneous diamond crystallisation environment that incorporated recycled Os. C1-normalized osmium, iridium and platinum (PGE) compositions from the analysed sulphide inclusions display enrichment in Ir (3.4 to 33) and Pt (2.3 to 28.1) in comparison to eclogitic xenolith data from Orapa that are depleted relative to chondrite. The Re-Os isochrons determined in this study are within error of previously reported ages from the adjacent (˜40km) Orapa diamond mine (1.0 to 2.9 Ga) based on sulphide inclusions and a multi-point 990 ± 50 Ma (2SD) isochron for composite (n=730) silicate inclusions. Together with additional new Sm-Nd isochron age determinations from individual silicate inclusions from Letlhakane (2.3 ± 0.02 (n = 3); 1.0 ± 0.14 (n = 4) and 0.25 ± 0.04 Ga (n = 3), all 2SE) these data suggest a phase of Mesoproterozoic diamond formation as well as Neoarchean/Paleoproterozoic and Mesozoic diamond growth, in punctuated events spanning >2.0 Ga.
DS201705-0877
2017
Pearson, D.G.Sommer, H., Jacob, D.E., Stern, R.A., Petts, D., Mattey, D.P., Pearson, D.G.Fluid induced transition from banded kyanite to bimineralic eclogite and implications for the evolution of cratons.Geochimica et Cosmochimica Acta, in press available 55p.Africa, South AfricaDeposit - Roberts Victor

Abstract: Heterogeneous, modally banded kyanite-bearing and bimineralic eclogites from the lithospheric mantle, collected at the Roberts Victor Diamond mine (South Africa), show a reaction texture in which kyanite is consumed. Geothermobarometric calculations using measured mineral compositions in Perple_X allowed the construction of a P-T path showing a steep, cool prograde metamorphic gradient of 2 °C/km to reach peak conditions of 5.8 GPa and 890 °C for the kyanite eclogite. The kyanite-out reaction formed bimineralic eclogite and is probably an integral part of the mineralogical evolution of most archetypal bimineralic eclogites at Roberts Victor and potentially elsewhere. The kyanite-out reaction occured at close to peak pressure (5.3 GPa) and was associated with a rise in temperature to 1380 °C. Mass balance calculations show that upon breakdown, the kyanite component is fully accommodated in garnet and omphacite via a reaction system with low water fugacity that required restricted fluid influx from metasomatic sources. The d18O values of garnets are consistently higher than normal mantle values. Each sample has its characteristic trend of d18O variance between garnets in the kyanite-bearing sections and those in the bimineralic parts covering a range between 5.1‰ and 6.8‰. No systematic change in O-isotope signature exists across the sample population. Differences in garnet trace element signatures between differing lithologies in the eclogites are significant. Grossular-rich garnets coexisting with kyanite have strong positive Eu-anomalies and low Gd/Yb ratios, while more pyrope-rich garnets in the bimineralic sections have lost their positive Eu-anomaly, have higher Gd/Yb ratios and generally higher heavy rare earth element contents. Garnets in the original kyanite-bearing portions thus reflect the provenance of the rocks as metamorphosed gabbros/troctolites. The kyanite-out reaction was most likely triggered by a heating event in the subcratonic lithosphere. As kyanite contains around 100 ppm of H2O it is suggested that the kyanite-out reaction, once initiated by heating and restricted metasomatic influx, was promoted by the release of water contained in the kyanite. The steep (high-P low-T) prograde P-T path defining rapid compression at low heating rates is atypical for subduction transport of eclogites into the lithospheric mantle. Such a trajectory is best explained in a model where strong lateral compression forces eclogites downward to higher pressures, supporting models of cratonic lithosphere formation by lateral collision and compression.
DS201706-1064
2017
Pearson, D.G.Bragagni, A., Luguet, A., Fonsecca, R.O.C., Pearson, D.G., Lorand, D.G., Nowell, G.M., Kjarsgaard, B.A.The geological record of base metal sulfides in the cratonic mantle: a microscale 187Os/188/Os study of peridotite xenoliths from Somerset Island, Rae craton,( Canada).Geochimica et Cosmochimica Acta, in press available 49p.Canada, Nunavut, Somerset Islandperidotite

Abstract: We report detailed petrographic investigations along with 187Os/188Os data in Base Metal Sulfide (BMS) on four cratonic mantle xenoliths from Somerset Island (Rae Craton, Canada). The results shed light on the processes affecting the Re-Os systematics and provide time constraints on the formation and evolution of the cratonic lithospheric mantle beneath the Rae craton. When devoid of alteration, BMS grains mainly consist of pentlandite + pyrrhotite ± chalcopyrite. The relatively high BMS modal abundance of the four investigated xenoliths cannot be reconciled with the residual nature of these peridotites, but requires addition of metasomatic BMS. This is especially evident in the two peridotites with the highest bulk Pd/Ir and Pd/Pt. Metasomatic BMS likely formed during melt/fluid percolation in the Sub Continental Lithospheric Mantle (SCLM) as well as during infiltration of the host kimberlite magma, when djerfisherite crystallized around older Fe-Ni-sulfides. On the whole-rock scale, kimberlite metasomatism is visible in a subset of bulk xenoliths, which defines a Re-Os errorchron that dates the host magma emplacement. The 187Os/188Os measured in the twenty analysed BMS grains vary from 0.1084 to >0.17 and it shows no systematic variation depending on the sulfide mineralogical assemblage. The largest range in 187Os/188Os is observed in BMS grains from the two xenoliths with the highest Pd/Ir, Pd/Pt, and sulfide modal abundance. The whole-rock TRD ages of these two samples underestimate the melting age obtained from BMS, demonstrating that bulk Re-Os model ages from peridotites with clear evidence of metasomatism should be treated with caution. The TRD ages determined in BMS grains are clustered around 2.8-2.7, ~2.2 and ~1.9 Ga. The 2.8-2.7 Ga TRD ages document the main SCLM building event in the Rae craton, which is likely related to the formation of the local greenstone belts in a continental rift setting. The Paleoproterozoic TRD ages can be explained by addition of metasomatic BMS during (i) major lithospheric rifting at ~2.2 Ga and (ii) the Taltson-Thelon orogeny at ~1.9 Ga. The data suggest that even metasomatic BMS can inherit 187Os/188Os from their original mantle source. The lack of isotopic equilibration, even at the micro-scale, allowed the preservation of different populations of BMS grains with distinct 187Os/188Os, providing age information on multiple magmatic events that affected the SCLM.
DS201707-1380
2016
Pearson, D.G.Wang, H., van Hunen, J., Pearson, D.G.Making Archean cratonic roots by lateral compression: a two stage thickening and stabilization model.Tectonophysics, in press availableMantlecraton

Abstract: Archean tectonics was capable of producing virtually indestructible cratonic mantle lithosphere, but the dominant mechanism of this process remains a topic of considerable discussion. Recent geophysical and petrological studies have refuelled the debate by suggesting that thickening and associated vertical movement of the cratonic mantle lithosphere after its formation are essential ingredients of the cratonization process. Here we present a geodynamical study that focuses on how the thick stable cratonic lithospheric roots can be made in a thermally evolving mantle. Our numerical experiments explore the viability of a cratonization process in which depleted mantle lithosphere grows via lateral compression into a > 200-km thick, stable cratonic root and on what timescales this may happen. Successful scenarios for craton formation, within the bounds of our models, are found to be composed of two stages: an initial phase of tectonic shortening and a later phase of gravitational self-thickening. The initial tectonic shortening of previously depleted mantle material is essential to initiate the cratonization process, while the subsequent gravitational self-thickening contributes to a second thickening phase that is comparable in magnitude to the initial tectonic phase. Our results show that a combination of intrinsic compositional buoyancy of the cratonic root, rapid cooling of the root after shortening, and the long-term secular cooling of the mantle prevents a Rayleigh-Taylor type collapse, and will stabilize the thick cratonic root for future preservation. This two-stage thickening model provides a geodynamically viable cratonization scenario that is consistent with petrological and geophysical constraints.
DS201708-1564
2017
Pearson, D.G.Abersteiner, A., Kamanetsky, V.S., Pearson, D.G., Kamenetsky, M., Ehrig, K., Goemann, K., Rodemann, T.Monticellite in group I kimberlites: implications for evolution of parallel melts and post emplacement CO2 degassing. Leslie, Pipe 1Chemical Geology, in press available, 54p.Canada, Northwest Territories, Europe, Finlanddeposit, Leslie

Abstract: Monticellite is a magmatic and/or deuteric mineral that is often present, but widely varying in concentrations in Group-I (or archetypal) kimberlites. To provide new constraints on the petrogenesis of monticellite and its potential significance to kimberlite melt evolution, we examine the petrography and geochemistry of the minimally altered hypabyssal monticellite-rich Leslie (Canada) and Pipe 1 (Finland) kimberlites. In these kimberlites, monticellite (Mtc) is abundant (25–45 vol%) and can be classified into two distinct morphological types: discrete and intergrown groundmass grains (Mtc-I), and replacement of olivine (Mtc-II). Monticellite in group-I kimberlites: Implications for evolution of parental melts and post-emplacement CO 2 degassing (PDF Download Available).
DS201709-1991
2017
Pearson, D.G.Goodarzi, P.Y., Berry, A.J., Pearson, D.G., Yaxley, G.M., Newville, M.Garnet as a recorder of metasomatism in the sub-continental lithospheric mantle. Goldschmidt Conference, abstract 1p.Africa, Namibiadeposit , Louwerensia

Abstract: Metasomatism by fluid or melt is commonly attributed as the cause of chemical and modal heterogeneity observed in peridotite xenoliths from the sub-continental lithospheric mantle. Documented manifestations are (1) perturbation of the oxygen fugacity (fO2), which may affect the stability of carbon-bearing phases, and (2) trace-element enrichment, typified by the shape of REEN patterns. Garnet, which contains Fe2+ and Fe3+ in measurable quantities, and exhibits prominent variation in REEN patterns between samples, may record the metasomatic history of the mantle. Here we report variations of fO2 and trace element concentrations for a suite of 22 garnet-bearing peridotite xenoliths from the Louwrensia kimberlite, south-central Namibia. The xenoliths span an estimated pressure range between 2.7 and 4.5 GPa. Fe3+/?Fe of garnet was determined by Fe K-edge XANES spectroscopy. Concomitant fO2 was calculated using the oxybarometer calibration of Miller et al. [1]. The trace element concentrations of all phases were determined by LA-ICP-MS. A global dataset comprising 454 garnet REEN patterns from 19 kimberlites has been compiled. The REEN pattern of each sample was fit to orthogonal polynomial functions that parameterise the abundance, slope, quadratic curvature, and cubic curvature [2]. Quadratic and cubic curvature correlate with abundance, albeit with considerable scatter. There is, however, an absence of correlation between REEN patterns and fO2, depth, or modal abundance. This is in contrast to correlations and trends observed for basaltic melts that clearly identify petrogenetic trends. The partitioning of REEs between garnet and co-existing phases in these samples highlights pronounced trace-element disequilibrium and hence question the validity of considering garnet REEN in isolation as a means of discerning metasomatic history
DS201709-2016
2017
Pearson, D.G.Kjarsgaard, B.A., Heaman, L.M., Sarkar, C., Pearson, D.G.The North American mid-Cretaceous kimberlite corridor: wet, edge-driven decompression melting of an OIB-type deep mantle source.Geochemistry, Geophysics, Geosystems: G3, Vol. 18, 7, pp. 2727-2747.Canada, Somerset Island, Saskatchewan, United States, Kansasmagmatism, convection, diamond genesis

Abstract: Thirty new high-precision U-Pb perovskite and zircon ages from kimberlites in central North America delineate a corridor of mid-Cretaceous (115–92 Ma) magmatism that extends ~4000 km from Somerset Island in Arctic Canada through central Saskatchewan to Kansas, USA. The least contaminated whole rock Sr, Nd, and Hf isotopic data, coupled with Sr isotopic data from groundmass perovskite indicates an exceptionally limited range in Sr-Nd-Hf isotopic compositions, clustering at the low ?Nd end of the OIB array. These isotopic compositions are distinct from other studied North American kimberlites and point to a sublithospheric source region. This mid-Cretaceous kimberlite magmatism cannot be related to mantle plumes associated with the African or Pacific large low-shear wave velocity province (LLSVP). All three kimberlite fields are adjacent to strongly attenuated lithosphere at the edge of the North American craton. This facilitated edge-driven convection, a top-down driven processes that caused decompression melting of the transition zone or overlying asthenosphere. The inversion of ringwoodite and/or wadsleyite and release of H2O, with subsequent metasomatism and synchronous wet partial melting generates a hot CO2 and H2O-rich protokimberlite melt. Emplacement in the crust is controlled by local lithospheric factors; all three kimberlite fields have mid-Cretaceous age, reactivated major deep-seated structures that facilitated kimberlite melt transit through the lithosphere.
DS201709-2048
2017
Pearson, D.G.Reimink, J.R., Carlson, R.W., Shirey, S.B., Pearson, D.G.Crustal evolution of the Archean Slave craton, NWT.Goldschmidt Conference, abstract 1p.Canada, Northwest Territoriesgeochronology

Abstract: The Slave craton, located in the northwestern portion of the Canadian Shield, contains the oldest known remnant of evolved crust on Earth [1-3] and more extensive suites of granitoid basement gneisses with crystallization ages that nearly span the breadth of the Archean. Portions of these basement gneisses form the Central Slave Basement Complex (CSBC), a belt of exposures recording magmatic events that occurred approximately every 100-150 million years from 3.5-2.7 Ga [4]. When considered with the 4.02 Ga Acasta Gneiss Complex, the good exposure and wide age range of basement gneisses of the Slave craton provide a unique record of the geological processes involved in continent formation. A suite of 3.5-2.7 gyr old Slave craton granitoids collected from a 200 km-long traverse of the CSBC has intermediate to felsic compositions, textures that range from migmatitic gneisses to preservation of primary magmatic features. Preliminary Sm-Nd isotope systematics, as well as zircon U-Pb and Hf isotope data suggest that the granitoids reflect both the products of reworking of Hadean crust, as indicated by the presence of 142Nd deficits in some of the units, but also new additions from the mantle as indicated both in the chemical composition and initial isotopic composition of other rock units. For those samples that derive from remelting of older crustal materials, the initial Hf isotopic composition of zircons are most consistent with a source component that includes Hadean mafic crust. The multiple U-Pb age peaks documented by accessory minerals show a close correspondence with age spectra from the welldocumented mantle lithosphere beneath this region [5] illustrating the coupled evolution of crust and mantle.
DS201709-2056
2017
Pearson, D.G.Sommer, H., Jacob, D.E., Stern, R.A., Petts, D., Mattey, D.P., Pearson, D.G.Fluid induced transition from banded kyanite to bimineralic eclogite and implications for the evolution of cratons.Goldschmidt Conference, abstract 1p.Africa, South Africadeposit - Roberts Victor

Abstract: Heterogeneous, modally banded kyanite-bearing and bimineralic eclogites from the lithospheric mantle, collected at the Roberts Victor Diamond mine (South Africa), show a reaction texture in which kyanite is consumed. Geothermobarometric calculations using measured mineral compositions in Perple_X allowed the construction of a P-T path showing a steep, cool prograde metamorphic gradient of 2 °C/km to reach peak conditions of 5.8 GPa and 890 °C for the kyanite eclogite. The kyanite-out reaction formed bimineralic eclogite and is probably an integral part of the mineralogical evolution of most archetypal bimineralic eclogites at Roberts Victor and potentially elsewhere. The kyanite-out reaction occured at close to peak pressure (5.3 GPa) and was associated with a rise in temperature to 1380 °C. Mass balance calculations show that upon breakdown, the kyanite component is fully accommodated in garnet and omphacite via a reaction system with low water fugacity that required restricted fluid influx from metasomatic sources. The d18O values of garnets are consistently higher than normal mantle values. Each sample has its characteristic trend of d18O variance between garnets in the kyanite-bearing sections and those in the bimineralic parts covering a range between 5.1‰ and 6.8‰. No systematic change in O-isotope signature exists across the sample population. Differences in garnet trace element signatures between differing lithologies in the eclogites are significant. Grossular-rich garnets coexisting with kyanite have strong positive Eu-anomalies and low Gd/Yb ratios, while more pyrope-rich garnets in the bimineralic sections have lost their positive Eu-anomaly, have higher Gd/Yb ratios and generally higher heavy rare earth element contents. Garnets in the original kyanite-bearing portions thus reflect the provenance of the rocks as metamorphosed gabbros/troctolites. The kyanite-out reaction was most likely triggered by a heating event in the subcratonic lithosphere. As kyanite contains around 100 ppm of H2O it is suggested that the kyanite-out reaction, once initiated by heating and restricted metasomatic influx, was promoted by the release of water contained in the kyanite. The steep (high-P low-T) prograde P-T path defining rapid compression at low heating rates is atypical for subduction transport of eclogites into the lithospheric mantle. Such a trajectory is best explained in a model where strong lateral compression forces eclogites downward to higher pressures, supporting models of cratonic lithosphere formation by lateral collision and compression.
DS201709-2063
2017
Pearson, D.G.Thomassot, E., Pearson, D.G., Kitayama, Y., Deloule, E.Sulfur isotope signature 33S/34S and 36S of sea water altered Archean oceanic crust in Siberia eclogite.Goldschmidt Conference, abstract 1p.Russia, Siberiaeclogites

Abstract: Eclogite xenoliths brought to the surface by kimberlites are high pressure mafic rocks whose origin (magmatic vs crustal) remains debated. In addition to disagreement on how to interpret eclogite compositions, mantle metasomatism overprints the mineralogy and geochemistry of some of these rocks, making the question of their protolith undoubtedly more complex. In this contribution we aim to test the robustness of multiple S-isotope signatures in highly metasomatized eclogitic sulfides. We selected 12 interstitial sulfides from Mir (n=4) and Udachnaya (n=8) eclogites, intergrown with garnet and omphacite. We analysed their lead (including Pb204) and S-isotope (32S, 33S, 34S and 36S) compositions, insitu, using a Cameca ims 1280. The samples consist of complex assemblages of pyrrhotite pentlandite intergrowth with K- and Cl-rich sulfides (djerfisherite) invaded by veinlets of alteration minerals (mainly chlorite). All our samples display internal zoning in Pb concentration (118 ppm to 4.2 wt%) but are homogeneous in isotopic compositions (e.g. 208Pb/204Pb = 38.09 ± 0.35‰). Pb-Pb ages of eclogitic sulfides are modern and undoubtedly reflect the metasomatic overprint by a Cl- and K-rich kimberlitic melt (consistent with the presence of djerfisherite). Sulfur isotope signatures of these sulfide (G34S = -1.3‰ ±2‰) fall within the canonical mantle range and cannot be distinguished from the composition of sulfides in the kimberlite (-1.4 ±2.2‰, Kitayama et al., 2016). Furthermore, Mir and Udachanaya eclogitic sulfides carry the largest mass independant fractionation (MIF) ever reported in mantle rocks. The overall trend reveals negative ?33S (down to - 1.1‰) associated to positive ?36S (up to 3‰). This observed correlation between ?33S and ?36S is consistent with the composition of sulfate aerosols formed in the Archean by photolysis reactions and likely dissolved in the ocean [4]. Our results indicate that multiple sulfur isotopes survive intense metasomatism (because isotope fractionation does not create S-MIF), and provide further evidence that the protoliths of Siberian eclogites were mafic rocks altered by seawater in the Archean.
DS201710-2217
2017
Pearson, D.G.Bragagni, A., Luguet, A., Fonseca, R.O.C., Pearson, D.G.,Lorand, J-P., Nowell, G.M., Kjarsgaard, B.A.The geological record of base metal sulfides in the cratonic mantle: a microscale 187Os/188Os study of peridotite xenoliths from Somerset Island, Rae Craton ( Canada).Geochimica et Cosmochimia Acta, Vol. 216, pp. 264-285.Canada, Nunavut, Somerset IslandGeochronology

Abstract: We report detailed petrographic investigations along with 187Os/188Os data in Base Metal Sulfide (BMS) on four cratonic mantle xenoliths from Somerset Island (Rae Craton, Canada). The results shed light on the processes affecting the Re-Os systematics and provide time constraints on the formation and evolution of the cratonic lithospheric mantle beneath the Rae craton. When devoid of alteration, BMS grains mainly consist of pentlandite + pyrrhotite ± chalcopyrite. The relatively high BMS modal abundance of the four investigated xenoliths cannot be reconciled with the residual nature of these peridotites, but requires addition of metasomatic BMS. This is especially evident in the two peridotites with the highest bulk Pd/Ir and Pd/Pt. Metasomatic BMS likely formed during melt/fluid percolation in the Sub Continental Lithospheric Mantle (SCLM) as well as during infiltration of the host kimberlite magma, when djerfisherite crystallized around older Fe-Ni-sulfides. On the whole-rock scale, kimberlite metasomatism is visible in a subset of bulk xenoliths, which defines a Re-Os errorchron that dates the host magma emplacement. The 187Os/188Os measured in the twenty analysed BMS grains vary from 0.1084 to >0.17 and it shows no systematic variation depending on the sulfide mineralogical assemblage. The largest range in 187Os/188Os is observed in BMS grains from the two xenoliths with the highest Pd/Ir, Pd/Pt, and sulfide modal abundance. The whole-rock TRD ages of these two samples underestimate the melting age obtained from BMS, demonstrating that bulk Re-Os model ages from peridotites with clear evidence of metasomatism should be treated with caution. The TRD ages determined in BMS grains are clustered around 2.8-2.7, ~2.2 and ~1.9 Ga. The 2.8-2.7 Ga TRD ages document the main SCLM building event in the Rae craton, which is likely related to the formation of the local greenstone belts in a continental rift setting. The Paleoproterozoic TRD ages can be explained by addition of metasomatic BMS during (i) major lithospheric rifting at ~2.2 Ga and (ii) the Taltson-Thelon orogeny at ~1.9 Ga. The data suggest that even metasomatic BMS can inherit 187Os/188Os from their original mantle source. The lack of isotopic equilibration, even at the micro-scale, allowed the preservation of different populations of BMS grains with distinct 187Os/188Os, providing age information on multiple magmatic events that affected the SCLM.
DS201712-2688
2017
Pearson, D.G.Harris, G.A., Pearson, D.G., Liu, J., Hardman, M.F., Kelsch, D.Mantle composition, age and geotherm beneath the Darby kimberlite field, west central Rae craton.45th. Annual Yellowknife Geoscience Forum, p. 33 abstractCanada, Northwest Territoriesdeposit - Darby

Abstract: New geological and geophysical research on Canada’s Rae craton are providing an increasingly good baseline for diamond exploration. This study uses mantle xenoliths and xenocrysts from the Darby property, located ~200 km southwest of the community of Kugaaruk, Nunavut, to provide new information on the lithospheric mantle and diamond potential of the western portion of the central Rae. Peridotite xenoliths containing enough fresh olivine have a median Mg# value of 92.5, indistinguishable from the median value of 92.6 typical of cratonic peridotites world-wide. Only of the 14 peridotitic xenoliths contain fresh garnet. Of these, garnet in one sample is classified as harzburgitic (G10), giving a minimum pressure of 4.7 GPa using the P38 geobarometer (38 mW/m2 model geothermal gradient), while garnets from three peridotites are classified as lherzolitic (G9). 52 garnets picked from concentrate have lherzolitic affinities. Lherzolitic diopsides from kimberlite heavy mineral concentrate yield a lithospheric thickness of ~ 200 km. The four garnet peridotite xenoliths and 49 peridotitic garnets from concentrate yield two distinct modes in mantle sampling depths using Ni thermometry, when projected to the Cpx geotherm. A cluster of samples from the higher Ca/Cr lherzolitic garnets equilibrated at 765 to 920 °C with a group of peridotitic garnets (50 % of xenoliths and 28 % of concentrate) from the lower Ca/Cr lherzolitic garnets with anomalously high Ti concentrations yielding super-adiabatic TNi values The aluminum-in-olivine thermometer applied to olivines filtered to be “garnet facies yielded a mantle sampling portion of the mantle cargo from the diamond stability field. A suite of pyroxenitic xenoliths are a feature of each Darby kimberlite target. New screening techniques indicate that these rocks likely originate close to the crust mantle boundary. Osmium isotope analyses of the Darby peridotites reveal whole-rock Re-depletion ages ranging from Mesoarchean to Paleoproterozoic. The pyroxenite xenoliths have very radiogenic Os isotope compositions and provide the first age information from pyroxenites/“eclogites” beneath the Rae craton. Their resulting Archean whole rock TMA ages are consistent with a Mesoarchean age of the western Central Rae lithosphere older than the lithosphere beneath the Repulse Bay block in the East section of the Rae craton (Liu et al., 2016. Precambrian Research 272). The highly depleted olivine compositions, thick cold lithosphere, and Archean ages of the Darby peridotite xenoliths clearly indicate the presence of 200 km thick cold cratonic lithospheric mantle beneath the western segment of the central Rae craton circa 540 Ma. The Archean model ages of most of the pyroxenites support this, notwithstanding the fact that some of these rocks could be sampling either crust or mantle lithologies very close to the crust-mantle boundary. Mantle sampling took place well into the diamond stability field at Darby.
DS201801-0078
2017
Pearson, D.G.Wang, H., van Hunen, J., Pearson, D.G.Making Archean cratonic roots by lateral compression: a two stage thickening and stabilization model.Tectonophysics, in press available, 10p.Mantlecraton

Abstract: Making Archean cratonic roots by lateral compression: a two stage thickening and stabilization model.
DS201802-0217
2018
Pearson, D.G.Abersteiner, A., Kamenetsky, V.S., Pearson, D.G., Kamenetsky, M., Goemann, K., Ehrig, K., Rodemann, T.Monticellite in group I kimberlites: implications for evolution of parental melts and post emplacement CO2 degassing.Chemical Geology, Vol. 478, pp. 76-88.Canada, Northwest Territories, Europe, Finlanddeposit - Leslie, Pipe 1

Abstract: Monticellite is a magmatic and/or deuteric mineral that is often present, but widely varying in concentrations in Group-I (or archetypal) kimberlites. To provide new constraints on the petrogenesis of monticellite and its potential significance to kimberlite melt evolution, we examine the petrography and geochemistry of the minimally altered hypabyssal monticellite-rich Leslie (Canada) and Pipe 1 (Finland) kimberlites. In these kimberlites, monticellite (Mtc) is abundant (25-45 vol%) and can be classified into two distinct morphological types: discrete and intergrown groundmass grains (Mtc-I), and replacement of olivine (Mtc-II). Primary multiphase melt inclusions in monticellite, perovskite and Mg-magnetite contain assemblages dominated by alkali (Na, K, Ba, Sr)-enriched Ca-Mg-carbonates, chlorides, phosphates, spinel, silicates (e.g. olivine, phlogopite) and sulphides. These melt inclusions probably represent snapshots of a variably differentiated kimberlite melt that evolved in-situ towards carbonatitic and silica-poor compositions. Although unconstrained in their concentration, the presence of alkali-carbonates and chlorides in melt inclusions suggests they are a more significant component of the kimberlite melt than commonly recorded by whole-rock analyses. We present petrographic and textural evidence showing that pseudomorphic Mtc-II resulted from an in-situ reaction between olivine and the carbonate component of the kimberlite melt in the decarbonation reactio. This reaction is supported by the preservation of abundant primary inclusions of periclase and to a lesser extent Fe-Mg-oxides in monticellite, perovskite and Mg-magnetite. Based on the preservation of primary periclase inclusions, we infer that periclase also existed in the groundmass, but was subsequently altered to brucite. We suggest that CO2 degassing in the latter stages of kimberlite emplacement into the crust is largely driven by the observed reaction between olivine and the carbonate melt. For this reaction to proceed, CO2 should be removed (i.e. degassed), which will cause further reaction and additional degassing in response to this chemical system change (Le Chatelier's principle). Our study demonstrates that these proposed decarbonation reactions may be a commonly overlooked process in the crystallisation of monticellite and exsolution of CO2, which may in turn contribute to the explosive eruption and brecciation processes that occur during kimberlite magma emplacement and pipe formation.
DS201802-0234
2018
Pearson, D.G.From, R.E., Camacho, A., Pearson, D.G., Luo, Y.U-Pb and Lu-Hf isotopes of the Archean orthogneiss complex on eastern Hall Peninsula, southern Baffin Island, Nunavut: identification of exotic Paleo to Mesoarchean crust beneath eastern Hall Peninsula.Precambrian Research, Vol. 305, pp. 341-357.Canada, Nunavut, Hall Peninsulageochronology

Abstract: Eastern Hall Peninsula on southeastern Baffin Island, lies at the junction of a complex Paleoproterozoic collision between the Rae craton, Meta Incognita microcontinent and the North Atlantic craton from ca. 1.88 to 1.80?Ga. Several different interpretations of crustal correlations and the location of intervening sutures have been proposed based on reconnaissance-scale geologic investigation. Therefore, in this study, complex zircon grains from Archean orthogneiss units on eastern Hall Peninsula were analyzed in-situ to elucidate the detailed magmatic history of the region and assess crustal provenance. Magmatic zircons yielded U-Pb crystallization ages between ca. 2976 and 2720?Ma and metamorphic zircons record tectonothermal disturbances between ca. 2740 and 2700?Ma, a period coinciding with metamorphism documented in adjacent crustal blocks (e.g., west Greenland and northern Labrador). Magmatic rocks older than ca. 2740?Ma generally have positive eHf(t) signatures between 0 and 7 (±2) and depleted mantle model ages of ca. 3.1-3.0?Ga indicating the time that protolith melt was extracted from the mantle. The oldest, granodioritic crust crystallized at ca. 2976?Ma and was then reworked periodically at ca. 2.93, 2.84-2.81 and 2.77-2.69?Ma. Zircons from two orthogneiss samples, with U-Pb crystallization ages younger than ca. 2740?Ma, yielded negative eHf(t) values ranging from -4 to -12 and mean depleted mantle model ages of ca. 3.4 and 3.3?Ga respectively, indicating derivation from an older, potentially exotic, crustal source yet to be identified in outcrop on Hall Peninsula. Synthesizing regional U-Pb data we propose a new regional correlation model that retains the essentials of previous models and incorporates new data from eastern Hall Peninsula and other recent studies. This new tectonic correlation model groups eastern Hall Peninsula, southern Cumberland Peninsula and the Aasiaat domain into a “Core zone” that shared a geologic history prior to 1.90?Ga and potentially prior to 2.75?Ga.
DS201802-0241
2018
Pearson, D.G.Hardman, M.F., Pearson, D.G., Stachel, T., Sweeney, R.J.Statistical approaches to the discrimination of crust and mantle derived low Cr garnet - Major element based methods and their application to diamond exploration.Journal of Geochemical Exploration, Vol. 186, pp. 24-35.Mantlegarnet diamond exploration

Abstract: In diamond exploration, the accurate distinction between garnets from the crust or mantle, or from those having a cognate origin with kimberlite (low-Cr megacrysts), is important for the assessment of indicator mineral samples; misclassifications potentially result in costly misdirection of exploration efforts. Existing literature databases and graphical classification schemes for garnets suffer from a paucity of craton-derived, lower-crustal garnets that - as shown here - are among the most difficult to distinguish from garnets of mantle origin. To improve this situation, a large database of new and literature garnet major element analyses has been compiled. Using this dataset, it is shown that the conventionally used Mg# (Mg/(Mg + Fe)) vs. Ca# (Ca/(Mg + Ca)) plot (Schulze, 2003) for discrimination of crust and mantle garnets results in significant overlap (39.2% crustal failure rate using our dataset). We propose a new graphical classification scheme that uses the parameters ln(Ti/Si) and ln(Mg/Fe) to discriminate low-Cr garnets of crust origin from those of a mantle eclogite-pyroxenite origin with an error rate of 10.1 ± 2.1% at the 95% confidence level (assessed via K-fold cross-validation with ten random test datasets), significantly lower than existing methods. Multivariate statistical solutions, which incorporate a wide selection of geochemical variables, represent additional possibilities for discrimination. Using our new database, logistic regression (LR) and linear discriminant analysis (LDA) approaches are evaluated and new crust-mantle garnet discrimination schemes derived. The resulting solutions, using a wide variety of cations in garnet, provide lower misclassification rates than existing literature schemes. Both LR and LDA are successful discrimination techniques with error rates for the discrimination of crust from mantle eclogite-pyroxenite of 7.5 ± 1.9% and 8.2 ± 2.3%, respectively. LR, however, involves fewer stipulations about the distribution of training data (i.e., it is more "robust") and can return an estimate for probability of classification certainty for single garnets. New data from diamond exploration programs can be readily classified using these new graphical and statistical methods. As the discrimination of low-Cr megacrysts from mantle eclogite-pyroxenite is not the focus of this study, we recommend the method of Schulze (2003) or Grütter et al. (2004) for low-Cr megacryst discrimination to identify megacrysts in the "mantle" suite. Runstreams for our LDA and LR approaches using the freeware "R" are provided for quick implementation.
DS201804-0714
2018
Pearson, D.G.Korolev, N.M., Kopylova, M., Bussweiller, Y., Pearson, D.G., Gurney, J., Davidson, J.The uniquely high temperature character of Culli nan diamonds: a signature of the Bushveld mantle plume?Lithos, Vol. 304, pp. 362-373.Africa, South Africadeposit - Cullinan

Abstract: The mantle beneath the Cullinan kimberlite (formerly known as "Premier") is a unique occurrence of diamondiferous cratonic mantle where diamonds were generated contemporaneously and shortly following a mantle upwelling that led to the formation of a Large Igneous Province that produced the world's largest igneous intrusion - the 2056?Ma Bushveld Igneous Complex (BIC). We studied 332 diamond inclusions from 202 Cullinan diamonds to investigate mantle thermal effects imposed by the formation of the BIC. The overwhelming majority of diamonds come from three parageneses: (1) lithospheric eclogitic (69%), (2) lithospheric peridotitic (21%), and (3) sublithospheric mafic (9%). The lithospheric eclogitic paragenesis is represented by clinopyroxene, garnet, coesite and kyanite. Main minerals of the lithospheric peridotitic paragenesis are forsterite, enstatite, Cr-pyrope, Cr-augite and spinel; the sublithospheric mafic association includes majorite, CaSiO3 phases and omphacite. Diamond formation conditions were calculated using an Al-in-olivine thermometer, a garnet-clinopyroxene thermometer, as well as majorite and Raman barometers. The Cullinan diamonds may be unique on the global stage in recording a cold geotherm of 40?mW/m2 in cratonic lithosphere that was in contact with underlying convecting mantle at temperatures of 1450-1550?°C. The studied Cullinan diamonds contain a high proportion of inclusions equilibrated at temperatures exceeding the ambient 1327?°C adiabat, i.e. 54% of eclogitic diamonds and 41% of peridotitic diamonds. By contrast, = 1% of peridotitic diamond inclusions globally yield equally high temperatures. We propose that the Cullinan diamond inclusions recorded transient, slow-dissipating thermal perturbations associated with the plume-related formation of the ~2?Ga Bushveld igneous province. The presence of inclusions in diamond from the mantle transition zone at 300-650?km supports this view. Cullinan xenoliths indicative of the thermal state of the cratonic lithosphere at ~1.2?Ga are equilibrated at the relatively low temperatures, not exceeding adiabatic. The ability of diamonds to record super-adiabatic temperatures may relate to their entrainment from the deeper, hotter parts of the upper mantle un-sampled by the kimberlite in the form of xenoliths or their equilibration in a younger lithosphere after a decay of the thermal disturbance.
DS201804-0723
2018
Pearson, D.G.Nestola, F., Korolev, N., Kopylova, M., Rotiroti, N., Pearson, D.G., Pamato, M.G., Alvaro, M., Peruzzo, L., Gurney, J.J., Moore, A.E., Davidson, J.CaSiO3 perovskite in diamond indicates the recycling of oceanic crust into the lower mantle.Nature, Vol. 555, March 8, pp. 237-241.Mantledeposit - Cullinan

Abstract: Laboratory experiments and seismology data have created a clear theoretical picture of the most abundant minerals that comprise the deeper parts of the Earth’s mantle. Discoveries of some of these minerals in ‘super-deep’ diamonds—formed between two hundred and about one thousand kilometres into the lower mantle—have confirmed part of this picture1,2,3,4,5. A notable exception is the high-pressure perovskite-structured polymorph of calcium silicate (CaSiO3). This mineral—expected to be the fourth most abundant in the Earth—has not previously been found in nature. Being the dominant host for calcium and, owing to its accommodating crystal structure, the major sink for heat-producing elements (potassium, uranium and thorium) in the transition zone and lower mantle, it is critical to establish its presence. Here we report the discovery of the perovskite-structured polymorph of CaSiO3 in a diamond from South African Cullinan kimberlite. The mineral is intergrown with about six per cent calcium titanate (CaTiO3). The titanium-rich composition of this inclusion indicates a bulk composition consistent with derivation from basaltic oceanic crust subducted to pressures equivalent to those present at the depths of the uppermost lower mantle. The relatively ‘heavy’ carbon isotopic composition of the surrounding diamond, together with the pristine high-pressure CaSiO3 structure, provides evidence for the recycling of oceanic crust and surficial carbon to lower-mantle depths.https://www.nature.com/articles/nature25972
DS201804-0726
2018
Pearson, D.G.Pearson, D.G.Making and stabilising the deep diamond bearing roots of continents.4th International Diamond School: Diamonds, Geology, Gemology and Exploration Bressanone Italy Jan. 29-Feb. 2nd., pp. 33-35. abstractMantlecraton - peridotites
DS201804-0735
2018
Pearson, D.G.Shirey, S.B., Pearson, D.G.How to obtain and interpret diamond ages.4th International Diamond School: Diamonds, Geology, Gemology and Exploration Bressanone Italy Jan. 29-Feb. 2nd., pp. 38-40. abstractTechnologydiamond ages
DS201807-1482
2018
Pearson, D.G.Bussweiler, Y., Pearson, D.G., Stachel, T., Kjarsgaard, B.A.Cr-rich megacrysts of clinopyroxene and garnet from Lac de Gras kimberlites, Slave Craton, Canada - implications for the origin of clinopyroxene and garnet in cratonic lherzolites.Mineralogy and Petrology, 10.1007/s00710 -018-0599-2, 14p. Canada, Northwest Territoriesdeposit - Diavik, Ekati

Abstract: Kimberlites from the Diavik and Ekati diamond mines in the Lac de Gras kimberlite field contain abundant large (>1 cm) clinopyroxene (Cr-diopside) and garnet (Cr-pyrope) crystals. We present the first extensive mineral chemical dataset for these megacrysts from Diavik and Ekati and compare their compositions to cratonic peridotites and megacrysts from the Slave and other cratons. The Diavik and Ekati Cr-diopside and Cr-pyrope megacrysts are interpreted to belong to the Cr-rich megacryst suite. Evidence for textural, compositional, and isotopic disequilibrium suggests that they constitute xenocrysts in their host kimberlites. Nevertheless, their formation may be linked to extensive kimberlite magmatism and accompanying mantle metasomatism preceding the eruption of their host kimberlites. It is proposed that the formation of megacrysts may be linked to failed kimberlites. In this scheme, the Cr-rich megacrysts are formed by progressive interaction of percolating melts with the surrounding depleted mantle (originally harzburgite). As these melts percolate outwards, they may contribute to the introduction of clinopyroxene and garnet into the depleted mantle, thereby forming lherzolite. This model hinges on the observation that lherzolitic clinopyroxenes and garnets at Lac de Gras have compositions that are strikingly similar to those of the Cr-rich megacrysts, in terms of major and trace elements, as well as Sr isotopes. As such, the Cr-rich megacrysts may have implications for the origin of clinopyroxene and garnet in cratonic lherzolites worldwide.
DS201807-1495
2018
Pearson, D.G.Gress, M.U., Pearson, D.G., Chinn, I.L., Koornneef, J.M., Pals, A.S.M., Van der Valk, E.A.S., Davies, G.R.Episodic eclogitic diamond genesis at Jwaneng diamond mine, Botswana.Goldschmidt2018, abstract 1p.Africa, Botswanadeposit - Jwaneng

Abstract: The diamondiferous Jwaneng kimberlite cluster (~240 Ma) is located on the NW rim of the Archaean Kaapvaal Craton in central Botswana. Previous studies report eclogitic diamond formation in the late Archean (2.9 Ga) and in the Middle Proterozoic (1.5 Ga) involving different mantle and sedimentary components [1;2;3]. Here we report newly acquired Sm- Nd ages of individual eclogitic pyrope-almandine and omphacite inclusions along with their major element data and nitrogen data from the diamond hosts to re-examine Jwaneng’s diamond formation ages. The Sm-Nd isotope analyses were performed via TIMS using 1013O resistors [4]. An initial suite of three pyropealmandine and 14 omphacite inclusions yield 143Nd/144Nd from 0.51102±7 to 0.5155±5. 147Sm/144Nd vary from 0.024 to 0.469. Major element data defines two inclusion populations: (1) seven omphacites with high Mg#, high Cr# and one pyropealmandine with low-Ca define an isochron age of 1.93±0.16 Ga with ?Ndi= +3.5; (2) seven omphacites with low Mg#, low Cr# and two pyrope-almandines with low-Ca define an isochron age of 0.82±0.06 Ga with ?Ndi= +3.7. Nitrogen contents of corresponding diamond host growth zones in Group (1) are = 50 at.ppm whereas Group (2) range between 50 to 700 at.ppm with N-aggregation > 70 %B. Additional data used to define “co-genetic” inclusion suites include Sr-isotopes and trace elements of the inclusions and carbon isotopes of the diamond hosts. Re-Os data of coexisting sulphide inclusions from the same silicate-bearing diamonds further validates the ages and indicates more periods of diamond formation at Jwaneng than previously assumed. The integrated data indicate the possibility of an extensive Paleoproterozoic diamond-forming event in southern Africa.
DS201807-1525
2018
Pearson, D.G.Shu, Q., Brey, G.P., Pearson, D.G.Eclogites and garnet pyroxenites from Kimberley, Kaapvaal craton, South Africa: their diverse origins and complex metasomatic signatures.Mineralogy and Petrology, June 14, DOI:10.1007/ s00710-018 -0595-6, 16p.Africa, South Africadeposit - Boshof

Abstract: We describe the petrography and mineral chemistry of sixteen eclogite and garnet pyroxenite xenoliths from the reworked Boshof road dump (Kimberley) and define three groups that stem from different depths. Group A, the shallowest derived, has low HREE (heavy rare earth element) abundances, flat middle to heavy REE patterns and high Mg# [= 100•Mg/(Mg?+?Fe)]. Their protoliths probably were higher pressure cumulates (~ 0.7 GPa) of mainly clinopyroxene (cpx) and subordinate orthopyroxene (opx) and olivine (ol). Group B1 xenoliths, derived from the graphite/diamond boundary and below show similarities to present-day N-MORB that were modified by partial melting (higher Mg# and positively inclined MREE (middle REE) and HREE (heavy REE) patterns of calculated bulk rocks). Group B2 samples from greatest depth are unique amongst eclogites reported so far worldwide. The calculated bulk rocks have humped REE patterns with very low La and Lu and prominent maxima at Sm or Eu and anomalously high Na2O (up to 5 wt%) which makes protolith identification difficult. The complex trace element signatures of the full spectrum of Kimberley eclogites belie a multi-stage history of melt depletion and metasomatism with the introduction of new phases especially of phlogopite (phlog). Phlogopite appears to be characteristic for Kimberley eclogites and garnet peridotites. Modelling the metasomatic overprint indicates that groups A and B1 were overprinted by volatile- and potassium-rich melts probably by a process of chromatographic fractionation. Using constraints from other metasomatized Kimberley mantle rocks suggest that much of the metasomatic phlogopite in the eclogites formed during an intense episode of metasomatism that affected the mantle beneath this region 1.1 Gyr ago.
DS201808-1750
2018
Pearson, D.G.Hardman, M.F., Pearson, D.G., Stachel, T., Sweeney, R.J.Statistical approaches to the discrimination of mantle - and crust derived low Cr garnets using major and trace element data.Mineralogy and Petrology, doi.org/10.1007/s00710-018-0622-7 10p.Technologygarnet classification
DS201808-1751
2018
Pearson, D.G.Harris, G.A., Pearson, D.G., Liu, J., Hardman, M.F., Snyder, D.B., Kelsch, D.Mantle composition, age and geotherm beneath the Darby kimberlite field, west central Rae craton.Mineralogy and Petrology, doi.org/10.1007/s00710-018-0609-4 14p.Canada, Northwest Territoriesdeposit - Darby

Abstract: New geological and geophysical research on Canada’s Rae craton are providing an increasingly good baseline for diamond exploration. This study uses mantle xenoliths and xenocrysts from the Darby property, located ~200 km southwest of the community of Kugaaruk, Nunavut, to provide new information on the lithospheric mantle and diamond potential of the western portion of the central Rae. Peridotite xenoliths containing enough fresh olivine have a median Mg# value of 92.5, indistinguishable from the median value of 92.6 typical of cratonic peridotites world-wide. Only of the 14 peridotitic xenoliths contain fresh garnet. Of these, garnet in one sample is classified as harzburgitic (G10), giving a minimum pressure of 4.7 GPa using the P38 geobarometer (38 mW/m2 model geothermal gradient), while garnets from three peridotites are classified as lherzolitic (G9). 52 garnets picked from concentrate have lherzolitic affinities. Lherzolitic diopsides from kimberlite heavy mineral concentrate yield a lithospheric thickness of ~ 200 km. The four garnet peridotite xenoliths and 49 peridotitic garnets from concentrate yield two distinct modes in mantle sampling depths using Ni thermometry, when projected to the Cpx geotherm. A cluster of samples from the higher Ca/Cr lherzolitic garnets equilibrated at 765 to 920 °C with a group of peridotitic garnets (50 % of xenoliths and 28 % of concentrate) from the lower Ca/Cr lherzolitic garnets with anomalously high Ti concentrations yielding super-adiabatic TNi values The aluminum-in-olivine thermometer applied to olivines filtered to be “garnet facies yielded a mantle sampling portion of the mantle cargo from the diamond stability field. A suite of pyroxenitic xenoliths are a feature of each Darby kimberlite target. New screening techniques indicate that these rocks likely originate close to the crust mantle boundary. Osmium isotope analyses of the Darby peridotites reveal whole-rock Re-depletion ages ranging from Mesoarchean to Paleoproterozoic. The pyroxenite xenoliths have very radiogenic Os isotope compositions and provide the first age information from pyroxenites/“eclogites” beneath the Rae craton. Their resulting Archean whole rock TMA ages are consistent with a Mesoarchean age of the western Central Rae lithosphere older than the lithosphere beneath the Repulse Bay block in the East section of the Rae craton (Liu et al., 2016. Precambrian Research 272). The highly depleted olivine compositions, thick cold lithosphere, and Archean ages of the Darby peridotite xenoliths clearly indicate the presence of 200 km thick cold cratonic lithospheric mantle beneath the western segment of the central Rae craton circa 540 Ma. The Archean model ages of most of the pyroxenites support this, notwithstanding the fact that some of these rocks could be sampling either crust or mantle lithologies very close to the crust-mantle boundary. Mantle sampling took place well into the diamond stability field at Darby.
DS201808-1769
2018
Pearson, D.G.Motsamai, T., Harris, J.W., Stachel, T., Pearson, D.G., Armstrong, J.Mineral inclusions in diamonds from Karowe mine, Botswana: super-deep sources for super-sized diamonds?Mineralogy and Petrology, doi.org/10.1007/s00710-018-0604-9 12p.Africa, Botswanadeposit - Karowe

Abstract: Mineral inclusions in diamonds play a critical role in constraining the relationship between diamonds and mantle lithologies. Here we report the first major and trace element study of mineral inclusions in diamonds from the Karowe Mine in north-east Botswana, along the western edge of the Zimbabwe Craton. From a total of 107 diamonds, 134 silicate, 15 oxide, and 22 sulphide inclusions were recovered. The results reveal that 53% of Karowe inclusion-bearing diamonds derived from eclogitic sources, 44% are peridotitic, 2% have a sublithospheric origin, and 1% are websteritic. The dominant eclogitic diamond substrates sampled at Karowe are compositionally heterogeneous, as reflected in wide ranges in the CaO contents (4-16 wt%) of garnets and the Mg# (69-92) and jadeite contents (14-48 mol%) of clinopyroxenes. Calculated bulk rock REEN patterns indicate that both shallow and deep levels of the subducted slab(s) were sampled, including cumulate-like protoliths. Peridotitic garnet compositions largely derive from harzburgite/dunite substrates (~90%), with almost half the garnets having CaO contents <1.8 wt%, consistent with pyroxene-free (dunitic) sources. The highly depleted character of the peridotitic diamond substrates is further documented by the high mean and median Mg# (93.1) of olivine inclusions. One low-Ca garnet records a very high Cr2O3 content (14.7 wt%), implying that highly depleted cratonic lithosphere at the time of diamond formation extended to at least 220 km depth. Inclusion geothermobarometry indicates that the formation of peridotitic diamonds occurred along a 39-40 mW/m2 model geotherm. A sublithospheric inclusion suite is established by three eclogitic garnets containing a majorite component, a feature so far unique within the Orapa cluster. These low- and high-Ca majoritic garnets follow pyroxenitic and eclogitic trends of majoritic substitution, respectively. The origin of the majorite-bearing diamonds is estimated to be between 330 to 420 km depth, straddling the asthenosphere-transition zone boundary. This new observation of superdeep mineral inclusions in Karowe diamonds is consistent with a sublithospheric origin for the exceptionally large diamonds from this mine.
DS201809-2038
2018
Pearson, D.G.Howell, D., Stachel, T., Pearson, D.G., Stern, R.A., Nestola, F., Shirey, S.B., Harris, J.W.Deep carbon through time: the diamond record.Goldschmidt Conference, 1p. AbstractAfrica, Australia, Russia, Canadadeposit - Argyle, De Beers Pool, Jwaneng, Orapa, Udachnaya, Venetia, Wawa, Diavik

Abstract: Earth’s mantle is by far the largest silicate-hosted reservoir of carbon. Diamonds are unrivalled in their ability to record the cycle of mantle carbon and other volatiles over a vast portion of the Earth’s history. They are the product of ascending, cooling, carbon-saturated, metasomatic fluidsmelts and/or redox reactions, predominantly within peridotitic and eclogitic domains in the mantle lithosphere. This paper reports the results of a major secondary ion mass spectrometry (SIMS) carbon isotope study, carried out on 127 diamond samples, spanning a large range of geological time. Detailed transects across the incremental growth zones within each diamond were measured for C isotopes, N abundances and, for samples with N >~200 at.ppm, N isotopes. Given that all of the samples are fragments, recovered when the original crystals were broken to liberate their inclusions, 81 of the analytical traverses have confirmed growth direction context. 98 samples are from studies that have confirmed the dates of the individual diamonds through analysis of their silicate or sulphide inclusions, from source localities including Argyle, De Beers Pool, Jwaneng, Orapa, Udachnaya & Venetia. Additional samples come from Wawa (a minimum age) and Diavik where the samples are tied via inclusion paragenesis to published ages. The peridotitic dataset covers the age range of ~3.3 - 2.0 Ga, with the eclogitic data from 2.9 - 1.0 Ga. In total, 751 carbon isotope and nitrogen concentration measurements have been obtained (425 on peridotitic diamonds, and 326 on eclogitic diamonds) with 470 nitrogen isotope measurements (190 P, 280 E). We attempt to constrain the diamond carbon isotope record through time and its implications for (i) the mantle carbon reservoir, (ii) its oxygen fugacity, (iii) the fluid / melt growth environment of diamonds, (iv) fractionation trends recorded in individual diamonds, and (v) diamond population studies using bulk combustion carbon isotope analysis.
DS201809-2060
2018
Pearson, D.G.Liu, J., Brin, L.E., Pearson, D.G., Bretschneider, L., Luguet, A., van Acken, D., Kjarsgaard, B., Riches, A., Miskovic, A.Diamondiferous Paleoproterozoic mantle roots beneath Arctic Canada: a study of mantle xenoliths from Parry Peninsula and Central Victoria Island.Geochimica et Cosmochimica Acta, doi.org/10.1016/j.gca.2018.08.010 78p.Canada, Nunavut, Parry Peninsula. Central Victoria Islandxenoliths

Abstract: While the mantle roots directly beneath Archean cratons have been relatively well studied because of their economic importance, much less is known about the genesis, age, composition and thickness of the mantle lithosphere beneath the regions that surround the cratons. Despite this knowledge gap, it is fundamentally important to establish the nature of relationships between this circum-cratonic mantle and that beneath the cratons, including the diamond potential of circum-cratonic regions. Here we present mineral and bulk elemental and isotopic compositions for kimberlite-borne mantle xenoliths from the Parry Peninsula and Central Victoria Island, Arctic Canada. These xenoliths provide key windows into the lithospheric mantle underpinning regions to the North and Northwest of the Archean Slave craton, where the presence of cratonic material has been proposed. The mantle xenolith data are supplemented by mineral concentrate data obtained during diamond exploration. The mineral and whole rock chemistry of peridotites from both localities is indistinguishable from that of typical cratonic mantle lithosphere. The cool mantle paleogeotherms defined by mineral thermobarometry reveal that the lithospheric mantle beneath the Parry Peninsula and Central Victoria Island terranes extended well into the diamond stability field at the time of kimberlite eruption, and this is consistent with the recovery of diamonds from both kimberlite fields. Bulk xenolith Se and Te contents, and highly siderophile element (including Os, Ir, Pt, Pd and Re) abundance systematics, plus corresponding depletion ages derived from Re-Os isotope data suggest that the mantle beneath these parts of Arctic Canada formed in the Paleoproterozoic Era, at ~2?Ga, rather than in the Archean. The presence of a diamondiferous Paleoproterozoic mantle root is part of the growing body of global evidence for diamond generation in mantle roots that stabilized well after the Archean. In the context of regional tectonics, we interpret the highly depleted mantle compositions beneath both studied regions as formed by mantle melting associated with hydrous metasomatism in the major Paleoproterozoic Wopmay-Great Bear-Hottah arc systems. These ~2?Ga arc systems were subsequently accreted along the margin of the Slave craton to form a craton-like thick lithosphere with diamond potential thereby demonstrating the importance of subduction accretion in building up Earth’s long-lived continental terranes.
DS201809-2061
2018
Pearson, D.G.Liu, J., Pearson, D.G., Shu, Q., Sigurdsson, H.Hafnium osmium isotope systematics of mantle peridotites from the Cameroon Volcanic Line: implications for dating post-Archean lithospheric mantle.Goldschmidt Conference, 1p. AbstractMantleperidotites

Abstract: The Re-Os isotope system is well suited to constraining the timing of melt depletion of Archean mantle peridotites. In contrast, the variability inherent in post-Archean mantle Os isotope evolution leads to increasing uncertainty in Re-Os model ages. The Lu-Hf isotopic system has shown some potential for dating peridotite formation ages, providing valuable ages that are complementary to the Re-Os system. For post-Archean mantle peridotites, the key target in the Lu-Hf isotopic work is clinopyroxene (Cpx), because of its high Lu and Hf concentrations and the typical absence of garnet in these rocks. However, orthopyroxene (Opx) can contrain 20% or more of the Hf budget of spinel peridotites and somethimes over 40% of the Lu budget, with Lu/Hf ratios 3-4 times those of Cpx. Thus, Opx Lu-Hf isotopic compositions cannot be ignored or simply calculated, as the equilibrium temperatures of mantle peridotites prior to eruption could be lower or higher than the Hf closure temperature (Tc(Hf)~900ºC). Here we explore Lu-Hf partitioning in spinel peridotite xenoliths from the Cameroon Volcanic Line in additin to WR Re-Os analyses. The Hf isotopic composition of Opx in these rocks is equal to or higher than that of Cpx, consistent with some samples having equilibrium temperatures close to Tc(Hf). Combining Cpx and Opx, the constructed WR Lu-Hf isochron yields an age of 2.01±0.36 Ga (2s; MSWD = 11.4; ?Hfi = -0.8±19.2), which is in accordance with the oldest of the variable Re-Os model ages. The continental sector of the Cameroon Line runs close to the edge of the Congo craton. The Hf-Os data indicate that the lithosphere underpinning this region formed in the Paleoproterozoic (~2Ga) most likely during the Paleoproterzoic assembly between the Congo and West African Cratons. We emphasize that Opx and Cpx should be combined together to construct the WR isochron in order to obtain the precise age and initial Hf isotope compositions of post-Archean spinel peridotites.
DS201809-2062
2018
Pearson, D.G.Liu, J., Pearson, D.G., Bretschneider, L., Luguet, A., Van Acken, D., Kjarsgaard, B., Riches, A., Miskovic, A.Diamondiferous Proterozoic mantle roots beneath Arctic Canada.Goldschmidt Conference, 1p. AbstractCanada, Parry Peninsula, Victoria Islandxenoliths

Abstract: The mantle roots directly beneath Archean cratons have been relatively well studied because of their economic importance, yet much less is known about the genesis, age, composition and thickness of the mantle lithosphere beneath the regions surrounding these cratons. However, it is critically important to establish the nature of the relationship between this circum-cratonic mantle and that beneath the cratons, including the diamond potential of circum-cratonic regions. Here we present mineral and bulk elemental and isotopic compositions for kimberlite-borne mantle xenoliths from the Parry Peninsula (PP) and Central Victoria Island (CVI), Arctic Canada. These xenoliths provide key windows into the lithospheric mantle underpinning regions to the North and Northwest of the Slave craton, where the presence of cratonic mantle has been proposed. The mineral and whole rock chemistry of peridotites from both localities is indistinguishable from that of typical cratonic mantle lithosphere. The cool mantle geotherms defined by mineral thermobarometry reveal that the lithospheric mantle beneath the PP and CVI terranes extended well into the diamond stability field at the time of kimberlite eruption, consistent with the recovery of diamonds from both kimberlite fields. Bulk Se, Te, and highly siderophile element abundance systematics, plus Re-Os isotope age data suggest that the mantle beneath these parts of Arctic Canada formed at ~2 Ga, rather than in the Archean. The presence of a diamondiferous Paleoproterozoic mantle root is part of the growing body of evidence for peridotitic diamond generation in mantle roots that stabilized well after the Archean. In the context of regional tectonics, the highly depleted mantle compositions beneath both regions developed during mantle melting associated with hydrous metasomatism in the major Paleoproterozoic Wopmay- Great Bear-Hottah arc systems. These terranes were subsequently accreted along the margin of the Slave craton to form a craton-like thick lithosphere with significant diamond potential.
DS201809-2079
2018
Pearson, D.G.Regier, M.E., Pearson, D.G., Stachel, T., Stern, R.A., Harris, J.W.Oxygen isotopes in Kankan super deep diamond inclusions reveal variable slab mantle interaction.Goldschmidt Conference, 1p. AbstractAfrica, South Africa, Guinea, South America, Brazildeposit - Kankan, Jagersfontein, Juina

Abstract: Inclusions in super-deep diamonds provide a unique window to the sublithospheric mantle (e.g. [1-4]). Here we present oxygen isotopes for Kankan majoritic garnet and former bridgmanite inclusions. The clustering of Kankan majorites around a d18O of +9‰ is nearly identical to those reported from Jagersfontein [1]. This elevated and nearly constant d18O signal indicates homogenization of partial melts from the uppermost part of altered basaltic slabs. Conversely, d18O values in Juina majorites are highly variable [2] due to crystallization from small, discrete melt pockets in a heterogeneous eclogitic source. While all these majorites have eclogitic/pyroxenitic Cr2O3 and CaO contents, charge-balance for Si[VI] is achieved very differently, with Jagersfontein [3], Kankan [4], and Juina [2] majorites transitioning from eclogitic Na[VIII]Si[VI] to peridotitic-pyroxenitic [5] Mg[VI]Si[VI] substitutions. We interpret this shift as the result of homogenized eclogitic partial melts infiltrating and reacting with adjacent pyrolitic mantle at Kankan and Jagersfontein. Increases in Mg# and Cr2O3 with reductions in d18O support this reaction. This model is in agreement with recent experiments in which majorites and diamonds form from a reaction of slab-derived carbonatite with reduced pyrolite at 300-700 km depth [6]. The Kankan diamonds also provide an opportunity to establish the chemical environment of the lower mantle. Four inclusions of MgSiO3, inferred to be former bridgmanite [4], provide the first-measured d18O values for lower mantle samples. These values suggest derivation from primitive mantle, or unaltered subducted oceanic lithospheric mantle. The Kankan super-deep inclusions thus provide a cross-section of deep mantle that highlights slab-pyrolite reactions in the asthenosphere and primitive compositions in the lower mantle.
DS201809-2082
2018
Pearson, D.G.Sarkar, C., Kjarsgaard, B.A., Pearson, D.G., Heaman, L.M., Locock, A.J., Armstrong, J.P.Geochronology, classification and mantle source characteristics of kimberlites and related rocks from the Rae craton, Melville Peninsula, Nunavut, Canada.Mineralogy and Petrology, doi.org/10.1007/ s00710-018-0632-5 20p.Canada, Nunavut, Melville Peninsuladeposit - Pelly Bay, Darby, Aviat, Qilalugaq

Abstract: Detailed geochronology along with petrographic, mineralogical and geochemical studies have been conducted on recently found diamond-bearing kimberlitic and related rocks in the Rae Craton at Aviat and Qilalugaq, Melville Peninsula, north-east Canada. Magmatic rocks from the Aviat pipes have geochemical (both bulk rock and isotopic) and mineralogical signatures (e.g., core to rim Al and Ba enrichment in phlogopite) similar to Group I kimberlite. In contrast, Aviat intrusive sheets are similar to ‘micaceous’ Group II kimberlite (orangeite) in their geochemical and mineralogical characteristics (e.g., phlogopite and spinel compositions, highly enriched Sr isotopic signature). Qilalugaq rocks with the least crustal contamination have geochemical and mineralogical signatures [e.g., high SiO2, Al2O3 and H2O; low TiO2 and CO2; less fractionated REE (rare earth elements), presence of primary clinopyroxene, phlogopite and spinel compositions] that are similar to features displayed by olivine lamproites from Argyle, Ellendale and West Greenland. The Naujaat dykes, in the vicinity of Qilalugaq, are highly altered due to extensive silicification and carbonation. However, their bulk rock geochemical signature and phlogopite chemistry are similar to Group I kimberlite. U-Pb perovskite geochronology reveals that Aviat pipes and all rocks from Qilalugaq have an early Cambrian emplacement age (540-530 Ma), with the Aviat sheets being ~30 Ma younger. This volatile-rich potassic ultramafic magmatism probably formed by varying degrees of involvement of asthenospheric and lithospherically derived melts. The spectrum of ages and compositions are similar to equivalent magmatic rocks observed from the nearby north-eastern North America and Western Greenland. The ultimate trigger for this magmatism could be linked to Neoproterozoic continental rifting during the opening of the Iapetus Ocean and breakup of the Rodinia supercontinent.
DS201810-2326
2018
Pearson, D.G.Guotana, J.M., Morishita, T., Yamaguchi, R., Nishio, I., Tamura, A., Tani, K., Harigane, Y., Szilas, K., Pearson, D.G.Contrasting textural and chemical signatures of chromitites in the Mesoarchean Ulamertoq peridotite body, southern West Greenland.MDPI Geosciences, Researchgate 19p.Europe, Greenlandperidotite

Abstract: Peridotites occur as lensoid bodies within the Mesoarchaean orthogneiss in the Akia terrane of Southern West Greenland. The Ulamertoq peridotite body is the largest of these peridotites hosted within the regional orthogneiss. It consists mainly of olivine, orthopyroxene, and amphibole-rich ultramafic rocks exhibiting metamorphic textural and chemical features. Chromitite layers from different localities in Ulamertoq show contrasting characteristics. In one locality, zoned chromites are hosted in orthopyroxene-amphibole peridotites. Compositional zonation in chromites is evident with decreasing Cr and Fe content from core to rim, while Al and Mg increase. Homogeneous chromites from another locality are fairly uniform and Fe-rich. The mineral chemistry of the major and accessory phases shows metamorphic signatures. Inferred temperature conditions suggest that the zoned chromites, homogeneous chromites, and their hosts are equilibrated at different metamorphic conditions. In this paper, various mechanisms during the cumulus to subsolidus stages are explored in order to understand the origin of the two contrasting types of chromites.
DS201810-2370
2018
Pearson, D.G.Ranger, I.M., Heaman, L.M., Pearson, D.G., Muntener, C., Zhuk, V.Punctuated, long lived emplacement history of the Renard 2 kimberlite, Canada, revealed by new high precision U-Pb groundmass perovskite dating. IF-TIMSMineralogy and Petrology, doi.org/101007/ s00710-018-0629-0 13p.Canada, Quebecdeposit - Renard

Abstract: Kimberlites are rare volatile-rich ultramafic magmas thought to erupt in short periods of time (<1 Myr) but there is a growing body of evidence that the emplacement history of a kimberlite can be significantly more protracted. In this study we report a detailed geochronology investigation of a single kimberlite pipe from the Renard cluster in north-central Québec. Ten new high precision ID-TIMS (isotope dilution - thermal ionization mass spectrometry) U-Pb groundmass perovskite dates from the main pipe-infilling kimberlites and several small hypabyssal kimberlites from the Renard 2 pipe indicate kimberlite magmatism lasted at least ~20 Myr. Two samples of the main pipe-infilling kimberlites yield identical weighted mean 206Pb/238U perovskite dates with a composite date of 643.8?±?1.0 Myr, interpreted to be the best estimate for main pipe emplacement. In contrast, six hypabyssal kimberlite samples yielded a range of weighted mean 206Pb/238U perovskite dates between ~652-632 Myr. Multiple dates determined from these early-, syn- and late-stage small hypabyssal kimberlites in the Renard 2 pipe demonstrate this rock type (commonly used to date kimberlites) help to constrain the duration of kimberlite intrusion history within a pipe but do not necessarily reliably record the emplacement age of the main diatreme in the Renard cluster. Our results provide the first robust geochronological data on a single kimberlite that confirms the field relationships initially observed by Wagner (1914) and Clement (1982); the presence of antecedent (diatreme precursor) intrusions, contemporaneous (syn-diatreme) intrusions, and consequent (post-diatreme) cross-cutting intrusions. The results of this detailed U-Pb geochronology study indicate a single kimberlite pipe can record millions of years of magmatism, much longer than previously thought from the classical viewpoint of a rapid and short-duration emplacement history.
DS201812-2773
2018
Pearson, D.G.Ali, H., Regier, M.E., Pearson, D.G.Increased recovery of diamonds from eclogite by electrical pulse disaggregation. SELFRAG2018 Yellowknife Geoscience Forum , p. 91-92. abstractAfrica, South Africadeposit - Roberts Victor

Abstract: It is well known that mechanical disaggregation, such as jaw crushing, can cause irreversible damage to valuable gemstones hosted in crystalline rocks. The SELFRAG Lab device uses electrical pulses at high voltages - typically between 150 and 200 kV - to separate material into individual grains along natural boundaries. The purpose of this research is to assess the viability of the SELFRAG as a tool to disaggregate diamond-bearing eclogites, and to assess if this method preserves grains that would otherwise be damaged through mechanical disaggregation. In order to test the applicability of the SELFRAG to diamond recovery from mechanically strong diamond-bearing lithologies, we studied its effects on a diamondiferous eclogite, RV09, from Roberts Victor mine. The Roberts Victor mine is located in South Africa and is renowned for its unusually high abundance of mantle-derived eclogite xenoliths1. Before the eclogite was disaggregated, we bisected the sample and used a CT scan to determine its constituent minerals and the spatial distribution of diamond. One half of the sample was then placed into the SELFRAG, where it was subjected to ~100 shots of 200 kV electrical discharges that segregated the sample into individual grains of similar sizes. The other half was jaw crushed, using a steel jaw crusher which produced non-uniform composite grains and abundant fine material. The varying sizes and aggregate pieces made it difficult to pick diamonds, and after no diamonds were found, the jaw-crushed portion underwent further disaggregation in the SELFRAG. After exerting the same time and effort picking through both portions of the RV09 sample, ten diamonds were recovered from the electronically disaggregated portion, while no diamonds were found in the conventionally disaggregated sample. The diamonds released from the SELFRAG were then imaged with a scanning electron microscope (SEM) to determine the extent to which the diamonds were damaged. Most of the released diamonds showed no evidence of breakage, but a few showed signs of damage that may have occurred prior to kimberlite eruption. The dramatic disparity between the number of diamonds recovered with the SELFRAG and the lack of diamonds in the jaw crushed portion indicates that electrical disaggregation is a superior method compared to the conventional mechanical comminution technique. There are little to no signs of breakage in the SELFRAG-liberated diamonds, whereas, the damage caused by jaw crushing was extensive enough to produce small fragments not readily visible via optical microscopy. The SELFRAG is a promising alternative to conventional disaggregation and offers a practical solution for lessening damage to valuable stones in rocks such as eclogites and kimberlites.
DS201812-2784
2018
Pearson, D.G.Bulanova, G.P., Smith, C.B., Pearson, D.G., Kohn, S.C., Davy, A.T., McKay, A., Marks, A.Murowa deposit: Diamonds from the Murowa kimberlites: formation within extremely depleted and metasomatized Zimbabwean peridotitic subcontinental mantle.Society of Economic Geology Geoscience and Exploration of the Argyle, Bunder, Diavik, and Murowa Diamond Deposits, Special Publication no. 20, pp. 425-Africa, Zimbabwedeposit - Murowa
DS201812-2813
2018
Pearson, D.G.Gruber, B.H., Chacko, T., Pearson, D.G.The thermochemical conditions of the Diavik lower crust: a kimberlite-hosted xenolith study.2018 Yellowknife Geoscience Forum , p. 25-26. abstractCanada, Northwest Territoriesdeposit - Diavik

Abstract: Thermochemical variables such as lower crustal heat production and Moho temperatures in cratonic regions offer critical insight in constraining the thermal and geodynamic evolution of the lithosphere. In this study, 15 lower crustal granulite xenoliths erupted via the A154N kimberlite at the Diavik mine in the NWT, Canada were studied to quantify the thermal properties of the local Moho and the effects of different heat production models on geotherm models. We quantitatively constrain the thermal properties of the local Moho and the effects of different heat production models on ancient Moho temperatures, the effects of crustal thickness on Moho temperatures, and potential lower crustal compositions. We evaluate the effect of these parameters on total lithospheric thickness estimates. In order to test the accuracy of deep crust thermal calculations, we estimated the ambient temperature of the lower crust at the time of kimberlite eruption through garnet-biotite Fe-Mg exchange geothermometry (Ferry & Spear, 1978). Rim compositions from touching garnet-biotite pairs were used in the calculations and yielded temperatures of 524 ± 77°C (n=20). These represent a maximum estimate of the ambient lower crustal temperature as the closure temperature of garnet-biotite Fe-Mg exchange between garnet and biotite may be higher than the ambient temperature. The primary objective of this study is to quantify lower crustal heat production and its effects on the thermal architecture of cratons. The concentrations of the main heat-producing elements (HPEs) U, Th, and K were quantified via LA-ICP-MS and EPMA in multiple mineral phases per xenolith. By combining these measurements with mineral modes, we derived reconstructed bulk-rock HPE concentrations that were utilized to calculate a range of lower crustal heat production values. This method is preferred over whole-rock analyses as 1) kimberlite is generally enriched in HPEs (Tappe et al. 2013) and can bias trace-element data for their xenoliths and 2) data on individual minerals allows for theoretical lower crustal compositions to be calculated on an idealized basis. A lower crust comprising exclusively mafic granulite (garnet, plagioclase, clinopyroxene ± orthopyroxene) provides a lower bound to heat production (0.07 ± 0.04 W/m3) whereas a lower crust made exclusively of high-grade metasedimentary rocks yields an upper bound (0.42 ± 0.08 W/m3). Both endmembers are present as xenoliths in the A154N kimberlite but mafic granulites predominate following the worldwide trend (Rudnick, 1992). We model the lower crust comprising 20% metasedimentary granulites and 80 % depleted mafic granulites, in accordance with the present xenolith collection. Using this preferred crustal model, we calculate an average heat production of 0.12 ± 0.05 W/m3) for the lower crust beneath Lac de Gras. Utilizing heat flow measurements (Russell et thickness estimates (Mareschal et al. 2004) in conjunction with these HPE determinations, the Moho temperature underlying A-154N can be calculated to be 502 ± 10°C. Using these values along with available mantle xenolith thermobaromtetry (Hasterok & Chapman, 2011) the geotherm is extrapolated to present a mantle potential temperature of 1365°C, at 200 km (FITPLOT, Mather et al, 2011).
DS201812-2822
2018
Pearson, D.G.Jaques, A.L., Luguet, A., Smith, C.B., Pearson, D.G., Yaxley, G.M., Kobussen, A.F.Argyle deposit: Nature of the mantle beneath the Argyle AK1 lamproite pipe: constraints from mantle xenoliths, diamonds, and lamproite geochemistry.Society of Economic Geology Geoscience and Exploration of the Argyle, Bunder, Diavik, and Murowa Diamond Deposits, Special Publication no. 20, pp. 119-144.Australia, western Australiadeposit - Argyle
DS201812-2831
2018
Pearson, D.G.Krebs, M.Y., Pearson, D.G., Stachel, T., Laiginhas, F., Woodland, S., Chinn, I., Kong, J.A common parentage - Low abundance trace element data of gem diamonds reveals similar fluids to fibrous diamonds. ( silicate/sulphide)Lithos, doi.org/10.1016/ jlithos.2018.11.025 49p.Canada, Ontario, Attawapiskat, Africa, South Africadeposit - Victor, Finsch, Newlands

Abstract: Quantitative trace element data from high-purity gem diamonds from the Victor Mine, Ontario, Canada as well as near-gem diamonds from peridotite and eclogite xenoliths from the Finsch and Newlands mines, South Africa, acquired using an off-line laser ablation method show that we see the same spectrum of fluids in both high-purity gem and near-gem diamonds that was previously documented in fibrous diamonds. “Planed” and “ribbed” trace element patterns characterize not only the high-density fluid (HDF) inclusions in fibrous diamonds but also in gem diamonds. Two diamonds from two Finsch harzburgite xenoliths show trace element patterns similar to those of saline fluids, documenting the involvement of saline fluids in the precipitation of gem diamonds, further strengthening the link between the parental fluids of both gem and fibrous diamonds. Differences in trace element characteristics are evident between Victor diamonds containing silicate inclusions compared with Victor diamonds containing sulphide inclusions. The sulphide-bearing diamonds show lower levels of inter-element fractionation and more widely varying siderophile element concentrations - indicating that the silicate and sulphide-bearing diamonds likely formed by gradations of the same processes, via melt-rock reaction or from a subtly different fluid source. The shallow negative LREEN-HREEN slopes displayed by the Victor diamonds establish a signature indicative of original derivation of the diamond forming agent during major melting (~10% melt). Consequently, this signature must have been passed on to HDFs separating from such silicate melts.
DS201812-2860
2018
Pearson, D.G.Pearson, D.G., Liu, J., Smith, C.B., Mather, K.A., Krebs, M.Y., Bulanova, G.P., Kobussen, A.F.Murowa deposit: Characteristics and origin of the mantle root beneath the Murowa diamond mine: implications for craton and diamond formation.Society of Economic Geology Geoscience and Exploration of the Argyle, Bunder, Diavik, and Murowa Diamond Deposits, Special Publication no. 20, pp. 403-424.Africa, Zimbabwedeposit - Murowa
DS201812-2867
2018
Pearson, D.G.Poitras, S.P., Pearson, D.G., Hardman, M.F., Stachel, T., Nowell, G.M.Evidence for a 200 km thick diamond bearing root beneath the Central Mackenzie Valley, Northwest Territories, Canada? Diamond indicator mineral geochemistry from the Horn Plateau and Trout Lake regions.Mineralogy and Petrology, doi.org/10.1007/ s00710-018-0641-4 18p.Canada, Northwest Territoriesindicator minerals, geocthermobarometry

Abstract: The Central Mackenzie Valley (CMV) area of Northwest Territories is underlain by Precambrian basement belonging to the North American Craton. The potential of this area to host kimberlitic diamond deposits is relatively high judging from the seismologically-defined lithospheric thickness, age of basement rocks (2.2-1.7 Ga) and presence of kimberlite indicator minerals (KIMs) in Quaternary sediments. This study presents data for a large collection of KIMs recovered from stream sediments and till samples from two study areas in the CMV, the Horn Plateau and Trout Lake. In the processed samples, peridotitic garnets dominate the KIM grain count for both regions (> 25% each) while eclogitic garnet is almost absent in both regions (< 1% each). KIM chemistry for the Horn Plateau indicates significant diamond potential, with a strong similarity to KIM systematics from the Central and Western Slave Craton. The most significant issue to resolve in assessing the local diamond potential is the degree to which KIM chemistry reflects local and/or distal kimberlite bodies. Radiogenic isotope analysis of detrital kimberlite-related CMV ilmenite and rutile grains requires at least two broad age groups for eroded source kimberlites. Statistical analysis of the data suggests that it is probable that some of these KIMs were derived from primary and/or secondary sources within the CMV area, while others may have been transported to the area from the east-northeast by Pleistocene glacial and/or glaciofluvial systems. At this stage, KIM chemistry does not allow the exact location of the kimberlitic source(s) to be constrained.
DS201812-2870
2018
Pearson, D.G.Regier, M.E., Pearson, D.G., Stachel, T., Stern, R.A., Harris, J.Tracing the formation and abundance of superdeep diamonds.2018 Yellowknife Geoscience Forum , p. 63. abstractAfrica, Guineadeposit - Kankan

Abstract: Super-deep diamonds from the transition zone and lower mantle are valuable targets for mining, as they are often large, gem-quality1 or ultra-valuable type IIb stones2. Hence, in mine prospects, it may become important to determine the various populations of sub-lithospheric diamonds. Unambiguously identifying a diamond’s depth of formation is difficult as some minerals can be indicative of various depth regimes (e.g., ferropericlase, Ca-walstromite, enstatite, clinopyroxene, coesite). Here, we use the oxygen isotope compositions of inclusions in Kankan diamonds from Guinea to distinguish between the various diamond-forming processes that happen at lithospheric, asthenospheric to transition zone, and lower mantle depths. In this way, we hope to establish a process by which isotope geochemistry can better constrain the populations of superdeep diamonds in kimberlites, and can assist in estimating a pipe’s propensity for large, valuable stones. Oxygen isotopic analysis by secondary ion mass spectrometry (SIMS) is a high-precision technique that can track hydrothermal alteration that occurred at or close below the ocean floor. Our analyses of inclusions from Kankan diamonds demonstrate that garnets with 3-3.03 Si cations (pfu) have d18O that are well-constrained within the normal values expected for peridotitic and eclogitic inclusions, but that garnets with =3.04 Si cations (pfu) have consistently high d18O (median: 10‰) that slightly decreases with increasing Cr2O3. We interpret this signal as the reaction between a melted carbonate-rich oceanic slab and normal convecting asthenosphere3. In contrast, retrogressed, or former, bridgmanite has d18O values similar to primitive mantle, suggesting little involvement of slab melts. In contrast to the worldwide suite of lithospheric inclusions of eclogitic paragenesis (median d18O of 7.03‰)4,5, diamonds derived from ~250 to 500 km have inclusions with consistent, extremely high oxygen isotopes (median: 9.32‰)6,7, due to the melting of extremely enriched carbonated oceanic crust. Diamonds from the lower mantle, however, have inclusions with primitive mantle oxygen isotopes, suggesting a different formation process. The clear distinction in inclusion d18O between lithospheric, asthenospheric to transition zone, and lower mantle diamond populations is useful in informing the depth regime of a suite of stones, especially those with inclusions of ambiguous depths (e.g., clinopyroxene, coesite, Ca-walstromite, enstatite, ferropericlase, etc.). For instance, we are currently searching for exotic oxygen isotopes in ferropericlase that indicate asthenospheric diamond growth, rather than the primitive mantle values expected for lower mantle ferropericlase. In conclusion, oxygen isotopic analyses of diamond inclusions can identify various sublithsopheric diamond populations, and may benefit the assessment of a mine’s potential for large gem-quality, or type IIb diamonds.
DS201812-2884
2018
Pearson, D.G.Siva-Jothy, W., Chinn, I., Stachel, T., Pearson, D.G.Resorption features of macro and micro diamonds from Gahcho Kue.2018 Yellowknife Geoscience Forum , p. 120. abstractCanada, Northwest Territoriesdeposit - Gahcho Kue

Abstract: Studies into the relationship between oxygen fugacity of mantle fluids/melts and etch features on diamond surfaces have shown specific fluid/melt compositions correspond to associated etch features. A classification scheme has been proposed to determine the fluid composition within a kimberlite by examining etch features associated with diamond surfaces as a proxy for fluid composition in an ascending diamondiferous kimberlite. A suite of 388 microdiamonds (defined as diamonds which pass through a 0.5 mm square mesh screen) and 88 macrodiamonds taken from various drill hole depths in the Hearne kimberlite and 88 inclusion-bearing macrodiamonds from the Gahcho Kué mine (NWT) were viewed under a secondary electron microscope for their surface features in accordance with this scheme. Two hundred and thirty specimens show shallow-depth etch features that can be easily classified: the main features observed were trigons and truncated trigons on the {111} faces and/or tetragons on the {100} faces (indicating etching by fluids of variable CO2:H2O ratios). Thirty-four specimens show deeper etched features that represent either extreme degrees of regular etching (such as deeply-etched tetragons), or corrosion type etching, wherein the diamond lattice is etched in a fluid-free melt. Variability between crystal habits exists between the size fractions studied, with cubic habits only being observed in the microdiamond population. This implies variable formation conditions for the two different diamond size fractions studied from Gahcho Kué. Among microdiamonds, surface textures associated with fluid-related etching are markedly more variable, with truncated trigons, tetragons, and both positive and negative trigons being observed. However, these often occur in combination with features showing a large variability in their depth to size ratio between samples, which is typically caused by mantle-related etching. These observations suggest repeated interaction of fluids/melts with the Gahcho Kué diamond population, with at least some of the fluids affecting the microdiamonds being more CO2-rich than those that etched the macrodiamond fraction.
DS201901-0054
2018
Pearson, D.G.Pearson, D.G.Modern advances in the understanding of diamond formation. KeynoteGems & Gemology, Sixth International Gemological Symposium Vol. 54, 3, 1p. Abstract p. 270.Globaldiamond genesis

Abstract: For the past 50 years, the majority of diamond research has focused on diamonds derived from the lithospheric mantle root underpinning ancient continents. While lithospheric diamonds are currently thought to form the mainstay of the world’s economic production, the continental mantle lithosphere reservoir comprises only ~2.5% of the total volume of Earth. Earth’s upper mantle and transition zone, extending from beneath the lithosphere to a depth of 670 km, occupy a volume approximately 10 times larger. Diamonds from these deeper parts of the earth—“superdeep diamonds”—are more abundant than previously thought. They appear to dominate the high-value large diamond population that comes to market. Recent measurements of the carbon and nitrogen isotope composition of superdeep diamonds from Brazil and southern Africa, using in situ ion probe techniques, show that they document the deep recycling of volatile elements (C, N, O) from the surface of the earth to great depths, at least as deep as the uppermost lower mantle. The recycled crust signatures in these superdeep diamonds suggest their formation in regions of subducting oceanic plates, either in the convecting upper mantle or the transition zone plus lower mantle. It is likely that the deep subduction processes involved in forming these diamonds also transport surficial hydrogen into the deep mantle. This notion is supported by the observation of a high-pressure olivine polymorph—ringwoodite—with close to saturation levels of water. Hence, superdeep dia­monds document a newly recognized, voluminous “diamond factory” in the deep earth, likely producing diamonds right up to the present day. Such diamonds also provide uniquely powerful views of how crustal material is recycled into the deep earth to replenish the mantle’s inventory of volatile elements. The increasing recognition of superdeep diamonds in terms of their contribution to the diamond economy opens new horizons in diamond exploration. Models are heavily influenced by the search for diamonds associated with highly depleted peridotite (dunites and harzburgites). Such harzburgitic diamonds were formed in the Archean eon (>2.5 Ga) within lithospheric mantle of similar age. It is currently unclear what the association is between these ancient lithospheric diamonds and large, high-value diamonds, but it is likely a weak one. In contrast, the strong association between superdeep diamonds and these larger stones opens up a new paradigm because the available age constraints for superdeep diamonds indicate that they are much younger than the ancient lithospheric diamonds. Their younger age means that superdeep diamonds may be formed in non-Archean mantle, or mantle that has been strongly overprinted by post-Archean events that would otherwise be deemed unfavorable for the preservation of ancient lithospheric diamonds. An additional factor in the search for new diamond deposits is the increasing recognition that major diamond deposits can form in lithospheric mantle that is younger than—or experienced major thermal disruption since—the canonical 2.5 billion years usually thought to be most favorable for diamond production. This talk will explore these new dimensions in terms of the potential for discovering new diamond sources in “unconventional” settings.
DS201901-0076
2018
Pearson, D.G.Shirey, S.B., Pearson, D.G.How to obtain and interpret diamond ages.Gems & Gemology, Sixth International Gemological Symposium Vol. 54, 3, 1p. Abstract p. 272-3.Africa, Sierra Leonegeochronology

Abstract: Diamond ages are obtained from radiogenic isotopic analysis (Rb-Sr, Sm-Nd, Re-Os, and Ar-Ar) of mineral inclusions (garnet, pyroxene, and sulfide). As diamonds are xenocrysts that cannot be dated directly, the ages obtained on mineral inclusions provide a unique set of interpretive challenges to assure accuracy and account for preexisting history. A primary source of geological/mineralogical uncertainty on diamond ages is any process affecting protogenetic mineral inclusions before encapsulation in the diamond, especially if it occurred long before diamond formation. In practical application, the isotopic systems discussed above also carry with them inherent systemic uncertainties. Isotopic equilibrium is the essential condition required for the generation of a statistically robust isochron. Thus, isochron ages from multiple diamonds will record a valid and accurate age when the diamond-forming fluid promotes a large degree of isotopic equilibrium across grain scales, even for preexisting (“protogenetic”) minerals. This clearly can and does occur. Furthermore, it can be analytically tested for, and has multiple analogues in the field of dating metamorphic rocks. In cases where an age might be suspect, an age will be valid if its regression uncertainties can encompass a known and plausible geological event (especially one for which an association exists between that event and the source of diamond-forming fluids) and petrogenetic links can be established between inclusions on the isochron. Diamonds can be dated in six basic ways: 1. model ages 2. radiogenic daughter Os ages (common-Os-free) 3. single-diamond mineral isochrons 4. core to rim ages 5. multiple single-diamond isochron/array ages 6. composite isochron/array ages Model ages (1) are produced by the intersection between the evolution line for the inclusion and a reference reservoir such as the mantle. The most accurate single-diamond age is determined on a diamond with multiple inclusions (3). In this case an internal isochron can be obtained that not only establishes equilibrium among the multiple grains but also unequivocally dates the time of diamond growth. With extreme luck in obtaining the right diamond, concentric diamond growth zones visible in UV fluorescence or cathodoluminescence can sometimes be shown to constrain inclusions to occur in the core of the diamond and in the exterior at the rim. These single grains can be extracted to give a minimum growth time (4) for the diamond. In optimal situations, multiple inclusions are present within single growth zones, in single diamonds, allowing internal isochrons to be constructed for individual growth zones in single diamonds. If enough diamonds with inclusions can be obtained for study, valid ages for diamond populations can be obtained on multiple single-diamond ages that agree (5) or on composited, mineralogically similar inclusions to give an average age (6).
DS201901-0085
2018
Pearson, D.G.Wang, H., van Hunen, J., Pearson, D.G.Making Archean cratonic roots by lateral compression: a two stage thickening and stabilization model.Tectonophysics, Vol. 746, pp. 562-571.Mantlemelting

Abstract: Archean tectonics was capable of producing virtually indestructible cratonic mantle lithosphere, but the dominant mechanism of this process remains a topic of considerable discussion. Recent geophysical and petrological studies have refuelled the debate by suggesting that thickening and associated vertical movement of the cratonic mantle lithosphere after its formation are essential ingredients of the cratonization process. Here we present a geodynamical study that focuses on how the thick stable cratonic lithospheric roots can be made in a thermally evolving mantle. Our numerical experiments explore the viability of a cratonization process in which depleted mantle lithosphere grows via lateral compression into a > 200-km thick, stable cratonic root and on what timescales this may happen. Successful scenarios for craton formation, within the bounds of our models, are found to be composed of two stages: an initial phase of tectonic shortening and a later phase of gravitational self-thickening. The initial tectonic shortening of previously depleted mantle material is essential to initiate the cratonization process, while the subsequent gravitational self-thickening contributes to a second thickening phase that is comparable in magnitude to the initial tectonic phase. Our results show that a combination of intrinsic compositional buoyancy of the cratonic root, rapid cooling of the root after shortening, and the long-term secular cooling of the mantle prevents a Rayleigh-Taylor type collapse, and will stabilize the thick cratonic root for future preservation. This two-stage thickening model provides a geodynamically viable cratonization scenario that is consistent with petrological and geophysical constraints.
DS201902-0288
2019
Pearson, D.G.Krebs, M.Y., Pearson, D.G., Stachel, T., Laiginhas, F., Woodland, S., Chinn, I., Kong, J.A common parentage low abundance trace element data of gem diamonds reveals similar fluids to fibrous diamonds.Lithos, Vol. 324, 1, pp. 356-370.Canada, Ontario, Africa, South Africadeposit - Victor, Finsch, Newlands

Abstract: Quantitative trace element data from high-purity gem diamonds from the Victor Mine, Ontario, Canada as well as near-gem diamonds from peridotite and eclogite xenoliths from the Finsch and Newlands mines, South Africa, acquired using an off-line laser ablation method show that we see the same spectrum of fluids in both high-purity gem and near-gem diamonds that was previously documented in fibrous diamonds. "Planed" and "ribbed" trace element patterns characterize not only the high-density fluid (HDF) inclusions in fibrous diamonds but also in gem diamonds. Two diamonds from two Finsch harzburgite xenoliths show trace element patterns similar to those of saline fluids, documenting the involvement of saline fluids in the precipitation of gem diamonds, further strengthening the link between the parental fluids of both gem and fibrous diamonds. Differences in trace element characteristics are evident between Victor diamonds containing silicate inclusions compared with Victor diamonds containing sulphide inclusions. The sulphide-bearing diamonds show lower levels of inter-element fractionation and more widely varying siderophile element concentrations - indicating that the silicate and sulphide-bearing diamonds likely formed by gradations of the same processes, via melt-rock reaction or from a subtly different fluid source. The shallow negative LREEN-HREEN slopes displayed by the Victor diamonds establish a signature indicative of original derivation of the diamond forming agent during major melting (~10% melt). Consequently, this signature must have been passed on to HDFs separating from such silicate melts.
DS201902-0310
2018
Pearson, D.G.Regier, M.E., Miskovic, A., Ickert, R.B., Pearson, D.G., Stachel, T., Stern, R.A., Kopylova, M.An oxygen isotope test for the origin of Archean mantle rootsGeochemical Perspectives Letters, Vol. 9, pp. 6-10. 10.7185/geochemlet.1830Mantleperidotites

Abstract: The origin of the peridotites that form cratonic mantle roots is a central issue in understanding the history and survival of Earth’s oldest continents. A long-standing hypothesis holds that the unusual bulk compositions of some cratonic peridotites stem from their origin as subducted oceanic serpentinite, dehydrated during subduction to form rigid buoyant keels (Schulze, 1986; Canil and Lee, 2009). We present oxygen isotope data from 93 mantle peridotites from five different Archean cratons to evaluate their possible origin as serpentinites. Cratonic mantle peridotite shows remarkably uniform d18O values, identical to modern MORB-source mantle, that do not vary with bulk rock Si-enrichment or Ca-depletion. These data clearly conflict with any model for cratonic lithosphere that invokes serpentinite as a protolith for cratonic peridotite, and place additional constraints on cratonic mantle origins. We posit that the uniform d18O was produced by sub-arc and/or MOR depletion processes and that the Si-enriched nature of some samples is unlikely to be related to slab melt infiltration. Instead, we suggest a peridotitic source of Si-enrichment, derived from ascending mantle melts, or a water-fluxed depleted mantle. These variably Si-enriched, cratonic mantle protoliths were then collisionally compressed into the thick cratonic roots that have protected Earth’s oldest continental crust for over 2.5 Gyr.
DS201902-0319
2019
Pearson, D.G.Scott, J.M., Liu, J., Pearson, D.G., Harris, G.A., Czertowicz, T.A., Woodland, S.J., Riches, A.J.V., Luth, R.W.Continent stabilization by lateral accretion of subduction zone-processed depleted mantle residues: insights from Zealandia.Earth and Planetary Science Letters, Vol. 507, pp. 175-186.Mantleperidotite

Abstract: To examine how the mantle lithosphere stabilises continents, we present a synthesis of the mantle beneath Zealandia in the SW Pacific Ocean. Zealandia, Earth's “8th continent”, occurs over 4.9 M km2 and comprises a fore-arc, arc and back-arc fragment rifted from the Australia-Antarctica Gondwana margin 85 Myr ago. The oldest extant crust is ~500 Ma and the majority is Permian-Jurassic. Peridotitic rocks from most known locations reveal the underpinning mantle to comprise regional domains varying from refractory (Al2O3 < 1 wt%, olivine Mg# > 92, spinel Cr# up to 80, Pt/Ir < 1) to moderately depleted (Al2O3 = 2-4 wt%, olivine Mg# ~90.5, spinel Cr# < ~60). There is no systematic distribution of these domains relative to the former arc configuration and some refractory domains underlie crust that is largely devoid of magmatic rocks. Re-depletion Os model ages have no correlation with depletion indices but do have a distribution that is very similar to global convecting mantle. Whole rock, mineral and isotopic data are interpreted to show that the Zealandia mantle lithosphere was constructed from isotopically heterogeneous convecting mantle fragments swept into the sub-arc environment, amalgamated, and variably re-melted under low-P hydrous conditions. The paucity of mafic melt volumes in most of the overlying crust that could relate to the depleted domains requires melting to have been followed by lateral accretion either during subduction or slab rollback. Recent Australia-Pacific convergence has thickened portions of the Zealandia mantle to >160 km. Zealandia shows that the generation of refractory and/or thick continental lithosphere is not restricted to the Archean. Since Archean cratons also commonly display crust-mantle age decoupling, contain spinel peridotites with extreme Cr# numbers that require low-P hydrous melting, and often have a paucity of mafic melts relative to the extreme depletion indicated by their peridotitic roots, they too may - in part - be compilations of peridotite shallowly melted and then laterally accreted at subduction margins.
DS201903-0528
2019
Pearson, D.G.Luguet, A., Pearson, D.G.Dating mantle peridotites using Re-Os isotopes: the complex message from whole rocks, base metal sulfides, and platinum group minerals. ReviewAmerican Mineralogist, Vol. 104, pp. 165-189.Mantleperidotites

Abstract: The Re-Os isotopic system is largely considered the geochronometer of choice to date partial melting of terrestrial peridotites and in constraining the evolution of Earth's dynamics from the mantle viewpoint. While whole-rock peridotite Re-Os isotopic signatures are the core of such investigations, the Re-Os dating of individual peridotite minerals—base metal sulfides (BMS) and platinum group minerals (PGM)—that are the main hosts for Re and Os in the mantle peridotites came into play two decades ago. These nanometric-micrometric BMS and PGM display an extreme complexity and heterogeneity in their 187Os/188Os and 187Re/188Os signatures that result from the origin of the BMS±PGM grains (residual vs. meta-somatic), the nature of the metasomatic agents, the transport/precipitation mechanisms, BMS±PGM mineral-ogy, and subsequent Re/Os fractionation. Corresponding whole-rock host peridotites, typically plot within the 187Os/188Os and 187Re/188Os ranges defined by the BMS±PGM, clearly demonstrating that their Re-Os signatures represent the average of the different BMS±PGM populations. The difference between the 187Os/188Os ratios of the least radiogenic BMS±PGM and the respective host peridotite increases with the fertility of the peridotite reflecting the increasing contribution of metasomatic BMS±PGM to the whole-rock mass balance of Re and Os concentrations and Os isotope compositions. Corollaries to these observations are that (1) BMS may provide a record of much older partial melting event, pushing back in time the age of the lithospheric mantle stabilization, (2) if only whole-rock peridotite Re-Os isotopic measurements are possible, then the best targets for constraining the timing of lithospheric stabilization are BMS-free/BMS-poor ultra-refractory spinel-bearing peridotites with very minimal metasomatic overprint, as their 187Os/188Os signatures may be geologically meaningful, (3) while lherzolites are “fertile” in terms of their geochemical composition, they do not have a “primitive,” unmodified composition, certainly in terms of their highly siderophile elements (HSE) and Re-Os isotopic systematics, and (4) the combined Re-Os isotopic investigations of BMS and whole-rock in BMS-rich mantle peridotites would provide a complementary view on the timing and nature of the petrological events responsible for the chemical and isotopic evolution and destruction of the lithospheric mantle. In addition, the 187Os/188Os composition of the BMS±PGM (both residual and metasomatic) within any single peridotite may define several age clusters—in contrast to the single whole-rock value—and thus provide a more accurate picture of the complex petrogenetic history of the lithospheric mantle. When coupled with a detailed BMS±PGM petrographical study and whole-rock lithophile and HSE systematics, these BMS age clusters highlight the timing and nature of the petrological events contributing to the formation and chemical and isotopic evolution of the lithospheric mantle. These BMS±PGM age clusters may match regional or the local crustal ages, suggesting that the formation and evolution of the lithospheric mantle and its overlying crust are linked, providing mirror records of their geological and chemical history. This is, however, not a rule of thumb as clear evidence of crust-mantle age decoupling also exist. Although the BMS±PGM Re-Os model ages push back in time the stabilization of lithospheric mantle, the dichotomy between Archean cratonic and circum-cratonic peridotites, and post-Archean non-cratonic peridotites and tectonites is preserved. This ability of BMS±PGM to preserve older ages than their host peridotite also underscores their survival for billions of years without being reset or reequilibrated despite the complex petrogenetic processes recorded by their host mantle peridotites. As such, they are the mantle equivalents of crustal zircons. Preservation of such old signatures in “young” oceanic peridotites ultimately rules out the use of the Re-Os signatures in both oceanic peridotites and their BMS to estimate the timescales of isotopic homogenization of the convecting mantle.
DS201904-0761
2019
Pearson, D.G.Nicklas, R.W., Puchtel, I.S., Ash, R.D., Piccoli, P.M., Hanski, M., Eero, Nisbet, E.G., Waterton, P., Pearson, D.G., Anbar, A.D.Secular mantle oxidation across the Archean - Proterozoic boundary: evidence from V partitioning in komatiites and picrites.Geochimica et Cosmochimica Acta, Vol. 250, 1, pp. 49-75.Mantlepicrites

Abstract: The oxygen fugacities of nine mantle-derived komatiitic and picritic systems ranging in age from 3.55?Ga to modern day were determined using the redox-sensitive partitioning of V between liquidus olivine and komatiitic/picritic melt. The combined set of the oxygen fugacity data for seven systems from this study and the six komatiite systems studied by Nicklas et al. (2018), all of which likely represent large regions of the mantle, defines a well-constrained trend indicating an increase in oxygen fugacity of the lavas of ~1.3 ?FMQ log units from 3.48 to 1.87?Ga, and a nearly constant oxygen fugacity from 1.87?Ga to the present. The oxygen fugacity data for the 3.55?Ga Schapenburg komatiite system, the mantle source region of which was previously argued to have been isolated from mantle convection within the first 30?Ma of the Solar System history, plot well above the trend and were not included in the regression. These komatiite’s anomalously high oxygen fugacity data likely reflect preservation of early-formed magma ocean redox heterogeneities until at least the Paleoarchean. The observed increase in the oxygen fugacity of the studied komatiite and picrite systems of ~1.3 ?FMQ log units is shown to be a feature of their mantle source regions and is interpreted to indicate secular oxidation of the mantle between 3.48 and 1.87?Ga. Three mechanisms are considered to account for the observed change in the redox state of the mantle: (1) recycling of altered oceanic crust, (2) venting of oxygen from the core due to inner core crystallization, and (3) convection-driven homogenization of an initially redox-heterogeneous primordial mantle. It is demonstrated that none of the three mechanisms alone can fully explain the observed trend, although mechanism (3) is best supported by the available geochemical data. These new data provide further evidence for mantle involvement in the dramatic increase in the oxygen concentration of the atmosphere leading up to the Great Oxidation Event at ~2.4?Ga.
DS201905-1037
2019
Pearson, D.G.Guotana, J.M., Morishita, T., Yamaguschi, R., Nishio, I., Tamura, A., Tani, K., Harigane, Y., Szilas, K., Pearson, D.G.Contrasting textural and chemical signatures of chromitites in the Mesoarchean Ulamertoq peridotite body, southern west Greenland.Geosciences ( MDPI), Vol. 8, 328- 19p.Europe, Greenlandchromitite

Abstract: Peridotites occur as lensoid bodies within the Mesoarchaean orthogneiss in the Akia terrane of Southern West Greenland. The Ulamertoq peridotite body is the largest of these peridotites hosted within the regional orthogneiss. It consists mainly of olivine, orthopyroxene, and amphibole-rich ultramafic rocks exhibiting metamorphic textural and chemical features. Chromitite layers from different localities in Ulamertoq show contrasting characteristics. In one locality, zoned chromites are hosted in orthopyroxene-amphibole peridotites. Compositional zonation in chromites is evident with decreasing Cr and Fe content from core to rim, while Al and Mg increase. Homogeneous chromites from another locality are fairly uniform and Fe-rich. The mineral chemistry of the major and accessory phases shows metamorphic signatures. Inferred temperature conditions suggest that the zoned chromites, homogeneous chromites, and their hosts are equilibrated at different metamorphic conditions. In this paper, various mechanisms during the cumulus to subsolidus stages are explored in order to understand the origin of the two contrasting types of chromites.
DS201905-1073
2019
Pearson, D.G.Reimink, J.R., Pearson, D.G., Shirey, S.B., Carlson, R.W., Ketchum, J.W.F.Onset of new, progressive crustal growth in the central Slave craton at 3.55 Ga.Geochemical Perspective Letters, Vol. 10, pp. 8-13. doi:10.7185/ geochemlet.1907Canada, Northwest Territoriesmagmatism

Abstract: Ancient rock samples are limited, hindering the investigation of the processes operative on the Earth early in its history. Here we present a detailed study of well-exposed crustal remnants in the central Slave craton that formed over a 1 billion year magmatic history. The tonalitic-granodioritic gneisses analysed here are broadly comparable to common suites of rocks found in Archean cratons globally. Zircon Hf isotope data allow us to identify a major change in the way continental crust was formed in this area, with a shift to distinctly positive eHf starting at ~3.55 Ga. The crust production processes and spatial distribution of isotopic compositions imply variable interaction with older crust, similar to the relationships seen in modern tectonic settings; specifically, long-lived plate margins. A majority of the Slave craton might have been formed by a similar mechanism.
DS201906-1305
2019
Pearson, D.G.Kopylova, M., Tso, E., Ma, F., Liu, J., Pearson, D.G.From regional to local metasomatism in the peridotitic mantle of the Chidliak kimberlite province ( Southern Baffin Island).GAC/MAC annual Meeting, 1p. Abstract p. 124.Canada, Baffin Islanddeposit - Chidliak

Abstract: We studied the petrography, mineralogy, thermobarometry and whole rock chemistry of 120 peridotite and pyroxenite xenoliths collected from the 156 - 138 Ma Chidliak kimberlites CH-1, -6, -7 and -44. The xenoliths have higher CaO contents relative to Al2O3, and high Al for a given Mg/Si ratio compared to other cratonic peridotites. We assign the complex Ca-Al systematics of the Chidliak peridotites to repeated episodes of Ca-rich, Si-poor metasomatism, which introduced clinopyroxene and garnet, and later replaced orthopyroxene and clinopyroxene with secondary clinopyroxene and monticellite. This carbonatitic metasomatism, manifest in formation of wehrlites, acted upon the entire sampled mantle depth on a regional scale, including the proximal blocks of the North Atlantic Craton and the Chidliak mantle, where clinopyroxene and garnet modes are uniformly and heterogeneously high in the ~ 110 km deep mantle segment. Another, more recent type of mantle metasomatism, is expressed as elevated Ti in clinopyroxene and elevated Na and Ti in garnet, typical of sheared peridotites from CH-1, -7, and -44, but absent from CH-6 xenolith suite. The Ti-Na imprint is most intense in xenoliths derived from depths equivalent to 5.5 to 6.5 GPa, where it is associated with higher strain, the presence of sheared peridotites and higher temperatures varying isobarically by up to 200 °C. The horizontal scale of the thermal-metasomatic imprint is more ambiguous and could be as regional as 10's of kilometers or as local as < 1 km. The latter is constrained by the varied abundance of Ti-enriched garnets within a single kimberlite. The time-scale of this metasomatism relates to a conductive length-scale and could be as short as 100's ka, shortly predating the kimberlite formation. The Ti-Na, megacryst-like metasomatism may have resulted from a highly localized influx of hot hydrous proto-kimberlite fluids that weakened the mantle and triggered the formation of sheared peridotites.
DS201906-1314
2019
Pearson, D.G.Li, K., Li, L., Pearson, D.G., Stachel, T.Diamond isotope compositions indicate altered igneous oceanic crust dominates deep carbon recycling. Earth and Planetary Science Letters, Vol. 516, pp. 190-201.Mantlecarbon

Abstract: A long-standing unresolved problem in understanding Earth's deep carbon cycle is whether crustal carbon is recycled beyond arc depths. While isotopic signatures of eclogitic diamonds and their inclusions suggest deep recycling of crustal material, the crustal carbon source remains controversial; seafloor sediment - the widely favored crustal carbon source - cannot explain the combined carbon and nitrogen isotopic characteristics of eclogitic diamonds. Here we examined the carbon and oxygen isotopic signatures of bulk-rock carbonate for 80 geographically diverse samples from altered mafic-ultramafic oceanic crust (AOC), which comprises 95 vol% of the crustal material in subducting slabs. The results show: (i) AOC contains carbonate with C values as low as -24‰, indicating the presence of biogenic carbonate; (ii) carbonate in AOC was mainly formed during low-temperature (<100 °C) alteration processes. Modeling accounting for this newly recognized carbon source in the oceanic crust with formation temperatures <100 °C yields a global carbon influx of 1.5±0.3 × 1012 mol C/yr carried by subducting AOC into the trench, which is 50-90% of previous estimates, but still of the same order of the carbon influx carried by subducting sediments into the trench. The AOC can retain carbon better than sediment during subduction into the asthenosphere, transition zone and lower mantle. Mixing of asthenospheric and AOC fluids provides the first consistent explanation of the diverse record of carbon and nitrogen isotopes in diamonds, suggesting that AOC, instead of sediment, is the key carrier of crustal carbon into the deep mantle.
DS201906-1354
2019
Pearson, D.G.Timmerman, S., Krebs, M.Y., Pearson, D.G., Honda, M.Diamond forming media through time - trace element and noble gas systematics of diamonds formed over 3 billion years of Earth's history.Geochimica et Cosmochimica Acta, in press available 29p.Africa, South Africa, Botswanadeposit - Koffiefontein, Letlhakane, Orapa, Finsch, De Beers Pool

Abstract: Ten individual gem-quality monocrystalline diamonds of known peridotite/eclogite paragenesis from Southern Africa (Koffiefontein, Letlhakane, Orapa) were studied for trace element concentrations and He and Ar abundances and isotopic compositions. In addition, two samples, consisting of pooled fragments of gem-quality peridotitic diamonds from Finsch and DeBeers Pool respectively, were analysed for noble gases. Previous studies (Richardson et al., 1984; Pearson et al., 1998; Gress et al., 2017; Timmerman et al., 2017) provided age constraints of 0.09, 1.0-1.1, 1.7, 2.3, and 3.2-3.4?Ga on mineral inclusions in the studied diamonds, allowing us to study trace elements and noble gases over 3 Gyr of geological time. Concentrations of trace elements in the diamonds are very low - a few hundred ppt to several tens of ppbs - and are likely dependent on the amount of sub-micron inclusions present. Trace element patterns and trace element/3He ratios of the studied monocrystalline diamonds are similar to those in fibrous diamonds, suggesting that trace elements and stable noble gas isotopes reside within the same locations in diamond and track the same processes that are reflected in the trace element patterns. We cannot discern any temporal differences in these geochemical tracers, suggesting that the processes generating them have been occurring over at least the past 2.3?Ga. 3He/4He ratios decrease and 4He and 40Ar* contents increase with increasing age of peridotitic and some eclogitic diamonds, showing the importance of in-situ radiogenic 4He and 40Ar ingrowth by the decay of U-Th-Sm and K respectively. For most gem-quality monocrystalline diamonds, uncertainties in the 3He/4He evolution of the continental lithospheric mantle combined with large analytical uncertainties and possible spatial variability in U-Th-Sm concentrations limit our ability to provide estimates of diamond formation ages using 4He ingrowth. However, the limited observed 4He ingrowth (low U?+?Th/3He) together with a R/Ra value of 5.3 for peridotitic diamond K306 is comparable to the present-day sub-continental lithospheric mantle value and supports the young diamond formation age found by Re-Os dating of sulphides in the same diamond by Pearson et al. (1998). After correction for in-situ radiogenic 4He produced since diamond formation a large variation in 3He/4He remains in ~1?Ga old eclogitic diamonds that is suggested to result from the variable influence of subducted altered oceanic crust that has low 3He/4He. Hence, the 3He/4He isotope tracer supports an origin of the diamond-forming fluids from recycled oceanic crust for eclogitic diamonds, as indicated by other geochemical proxies.
DS201906-1355
2019
Pearson, D.G.Timmerman, S., Yeow, H., Honda, M., Howell, D., Jaques, A.L., Krebs, M.Y., Woodland, S., Pearson, D.G., Avila, J.N., Ireland, T.R.U-Th/He systematics of fluid rich 'fibrous' diamonds - evidence for pre- and syn-kimberlite eruption ages.Chemical Geology, Vol. 515, pp. 22-36.Africa, Democratic Republic of Congo, Botswanadeposit - Jwaneng

Abstract: The physical characteristics and impermeability of diamonds allow them to retain radiogenic 4He produced in-situ from radioactive decay of U, Th and Sm. This study investigates the U-Th/He systematics of fibrous diamonds and provides a first step in quantification of the uncertainties associated with determining the in-situ produced radiogenic 4He concentration. Factors determining the total amount of measured helium in a diamond are the initial trapped 4He, the in-situ produced radiogenic 4He, a-implantation, a-ejection, diffusion, and cosmogenic 3He production. Alpha implantation is negligible, and diffusion is slow, but the cosmogenic 3He component can be significant for alluvial diamonds as the recovery depth is unknown. Therefore, samples were grouped based on similar major and trace element compositions to determine possible genetically related samples. A correlation between the 4He and U-Th concentrations approximates the initial 4He concentration at the axis-intersect and age as the slope. In this study, the corrections were applied to eight fibrous cubic diamonds from the Democratic Republic of the Congo and two diamonds from the Jwaneng kimberlite in Botswana. A correlation exists between the 4He and U-Th concentrations of the group ZRC2, 3, and 6, and of the group CNG2, 3, and 4 and both correlations deviate significantly from a 71?Ma kimberlite eruption isochron. The U-Th/He dating method appears a promising new approach to date metasomatic fluid events that result in fibrous diamond formation and this is the first evidence that some fibrous diamonds can be formed 10s to 100s Myr before the kimberlite eruption.
DS201906-1358
2019
Pearson, D.G.Veglio, C., Lawley, C., Kjarsgaard, B., Pearson, D.G.Behaviour of ore forming elements in the subcontinental lithospheric mantle below the Slave craton.GAC/MAC annual Meeting, 1p. Abstract p. 187.Canada, Northwest Territoriesdeposit - Jericho, Muskox

Abstract: The fertility of the subcontinental lithospheric mantle as source for metal-rich magmas remains poorly understood. We report new major (EPMA), minor and trace element (LA-ICP-MS) results for olivine mantle xenocrysts sourced from the Jurassic age Jericho, Muskox and Voyageur kimberlites, western Nunavut in the Slave Craton, approximately 30 km north of the Lupin gold mine. Target elements include a suite of ore-forming elements that are unconventional for mantle petrology studies, but may represent important geochemical tracers for metal metasomatism. Using single-grain aluminum-in-olivine thermometry, formation temperatures for the olivine grains were calculated and projected on to a mantle geotherm to estimate PT conditions. The suite of xenocrysts corresponds to mantle sampling between 100-190 km depth. Their range in Mg# indicates that all 3 kimberlites sampled variably depleted mantle peridotite. The patterns of trace element enrichments found are consistent with those documented previously for mantle olivine xenocryst samples from the lithosphere below the Superior Craton in Kirkland Lake, Ontario. In both studies, some ore-forming elements were found to partition into mantle silicates more at the higher temperatures and pressure prevalent at the base of the lithospheric mantle, notably copper, with concentrations varying from ~ 1 ppm in shallow samples up to 11 ppm at the maximum depth sampled. Because the concentration of metals in melt-depleted lithospheric peridotite is expected to be low (< 20 ppm Cu), mantle silicates likely become a significant host for some ore elements at depth. Highly incompatible high field strength elements yield decreasing concentrations with depth, possibly the result of mantle metasomatic processes. Fluid metasomatized mantle peridotite domains are also inferred from olivine xenocrysts that yield unexpected trace element concentrations (ppb to ppm) for other highly incompatible ore-elements (e.g. As, Mo). We expect that some of these fluid-mobile and highly incompatible ore-elements represent trapped fluid and/or melt inclusions.
DS201907-1524
2019
Pearson, D.G.Anzolini, C., Wang, F., Harris, G.A., Locock, A.J., Zhang, D., Nestola, F., Peruzzo, L., Jacobsen, S.D., Pearson, D.G.Nixonite, Na2Ti6O13, a new mineral from a metasomatized mantle garnet pyroxenite from the western Rae Craton, Darby kimberlite field, Canada.American Mineralogist, in press available 26p.Canada, Nunavutdeposit - Darby

Abstract: Nixonite (IMA 2018-133), ideally Na2Ti6O13, is a new mineral found within a heavily-metasomatized pyroxenite xenolith from the Darby kimberlite field, beneath the west central Rae Craton, Canada. It occurs as microcrystalline aggregates, 15 to 40 µm in length. Nixonite is isostructural with jeppeite, K2Ti6O13, with a structure consisting of edge- and corner-shared titanium-centered octahedra that enclose alkali-metal ions. The Mohs hardness is estimated to be between 5 and 6 by comparison to jeppeite and the calculated density is 3.51(1) g/cm3. Electron microprobe wavelength-dispersive spectroscopic analysis (average of 6 points) yielded: Na2O 6.87, K2O 5.67 CaO 0.57, TiO2 84.99, V2O3 0.31, Cr2O3 0.04, MnO 0.01, Fe2O3 0.26, SrO 0.07, total 98.79 wt%. The empirical formula, based on 13 O atoms, is: (Na1.24K0.67Ca0.06)S1.97(Ti5.96V0.023Fe0.018)S6.00O13 with minor amounts of Cr and Mn. Nixonite is monoclinic, space group C2/m, with unit-cell parameters a = 15.3632(26) Å, b = 3.7782(7) Å, c = 9.1266(15) Å, ß = 99.35(15)º and V = 522.72(1) Å3, Z = 2. Based on the average of seven integrated multi-grain diffraction images, the strongest diffraction lines are [dobs in Å (I in %) (h k l)]: 3.02 (100) (3 1 0) , 3.66 (75) (1 1 0), 7.57 (73) (2 0 0), 6.31 (68) (2 0 -1), 2.96 (63) (3 1 -1), 2.96 (63) (2 0 -3) and 2.71 (62) (4 0 2). The five main Raman peaks of nixonite, in order of decreasing intensity, are at: 863, 280, 664, 135 and 113 cm-1. Nixonite is named after Peter H. Nixon, a renowned scientist in the field of kimberlites and mantle xenoliths. Nixonite occurs within a pyroxenite xenolith in a kimberlite, in association with rutile, priderite, perovskite, freudenbergite and ilmenite. This complex Na-K-Ti rich metasomatic mineral assemblage may have been produced by a fractionated Na-rich kimberlitic melt that infiltrated a mantle-derived garnet pyroxenite and reacted with rutile during kimberlite crystallization.
DS201908-1773
2019
Pearson, D.G.Bussweiler, Y., Giuliani, A., Greig, A., Kjarsgaard, B.A., Petts, D., Jackson, S.E., Barrett, N., Luo, Y., Pearson, D.G.Trace element analysis of high-Mg olivine by LA-ICP-MS - characterization of natural olivine standards for matrix-matched calibration and application to mantle peridotites.Chemical Geology, Vol. 524, pp. 136-157.Mantleperidotite

Abstract: The trace element composition of olivine is becoming increasingly important in petrological studies due to the ubiquity of olivine in the Earth's upper mantle and in primitive magmatic rocks. The LA-ICP-MS method allows for the routine analysis of trace elements in olivine to sub-ppm levels, but a major drawback of this method is the lack of knowledge about possible downhole fractionation effects when non matrix-matched calibration is used. In this contribution, we show that matrix-matched (i.e., olivine-based) calibration is preferable for small laser spot sizes (<100?µm) due to significant laser-induced inter-element fractionation between olivine and commonly used silicate glass calibration materials, e.g., NIST SRM 612, GSD-1G and BHVO-2G. As a result, we present two Mg-rich natural olivine standards (355OL and SC-GB) that have been characterized by independent methods (EPMA, solution ICP-MS), and by LA-ICP-MS in four different laboratories. These natural olivines have been used 1) as primary standards for the matrix-matched calibration of olivine samples for most elements of interest (e.g., Li, Na, Al, P, Ca, Sc, Ti, V, Cr, Mn, Co, Ni, Cu, Zn), and 2) as secondary standards to assess the accuracy of results. Comparison of olivine- and silicate glass-calibrated results for natural peridotitic olivine reveals that matrix-matched calibration is essential when using small laser spot sizes (<100?µm) in order to mitigate downhole fractionation effects for certain elements, especially Na, P, Mn, Co, Ni and Zn. If matrix-matched calibration is not feasible, we recommend that spot sizes of =100?µm, laser fluence of =4.0?J/cm2, and total laser shot counts of =250 (e.g., 5?Hz repetition rate for 50?s) are used in order to minimize fractionation effects between olivine and silicate glass calibration materials. We demonstrate the applicability of matrix-matched calibration on olivine from a suite of different mantle peridotite xenoliths sampled by kimberlites and alkali basalts from on-craton and off-craton localities.
DS201908-1783
2019
Pearson, D.G.Krebs, M.Y., Pearson, D.G.Determining the provenance pf coloured gemstones.www.minsocam.org/ MSA/Centennial/ MSA_Centennial _Symposium.html The next 100 years of mineral science, June 20-21, p. 36. AbstractAsia, Pakistan, Kashmir, South America, Colombiasapphire, emerald

Abstract: The geographic origin of gemstones has emerged as one of the major factors affecting their sale on the colored stone market, in large part due to the prestige attributed to certain regions (e.g. sapphires from Kashmir or emeralds from Colombia) but also because of political, environmental and ethical considerations. Identifying the geographic provenance of a colored stone has, therefore, developed into one of the main tasks for gem-testing laboratories, providing a strong motivation to establish accurate scientific methods. The properties and features of individual gemstones reflect the specific geological conditions of their formation and the main challenge of origin determination is to find the link between the two. In addition, access to a complete collection of authentic reference samples and analytical data for all economically relevant mining areas worldwide is key. Different techniques have been developed for determining gemstone provenance, including a range of gemological observations, and spectroscopic, chemical, and isotopic analyses[1]. These have proven useful in distinguishing the origin of gemstones from different geological settings but for many gemstones (including ruby and sapphire) to reliably distinguish between gems from different geographic regions that share a similar geological setting is not always possible. So far, no unique fingerprint exists, and the geographic origin remains a challenge, especially for high-clarity stones, emphasizing the need for a more powerful tool. Here we will give an overview of the current techniques, and outline some of the challenges and limitations of geographical origin determination of colored gemstones. In addition, we present new trace element data and the first radiogenic isotope compositions (Sr and Pb) obtained for ruby and sapphire from several different localities of geologically similar deposits. The acquisition of quantitative data of a range of ultra-trace elements along with the most commonly observed elements in ruby and sapphire (Mg, Fe, Ti, Ca, Ga, V and Cr) makes it possible to explore new elements as potential provenance discriminators. Among the elements consistently above the limits of quantification (Zn, Nb, Ni, and Pb), Ni in particular shows promise as a discriminator for amphibolite-type ruby. Measured 87Sr/86Sr and Pb isotope ratios clearly show distinct ranges for the different localities of amphibolitetype ruby, ranges for marble-related ruby and metamorphic blue sapphires from different geographic regions overlap. These results suggest that radiogenic isotopes potentially offer a powerful means of provenance discrimination for different localities of amphibolite-type ruby, their potential for geographical origin determination among marble-hosted ruby and metamorphic sapphire, however, appears to be limited.
DS201908-1802
2019
Pearson, D.G.Pearson, D.G., Stachel, T., Li, L., Li, K., Stern, R., Howell, D., Regier, M.Diamonds and their inclusions: a unique record of plate tectonic recycling. AOCwww.minsocam.org/ MSA/Centennial/ MSA_Centennial _Symposium.html The next 100 years of mineral science, June 20-21, p. 22. AbstractMantlediamond inclusions

Abstract: Much of the temporal record of Earth’s evolution, including its trace of plate tectonics, is blurred due to the dynamic nature of the crust-mantle system. While zircon provides the highest fidelity crustal record, diamond takes over in the mantle as the go-to mineral, capable of retaining critical information for a variety of geochemical proxies, over billion year timescales. Here we use diamond and its inclusions to tell the story of the recycling of C, N, O, H and B from the crust to various depths in Earth’s mantle. In this story, altered oceanic crust (AOC) and lithospheric mantle will play a prominent role. The carbon isotope record of diamond has long been thought to reflect the mixing of primitive mantle carbon with carbon recycled from isotopically light organic material originating from the crust. A major difficulty has been reconciling this view with the highly varied nitrogen and carbon isotope signatures in diamonds of eclogitic paragenesis, which cannot be interpreted by the same mechanism. Recent work on AOC of igneous origin (Li et al., EPSL in press) shows how isotopically varied carbon and nitrogen can be subducted to great depth and retained in spatial juxtaposition with the mafic silicate component of AOC to form the complex C-N isotope systematics observed in diamonds and the varied O isotope compositions of their inclusions. In this model a large portion of the 13C depleted carbon originated from biogenic carbonate within the AOC rather than from overlying sediments. Metamorphosed and partially devolatilized AOC will have very variable C/N ratios and highly variable nitrogen isotopes, explaining why simple two component mixing between organic matter and convecting upper mantle cannot explain the complexity of C-N isotope systematics in diamonds. Igneous AOC and its underlying altered mantle are considerably more efficient than subducted sediment at retaining their volatile inventory when recycled to transition zone and even lower mantle depths. Hence, this combination of mixing between AOC-derived volatiles and those from the convecting mantle produces the isotopic fingerprints of superdeep diamonds and their inclusions. These amazing diamonds, some worth millions of dollars, can contain pristine ultra-high pressure mineral phases never before seen in terrestrial samples. The first hydrous ringwoodite found in Earth provides evidence in support of a locally water-saturated transition zone that may result from altered oceanic lithospheric mantle foundering at that depth in the mantle. The O isotope composition of deep asthenosphere and transition zone phases document clearly crustal precursors that have interacted with the hydrosphere before residing hundreds of km deep within the Earth. Finally, spectacular blue diamonds contain boron, an element of strong crustal affinities, transported into the deep Earth along with crustal carbon, by the plate tectonic conveyor system. Diamond - such a simple mineral - and its inclusions, will continue to provide a unique, brightly illuminating light into the darkest recesses of Earth’s mantle for many years to come.
DS201908-1825
2019
Pearson, D.G.Wenz, M.D., Jacobsen, S.D., Zhang, D., Regier, M., Bausch, H.J., Dera, P.K., Rivers, M., Eng, P., Shirey, S.B., Pearson, D.G.Fast identification of mineral inclusions in diamond at GSECARS using synchrotron X-ray microtomography, radiography and diffraction.Journal of Synchrotron Radiation, Vol. 26, doi.org/10.1107 /S1600577519006854 6p. PdfMantlediamond inclusions

Abstract: Mineral inclusions in natural diamond are widely studied for the insight that they provide into the geochemistry and dynamics of the Earth's interior. A major challenge in achieving thorough yet high rates of analysis of mineral inclusions in diamond derives from the micrometre-scale of most inclusions, often requiring synchrotron radiation sources for diffraction. Centering microinclusions for diffraction with a highly focused synchrotron beam cannot be achieved optically because of the very high index of refraction of diamond. A fast, high-throughput method for identification of micromineral inclusions in diamond has been developed at the GeoSoilEnviro Center for Advanced Radiation Sources (GSECARS), Advanced Photon Source, Argonne National Laboratory, USA. Diamonds and their inclusions are imaged using synchrotron 3D computed X-ray microtomography on beamline 13-BM-D of GSECARS. The location of every inclusion is then pinpointed onto the coordinate system of the six-circle goniometer of the single-crystal diffractometer on beamline 13-BM-C. Because the bending magnet branch 13-BM is divided and delivered into 13-BM-C and 13-BM-D stations simultaneously, numerous diamonds can be examined during coordinated runs. The fast, high-throughput capability of the methodology is demonstrated by collecting 3D diffraction data on 53 diamond inclusions from Juína, Brazil, within a total of about 72 h of beam time.
DS201909-2074
2019
Pearson, D.G.Pernet-Fisher, J.F., Barry, P.H., Day, J.M.D., Pearson, D.G., Woodland, S., Agashev, A.M., Pokhilenko, L.N., Pokhilenko, N.P.Heterogeneous kimberlite metasomatism revealed from a combined He-Os isotope study of Siberian megacrustalline dunite xenoliths.Geochimica et Cosmochimica Acta, in press available 45p. PdfRussia, Siberiadeposit - Udachnaya East
DS201909-2098
2019
Pearson, D.G.Timmerman, S., Honda, M., Burnham, A.D., Amelin, Y., Woodland, S., Pearson, D.G., Jaques, A.L., Le Losq, C., Bennett, V.C., Bulanova, G.P., Smith, C.B., Harris, J.W., Tohver, E.Primordial and recycled helium isotope signatures in the mantle transition zone. Science, Vol. 365, 6454, pp. 692-694.Mantlediamond genesis

Abstract: Isotope compositions of basalts provide information about the chemical reservoirs in Earth’s interior and play a critical role in defining models of Earth’s structure. However, the helium isotope signature of the mantle below depths of a few hundred kilometers has been difficult to measure directly. This information is a vital baseline for understanding helium isotopes in erupted basalts. We measured He-Sr-Pb isotope ratios in superdeep diamond fluid inclusions from the transition zone (depth of 410 to 660 kilometers) unaffected by degassing and shallow crustal contamination. We found extreme He-C-Pb-Sr isotope variability, with high 3He/4He ratios related to higher helium concentrations. This indicates that a less degassed, high-3He/4He deep mantle source infiltrates the transition zone, where it interacts with recycled material, creating the diverse compositions recorded in ocean island basalts.
DS201910-2252
2019
Pearson, D.G.Czas, J., Pearson, D.G., Stachel, T., Kjarsgaard, B.A., Read, G.A diamondiferous paleoproterozoic mantle root beneath the Sask craton ( western Canada).Goldschmidt2019, 1p. AbstractCanada, Saskatchewancraton

Abstract: Primary diamond deposits are typically restricted to the stable Archean cores of continents, an association known as Clifford’s rule. Archean to Palaeoproterozoic crustal ages (3.3 - 2.1 Ga) have been reported for the Sask Craton, a small terrane in Western Canada, which hosts the diamondiferous Cretaceous Fort à la Corne (FALC) Kimberlite Field. Yet the craton is enclosed by the Palaeoproterozoic (1.9 - 1.8 Ga) Trans Hudson Orogen (THO). In this study we evaluate the age and geochemistry (major, trace, and platinum group elements data, as well as Re-Os isotope systematics) of the lithospheric mantle root beneath the Sask Craton to assess the timing of craton formation and the potential role played by the THO in its evolution. The lithospheric mantle root is dominated by lherzolite with average olivine Mg# of 91.5, which is more fertile than observed in other cratons. Garnets from concentrate further highlight the rarity of harzburgite in the lithospheric mantle. Single clinopyroxene thermobarometry provides temperaturepressure constraints for the garnet-bearing lithospheric mantle (840 to 1250 °C and 2.7 to 5.5 GPa), indicative of a cool geotherm (38 mW/m2) and a large diamond window of ~100 km thickness (from ~120-220 km depth). Most of the studied xenoliths show evidence for melt metasomatism in their trace and major element compositions, while retaining platinum group element patterns expected for melt residues. 187Os/188Os compositions span a broad range from 0.1109 to 0.1507, corresponding to Re-depletion (TRD) ages between 2.4 to 0.3 Ga, with a main mode in the Palaeoproterozoic (2.4 to 1.7 Ga). With the absence of Archean ages, the main depletion and stabilisation of the Sask Craton occurred in the Palaeoproterozoic, closely associated with the Wilson cycle of the THO. From a diamond exploration perspective this indicates that major diamond deposits can be found on cratons that were stabilised in the Palaeoproterozoic.
DS201910-2282
2019
Pearson, D.G.Liu, J., Pearson, D.G., Mather, K., Kjarsgaard, B., Kopylova, M.Destruction and regeneration of cratonic lithosphere rocks: evidence from the Slave craton, Canada.Goldschmidt2019, 1p. AbstractCanada, Northwest Territoriesgeodynamics

Abstract: Cratons are the ancient landmasses that remain stable for billions of years on Earth but also have experienced episodic events of modification and rejuvenation throughout their history [1]. These alteration processes have modified the cratonic lithospheric mantle roots to different extents, e.g., ubiquitous cryptic/modal metasomatism, partial to entire loss of the mantle roots, to rifting apart of the craton. It remains unclear to what extent a cratonic mantle root can withstand modification and retain its integrity. We attempt to discuss this issue from the perspective of the Slave craton that has experienced the multiple impacts of major circum-cratonic Paleoproterozoic (1.93-1.84 Ga) orogenies and the intrusion of several 2.23-1.67 Proterozoic diabase dyke swarms. We use kimberlite-borne peridotite xenoliths to construct a N-S transect across the craton with an aim of probing the effects of these post-Archean events on the composition, age and depth of the lithospheric root. Chemically, all of these rocks are of typical cratonic refractory composition. P-T calculations and paleogeotherms show that they were derived from thick lithospheric mantle roots (>180 km), consistent with their diamondiferous nature. However, these peridotites exhibit variable N-S variation of modes in their Re-depletion Os model ages (TRD). Neoarchean TRD ages dominate in the Central and Southern Slave mantle. Progressing North there is a decreasing proportion of Archean TRD ages through Jericho to Artemisa in the Northern Slave craton. About 70% of the peridotites at Artemisia give TRD ages within error of the ~1.27 Ga Mackenzie LIP event, with the remaining (~ 30%) close to the Paleoproterozoic orogenic events. Combined with new data from regions to the N and NW of the Slave craton [2], the observed age spectrum in the far North of the craton indicates the likelihood of major new generation of lithospheric roots in both the Paleoproterozoic and Mesoproterozoic. Despite its complex history, the Northern Slave craton retains a ‘cratonic-like’ lithospheric root that allowed diamond mineralization.
DS201910-2308
2019
Pearson, D.G.Woodhead, J., Hergt, J., Giuliani, A., Maas, R., Philips, D., Pearson, D.G., Nowell, G.Kimberlites reveal 2.5-nillion year evolution of a deep, isolated mantle reservoir.Nature, Vol. 573, pp. 578-581.Mantlemelting

Abstract: The widely accepted paradigm of Earth's geochemical evolution states that the successive extraction of melts from the mantle over the past 4.5 billion years formed the continental crust, and produced at least one complementary melt-depleted reservoir that is now recognized as the upper-mantle source of mid-ocean-ridge basalts1. However, geochemical modelling and the occurrence of high 3He/4He (that is, primordial) signatures in some volcanic rocks suggest that volumes of relatively undifferentiated mantle may reside in deeper, isolated regions2. Some basalts from large igneous provinces may provide temporally restricted glimpses of the most primitive parts of the mantle3,4, but key questions regarding the longevity of such sources on planetary timescales—and whether any survive today—remain unresolved. Kimberlites, small-volume volcanic rocks that are the source of most diamonds, offer rare insights into aspects of the composition of the Earth’s deep mantle. The radiogenic isotope ratios of kimberlites of different ages enable us to map the evolution of this domain through time. Here we show that globally distributed kimberlites originate from a single homogeneous reservoir with an isotopic composition that is indicative of a uniform and pristine mantle source, which evolved in isolation over at least 2.5 billion years of Earth history—to our knowledge, the only such reservoir that has been identified to date. Around 200 million years ago, extensive volumes of the same source were perturbed, probably as a result of contamination by exogenic material. The distribution of affected kimberlites suggests that this event may be related to subduction along the margin of the Pangaea supercontinent. These results reveal a long-lived and globally extensive mantle reservoir that underwent subsequent disruption, possibly heralding a marked change to large-scale mantle-mixing regimes. These processes may explain why uncontaminated primordial mantle is so difficult to identify in recent mantle-derived melts.
DS201911-2541
2019
Pearson, D.G.Liu, J., Pearson, D.G., Shu, Q., Sigurdsson, H., Thomassot, E., Alard, O.Dating the post-Archean lithospheric mantle: insights from Re-Os and Lu-Hf isotopic systematics of the Cameroon volcanic line peridotites.Geochimica et Cosmochimica Acta, in press available. 13p.Africa, Cameroonperidotite

Abstract: Highly depleted Archean peridotites have proven very amenable to Re-Os model age dating. In contrast, due to the increasing heterogeneity of mantle Os isotope compositions with time, the Re-Os system has not been as effective in dating post-Archean peridotites. The timing of depletion and accretion of post-Archean lithospheric mantle around cratons is important to understand within the context of the evolution of the continents. In an attempt to precisely date post-Archean peridotite xenoliths, we present a study of the petrology, mineralogy and geochemistry, including whole-rock Re-Os isotopes, highly siderophile elements and clinopyroxene-orthopyroxene Sr-Nd-Hf isotopes of peridotite xenoliths from Lake Nyos in the Cameroon Volcanic Line (CVL). Eight Nyos peridotite xenoliths, all fresh spinel lherzolites, are characterized by low to moderate olivine Fo contents (88.9-91.2) and low spinel Cr# (8.4-19.3), together with moderate to high whole-rock Al2O3 contents (2.0-3.7%). These chemical characteristics indicate that they are mantle residues of a few percent to <20% partial melting. However, trace element patterns of both clinopyroxene and orthopyroxene are not a pristine reflection of melt depletion but instead show various extents of evidence of metasomatic enrichment. Some of the samples contain orthopyroxene with 143Nd/144Nd lower than its coexisting clinopyroxene, which is best explained by recent short-timescale alteration, most likely by infiltration of the host basalt. Because of these metasomatic effects, the Sr-Nd isotope systematics in pyroxenes cannot sufficiently reflect melt depletion signatures. Unlike Sr-Nd isotopes, the Lu-Hf isotope system is less sensitive to recent metasomatic overprinting. Given that orthopyroxene hosts up to 33% of the Lu and 14% of the Hf in the whole rock budget of these rocks and has 176Hf/177Hf similar to, or higher than, coexisting clinopyroxene, it is necessary to reconstruct a whole-rock Lu-Hf isochron in order to constrain the melt depletion age of peridotites. The reconstructed Nyos Lu-Hf isochron from ortho- and clinopyroxenes gives an age of 2.01?±?0.18?Ga (1s), and when olivine and spinel are considered, is 1.82?±?0.14?Ga (1s). Both ages are identical within error, and they are within error of the alumina-187Os/188Os pseudo-isochron ages (1.2-2.4?Ga) produced on the peridotites from Lake Nyos, consistent with their oldest rhenium depletion Os model ages (2.0?Ga). We conclude that the Nyos peridotites, and the lithospheric mantle that they represent, were formed at ~2.0?Ga, indicating that the reconstructed whole-rock Lu-Hf isotope system can be a powerful radiometric dating tool that is complementary to and in some instances, more precise than the Re-Os isotope system in dating well-preserved post-Archean peridotites. The recognition of ~2.0?Ga subcontinental lithospheric mantle (SCLM) in the Nyos area suggests that the Nyos region was assembled as a Paleoproterozoic block, or that it represents fragments of the SCLM from the nearby Paleoproterozoic domain juxtaposed through collisional emplacement during the Pan African Orogeny. With regards to the origin of the CVL, our data reveal that the Hf isotopic compositions of the Nyos peridotites are too radiogenic to be the main source of the CVL basalts.
DS201911-2551
2019
Pearson, D.G.Ootes, L., Sandemann, H., Cousens, B.L.,Luo, Y., Pearson, D.G., Jackson, V.Pyroxenite magma conduits ( ca 1.86 Ga) in Wopmay orogen and Slave craton: petrogenetic constrainst from whole rock and mineral chemistry.Lithos, in press available, 54p.Canada, Northwest Territorieslamprophyres
DS201911-2575
2019
Pearson, D.G.Woodhead, J., Hergt, J., Giuliani, A., Maas, R., Phillips, D., Pearson, D.G., Nowell, G.Kimberlites reveal 2.5 billion year evolution of a deep, isolated mantle reservoir.Nature , Vol. 573, pp. 578-581.Mantlediamond genesis

Abstract: The widely accepted paradigm of Earth's geochemical evolution states that the successive extraction of melts from the mantle over the past 4.5 billion years formed the continental crust, and produced at least one complementary melt-depleted reservoir that is now recognized as the upper-mantle source of mid-ocean-ridge basalts1. However, geochemical modelling and the occurrence of high 3He/4He (that is, primordial) signatures in some volcanic rocks suggest that volumes of relatively undifferentiated mantle may reside in deeper, isolated regions2. Some basalts from large igneous provinces may provide temporally restricted glimpses of the most primitive parts of the mantle3,4, but key questions regarding the longevity of such sources on planetary timescales—and whether any survive today—remain unresolved. Kimberlites, small-volume volcanic rocks that are the source of most diamonds, offer rare insights into aspects of the composition of the Earth’s deep mantle. The radiogenic isotope ratios of kimberlites of different ages enable us to map the evolution of this domain through time. Here we show that globally distributed kimberlites originate from a single homogeneous reservoir with an isotopic composition that is indicative of a uniform and pristine mantle source, which evolved in isolation over at least 2.5 billion years of Earth history—to our knowledge, the only such reservoir that has been identified to date. Around 200 million years ago, extensive volumes of the same source were perturbed, probably as a result of contamination by exogenic material. The distribution of affected kimberlites suggests that this event may be related to subduction along the margin of the Pangaea supercontinent. These results reveal a long-lived and globally extensive mantle reservoir that underwent subsequent disruption, possibly heralding a marked change to large-scale mantle-mixing regimes. These processes may explain why uncontaminated primordial mantle is so difficult to identify in recent mantle-derived melts.
DS201912-2785
2019
Pearson, D.G.Giuliani, A., Pearson, D.G.Kimberlites: from deep Earth to diamond mines. An introduction.Elements, Vol. 15, 6, pp.Mantlediamond genesis
DS201912-2789
2019
Pearson, D.G.Heaman, L.H., Phillips, D., Pearson, D.G.Dating kimberlite: methods and emplacement patterns through time.Elements, Vol. 15, 6, pp.Mantlegeochronology
DS201912-2810
2019
Pearson, D.G.Pearson, D.G., Woodhead, J.D., Janney, P.E.Kimberlites as geochemical probes of Earth's mantle.Elements, Vol. 15, 6, pp.Mantlegeochemistry

Abstract: Kimberlites are ultrabasic, Si-undersaturated, low Al, low Na rocks rich in CO2 and H2O. The distinctive geochemical character of kimberlite is strongly influenced by the nature of the local underlying lithospheric mantle. Despite this, incompatible trace element ratios and radiogenic isotope characteristics of kimberlites, filtered for the effects of crustal contamination and alteration, closely resemble rocks derived from the deeper, more primitive, convecting mantle. This suggests that the ultimate magma source is sub-lithospheric. Although the composition of primitive kimberlite melt remains unresolved, kimberlites are likely derived from the convecting mantle, with possible source regions ranging from just below the lithosphere, through the transition zone, to the core-mantle boundary.
DS201912-2825
2020
Pearson, D.G.Shirey, S.B., Smit, K.V., Pearson, D.G., Walter, M.J., Aulbach, S., Brenker, F.E., Bureau, H., Burnham, A.D., Cartigny, P., Chacko, T., Frost, D.J., Hauri, E.H., Jacob, D.E., Jacobsen, S.D., Kohn, S.C., Luth, R.W., Mikhail, S., Navon, O., Nestola, F., NimDiamonds and the mantle geodynamics of carbon: deep mantle carbon and evolution from the diamond record.IN: Deep carbon: past to present, Orcutt, Daniel, Dasgupta eds., pp. 89-128.Mantlegeodynamics

Abstract: The science of studying diamond inclusions for understanding Earth history has developed significantly over the past decades, with new instrumentation and techniques applied to diamond sample archives revealing the stories contained within diamond inclusions. This chapter reviews what diamonds can tell us about the deep carbon cycle over the course of Earth’s history. It reviews how the geochemistry of diamonds and their inclusions inform us about the deep carbon cycle, the origin of the diamonds in Earth’s mantle, and the evolution of diamonds through time.
DS202001-0039
2020
Pearson, D.G.Shirey, S.B., Smit, K.V., Pearson, D.G., Walter, M.J., Aulbach, S., Brenker, F.E., Bureau, H., Burnham, A.D., Cartigny, P., Chacko, T., Frost, D.J., Hauri, E.H., Jacob, D.E., Jacobsen, S.D., Kohn, S.C., Luth, R.W., Mikhail, S., Navon, O., Nestola, F., NimDiamonds and mantle geodynamics of carbon: IN: Deep Carbon: past to present. Editors Orcutt, Danielle, Dasgupta, pp. 89-128.Mantlegeodynamics

Abstract: The science of studying diamond inclusions for understanding Earth history has developed significantly over the past decades, with new instrumentation and techniques applied to diamond sample archives revealing the stories contained within diamond inclusions. This chapter reviews what diamonds can tell us about the deep carbon cycle over the course of Earth’s history. It reviews how the geochemistry of diamonds and their inclusions inform us about the deep carbon cycle, the origin of the diamonds in Earth’s mantle, and the evolution of diamonds through time.
DS202002-0197
2019
Pearson, D.G.Krebs, M.Y., Pearson, D.G., Fagan, A.J., Bussweiler, Y., Sarkar, C.The application of trace elements and Sr-Pb isotopes to dating and tracing ruby formation: the Aappaluttoq deposit, SW Greenland.Chemical Geology, Vol. 523, pp. 42-58.Europe, Greenlandruby

Abstract: Trace element characteristics of rubies from the Aappaluttoq deposit, SW Greenland, were measured using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), laser ablation - inductively coupled plasma-time of flight-mass spectrometry (LA-ICP-TOF-MS) and offline laser ablation followed by solution ICP-MS. LA-ICP-TOF-MS - applied to rubies for the first time - effectively maps trace element spatial variation in these gems. With the exception of a small number of elements that can substitute for Al3+ in the crystal structure (e.g., Ti, Fe, V, Cr, Mg), trace element mapping clearly demonstrates that most elements such as Th, U, Sr and Rb are hosted in mineral and fluid inclusions or are present along fractures. Primitive mantle normalized trace element patterns show characteristics that are broadly correlative to mineral inclusions within the analysed rubies. These minerals include rutile (enrichment of HFSE over LREE, high Ta/Nb and Hf/Zr ratios and low Th/U ratios), phlogopite (enrichment in Rb and Ba and positive Sr anomalies), and zircon (extreme enrichment in Zr-Hf, U and Th, HREE enrichment over LREE and positive Ce anomalies). The sample suite analysed here is derived from a bulk sample of ore composed of three different rock types (sapphirine-gedrite, leucogabbro and phlogopitite). Two different populations of ruby were identified at Aappaluttoq; these can be defined on the basis of their different V content within the corundum lattice. Therefore, V content may be able to geochemically define rubies from different host rocks within the same deposit. Using offline laser ablation followed by thermal ionization mass spectrometry (TIMS) we measured the radiogenic isotope compositions in ruby for the first time. A Pb-Pb isochron age of 2686 +300/-74?Ma, was defined for gem formation at Aappaluttoq. We believe that this is the first ever direct age determined on a ruby suite, independent of associated minerals, derived by bulk sampling sub-micron to micron sized inclusions in the corundum lattice. This age likely reflects the re-crystallization and re-setting of the ruby (and its U-Pb system) during the Neoarchean in SW Greenland, due to regional granulite to upper-amphibolite facies metamorphism.
DS202004-0519
2020
Pearson, D.G.Howell, D., Stachel, T., Stern, R.A., Pearson, D.G., Nestola, F., Hardman, M.F., Harris, J.W., Jaques, A.L., Shirery, S.B., Cartigny, P., Smit, K.V., Aulbach, S., Brenker, F.E., Jacob, D.E., Thomassot, E., Walter, M.J., Navon, O.Deep carbon through time: Earth's diamond record and its implications for carbon cycling and fluid speciation in the mantle.(peridotite and eclogite used)Geochimica et Cosmochimica Acta, Vol. 275, pp. 99-122.Mantlecarbon

Abstract: Diamonds are unrivalled in their ability to record the mantle carbon cycle and mantle fO2 over a vast portion of Earth’s history. Diamonds’ inertness and antiquity means their carbon isotopic characteristics directly reflect their growth environment within the mantle as far back as ~3.5 Ga. This paper reports the results of a thorough secondary ion mass spectrometry (SIMS) carbon isotope and nitrogen concentration study, carried out on fragments of 144 diamond samples from various locations, from ~3.5 to 1.4 Ga for P [peridotitic]-type diamonds and 3.0 to 1.0 Ga for E [eclogitic]-type diamonds. The majority of the studied samples were from diamonds used to establish formation ages and thus provide a direct connection between the carbon isotope values, nitrogen contents and the formation ages. In total, 908 carbon isotope and nitrogen concentration measurements were obtained. The total d¹³C data range from -17.1 to -1.9 ‰ (P = -8.4 to -1.9 ‰; E = -17.1 to -2.1‰) and N contents range from 0 to 3073 at. ppm (P = 0 to 3073 at. ppm; E = 1 to 2661 at. ppm). In general, there is no systematic variation with time in the mantle carbon isotope record since > 3 Ga. The mode in d¹³C of peridotitic diamonds has been at -5 (±2) ‰ since the earliest diamond growth ~3.5 Ga, and this mode is also observed in the eclogitic diamond record since ~3 Ga. The skewness of eclogitic diamonds’ d¹³C distributions to more negative values, which the data establishes began around 3 Ga, is also consistent through time, with no global trends apparent. No isotopic and concentration trends were recorded within individual samples, indicating that, firstly, closed system fractionation trends are rare. This implies that diamonds typically grow in systems with high excess of carbon in the fluid (i.e. relative to the mass of the growing diamond). Any minerals included into diamond during the growth process are more likely to be isotopically reset at the time of diamond formation, meaning inclusion ages would be representative of the diamond growth event irrespective of whether they are syngenetic or protogenetic. Secondly, the lack of significant variation seen in the peridotitic diamonds studied is in keeping with modeling of Rayleigh isotopic fractionation in multicomponent systems (RIFMS) during isochemical diamond precipitation in harzburgitic mantle. The RIFMS model not only showed that in water-maximum fluids at constant depths along a geotherm, fractionation can only account for variations of <1‰, but also that the principal d¹³C mode of -5 ± 1‰ in the global harzburgitic diamond record occurs if the variation in fO2 is only 0.4 log units. Due to the wide age distribution of P-type diamonds, this leads to the conclusion that the speciation and oxygen fugacity of diamond forming fluids has been relatively consistent. The deep mantle has therefore generated fluids with near constant carbon speciation for 3.5 Ga.
DS202005-0721
2020
Pearson, D.G.Bauer, A.M., Reimink, J.R., Chacko, T., Foley, B.J., Shirey, S.B., Pearson, D.G.Hafnium isotopes in zircons document the gradual onset of mobile-lid tectonics. ( Pilbara, Zimbabwe, Slave, Singhbhum, Rae, Wyoming, Jack HillsGeochemical Perspectives Letters, Vol. 14, pp. 1-6.GlobalTectonics

Abstract: The tectonic regime of the early Earth has proven enigmatic due to a scarcity of preserved continental crust, yet how early continents were generated is key to deciphering Earth’s evolution. Here we show that a compilation of data from 4.3 to 3.4 Ga igneous and detrital zircons records a secular shift to higher 176Hf/177Hf after ~3.8-3.6 Ga. This globally evident shift indicates that continental crust formation before ~3.8-3.6 Ga largely occurred by internal reworking of long-lived mafic protocrust, whereas later continental crust formation involved extensive input of relatively juvenile magmas, which were produced from rapid remelting of oceanic lithosphere. We propose that this secular shift in the global hafnium isotope record reflects a gradual yet widespread transition from stagnant-lid to mobile-lid tectonics on the early Earth.
DS202006-0932
2020
Pearson, D.G.Liu, J., Pearson, D.G., Shu, Q., Sigurdsson, H., Thomassot, E., Alard, O.Dating post-Archean lithospheric mantle: insights from Re-Os and Lu-Hf isotopic systematics of the Cameroon volcanic line peridotites.Geochimica et Cosmochimica Acta, Vol. 278, pp. 177-198.Africa, Cameroonperidotites

Abstract: Highly depleted Archean peridotites have proven very amenable to Re-Os model age dating. In contrast, due to the increasing heterogeneity of mantle Os isotope compositions with time, the Re-Os system has not been as effective in dating post-Archean peridotites. The timing of depletion and accretion of post-Archean lithospheric mantle around cratons is important to understand within the context of the evolution of the continents. In an attempt to precisely date post-Archean peridotite xenoliths, we present a study of the petrology, mineralogy and geochemistry, including whole-rock Re-Os isotopes, highly siderophile elements and clinopyroxene-orthopyroxene Sr-Nd-Hf isotopes of peridotite xenoliths from Lake Nyos in the Cameroon Volcanic Line (CVL). Eight Nyos peridotite xenoliths, all fresh spinel lherzolites, are characterized by low to moderate olivine Fo contents (88.9-91.2) and low spinel Cr# (8.4-19.3), together with moderate to high whole-rock Al2O3 contents (2.0-3.7%). These chemical characteristics indicate that they are mantle residues of a few percent to <20% partial melting. However, trace element patterns of both clinopyroxene and orthopyroxene are not a pristine reflection of melt depletion but instead show various extents of evidence of metasomatic enrichment. Some of the samples contain orthopyroxene with 143Nd/144Nd lower than its coexisting clinopyroxene, which is best explained by recent short-timescale alteration, most likely by infiltration of the host basalt. Because of these metasomatic effects, the Sr-Nd isotope systematics in pyroxenes cannot sufficiently reflect melt depletion signatures. Unlike Sr-Nd isotopes, the Lu-Hf isotope system is less sensitive to recent metasomatic overprinting. Given that orthopyroxene hosts up to 33% of the Lu and 14% of the Hf in the whole rock budget of these rocks and has 176Hf/177Hf similar to, or higher than, coexisting clinopyroxene, it is necessary to reconstruct a whole-rock Lu-Hf isochron in order to constrain the melt depletion age of peridotites. The reconstructed Nyos Lu-Hf isochron from ortho- and clinopyroxenes gives an age of 2.01?±?0.18?Ga (1s), and when olivine and spinel are considered, is 1.82?±?0.14?Ga (1s). Both ages are identical within error, and they are within error of the alumina-187Os/188Os pseudo-isochron ages (1.2-2.4?Ga) produced on the peridotites from Lake Nyos, consistent with their oldest rhenium depletion Os model ages (2.0?Ga). We conclude that the Nyos peridotites, and the lithospheric mantle that they represent, were formed at ~2.0?Ga, indicating that the reconstructed whole-rock Lu-Hf isotope system can be a powerful radiometric dating tool that is complementary to and in some instances, more precise than the Re-Os isotope system in dating well-preserved post-Archean peridotites. The recognition of ~2.0?Ga subcontinental lithospheric mantle (SCLM) in the Nyos area suggests that the Nyos region was assembled as a Paleoproterozoic block, or that it represents fragments of the SCLM from the nearby Paleoproterozoic domain juxtaposed through collisional emplacement during the Pan African Orogeny. With regards to the origin of the CVL, our data reveal that the Hf isotopic compositions of the Nyos peridotites are too radiogenic to be the main source of the CVL basalts.
DS202007-1123
2020
Pearson, D.G.Anzolini, C., Siva-Jothy, W., Locock, A.J., Nestola, F., Balic-Zunic, T., Alvaro, M., Stachel, T., Pearson, D.G.Heamanite-(Ce) (K0.5Ce0.5)Ti03 Mineralogical Magazine reports CNMNC Newsletter , No. 55, Vol. 84, https://doi.org/ 10.1180/mgm. 2020.39Canada, Northwest Territoriesdeposit - Gahcho Kue
DS202007-1142
2020
Pearson, D.G.Giuliani, A., Pearson, D.G., Soltys, A., Dalton, H., Phillips, D., Foley, S.F., Lim, E.Kimberlite genesis from a common primary melt modified by lithospheric mantle assimilation.Science Advances, Vol. 6, eeaz0424Mantlemelting

Abstract: Quantifying the compositional evolution of mantle-derived melts from source to surface is fundamental for constraining the nature of primary melts and deep Earth composition. Despite abundant evidence for interaction between carbonate-rich melts, including diamondiferous kimberlites, and mantle wall rocks en route to surface, the effects of this interaction on melt compositions are poorly constrained. Here, we demonstrate a robust linear correlation between the Mg/Si ratios of kimberlites and their entrained mantle components and between Mg/Fe ratios of mantle-derived olivine cores and magmatic olivine rims in kimberlites worldwide. Combined with numerical modeling, these findings indicate that kimberlite melts with highly variable composition were broadly similar before lithosphere assimilation. This implies that kimberlites worldwide originated by partial melting of compositionally similar convective mantle sources under comparable physical conditions. We conclude that mantle assimilation markedly alters the major element composition of carbonate-rich melts and is a major process in the evolution of mantle-derived magmas.
DS202008-1422
2020
Pearson, D.G.McKensie, L., Kilgore, A.H., Peslier, A.D., Brandon, L.A., Schaffer, R.V., Graff, T.G., Agresti, D.G., O'Reilly, S.Y., Griffin, W.L., Pearson, D.G., Hangi, K., Shaulis, B.J.Metasomatic control of hydrogen contents in the layered cratonic mantle lithosphere sampled by Lac de Gras xenoliths in the central Slave craton, Canada.Geochimica et Cosmochimica Acta, in press available, doi.org/101016 /j.gca.2020.07.013 45p. PdfCanada, Northwest Territoriesdeposit - Lac de Gras

Abstract: Whether hydrogen incorporated in nominally anhydrous mantle minerals plays a role in the strength and longevity of the thick cratonic lithosphere is a matter of debate. In particular, the percolation of hydrogen-bearing melts and fluids could potentially add hydrogen to the mantle lithosphere, weaken its olivines (the dominant mineral in mantle peridotite), and cause delamination of the lithosphere's base. The influence of metasomatism on hydrogen contents of cratonic mantle minerals can be tested in mantle xenoliths from the Slave Craton (Canada) because they show extensive evidence for metasomatism of a layered cratonic mantle. Minerals from mantle xenoliths from the Diavik mine in the Lac de Gras kimberlite area located at the center of the Archean Slave craton were analyzed by FTIR for hydrogen contents. The 18 peridotites, two pyroxenites, one websterite and one wehrlite span an equilibration pressure range from 3.1 to 6.6 GPa and include samples from the shallow (= 145 km), oxidized ultra-depleted layer; the deeper (~145-180 km), reduced less depleted layer; and an ultra-deep (= 180 km) layer near the base of the lithosphere. Olivine, orthopyroxene, clinopyroxene and garnet from peridotites contain 30 - 145, 110 - 225, 105 - 285, 2 - 105 ppm H2O, respectively. Within each deep and ultra-deep layer, correlations of hydrogen contents in minerals and tracers of metasomatism (for example light over heavy rare-earth-element ratio (LREE/HREE), high-field-strength-element (HFSE) content with equilibration pressure) can be explained by a chromatographic process occurring during the percolation of kimberlite-like melts through garnet peridotite. The hydrogen content of peridotite minerals is controlled by the compositions of the evolving melt and of the minerals and by mineral/melt partition coefficients. At the beginning of the process, clinopyroxene scavenges most of the hydrogen and garnet most of the HFSE. As the melt evolves and becomes enriched in hydrogen and LREE, olivine and garnet start to incorporate hydrogen and pyroxenes become enriched in LREE. The hydrogen content of peridotite increases with decreasing depth, overall (e.g., from 75 to 138 ppm H2O in the deep peridotites). Effective viscosity calculated using olivine hydrogen content for the deepest xenoliths near the lithosphere-asthenosphere boundary overlaps with estimates of asthenospheric viscosities. These xenoliths cannot be representative of the overall cratonic root because the lack of viscosity contrast would have caused basal erosion of lithosphere. Instead, metasomatism must be confined in narrow zones channeling kimberlite melts through the lithosphere and from where xenoliths are preferentially sampled. Such localized metasomatism by hydrogen-bearing melts therefore does not necessarily result in delamination of the cratonic root.
DS202008-1423
2020
Pearson, D.G.Meyer, N.A., Stachel, T., Pearson, D.G., Stern, R.A., Harris, J.W.Diamond formation from the lithosphere to the lower mantle revealed by Koffiefontein diamonds.Goldschmidt 2020, 1p. AbstractAfrica, South Africadeposit - Koffiefontein

Abstract: Because of their robust nature, diamonds survive mantle processes and protect occluded minerals since the time of diamond formation. For the Kaapvaal Craton - the archetype for craton formation and evolution - the geochemical signatures of inclusions in Koffiefontein diamonds tell a story from craton formation to evolution and from lithospheric (below about 160 km) to lower mantle (>660 km) environs. We analysed a suite of 94 lithospheric to lower mantle diamonds and their silicate and oxide inclusions. Geochemical results confirm that the diamond substrates are very depleted, with Mg#OL of 91.5-95.0 and a dominance of low-Ca (<1.8 wt% CaO), presumably dunite-derived garnet. The Si-rich nature and preserved high Mg# of the peridotitic diamond substrates beneath Koffiefontein and the formation of KNbO3 (goldschmidtite) from an extremely fractionated melt/fluid indicate that potentially both mantle- and subduction-related fluids are the cause of metasomatism in the Kaapvaal cratonic root. Mantle-like, restricted carbon isotopic compositions of both P- and E-type diamonds (avg. d13C -5.7 ‰ and -6.6 ‰, respectively) indicate that an abundant, mantle-derived CHO fluid is responsible for diamond formation. Diamonds have a large range in nitrogen concentrations and isotopic compositions, suggesting decoupling from carbon and heterogeneous sources. d18O of former bridgmanite and d13C of its host diamond document a purely mantle-derived lower mantle component. Combined, these results reveal a complex and multistage evolution of the Kaapvaal Craton whereby multiple episodes of fluid and melt metasomatism re-enriched the craton already, prior to diamond formation, followed by diamond entrainment in a kimberlite possibly derived from the lower mantle.
DS202008-1429
2020
Pearson, D.G.Palmato, M.G., Nestola, F., Novella, D, Pearson, D.G., Stachel, T.In-situ mineralogical characterization of sulphide inclusions in diamonds.Goldschmidt 2020, 1p. AbstractCanada, Ontariodeposit - Victor

Abstract: Among mineral inclusions in diamond, sulphides are the most abundant. Also, they are the keel tool for dating diamond formation given their high concentration of highlysiderophile elements. However, the mineralogical nature of these inclusions is not well understood, mainly due to the exsolution of the original, high temperature monosulphide solid solution (Mss) to Fe-, Ni- and Cu-rich endmembers during cooling, obscuring the original composition. This complex exsolution observed in sulphide inclusions in diamonds can also cause problems with Re-Os age determinations if the whole inclusion is not extracted. To overcome this issue, recently, sulphide inclusions have been homogenized at high temperature and controlled oxygen fugacity [1]. However, X-ray diffraction or Raman spectroscopy analyses, required to accurately identify the inclusion phases, and define their degree of crystallographic plus compositional homogeneity, have not been reported. Here we combine for the first time a thorough nondestructive multi-technique characterization of sulphide inclusions in diamonds from the Victor Mine (Canada) with homogenization experiments and isotopic analyses. In particular, we report X-ray diffraction data of the sulphides before and after homogenization, confirming a change from a polycrystalline assemblage of pyrrothite, pentlandite and chalcopyrite to single-crystal Mss. The data are used to reconstruct the Mss’ original bulk composition, define the true bulk isotopic ratios and document any difference in Re- Os isotope systematics.
DS202008-1444
2020
Pearson, D.G.Smit, K.V., Pearson, D.G., Krebs, M.Y., Woodland, S.Trace elements of rare CH4-bearing fluids in Zimbabwe diamonds.Goldschmidt 2020, 1p. AbstractAfrica, Zimbabwedeposit - Marange

Abstract: Marange diamonds (Zimbabwe) contain both fluid-poor (gem-quality) and fluid-bearing growth zones with abundant CH4. As such, they provide the unique opportunity to compare trace element compositions of CH4-bearing diamonds with those of carbonatitic and saline high density fluid (HDF)-bearing diamonds (gem-quality and fibrous) to obtain an overview of mantle source fluids for diamond growth. HDF’s in fibrous diamonds and some gem-quality diamonds have been linked to subduction of surficial material, consistent with the global link between diamond age and collisional tectonic events. Even though Marange diamonds have +d15N indicative of surficial recycling, they do not display the expected Eu or Sr anomalies. Fibrous diamonds have the most fractionated REE patterns, with negligible HREE and high (La/Yb)N ˜ 100- 10000. Gem-quality diamonds have highly variable (La/Yb)N; the most unfractionated HDF’s are in Victor and Cullinan diamonds with low (La/Yb)N <76. HDF’s in Marange diamonds are intermediate between these two extremes, with (La/Yb)N = 23-240. Differences in (La/Yb)N between different diamond suites relate either to varying initial compositions (where low (La/Yb)N reflects derivation during higher degrees of melting) or to the increasing interaction of HDF’s in fibrous diamonds with mantle rocks during fluid infiltration. Marange diamonds have rare +Ce anomalies, that have so far only been reported for Victor and Brazil (sub-lithospheric) gem-quality diamonds. The oxidation state of Ce (Ce4+ vs Ce3+) and development of Ce anomalies could be attributed to ƒO2, melt/fluid composition, and PT conditions. In Marange, Victor and Brazil diamonds, Ce4+ substitution for Zr4+ does not appear to be a factor since we find no correlation between Zr content and Ce anomalies. However, in Marange diamonds, CH4-bearing zones have less variable Ce anomalies compared to the CH4-free zones, which may suggest Ce anomalies are indicative of fluid oxidation state.
DS202008-1452
2020
Pearson, D.G.Tovey, M., Giuliani, A., Phillips, D., Sarkar, C., Pearson, D.G., Nowicki, T., Carlson, J.Decoupling of kimberlite source and primitive melt compositions.Goldschmidt 2020, 1p. AbstractSouth America, Brazil, Africa, South Africa, Canada, Northwest Territoriesgeochronology

Abstract: Kimberlites emplaced since ~2 Ga show Nd and Hf isotopic compositions that follow a remarkably consistent linear evolution [1]. However, kimberlites emplaced <200 Ma within a few thousand kilometers of the western paleo-margin of Pangea (i.e. Brazil, southern Africa, and Lac de Gras in western Canada) deviate towards more enriched Nd and Hf isotopic compositions possibly due to contribution by recycled crustal material, introduced to the deep kimberlite source via subduction [1]. To address this anomaly further we have compared new and existing geochronological and Nd isotopic data for 28 kimberlites from Lac de Gras (LDG; ca. 47 - 75 Ma) with their olivine and spinel mineral chemistries. Olivine grains typically include mantle-derived xenocrystic cores (Mg# = 83.5-94.2) overgrown by magmatic rims with relatively constant Mg# values. Olivine rims and chromite are the first magmatic phases to crystallise from kimberlite and can be used as proxies for primitive melt compositions. The average Mg# of olivine cores from each kimberlite is positively correlated with average olivine rim Mg#, suggesting that assimilation of heterogeneous lithospheric mantle contributed to the primitive melt compositions. The eNd(i) values from whole-rock and perovskite from LDG kimberlites vary between -3.4 and -0.4 that are negatively correlated with their emplacement ages. This correlation is indicative of an evolving kimberlite source which may have resulted from a progressively lower contribution of recycled material. No systematic relationships were observed between olivine rim or chromite compositions and age or Nd isotopic composition. This observation highlights decoupling between kimberlite source evolution and primitive melt compositions due to the combined effects of crustal recycling in the kimberlite source and lithospheric mantle assimilation during kimberlite ascent.
DS202010-1872
2020
Pearson, D.G.Regier, M.E., Pearson, D.G., Stachel, T., Luth, R.W., Stern, R.A., Harris, J.W.The lithospheric-to-lower-mantle carbon cycle recorded in superdeep diamonds. ( Kankan)Nature, Vol. 585, pp. 234-238. pdfAfrica, Guineadiamond inclusions

Abstract: The transport of carbon into Earth’s mantle is a critical pathway in Earth’s carbon cycle, affecting both the climate and the redox conditions of the surface and mantle. The largest unconstrained variables in this cycle are the depths to which carbon in sediments and altered oceanic crust can be subducted and the relative contributions of these reservoirs to the sequestration of carbon in the deep mantle1. Mineral inclusions in sublithospheric, or ‘superdeep’, diamonds (derived from depths greater than 250 kilometres) can be used to constrain these variables. Here we present oxygen isotope measurements of mineral inclusions within diamonds from Kankan, Guinea that are derived from depths extending from the lithosphere to the lower mantle (greater than 660 kilometres). These data, combined with the carbon and nitrogen isotope contents of the diamonds, indicate that carbonated igneous oceanic crust, not sediment, is the primary carbon-bearing reservoir in slabs subducted to deep-lithospheric and transition-zone depths (less than 660 kilometres). Within this depth regime, sublithospheric inclusions are distinctly enriched in 18O relative to eclogitic lithospheric inclusions derived from crustal protoliths. The increased 18O content of these sublithospheric inclusions results from their crystallization from melts of carbonate-rich subducted oceanic crust. In contrast, lower-mantle mineral inclusions and their host diamonds (deeper than 660 kilometres) have a narrow range of isotopic values that are typical of mantle that has experienced little or no crustal interaction. Because carbon is hosted in metals, rather than in diamond, in the reduced, volatile-poor lower mantle2, carbon must be mobilized and concentrated to form lower-mantle diamonds. Our data support a model in which the hydration of the uppermost lower mantle by subducted oceanic lithosphere destabilizes carbon-bearing metals to form diamond, without disturbing the ambient-mantle stable-isotope signatures. This transition from carbonate slab melting in the transition zone to slab dehydration in the lower mantle supports a lower-mantle barrier for carbon subduction.
DS202011-2047
2020
Pearson, D.G.Kilgore, M.L., Peslier, A.H., Brandon, A.D., Schaffer, L.A., Morris, R.V., Graff, T.G., Agresti, D.G., O'Reilly, S.Y., Griffin, W.L., Pearson, D.G., Barry, K.G., Shaulis, J.Metasomatic control of hydrogen contents in the layered cratonic mantle lithosphere sampled by Lac de Gras xenoliths in the central Slave Craton, Canada.Geochimica et Cosmochimica Acta, Vol. 286, pp. 29-83. pdfCanada, Northwest Territoriesxenoliths

Abstract: Whether hydrogen incorporated in nominally anhydrous mantle minerals plays a role in the strength and longevity of the thick cratonic lithosphere is a matter of debate. In particular, the percolation of hydrogen-bearing melts and fluids could potentially add hydrogen to the mantle lithosphere, weaken its olivines (the dominant mineral in mantle peridotite), and cause delamination of the lithosphere's base. The influence of metasomatism on hydrogen contents of cratonic mantle minerals can be tested in mantle xenoliths from the Slave Craton (Canada) because they show extensive evidence for metasomatism of a layered cratonic mantle. Minerals from mantle xenoliths from the Diavik mine in the Lac de Gras kimberlite area located at the center of the Archean Slave craton were analyzed by FTIR for hydrogen contents. The 18 peridotites, two pyroxenites, one websterite and one wehrlite span an equilibration pressure range from 3.1 to 6.6 GPa and include samples from the shallow (=145?km), oxidized ultra-depleted layer; the deeper (~145-180?km), reduced less depleted layer; and an ultra-deep (=180?km) layer near the base of the lithosphere. Olivine, orthopyroxene, clinopyroxene and garnet from peridotites contain 30-145, 110-225, 105-285, 2-105?ppm H2O, respectively. Within each deep and ultra-deep layer, correlations of hydrogen contents in minerals and tracers of metasomatism (for example light over heavy rare-earth-element ratio (LREE/HREE), high-field-strength-element (HFSE) content with equilibration pressure) can be explained by a chromatographic process occurring during the percolation of kimberlite-like melts through garnet peridotite. The hydrogen content of peridotite minerals is controlled by the compositions of the evolving melt and of the minerals and by mineral/melt partition coefficients. At the beginning of the process, clinopyroxene scavenges most of the hydrogen and garnet most of the HFSE. As the melt evolves and becomes enriched in hydrogen and LREE, olivine and garnet start to incorporate hydrogen and pyroxenes become enriched in LREE. The hydrogen content of peridotite increases with decreasing depth, overall (e.g., from 75 to 138?ppm H2O in the deep peridotites). Effective viscosity calculated using olivine hydrogen content for the deepest xenoliths near the lithosphere-asthenosphere boundary overlaps with estimates of asthenospheric viscosities. These xenoliths cannot be representative of the overall cratonic root because the lack of viscosity contrast would have caused basal erosion of lithosphere. Instead, metasomatism must be confined in narrow zones channeling kimberlite melts through the lithosphere and from where xenoliths are preferentially sampled. Such localized metasomatism by hydrogen-bearing melts therefore does not necessarily result in delamination of the cratonic root.
DS202011-2064
2020
Pearson, D.G.Tian, G., Liu, J., Scott, J.M., Chen, L-H., Pearson, D.G., Chu, Z.Architecture and evolution of the lithospheric roots beneath circum-cratonic orogenic belts - the Xing'an Mongolian orogenic belt and its relationship with adjacent North China and Siberian cratonic roots.Lithos, Vol. 376-377, 18p. PdfChina, Russia, Siberiaxenoliths

Abstract: The accretionary mobile belts surrounding ancient cratonic cores are an important facet of the growth and preservation of continental landmasses. Peridotites from Nuominhe in the Xing'an Mongolia Orogenic Belt (XMOB) provide an additional opportunity to examine the age, structure and evolution of mantle lithosphere separating two of the largest existing ancient continental nuclei: the North China Craton and the Siberian Craton. This suite of mantle rocks comprises fertile to refractory garnet- and spinel-facies harzburgites and lherzolites. Their lithophile element systematics show that the peridotites were metasomatized to variable extent by silicate-carbonate melts. Despite this, the highly siderophile element and Os isotope systematics appear to have been largely undisturbed. The Nuominhe peridotites have Re-depletion Os model ages (TRD) that range from 0.5 Ga to 2.4 Ga, with three peaks/major ranges at ~2.0-2.4 Ga, ~1.4-1.5 Ga and ~ 0.8 Ga, of which the latter two are closely similar to those data from other XMOB localities reported in the literature. The only section of the mantle that appears to have ages which correlate with crust formation is the suite with Neoproterozoic (~0.8 Ga) depletion ages, while the older mantle domains document older episodes of mantle depletion. Given the lack of correlation between equilibrium temperatures and bulk composition or TRD ages, the Nuominhe peridotites were inter-mixed in the mantle column, most likely as a result of incorporation of recycled older continental mantle fragments into juvenile Neoproterozoic mantle during the orogenic processes responsible for new lithosphere formation. Geothermobarometry of the Nuominhe peridotites indicates a conductive geotherm of ~60 mWm-2 and therefore a lithosphere thickness of ~125 km, which is thicker than most Phanerozoic continental terranes, and even thicker than Proterozoic regions that comprise the larger cratonic unit of the Siberian craton. This thick Proterozoic lithosphere sandwiched between the converging North China and Siberian cratons was evidently partly constructed from recycled refractory continental mantle fragments, perhaps extant in the convecting mantle, or in-part derived from the surrounding cratons, leading to a composite nature of the mantle in this re-healed continental suture. Re-accretion of recycled refractory old continental mantle fragments plays a significant role in affecting mantle composition and controlling the thickness of circum-cratonic landmasses between cratonic blocks.
DS202101-0014
2020
Pearson, D.G.Gruber, B., Chacko, T., Pearson, D.G., Currie, C., Menzies, A.Heat production and moho temperatures in cratonic crust: evidence from lower crustal xenoliths from the Slave craton.Lithos, doi.org/10.1016/ j.lithos.2020.105889 13p. PdfCanada, Northwest Territoriesdeposit - Diavik A-154

Abstract: Ambient Moho temperatures and lower crustal heat production are surprisingly poorly constrained in cratons. Here we address these problems using 15 lower crustal xenoliths from the Diavik A-154 kimberlite, Slave craton, Canada. Iron-magnesium exchange geothermometry on small biotite and amphibole inclusions in garnet indicates that the Slave craton lower crust was at a temperature of =500 °C at the time of kimberlite eruption (~55 Ma). The ambient lower crustal temperature was likely lower than 500 °C because the thermometers record the closure temperature of diffusional Fe2+-Mg exchange between touching mineral pairs. New measurements of K, U and Th concentrations in the constituent minerals, together with xenolith modes, allow reconstruction of the heat-producing element (HPE) K, U, and Th budget of the Slave craton lower crust. Metasedimentary granulites have an average heat production of 0.29 ± 0.01 µW/m3 (n = 3) whereas mafic granulites have an average heat production of 0.13 ± 0.03 µW/m3 (n = 12). Our new data clearly show that plagioclase abundance in both lithologies has a major influence on overall lower crustal heat production, being an important reservoir of all three HPE. Combining the heat production of mafic and metasedimentary granulites in their observed 80:20 proportions results in an average heat production value for the Slave craton lower crust of 0.16 ± 0.03 µW/m3. Using these heat production estimates, modeled Moho temperatures beneath Diavik of ~450-470 °C are broadly consistent with maximum lower crustal temperatures indicated by geothermometry. The low HPE contents predicted for cratonic lower crust must result in lower temperatures in the deep crust and mantle lithosphere, and in turn higher estimates for the thickness of mantle lithosphere. This effect becomes larger as the thickness of the low-HPE lower crustal layer increases. In the specific case of the central Slave craton, we find that model estimates of the diamond potential of the mantle lithosphere, as judged by the proportion of lithospheric mantle in the diamond stability field, are not strongly affected by small variations in lower crustal heat production and Moho temperature.
DS200712-0823
2006
Pearson, D.J.Pearson, D.J., O'Reilly, S.Y., Griffin, W.L., Alard, O., Belousova, E.Linking crustal and mantle events using in situ trace element and isotope analysis.Geochimica et Cosmochimica Acta, In press availableMantleGeochronology
DS200812-0705
2008
Pearson, D.J.Malarkey, J., Pearson, D.J., Nowell, G.M., Davidson, J.P., Ottley, C.J., Kjarsgaard, B., Mitchell, R.H., Kopylova, M.Constraining the crust and mantle contributions to kimberlite - a multi phase micro sampling approach.9IKC.com, 3p. extended abstractCanada, OntarioDeposit - C 14 perovskite crystals
DS201312-0337
2013
Pearson, D.J.Griffin, W.L., Yang, J.S., Robinson, P., Howell, D., Shi, R., O'Reilly, S.Y., Pearson, D.J.Diamonds and super reducing UHP assemblages in ophiolitic mantle, Tibet: where are the eclogites?X International Eclogite Conference, 1p. abstractAsia, TibetDiamond genesis
DS1998-0154
1998
Pearson, D.R.Boyd, F.R., Pearson, D.R., Mertzman, S.A.Spinel facies peridotites from the Kaapvaal root7th International Kimberlite Conference Abstract, pp. 100-102.South Africa, LesothoPeridotites - spinel, Deposit - Premier, Kimberley, Letseng, Frank Smith, Wel
DS1983-0510
1983
Pearson, G.Pearson, G.Seismic Gem ProspectingAustralian Gemologist., Vol. 15, No. 1, PP. 17-18.AustraliaDiamonds
DS1994-0387
1994
Pearson, G.Davies, G.R., Nixon, P.H., Pearson, G., Obata, M.Octahedral graphite bearing pyroxenites from Ronda, S. SpainProceedings of Fifth International Kimberlite Conference, Vol. 1, pp. 318-326.GlobalPyroxenites, Ronda
DS2002-0678
2002
Pearson, G.Hauri, E., Bulanova, G., Pearson, G., Griffin, B.Carbon and nitrogen isotope systematics in a sector zoned diamond from the Mir kimberlite, Yakutia.Eos, American Geophysical Union, Spring Abstract Volume, Vol.83,19, 1p.Russia, YakutiaGeochronology - diamond morphology, Deposit - Mir
DS201312-0693
2013
Pearson, G.Pearson, G.How much Archean lithospheric mantle is there in Arctic Canada?GEM Diamond Workshop Feb. 21-22, Noted onlyCanadaPetrology
DS201702-0231
2017
Pearson, G.Pearson, G.The complex history of the mantle roots beneath the Slave Craton and surrounding regions.Vancouver Kimberlite Cluster, Jan. 26, 1/4p. AbstractCanada, Northwest Territories, NunavutGeochronology
DS201705-0870
2017
Pearson, G.Pearson, G., Krebs, M., Stachel. T., Woodland, S., Chinn, I., Kong, J.Trace elements in gem-quality diamonds: origin and evolution of diamond-forming fluid inclusions.European Geosciences Union General Assembly 2017, Vienna April 23-28, 1p. 19281 AbstractTechnologyDiamond inclusions
DS201708-1730
2017
Pearson, G.Pearson, G.Trace elements in gem quality diamonds from the De Beers Victor mine, Ontario, Canada.11th. International Kimberlite Conference, PosterCanada, Ontario, Attawapiskatdeposit - Victor
DS201709-1968
2017
Pearson, G.Bussweiler, Y., Poitras, S., Borovinskaya, O., Tanner, M., Pearson, G.Rapid multielemental analysis of garnet with LA-ICP-TOF-MS implications for diamond exploration studies.Goldschmidt Conference, abstract 1p.Canada, Northwest Territoriesdiamond potential

Abstract: Garnet arguably constitutes the most important mineral in diamond exploration studies; not only can the presence of mantle garnet in exploration samples point to kimberlite occurrences, but its minor and trace element composition can further be used to assess the “diamond potential” of a kimberlite. The content of Cr and Ca, especially, has been found to be a reliable tool to test whether garnets originate from within the diamond stability field in the mantle [1]. Trace element patterns can further indicate the mantle host rock of the garnets, for example, whether they originate from a depleted or ultra-depleted mantle section [2]. Routinely, two separate analytical methods are necessary to fully characterize the composition of garnet; major and minor elements are usually determined by electron probe micro-analysis (EPMA), whereas determination of trace elements requires the more sensitive method of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Here, we demonstrate rapid measurement of the entire suite of elements in garnet employing a new, commercially available timeof-flight (TOF) mass spectrometer, the icpTOF (TOFWERK AG, Thun, Switzerland), coupled to a fast wash-out laser ablation system (Teledyne Cetac Technologies Inc., Omaha, NE, USA). Using garnets from exploration samples taken from the Horn Plateau, Northwest Territories, Canada [3], we directly compare the icpTOF results to EPMA and LA-ICP-MS data. We examine whether the icpTOF can reliably characterize the garnets in Cr versus Ca space and at the same time reproduce their trace element patterns, thereby offering a cost effective method of analysis. The method of LA-ICP-TOF-MS, with its high speed of data acquisition and its ability to record the entire mass spectrum simultaneously, may have great benefits for (diamond) exploration studies. Moreover, the method can be used for fast, highresolution imaging, which is applicable to a wide range of geological materials and settings [4].
DS201811-2575
2018
Pearson, G.Guotana, J.M., Morishita, T., Yamaguchi, R., Nishio, I., Tamura, A., Harigane, Y., Szilas, K., Pearson, G.Contrasting textural and chemical signatures of chromitites in the Mesoarchean Ulamertoq peridotite body, southern West Greenland.Geosciences, Vol. 8, no. 9, p. 328-Europe, Greenlandperidotite

Abstract: Peridotites occur as lensoid bodies within the Mesoarchaean orthogneiss in the Akia terrane of Southern West Greenland. The Ulamertoq peridotite body is the largest of these peridotites hosted within the regional orthogneiss. It consists mainly of olivine, orthopyroxene, and amphibole-rich ultramafic rocks exhibiting metamorphic textural and chemical features. Chromitite layers from different localities in Ulamertoq show contrasting characteristics. In one locality, zoned chromites are hosted in orthopyroxene-amphibole peridotites. Compositional zonation in chromites is evident with decreasing Cr and Fe content from core to rim, while Al and Mg increase. Homogeneous chromites from another locality are fairly uniform and Fe-rich. The mineral chemistry of the major and accessory phases shows metamorphic signatures. Inferred temperature conditions suggest that the zoned chromites, homogeneous chromites, and their hosts are equilibrated at different metamorphic conditions. In this paper, various mechanisms during the cumulus to subsolidus stages are explored in order to understand the origin of the two contrasting types of chromites.
DS201905-1064
2019
Pearson, G.Nishio, I., Morishita, T., Szilas, K., Pearson, G., Tani, K-I., Tamura, A., Harigane, Y., Guotana, J.M.Titanium clinohumite bearing peridotite from the Ulamertoq ultramafic body in the 3.0 Ga Akia terrane of southern west Greenland.Geosciences ( MDPI), 20p. Europe, Greenlandperidotite

Abstract: A titanian clinohumite-bearing dunite was recently found in the Ulamertoq ultramafic body within the 3.0 Ga Akia Terrane of southern West Greenland. Titanian clinohumite occurs as disseminated and discrete grains. Titanian clinohumite contains relatively high amounts of fluorine, reaching up to 2.4 wt.%. The high-Fo content of olivine (Fo93) coupled with low Cr/(Cr + Al) ratio of orthopyroxene implies that the dunite host is not of residual origin after melt extraction by partial melting of the primitive mantle. Olivine grains are classified into two types based on abundances of opaque mineral inclusions: (1) dusty inclusion-rich and (2) clear inclusion-free olivines. Opaque inclusions in coarse-grained olivines are mainly magnetite. Small amounts of ilmenite are also present around titanian clinohumite grains. The observed mineral association indicates partial replacement of titanian clinohumite to ilmenite (+magnetite) and olivine following the reaction: titanian clinohumite = ilmenite + olivine + hydrous fluid. The coexistence of F-bearing titanian clinohumite, olivine, and chromian chlorite indicates equilibration at around 800-900 °C under garnet-free conditions (<2 GPa). Petrological and mineralogical characteristics of the studied titanian clinohumite-bearing dunite are comparable to deserpentinized peridotites derived from former serpentinites. This study demonstrates the importance of considering the effects of hydration/dehydration processes for the origin of ultramafic bodies found in polymetamorphic Archaean terranes.
DS201907-1558
2019
Pearson, G.Liu, J., Cai, R., Pearson, G., Scott, J.M.Thinning and destruction of the lithospheric mantle root beneath the North China craton: a review.Earth Science Reviews, doi:10.1016/j.earscirev.2019.05.017 19p. Chinacraton

Abstract: It is widely accepted that the lithosphere beneath the eastern portion of the North China Craton (NCC) has suffered extensive thinning and destruction since the Mesozoic. The driving force for this transformation remains debated, although most models make a first-order link with the evolution of the Paleo-Pacific subduction and the effects of the Pacific slab subduction. In this review, we discuss the temporal and spatial relationships between the Paleo-Pacific and the Pacific slab subduction and the lithospheric thinning/destruction processes experienced by the NCC. We recognize four key stages: 1) an initial stage of low angle flat subduction of the Paleo-Pacific slab between ~170-145?Ma, 2) the sinking or rollback of the Paleo-Pacific slab and associated asthenosphere upwelling (145-110?Ma), 3) the disappearance of the Paleo-Pacific slab into lower mantle (110-55?Ma), and 4) the initiation of subduction of the present-day Pacific slab and associated formation of a Big Mantle Wedge (BMW) beneath East Asia (<55?Ma). The initial flat subduction of the Paleo-Pacific plate inhibited mantle-derived magmatism in the period between 170 and 145?Ma beneath the NCC. However, during this stage, intraplate deformation and crustal magmatism migrated westward from craton margin to interior. The cratonic subcontinental lithospheric mantle (SCLM) was further hydrated and metasomatized in addition to that caused by prior circum-cratonic orogenies/subductions. At ca. 155?Ma, the Paleo-Pacific plate began to sink or roll back, causing asthenosphere upwelling and triggering melting of the metasomatized SCLM to form arc-like basalts and low degree melts such as lamprophyres. Vigorous mantle flow/convection transported the metasomatically refertilized and weakened cratonic SCLM into the deep mantle and resulted in the thinning of the lithosphere. At the craton margins, where the lithosphere, thickened by collision, had lost a lower portion of the cratonic SCLM by mantle erosion, delamination of the eclogitic lower crust and underlying pre-thinned SCLM occurred. Upwelling asthenosphere replaced the detached lithosphere and then cooled by conduction to form new lithospheric mantle. This process may have continued to ca. 125?Ma when mantle-derived melts transitioned from arc-like to OIB-like basalts. Replacement of the mantle lithosphere by asthenosphere elevated the lithospheric geotherm and led to extensive crustal melting and the generation of massive volumes of felsic-intermediate magmatism in the eastern NCC until ~110?Ma. After the termination of lithosphere replacement, the speed of subduction of the Paleo-Pacific plate may have increased and by ca. 55?Ma, the whole slab vanished into the lower mantle. We suggest that the subsequent formation of present-day Pacific ocean lithosphere led to a new phase of low angle subduction of the Pacific plate margin. At ca. 35?Ma, the Pacific plate started to descend forming a BMW, accompanied by upwelling of asthenosphere and widespread eruption of alkali basalts across eastern China. The ongoing subduction of the Pacific plate may also lead to further lithospheric thinning.
DS201908-1815
2019
Pearson, G.Shu, Q, Brey, G.P., Pearson, G., Liu, J., Gibson, S.A., Becker, H.The evolution of the Kaapvaal craton: a multi-isotopic perspective from lithospheric peridotites from Finsch diamond mine.Precambrian Research, 105380, 21p. PdfAfrica, South Africadeposit - Finsch

Abstract: Accurately dating the formation and modification of Earth’s sub-cratonic mantle still faces many challenges, primarily due to the long and complex history of depletion and subsequent metasomatism of this reservoir. In an attempt to improve this, we carried out the first study on peridotites from the Kaapvaal craton (Finsch Mine) that integrates results from Re-Os, Lu-Hf, Sm-Nd and Sr-isotope systems together with analyses of major-, trace- and platinum-group elements. The Finsch peridotites are well-suited for such a study because certain compositional features reflect they were highly depleted residues of shallow melting (1.5?GPa) at ambient Archean mantle temperatures. Yet, many of them have overabundant orthopyroxene, garnet and clinopyroxene compared to expected modal amounts for residues from partial melting. Finsch peridotites exhibit a wide range of rhenium depletion ages (TRD) from present day to 2.7?Ga, with a prominent mode at 2.5?Ga. This age overlaps well with a Lu-Hf isochron of 2.64?Ga (eHf (t)?=?+26) which records silico-carbonatitic metasomatism of the refractory residues. This late Archean metasomatism is manifested by positive correlations of Pt/Ir and Pd/Ir with 187Os/188Os ratios and good correlations of modal amounts of silicates, especially garnet, with Os isotope ratios. These correlations suggest that the Highly Siderophile Elements (HSE) and incompatible element reenrichment and modal metasomatism result from one single major metasomatic event at late Archean. Our detailed study of Finsch peridotites highlights the importance of using multiple isotopic systems, to constrain the ages of events defining the evolution of lithospheric mantle. The Re-Os isotope system is very effective in documenting the presence of Archean lithosphere, but only the oldest TRD ages may accurately date or closely approach the age of the last major partial melting event. For a meaningful interpretation of the Re-Os isotope systematics the data must be combined with HSE patterns, trace-element compositions and ideally other isotopic systems, e.g. Lu-Hf. This is highlighted by the widespread evidence in Finsch peridotites of Pt, Pd and Re enrichment through significant Base Metal Sulfide (BMS) addition (mainly in the range of 0.002-0.08?wt%) that systematically shifts the mode of TRD model ages to younger ages.
DS201910-2260
2019
Pearson, G.Graf, C., Sandner, T., Woodland, A., Hofer, H., Seitz, H-M., Pearson, G., Kjarsgaard, B.Metasomatism, oxidation state of the mantle beneath the Rae craton, Canada.Goldschmidt2019, 1p. AbstractCanadacraton

Abstract: The Rae craton is an important part of the Canadian Shield and was amalgamated to the Slave craton at ?? 1.9 Ga [1]. Recent geophysical and geochemical data indicate a protracted geodynamic history [1, 2]. Even though the oxidation state of the Earth’s mantle has an important influence of fluid compositions and melting behavior, no data on the oxidation state of the Rae’s mantle are available. The aims of this study were to 1) determine the oxidation state (ƒO2) of the lithosphere beneath the Rae craton, 2) link these results to potential metasomatic overprints and 3) compare the geochemical evolution with the Slave craton. We studied 5 peridotite xenoliths from Pelly Bay (central craton) and 22 peridotites from Somerset Island (craton margin). Pelly Bay peridotites give T < 905°C and depths of ??80- 130 km. Garnets have depleted or “normal” REE patterns, the latter samples recording fO2 values ??0.5 log units higher. The deeper samples are more enriched and oxidised. Peridotites from Somerset Island record T ??825-1190°C, a ?logfO2 ranging from ?? FMQ - FMQ-3.6 from a depth interval of ??100-150 km. Garnets exhibit two REE signatures - sinusoidal and “normal” - indicating an evolutionary sequence of increasing metasomatic re-enrichment and a shift from fluid to melt dominated metasomatism. Compared to the Slave craton, the Rae mantle is more reduced at ??80km but becomes up to 2 log units more oxidised (up to ??FMQ-1) at ??100-130 km. Similar oxidising conditions can be found >140 km in the Slave mantle [3]. Especially under Somerset Island, the lithospheric mantle has contrasting fO2 and metasomatic overprints in the same depth range, which may represent juxtaposed old and rejuvenated domains [2].
DS201911-2563
2019
Pearson, G.Smit, K.V., Walter, M.J., Pearson, G., Aulbach, S.Diamonds and the mantle geodynamics of carbon.Researchgate, Chapter 5, pp. 89-128. pdfMantlemineralogy

Abstract: he science of studying diamond inclusions for understanding Earth history has developed significantly over the past decades, with new instrumentation and techniques applied to diamond sample archives revealing the stories contained within diamond inclusions. This chapter reviews what diamonds can tell us about the deep carbon cycle over the course of Earth’s history. It reviews how the geochemistry of diamonds and their inclusions inform us about the deep carbon cycle, the origin of the diamonds in Earth’s mantle, and the evolution of diamonds through time.
DS201912-2775
2019
Pearson, G.Czas, J., Pearson, G., Stachel, T., Kjarsgaard, B.A., Read, G.A Paleoproterozic diamond bearing lithospheric mantle root beneath the Archean Sask Craton.Lithos, 10.1016/j.lithos.2019.105301 63p. PdfCanada, Saskatchewancraton

Abstract: The recently recognised Sask Craton, a small terrane with Archean (3.3-2.5 Ga) crustal ages, is enclosed in the Paleoproterozoic (1.9-1.8 Ga) Trans Hudson Orogen (THO). Only limited research has been conducted on this craton, yet it hosts major diamond deposits within the Cretaceous (~106 to ~95 Ma) Fort à la Corne (FALC) Kimberlite Field. This study describes major, trace and platinum group element data, as well as osmium isotopic data from peridotitic mantle xenoliths (n = 26) from the Star and Orion South kimberlites. The garnet-bearing lithospheric mantle is dominated by moderately depleted lherzolite. Equilibration pressures and temperatures (2.7 to 5.5 GPa and 840 to 1250 °C) for these garnet peridotites define a cool geotherm indicative of a 210 km thick lithosphere, similar to other cratons worldwide. Many of the peridotite xenoliths show the major and trace element signatures of carbonatitic and kimberlitic melt metasomatism. The Re-Os isotopic data yield TRD (time of Re-depletion) model ages, which provide minimum estimates for the timing of melt depletion, ranging from 2.4 to 0.3 Ga, with a main mode spanning from 2.4 to 1.7 Ga. No Archean ages were recorded. This finding and the complex nature of events affecting this terrane from the Archean through the Palaeoproterozoic provide evidence that the majority of the lithospheric mantle was depleted and stabilised in the Palaeoproterozoic, significantly later than the Archean crust. The timing of the dominant lithosphere formation is linked to rifting (~2.2 Ga - 2.0 Ga), and subsequent collision (1.9-1.8 Ga) of the Superior and Hearne craton during the Wilson cycle of the Trans Hudson Orogen.
DS202002-0172
2019
Pearson, G.Czas, J., Pearson, G., Stachel, T., Kjarsgaard, B., Read, G.H. J. Pearson, G., Stachel, T., KjaA Paleoproterozoic diamond bearing lithospheric mantle root beneath the Archean Sask craton, Canada.Lithos, DOI:10.1016/ j.lithos.2019.105301Canada, Saskatchewandiamond genesis
DS202002-0202
2020
Pearson, G.Lawley, C.J.M., Pearson, G., Waterton, P., Zagorevski, A., Bedard, J.H., Jackson, S.E., Petts, D.C., Kjarsgaard, B.A., Zhang, S., Wright, D.Element and isotopic signature of re-fertilized mantle peridotite as determined by nanopower and olivine LA-ICPMS analyses.Chemical Geology, DOI:101016/ j.chemgeo.2020.119464Mantleperidotite

Abstract: The lithospheric mantle should be depleted in base- and precious-metals as these elements are transferred to the crust during partial melting. However, some melt-depleted mantle peridotites are enriched in these ore-forming elements. This may reflect re-fertilization of the mantle lithosphere and/or sequestering of these elements by residual mantle phase(s). Both processes remain poorly understood because of the low abundances of incompatible elements in peridotite and the nugget-like distribution of digestion-resistant mantle phases that pose analytical challenges for conventional geochemical methods. Herein we report new major and trace element concentrations for a suite of mantle peridotite and pyroxenite samples from the Late Permian to Middle Triassic Nahlin ophiolite (Cache Creek terrane, British Columbia, Canada) using Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICPMS) analysis of nanoparticulate powders and olivine. Compatible to moderately incompatible element concentrations suggest that Nahlin ophiolite peridotites represent residues after =20% melt extraction. Pyroxenite dykes and replacive dunite bands are folded and closely intercalated with residual harzburgite. These field relationships, coupled with the presence of intergranular base metal sulphide, clinopyroxene and Cr-spinel at the microscale, point to percolating melts that variably re-fertilized melt-depleted mantle peridotite. Radiogenic Pb (206Pb/204Pb?=?15.402-19.050; 207Pb/204Pb?=?15.127-15.633; 208Pb/204Pb?=?34.980-38.434; n?=?45) and Os (187Os/188Os 0.1143-0.5745; n?=?58) isotope compositions for a subset of melt-depleted peridotite samples further support metasomatic re-fertilization of these elements. Other ore-forming elements are also implicated in these metasomatic reactions because some melt-depleted peridotite samples are enriched relative to the primitive mantle, opposite to their expected behaviour during partial melting. New LA-ICPMS analysis of fresh olivine further demonstrates that a significant proportion of the highly incompatible element budget for the most melt-depleted rocks is either hosted by, and/or occurs as trapped inclusions within, the olivine-rich residues. Trapped phases from past melting and/or re-fertilization events are the preferred explanation for unradiogenic Pb isotope compositions and Paleozoic to Paleoproterozoic Re-depletion model ages, which predate the Nahlin ophiolite by over one billion years.
DS202011-2059
2020
Pearson, G.Pearson, G.Diamonds found with gold in Canada's Far North offer clues to Earth's early history: discovery of diamonds in small rock sample hints at possibility of new deposits in area similar to world's richest gold mine in South Africa.www.sciencedaily.com/releases/2020/10/201006153459.htm>., Oct. 6, 3p. Canada, Nunavutdiamond genesis

Abstract: The presence of diamonds in an outcrop atop an unrealized gold deposit in Canada's Far North mirrors the association found above the world's richest gold mine, according to University of Alberta research that fills in blanks about the thermal conditions of Earth's crust three billion years ago.
DS200612-0945
2006
Pearson, G.D.Morel, M.L.A., Simon, N.S.C., Davies, G.F., Pearson, G.D.Modification of cratonic lithosphere: influence of tectono magmatic events on Kaapvaal craton ( South Africa).Geochimica et Cosmochimica Acta, Vol. 70, 18, p. 428. abstract only.Africa, South AfricaMagmatism, tectonics
DS200612-1178
2006
Pearson, G.D.Rosenthal, A., Foley, S.F., Pearson, G.D., Nowell, G., Tappe, S.Ugand an kamafugites: re-melting of a variable enriched veined subcontinental lithospheric mantle.Geochimica et Cosmochimica Acta, Vol. 70, 18, p. 26, abstract only.Africa, UgandaGeochemistry - melting
DS201712-2668
2017
Pearson, G.D.Agrosi, G., Tempesta, G., Mele, D., Allegretta, I., Terzano, R., Shirery, S.B., Pearson, G.D., Nestola, F.Non-destructive, multi-method, internal analysis of multiple inclusions in a single diamond: first occurrence of mackinawite ( Fe,Ni)1+xSAmerican Mineralogist, Vol. 102, pp. 2235-2243.Russia, Siberiadeposit - Udachnaya

Abstract: A single gem lithospheric diamond with five sulfide inclusions from the Udachnaya kimberlite (Siberia, Russia) has been analyzed non-destructively to track the growth conditions of the diamond. Sulfides are the most abundant mineral inclusions in many lithospheric diamond crystals and are the most favorable minerals to date diamond crystals by Re-Os isotope systematics. Our investigation used non-destructive, micro-techniques, combining X-ray tomography, X-ray fluorescence, X-ray powder diffraction, and Raman spectroscopy. This approach allowed us to determine the spatial distribution of the inclusions, their chemical and mineralogical composition on the microscale, and, finally, the paragenetic association, leaving the diamond host completely unaffected. The sample was also studied by X-ray diffraction topography to characterize the structural defects of the diamond and to obtain genetic information about its growth history. The X-ray topographic images show that the sample investigated exhibits plastic deformation. One set of {111} slip lamellae, corresponding to polysynthetic twinning, affects the entire sample. Chemical data on the inclusions still trapped within the diamond show they are monosulfide solid solutions of Fe, Ni and indicate a peridotitic paragenesis. Micro-X-ray diffraction reveals that the inclusions mainly consist of a polycrystalline aggregate of pentlandite and pyrrothite. A thorough analysis of the Raman data suggests the presence of a further Fe, Ni sulfide, never reported so far in diamonds: mackinawite. The total absence of any oxides in the sulfide assemblage clearly indicates that mackinawite is not simply a “late” alteration of pyrrhotite and pentlandite due to secondary oxidizing fluids entering diamond fractures after the diamond transport to the surface. Instead, it is likely formed as a low-temperature phase that grew in a closed system within the diamond host. It is possible that mackinawite is a more common phase in sulfide assemblages within diamond crystals than has previously been presumed, and that the percentage of mackinawite within a given sulfide assemblage could vary from diamond to diamond and from locality to locality.
DS1920-0293
1926
Pearson, H.Pearson, H.The Diamond Trail. an Account of Travel Among the Little Known Bahian Diamond Fields of Brasil.London: H.f. And G. Witherby, 230P.BrazilTravelogue
DS1995-1463
1995
Pearson, J.Pearson, J.Geology of the Mesoproterozoic Gifford Creek alkaline igneous complex, Gascoyne Province, Western Australia.University of West. Australian Key Centre, held Feb. 15, 16th., 12p.AustraliaAlkaline rocks, Gifford Creek complex
DS201012-0263
2010
Pearson, J.Halpin, K., Ansdell, K., Pearson, J.The characteristics and origin of Great Western Minerals Group Ltd.'s Hoidas Lake REE deposit, Rae province, Northwestern Saskatchewan.International Workshop Geology of Rare Metals, held Nov9-10, Victoria BC, Open file 2010-10, extended abstract pp.45.Canada, SaskatchewanAlkalic
DS200412-1510
2004
Pearson, J.G.Pearson, J.G., Nowell, G.M.Re Os and Lu Hf isotope constraints on the origin and age of pyroxenites from the Beni Bousera peridotite massif: implications fJournal of Petrology, Vol. 45, 2, pp. 439-455.Africa, MoroccoGeochronology
DS200912-0490
2009
Pearson, J.G.McNeill, J., Pearson, J.G., Klein Ben-David, O., Nowell, G.M., Ottlet, C.J., Chinn, I.Quantitative analysis of trace element concentration in some gem quality diamonds.Journal of Physics Condensed Matter, in pressSouth America, Venezuela, Russia, Siberia, South AfricaDeposit - Cullinan, Mir, Udachnaya
DS1994-1349
1994
Pearson, J.M.Pearson, J.M., Barley, M.E., Taylor, W.R.Alkaline rocks and fenites of the Proterozoic Gifford Creek Complex, Gascoyne Province, Western Australia.Geological Association of Canada (GAC) Abstract Volume, Vol. 19, p. posterAustraliaAlkaline rocks, Gifford Creek
DS1995-1464
1995
Pearson, J.M.Pearson, J.M.Gascoyne alkaline rocks: mineralization potential, petrogenesis and tectonic significance.Ph.d. Thesis, University of of Western Australia, AustraliaAlkaline rocks, Deposit -Gascoyne area
DS1996-1086
1996
Pearson, J.M.Pearson, J.M., Taylor, W.R.Mineralogy and geochemistry of fenitized alkaline ultrabasic sills of the Gifford Creek Complex, GascoyneCanadian Mineralogist, Vol. 34, pt. 2, April pp. 201-220.Australia, Western AustraliaAlkaline sills
DS1996-1087
1996
Pearson, J.M.Pearson, J.M., Taylor, W.R., Barley, M.E.Geology of the alkaline Gifford Creek Complex, Gascoyne Complex, westernAustralia.Australian Journal of Earth Sciences, Vol. 43, No. 3, June 1, pp. 299-310.AustraliaAlkaline rocks, Gifford Creek Complex
DS1993-0252
1993
Pearson, L.M.Christensen, R., Johnson, W., Pearson, L.M.Covariance function diagnostics for spatial linear modelsMathematical Geology, Vol. 25, No. 2, pp. 145-160GlobalGeostatistics, Kriging
DS2000-0363
2000
Pearson, N.Griffin, W.L., Pearson, N., Bolousova, Van AchterberghThe hafnium isotope composition of cratonic mantle: LAM MC ICPMS analysis of zircon megacrysts in kimberlites.Geochimica et Cosmochimica Acta, Vol. 64, pp. 133-47.AustraliaGeochronology
DS2001-0258
2001
Pearson, N.Djomani, Y.P., Griffin, B., O'Reilly, S., Pearson, N.The Slave Craton ( Canada) in deep analysisGemoc Annual Report 2000, p. 28-9.Northwest TerritoriesGeophysics - gravity, Lithosphere
DS2001-0412
2001
Pearson, N.Griffin, B., Pearson, N., O'Reilly, S.Sorting out the mantle: in situ measurement of Rhenium- Osmium (Re-Os) isotopes in mantle sulphides by LAM MC ICPNSGemoc Annual Report 2000, p. 32-3.FranceGeochronology - lherzolite
DS2003-0869
2003
Pearson, N.Malkovets, V.G., Taylor, L.A., Griffin, W., O'Reilly, S., Pearson, N., PokhilenkoCratonic considitons beneath Arkhangelsk, Russia: garnet peridotites form the Grib8ikc, Www.venuewest.com/8ikc/program.htm, Session 4, POSTER abstractRussia, Kola PeninsulaMantle geochemistry, Deposit - Grib
DS2003-1557
2003
Pearson, N.Zheng, J., Sun, M., Lu,. F., Pearson, N.Mesozoic lower crustal xenoliths and their significance in lithospheric evolution beneathTectonophysics, Vol. 361, No. 1-2, pp. 37-60.ChinaXenoliths
DS200612-1060
2006
Pearson, N.Pearson, N.Isotopic ratio measurement using microbeam methods: where do we stand and where are we going?GEMOC Annual Report, 2005, p. 32-33.MantleGeochronology - laser ablation
DS200612-1605
2006
Pearson, N.Zheng, J., Griffin, W.L., O'Reilly, S.Y., Zhang, M., Pearson, N.Zircons in mantle xenoliths record the Triassic Yangtze North Chin a continental collision.Earth and Planetary Science Letters, in press availableChinaGeochronology, peridotite, North China Craton
DS200612-1606
2006
Pearson, N.Zheng, J., Griffin, W.L., O'Reilly, S.Y., Zhang, M., Pearson, N., Luo, Z.The lithospheric mantle beneath the southeastern Tian Shan area, northwest China.Contributions to Mineralogy and Petrology, Vol. 141, 4, April pp. 457-479.Asia, ChinaPetrology
DS200612-1607
2006
Pearson, N.Zheng, J., Griffin, W.L., O'Reilly, S.Y., Zhang, M., Pearson, N., Pan, Y.Wide spread Archean basement beneath the Yangtze Craton.Geology, Vol. 34, 6, June pp. 417-420.Asia, ChinaGeochronology
DS200712-1239
2007
Pearson, N.Zheng, J.P., Griffin, W.L., O'Reilly, S.Y., Yu, C.M., Zhang, H.F., Pearson, N., Zhang, M.Mechanism and timing of lithospheric modification and replacement beneath the eastern North Chin a Craton: peridotitic xenoliths from the 100 Ma Fuxin basaltsGeochimica et Cosmochimica Acta, In press, availableChinaXenoliths
DS200712-1240
2007
Pearson, N.Zheng, J.P., Griffin, W.L., O'Reilly, S.Y., Yu, C.M., Zhang, H.F., Pearson, N., Zhang, M.Mechanism and timing of lithospheric modification and replacement beneath the eastern North Chin a Craton: peridotitic xenoliths from the 100 Ma Fuxin basalts...Geochimica et Cosmochimica Acta, Vol. 71, 21, pp. 5303-5225.ChinaXenoliths - regional synthesis
DS200912-0859
2009
Pearson, N.Zheng, J., Griffin, W.L., O'Reilly, S.Y., Liu, G.L., Pearson, N., Zhang, W., Yu, C.M., Su, Tang, ZhaoNeoarchean ( 2.7-2.8 Ga) accretion beneath the North Chin a Craton: U Pn age.trace elemens and hf isotopes of zircons in Diamondiferous kimberlites.Lithos, Vol. 112, 3-4, pp. 188-202.ChinaGeochronology
DS200912-0860
2009
Pearson, N.Zheng, J.P., Griffin, W.L., O'Reilly, S.Y., Sun, M., Zheng, S., Pearson, N., Gao, Yu, Su, Tang, Liu, WuAge and composition of granulite and pyroxenite xenoliths in Hannuoba basalts reflect Paleogene underplating beneath the North Chin a craton.Chemical Geology, Vol. 264, 1-4, pp. 266-280.ChinaXenoliths
DS201112-0454
2011
Pearson, N.Howell, D., Griffin, W.L., O'Reilly, S.Y., O'Neill, C., Pearson, N., Piazolo, Stachel, Stern, NasdalaMixed habit diamonds: evidence of a specific mantle fluid chemistry?Goldschmidt Conference 2011, abstract p.1051.TechnologyDiamond morphology, growth
DS1990-1166
1990
Pearson, N.J.Pearson, N.J., O'Reilly, S.Y., Griffin, W.L.The lower crust beneath the eastern margin of the Australian craton:xenolith evidence for the gabbroto eclogite transitionGeological Society of Australia Abstracts, No. 25, No. A12.11 pp. 237. AbstractAustraliaXenolith, Eclogites
DS1991-0264
1991
Pearson, N.j.Chen, Y.D., Pearson, N.j., O'Reilly, S.Y., Griffin, W.L.Applications of olivine: orthopyroxene-spinel oxygen geobarometers to the redox state of the upper mantleProceedings of Fifth International Kimberlite Conference held Araxa June 1991, Servico Geologico do Brasil (CPRM) Special, pp. 42-44Australia, China, South Africa, TanzaniaGeobarometry, Mantle
DS1991-1315
1991
Pearson, N.J.Pearson, N.J., O'Reilly, S.Y.Thermobarometry and P-T-t paths: the granulite to eclogite transition in lower crustal xenoliths from eastern AustraliaJournal of Metamorphic Geology, Vol. 9, No. 3, May pp. 349-359AustraliaEclogites, Geothermobarometry
DS1991-1316
1991
Pearson, N.J.Pearson, N.J., O'Reilly, S.Y., Griffin, W.L.The granulite to eclogite transition beneath the eastern margin of the Australian cratonEuropean Journal of Mineralogy, Vol. 3, No. 2, pp. 293-322AustraliaEclogite, Craton
DS1991-1317
1991
Pearson, N.J.Pearson, N.J., O'Reilly, S.Y., Griffin, W.L.Heterogeneity in the thermal state of the lower crust and upper mantle beneath eastern AustraliaAustralian Society of Exploration Geophysicists and Geological Society of Australia, 8th. Exploration Conference in the Bulletin., Vol. 22, No. 2, June pp. 295-298AustraliaMantle, Geothermometry
DS1992-0246
1992
Pearson, N.J.Chen, Y.D., Pearson, N.J., O'Reilly, S.Y., Griffin, W.L.Application of the olivine-orthopyroxene spinel oxygen geobarometers to redox state of upper mantle11th. Australian Geol. Convention Held Ballarat University College, Jan., Abstract onlyAustraliaMantle, Geobarometry
DS1993-1208
1993
Pearson, N.J.Pearson, N.J., O'Reilly, S.Y., Griffin, W.L.Thermal states of diverse lithospheric sections: lower crustal xenoliths across carton boundaries from South Africa and Australia.The Xenolith window into the lower crust, abstract volume and workshop, p. 16.South Africa, AustraliaKaapvaal craton, Tasman Fold Belt
DS1995-1465
1995
Pearson, N.J.Pearson, N.J., O'Reilly, S.Y., Griffin, W.L.The crust mantle boundary beneath cratons and craton margins: a transect across southwest margin KaapvaalLithos, Vol. 36, No. 3/4, Dec. 1, pp. 257-288.South AfricaCraton -Kaapvaal, Geothermometry
DS1995-1635
1995
Pearson, N.J.Ryan, C.G., Griffin, W.L., Pearson, N.J., Win, T.T.Garnet geotherms: derivation of P-T dat a from chromium-Pyrope garnetsProceedings of the Sixth International Kimberlite Conference Abstracts, pp. 476-478.South Africa, Russia, Siberia, Mongolia, China, Solomon IslandsGeothermometry, Deposit -Kaapvaal area and Dadlyn area
DS1996-1088
1996
Pearson, N.J.Pearson, N.J.Laser ablation ICPMS: applications to diamond explorationGeological Society of Australia 13th. Convention held Feb., No. 41, abstracts p. 338.AustraliaPetrogenesis, Technology -LAM-ICPMS
DS1996-1089
1996
Pearson, N.J.Pearson, N.J., O.Reilly, S.Y., Griffin, W.L.Lower crust geothermsInternational Geological Congress 30th Session Beijing, Abstracts, Vol. 1, p. 119.South AfricaKaapvaal Craton, Geothermometry
DS1998-0108
1998
Pearson, N.J.Belousova, E.A., Griffin, W.L., Pearson, N.J.Trace element composition and cathodluminescence properties of Southern african kimberlitic zircons.Mineralogical Magazine, Vol. 62, No. 3, June pp. 355-66.South AfricaDiamond inclusions, Mineral chemistry
DS1998-0306
1998
Pearson, N.J.Davies, R., Griffin, W.L., Pearson, N.J., Andrew, DoyleDiamonds from the Deep: Pipe DO 27, Slave Craton, Canada7th International Kimberlite Conference Abstract, pp. 170-172.Northwest TerritoriesDiamond inclusions, Deposit - Pipe DO-27
DS1998-1139
1998
Pearson, N.J.Pearson, N.J., Griffin, Kaminsky, Van AchterberghTrace element discrimination of garnet from Diamondiferous kimberlites andlamproites.7th. Kimberlite Conference abstract, pp. 673-5.South Africa, Russia, Siberia, Yakutia, Venezuela, GhanaGeochemistry, Garnets
DS1998-1140
1998
Pearson, N.J.Pearson, N.J., Griffin, W.L., Doyle, O'Reilly, KiviXenoliths from kimberlite pipes of the Lac de Gras area, Slave Craton, Canada.7th. Kimberlite Conference abstract, pp. 670-2.Northwest TerritoriesGeothermometry, Xenoliths
DS1998-1596
1998
Pearson, N.J.Wyatt, B.A., Morfi, L., Gurney, J.J., Pearson, N.J.Garnets in a polymict xenolith from the Bultfontein Mine: new preliminary geochemical and textural data.7th International Kimberlite Conference Abstract, pp. 968-70.South AfricaPeridotite, mineral chemistry, Deposit - Bultfontein
DS2000-0320
2000
Pearson, N.J.Gaul, O.F., Griffin, W.L., Pearson, N.J.Mapping olivine composition in the lithospheric mantleEarth and Planetary Science Letters, Vol. 182, No. 3-4, Nov. 15, pp. 223-35.MantleOlivine
DS2001-0897
2001
Pearson, N.J.Pearson, N.J., Griffin, Spetsius, O'ReillyIn situ Re Os analysis of mantle sulphides: a new microanalytical technique to unravel the evolution...Slave-Kaapvaal Workshop, Sept. Ottawa, 6p. abstractRussia, Siberia, YakutiaGeochronology, Deposit - Udachnaya
DS2002-0015
2002
Pearson, N.J.Alard, O., Griffin, W.L., Pearson, N.J., Lorand, J.P., O'Reilly, S.Y.New insights into the Re Os systematics of sub-continental lithospheric mantle from an insitu analysis of sulphides.Earth and Planetary Science Letters, Vol. 203, 3, pp. 651-663.MantleGeochronology
DS2002-0035
2002
Pearson, N.J.Andersen, T., Griffin, W.L., Pearson, N.J.Crustal evolution in the southwest part of the Baltic Shield: the Hf isotope evidenceJournal of Petrology, Vol. 43, 9, Sept.pp. 1725-48.Baltic Shield, NorwayTectonics, Geochronology
DS2002-0606
2002
Pearson, N.J.Graham, S., Lambert, D.D., Shee, S.R., Pearson, N.J.Juvenile lithospheric mantle enrichment and the formation of alkaline ultramafic magmaChemical Geology, Vol. 186, No. 2-4, pp. 215-33.Australia, westernMelnoites, Geochronology
DS2002-1236
2002
Pearson, N.J.Pearson, N.J., Alard, O., Griffin, Jackson, O'ReillyIn situ measurement of Re Os isotopes in mantle sulfides by laser ablation multicollector inductively..Geochimica et Cosmochimica Acta, Vol. 66, 6, pp. 1037-50.Russia, Siberia, Northwest TerritoriesCraton - mass spectrometry, rhenium, osmium, Peridotites
DS2002-1636
2002
Pearson, N.J.Van Achterbergh, E., Griffin, W.L., Ryan, C.G., O'Reilly, S.Y., Pearson, N.J.Subduction signature for quenched carbonatites from the deep lithosphereGeology, Vol.30,8,Aug.pp.743-6.MantleSubduction, Carbonatite
DS2003-0050
2003
Pearson, N.J.Aulbach, S., Griffin, W.L., Pearson, N.J., O'Reilly, S.Y., Kivi, K., Doyle, B.J.Origins of eclogites beneath the central Slave Craton8ikc, Www.venuewest.com/8ikc/program.htm, Session 2, POSTER abstractNorthwest TerritoriesEclogites and Diamonds
DS2003-0493
2003
Pearson, N.J.Graham, S., Lambert, D.D., Shee, S.R., Pearson, N.J.Erratum to juvenile lithospheric mantle enrichment and the formation of alkalineChemical Geology, Vol. Sept. 15, p.. 361. Original Vol. 186, pp. 215-233.AustraliaMelnoites, Geochronology
DS2003-0502
2003
Pearson, N.J.Griffin, W.L., O'Reilly, S.Y., Abe, N., Aulbach, S., Davies, R.M., Pearson, N.J.The origin and evolution of Archean lithospheric mantlePrecambrian Research, Vol. 127, 1-2, Nov. pp. 19-41.China, South Africa, Siberia, Northwest Territories, BoGeochemistry, SCLM, continental, Archon, metasomatism
DS2003-1051
2003
Pearson, N.J.Pearson, N.J., Griffin, W.L., O'Reilly, S.Y., Delpech, G.Magnesium isotopic compositions of olivine from the lithospheric mantle8 Ikc Www.venuewest.com/8ikc/program.htm, Session 4, AbstractRussia, Siberia, South Africa, Northwest TerritoriesMantle geochemistry
DS2003-1407
2003
Pearson, N.J.Van Achterbergh, E., Griffin, W.L., O'Reilly, S.Y., Ryan, C.G., Pearson, N.J.Melt inclusions from the deep Slave lithosphere: constraints on the origin and evolution8 Ikc Www.venuewest.com/8ikc/program.htm, Session 3, AbstractNorthwest TerritoriesDiamonds - melting
DS2003-1447
2003
Pearson, N.J.Wang, K.L., O'Reilly, S.Y., Griffin, W.L., Chung, S.L., Pearson, N.J.Proterozoic mantle lithosphere beneath the extended margin of the South Chin a block:Geology, Vol. 31, 8, pp. 709-712.ChinaGeochronology
DS200412-0034
2004
Pearson, N.J.Andersen, T., Griffin, W.L., Jackson, S.E., Knudsen, T.L., Pearson, N.J.Mid-Proterozoic magmatic arc evolution at the southwest margin of the Baltic Shield.Lithos, Vol. 73, 3-4, April pp. 289-318.Europe, Norway, Baltic ShieldMagmatism, Laser ablation, geochronology
DS200412-0076
2004
Pearson, N.J.Aulbach, S., Griffin, W.L., Pearson, N.J., O'Reilly, S.Y., Kivi, K., Doyle, B.J.Mantle formation and evolution, Slave Craton: constraints from HSE abundances and Re Os isotope systematics of sulfide inclusionChemical Geology, Vol. 208, 1-4, pp. 61-88.Canada, Northwest TerritoriesGeochronology, Lac de Gras, metasomatism, melt-deletion
DS200412-0708
2003
Pearson, N.J.Graham, S., Lambert, D.D., Shee, S.R., Pearson, N.J.Erratum to juvenile lithospheric mantle enrichment and the formation of alkaline ultramafic magma sources: Re Os Lu Hf and Sm NdChemical Geology, Vol. Sept. 15, p.. 361. Original Vol. 186, pp. 215-233.AustraliaMelnoites, geochronology
DS200412-0720
2004
Pearson, N.J.Griffin, W.L., Belousova, E.A., Shee, S.R., Pearson, N.J., O'Reilly, S.Y.Archean crustal evolution in the northern Yilgarn Craton: U Pb and Hf isotope evidence from detrital zircons.Precambrian Research, Vol. 131, 3-4, pp. 231-282.AustraliaGeochronology - Yilgarn
DS200412-0722
2004
Pearson, N.J.Griffin, W.L., Graham, S., O'Reilly, S.Y., Pearson, N.J.Lithosphere evolution beneath the Kaapvaal Craton: Re-Os systematics of sulfides in mantle derived peridotites.Chemical Geology, Vol. 208, 1-4, pp. 89-118.Africa, South Africa, LesothoGeochronology, Finsch, Kimberley, Jagersfontein
DS200412-0723
2003
Pearson, N.J.Griffin, W.L., O'Reilly, S.Y., Abe, N., Aulbach, S., Davies, R.M., Pearson, N.J., Doyle, B.J.,Kivi, K.The origin and evolution of Archean lithospheric mantle.Precambrian Research, Vol. 127, 1-2, Nov. pp. 19-41.China, Africa, Russia, Canada, Northwest TerritoriesGeochemistry, SCLM, continental, Archon, metasomatism
DS200412-0725
2004
Pearson, N.J.Griffin, W.L., O'Reilly, S.Y., Doyle, B.J., Pearson, N.J., Coopersmith, H., Kivi, K., Melkovets, V., PokhilenkLithosphere mapping beneath the North American plate.Lithos, Vol. 77, 1-4, Sept. pp. 873-922.Canada, Northwest Territories, Europe, GreenlandArchon, Proton, Tecton, Slave Craton, Kapuskasing Struc
DS200412-1511
2003
Pearson, N.J.Pearson, N.J., Griffin, W.L., O'Reilly, S.Y., Delpech, G.Magnesium isotopic compositions of olivine from the lithospheric mantle.8 IKC Program, Session 4, AbstractRussia, Siberia, Canada, Northwest territories, Africa, South AfricaMantle geochemistry
DS200412-2033
2003
Pearson, N.J.Van Achterbergh, E., Griffin, W.L., O'Reilly, S.Y., Ryan, C.G., Pearson, N.J., Kivi, K., Doyle, B.J.Melt inclusions from the deep Slave lithosphere: constraints on the origin and evolution of mantle derived carbonatite and kimbe8 IKC Program, Session 3, AbstractCanada, Northwest TerritoriesDiamonds - melting
DS200412-2080
2003
Pearson, N.J.Wang, K.L., O'Reilly, S.Y., Griffin, W.L., Chung, S.L., Pearson, N.J.Proterozoic mantle lithosphere beneath the extended margin of the South Chin a block: in situ Re Os evidence.Geology, Vol. 31, 8, pp. 709-712.ChinaGeochronology
DS200512-0008
2005
Pearson, N.J.Alard, O., Luguet, A., Pearson, N.J., Griffin, W.L., Lorand, J.P., Gannoun, A., Burton, K.W., O'Reilly, S.Y.In situ Os isotopes in abyssal peridotites bridge the isotopic gap between MORBS and their source mantle.Nature, Vol. 436, No. 7053, Aug. 18, pp. 1005-1108.MantleGeochronology
DS200512-0040
2005
Pearson, N.J.Aulbach, S., Griffin, W.L., Pearson, N.J., O'Reilly, S.Y., Kivi, K.Origin and evolution of the lithospheric mantle beneath the central Slave Craton, Canada.GAC Annual Meeting Halifax May 15-19, Abstract 1p.Canada, Northwest TerritoriesGeochronology, Lac de Gras, metasomatism
DS200512-0166
2005
Pearson, N.J.Choukroun, M., O'Reilly, S., Griffin, W.L., Pearson, N.J., Dawson, J.B.Hf isotopes of MARID (mica amphibole rutile ilmenite diopside) rutile trace metasomatic processes in the lithospheric mantle.Geology, Vol. 33, 1, Jan. pp. 45-48.Africa, South AfricaKimberley, metasomatism, xenoliths
DS200512-0234
2005
Pearson, N.J.Djomani, Y.H.P., O'Reilly, S.Y., Griffin, W.L., Natapov, L.M., Pearson, N.J., Doyle, B.J.Variations of the effective elastic thickness (Te) and structure of the lithosphere beneath the Slave Province, Canada.Exploration Geophysics, Vol. 36, 3, pp. 266-271.Canada, Northwest TerritoriesGeophysics - seismics, telurics
DS200512-1209
2005
Pearson, N.J.Xu, X., O'Reilly, S.Y., Griffin, W.L., Deng, P., Pearson, N.J.Relict Proterozoic basement in the Nanling Mountains (SE China) and its tectonothermal.Tectonics, Vol. 24, 2, TC2003001652ChinaGeothermometry
DS200612-0064
2005
Pearson, N.J.Babu, E.V.S.S.K., Griffin, W.L., O'Reilly, S.Y., Pearson, N.J.Sub-continental lithospheric mantle structure of the eastern Dharwar Craton, southern India at 1.1Ga: study of garnet xenocrysts from kimberlites.Geological Society of India, Bangalore November Meeting Group Discussion on Kimberlites and Related Rocks India, Abstract p. 73-74.India, Andhra Pradesh, Dharwar CratonTectonics
DS200612-0149
2006
Pearson, N.J.Bonadiman, C., Coltorti, M., Siena,F., O'Reilly, S.Y., Griffin, W.L., Pearson, N.J.Archean to Proterozoic depletion in Cape Verde lithospheric mantle.Geochimica et Cosmochimica Acta, Vol. 70, 18, p. 1, abstract only.Europe, Cape Verde IslandsGeochemistry
DS200612-0500
2006
Pearson, N.J.Griffin, W.L., Pearson, N.J., Belousova, E.A., Saeed, A.Hf isotope heterogeneity in zircon 91500.... comment.Chemical Geology, Vol. 233, 3-4, Oct. 15, pp. 358-363.TechnologyGeochronology
DS200612-0501
2006
Pearson, N.J.Griffin, W.L., Rege, S., O'Reilly, S.Y., Jackson, S.E., Pearson, N.J., Zedgenizov, D., Kurat, G.Trace element patterns of diamond: toward a unified genetic model.Geochimica et Cosmochimica Acta, Vol. 70, 18, p. 218. abstract only.TechnologyDiamond genesis geochemistry
DS200612-0705
2006
Pearson, N.J.Kinny, P.D., Love, G.J., Pearson, N.J.Hf isotopes and zircon recrystallization: a case study.Geochimica et Cosmochimica Acta, Vol. 70, 18, p. 18. abstract only.AustraliaGeochronology
DS200612-1061
2006
Pearson, N.J.Pearson, N.J., Griffin, W.L., Alard, O., O'Reilly, S.Y.The isotopic composition of magnesium in mantle olivine: records of depletion and metasomatism.Chemical Geology, Vol. 226, 3-4, pp. 115-133.Russia, Canada, Northwest Territories, AustraliaGeochronology
DS200612-1528
2006
Pearson, N.J.Wieland, P.R., Beyer, E., Jackson, S.E., Pearson, N.J., O'Reilly, S.Y.Evaluation of a method of the separation of Ni in geological samples.Geochimica et Cosmochimica Acta, Vol. 70, 18, p. 19 abstract only.TechnologyGeochemistry - nickel
DS200712-0037
2007
Pearson, N.J.Aulbach, S., Griffin, W.L., Pearson, N.J., O'Reilly, S.Y., Doyle, B.J.Lithosphere formation in the central Slave Craton ( Canada): plume subcretion or lithosphere accretion.Contributions to Mineralogy and Petrology, Vol. 154, 4, pp. 409-427.Canada, Northwest TerritoriesAccretion
DS200712-0038
2007
Pearson, N.J.Aulbach, S., Pearson, N.J., O'Reilly, S.Y., Doyle, B.J.Origins of xenolithic eclogites and pyroxenites from the Central Slave Craton, Canada.Journal of Petrology, Vol. 48, 10, pp. 1843-1873.Canada, Northwest TerritoriesEclogite, geochemistry, geochronology, isotopes
DS200812-0060
2008
Pearson, N.J.Aulbach, S., O'Reilly, S.Y., Griffin, W.L., Pearson, N.J.Subcontinental lithospheric mantle origin of high niobium/tantalum ratios in eclogites.Nature Geoscience, Vol. 1, 7, pp. 468-472.MantleEclogite
DS200812-0089
2008
Pearson, N.J.Batumike, J.M., Griffin, W.L., Belousa, E.A., Pearson, N.J., O'Reilly, S.Y., Shee, S.R.LAM-ICPMS U-Pb dating of kimberlite perovskite: Eocene-Oligocene kimberlites from the Kundelungu Plateau D.R. Congo.Earth and Planetary Science Letters, Vol. 267, 3-4, pp.609-619.Africa, Democratic Republic of CongoGeochrononoloy - Kundelungu
DS200812-0829
2008
Pearson, N.J.O'Reilly, S.Y., Griffin, W.L., Pearson, N.J., Jackson, S.E., Belousova, E.A., Alard, O., Saeed, A.Taking the pulse of the Earth: linking crustal and mantle events.Australian Journal of Earth Sciences, Vol. 55, pp. 983-995.MantleGeochronology
DS200812-0945
2008
Pearson, N.J.Rege, S., Griffin, W.L., Kurat, G., Jackson, S.E., Pearson, N.J., OReilly, S.Y.Trace element geochemistry of diamondite: crystallization of diamond from kimberlite carbonatite melts.Lithos, Vol. 106, 1-2, pp. 39-54.TechnologyDiamondite
DS200812-1283
2008
Pearson, N.J.Xu, X., Griffin, W.L., O'Reilly, S.Y., Pearson, N.J., Geng, H., Zheng, J.Re-Os isotopes of sulfides in mantle xenoliths from eastern China: progressive modifications of lithospheric mantle.Lithos, Vol. 102, 3-4, pp.43-64.ChinaGeochronology
DS200912-0018
2009
Pearson, N.J.Aulbach, S., Creaser, R.A., Pearson, N.J., Simonetti, S.S., Heaman, L.M., Griffin, W.L., Stachel, T.Sulfide and whole rock Re-Os systematics of eclogite and pyroxenite xenoliths from the Slave Craton, Canada.Earth and Planetary Science Letters, in press available,Canada, Northwest TerritoriesDeposit - Diavik
DS201012-0163
2010
Pearson, N.J.Donnelly, C.L., Griffin, W.L., O'Reilly, S.Y.,Pearson, N.J., Shee, S.R.The kimberlites and related rocks of the Kuruman kimberlite Province, Kaapvaal Craton, South Africa.Contributions to Mineralogy and Petrology, in press available 21p.Africa, South AfricaGeochemistry - trace elements
DS201012-0473
2010
Pearson, N.J.Marchesi, C., Griffin, W.L., Garrido, C.J., Bodinier, J-L., O'Reilly, S.Y., Pearson, N.J.Persistence of mantle lithospheric Re-Os signature during asthenospherization of the subcontinental lithospheric mantle: insights in situ sulphides....Contributions to Mineralogy and Petrology, Vol. 159, 3, pp. 315-330.Europe, SpainRonda peridotite
DS201112-0042
2011
Pearson, N.J.Aulbach, S., O'Reilly, S.Y., Pearson, N.J.Constraints from eclogite and MARID xenoliths on origins of mantle Zr/Hf-Nb/Ta variability.Contributions to Mineralogy and Petrology, Vol. 162, 5, pp. 1047-1062.Canada, Northwest Territories, Africa, South AfricaCarbonatite, kimberlites, Slave craton
DS201112-0043
2011
Pearson, N.J.Aulbach, S., O'Reilly, S.Y., Pearson, N.J.Constraints from eclogite and MARID xenoliths on origins of mantle Zr/Hf-Nb/Ta variability.Contributions to Mineralogy and Petrology, Vol. 162, 5, pp. 1047-1062.MantleEclogite
DS201112-0283
2011
Pearson, N.J.Donnelly, C.L., Griffin, W.L., O'Reilly, S.Y.,Pearson, N.J., Shee, S.R.The kimberlites and related rocks of the Kuruman kimberlite province, Kaapvaal craton, South Africa.Contributions to Mineralogy and Petrology, Vol. 161, 3, pp. 351-371.Africa, South AfricaDeposit -
DS201112-0387
2011
Pearson, N.J.Griffin, W.L., Begg, G., O'Reilly, S.Y., Pearson, N.J.Ore deposits and the SCLM.Goldschmidt Conference 2011, abstract p.946.MantleKimberlites - low degree melting prev. metasomatised
DS201112-1101
2011
Pearson, N.J.Wang, K-L., O'Reilly, S.Y., Griffin, W.L., Pearson, N.J., Kovach, V., Yarmolyuk, V.Primordial ages of lithospheric mantle vs ancient relicts in the asthenospheric mantle: in situ Os perspective.Goldschmidt Conference 2011, abstract p.2121.Russia, MongoliaConvection
DS201212-0167
2012
Pearson, N.J.Donnelly, C.L., Griffin, W.L., Yang, J-H., O'Reilly, Z.Y., li Li, Q., Pearson, N.J., Li, X-H.In situ U Pb dating and Sr Nd isotopic analysis of perovskite: constraints on the age and petrogenesis of the Kuruman kimberlite province, Kaapvaal Craton, South Africa.Journal of Petrology, Vol. 53, 12, pp. 2407-2522.Africa, South AfricaDeposit - Kuruman
DS201212-0310
2012
Pearson, N.J.Howell, D., O'Neill, C.J., Grant, K.J., Griffin, W.L., O'Reilly, S.Y., Pearson, N.J., Stern, R.A., Stachel, T.Platelet development in cuboid diamonds: insights from micro-FTIR mapping.Contributions to Mineralogy and Petrology, Vol. 164, 6, pp. 1011-1025.TechnologyDiamond morphology
DS201212-0314
2012
Pearson, N.J.Huang, J-X., Greau, Y., Griffin, W.L., O'Reilly, S.Y., Pearson, N.J.Multi-stage origin of Roberts Victor eclogites: progressive metasomatism and its isotopic effects.Lithos, in press availableAfrica, South AfricaDeposit - Roberts Victor
DS201212-0438
2012
Pearson, N.J.Malkovets, V.G., Griffin, W.L., Pearson, N.J., Rezvukhin, D.I., Oreilly, S.Y., Pokhilenko, N.P., Garanin, V.K., Spetsius, Z.V., Litasov, K.D.Late metasomatic addition of garnet to the SCLM: Os-itope evidence.10th. International Kimberlite Conference Feb. 6-11, Bangalore India, AbstractMantleMetasomatism
DS201312-0039
2013
Pearson, N.J.Aulbach, S., Griffin, W.L., Pearson, N.J., O'Reilly, S.Y.Nature and timing of metasomatism in the stratified mantle lithosphere beneath the Central Slave Craton ( Canada).Chemical Geology, Vol. 352, pp. 153-169.Canada, Northwest TerritoriesCraton
DS201312-0320
2013
Pearson, N.J.Gonzalez-Jimienez, J.M., Marchesi, C., Griffin, W.L., Gutierrez-Narbona, R., Lorand, J-P., O'Reilly, S.Y., Garrido, C.J., Gervilla, F., Pearson, N.J., Hidas, K.Transfer of Os isotopic signatures from peridotite to chromitite in the subcontinental mantle: insights from in situ analysis of platinum-group and base metal minerals (Ojen peridotite massif, southern Spain.Lithos, Vol. 164-167, pp. 74-85.Europe, SpainChromitite
DS201312-0322
2013
Pearson, N.J.Gonzalez-Jimienez, J.M., Griffin, W.L., Gervilla, F., Proenza, J.A., O'Reilly, S.Y., Pearson, N.J.Chromitites in ophiolites: how, where, when, why? Part 1. A review of new ideas on the origin and significance of platinum-group minerals.Lithos, Vol. 189, pp. 127-139.MantleGeodynamics
DS201312-0336
2013
Pearson, N.J.Griffin, W.L., Belousova, E.A., O'Neill, C., O'Reilly, S.Y., Malkovets, V., Pearson, N.J., Spetsius, S., Wilde, S.A.The world turns over: Hadean-Archean crust mantle evolution.Lithos, Vol. 189, pp. 2-15.MantleCrust- mantle review
DS201312-0403
2013
Pearson, N.J.Howell, D., Griffin, W.L., Pearson, N.J., Powell, W., Wieland, P., O'Reilly, S.Y.Trace element partitioning in mixed habit diamonds.Chemical Geology, Vol. 355, pp. 134-143.TechnologyCrystallography
DS201312-0404
2013
Pearson, N.J.Howell, D., Stern, R.A., Griffin, W.L., Southworth, R., Mikhail, S., Stachel, T., Verchovsky, A.B., O'Reilly, S.Y., Pearson, N.J.New thermodynamic models and calculated phase equilibration temperatures in NCFMAS for basic and ultrabasic compositions through the transition zone into the uppermost lower mantle.Goldschmidt 2013, AbstractTechnologyCrystallography
DS201312-0407
2013
Pearson, N.J.Huang, J-X., Griffin, W.L., Greau, Y., Pearson, N.J., O'Reilly, S.Y.Unmasking enigmatic xenolithic eclogites: progressive metasomatism on a key Roberts Victor sample.Goldschmidt 2013, AbstractAfricaKamafugite
DS201412-0314
2014
Pearson, N.J.Griffin, W.L., Batumike, J.M., Greau, Y., Pearson, N.J., Shee, S.R., O'Reilly, S.Y.Emplacement ages and sources of kimberlites and related rocks in southern Africa: U-Pb ages and Sr-Nd isotopes of groundmass perovskite.Contributions to Mineralogy and Petrology, Vol. 167, pp. 1032-37.Africa, southern AfricaDeposit - geochronology
DS201412-0315
2014
Pearson, N.J.Griffin, W.L., Pearson, N.J., Andersen, T., Jackson, S.E., O'Reilly, S.Y., Zhang, M.Sources of cratonic metasomatic fluids: In-situ LA-MC-ICPMS analysis of Sr, Nd and Pb isotopes in Lima from the Jagersfontein kimberlite.American Journal of Science, Vol. 314, pp. 435-461.Africa, South AfricaDeposit - Jagersfontein
DS201412-0380
2014
Pearson, N.J.Huang, J-X., Griffin, W.L., Greau, Y., Pearson, N.J., O'Reilly, S.Y., Cliff, J., Martin, L.Unmasking xenolithic eclogites: progressive metasomatism of a key Roberts Victor sample.Chemical Geology, Vol. 364, pp. 55-65.Africa, South AfricaDeposit - Roberts Victor
DS201412-0381
2014
Pearson, N.J.Huang, J-X., Li, P., Griffin, W.L., Xia, Q-K, Greau, Y., Pearson, N.J., O'Reilly, S.Y.Water contents of Roberts Victor xenolithic eclogites: primary and metasomatic controls.Contributions to Mineralogy and Petrology, Vol. 168, pp. 1092-1095Africa, South AfricaDeposit - Roberts Victor
DS201502-0063
2014
Pearson, N.J.Huang, J-X., Li, P., Griffin, W.L., Xia, Q-K, Greau, Y., Pearson, N.J., O'Reilly, S.Y.Water contents of Roberts Victor xenolithic eclogites: primary and metasomatic controls.Contributions to Mineralogy and Petrology, Vol. 168, pp. 1092-1105.Africa, South AfricaDeposit - Roberts Victor
DS201504-0231
2015
Pearson, N.J.Xiong, Q., Griffin, W.L., Zheng, J-P., O'Reilly, S.Y., Pearson, N.J.Episodic refertilization and metasomatism of Archean mantle: evidence from an orogenic peridotite in North Qaidam ( NE Tibet) China.Contributions to Mineralogy and Petrology, Vol. 169, 24p.China, TibetPeridotite
DS201505-0246
2015
Pearson, N.J.Griffin, W.L., Gain, S.E.M., Toledo, V., O'Reilly, S.Y., Jacob, D., Pearson, N.J.Corundum, moissanite and super reducing conditions in the upper mantle beneath the lower ( southern) Galilee ( Israel).Israel Geological Society, 1p.posterEurope, IsraelMineralogy
DS201508-0379
2015
Pearson, N.J.Wang, K-L., Prikhodko, V., O'Reilly, S.Y., Griffin, W.L., Pearson, N.J., Kovach, V., Lizuka, Y., Chien, Y-H.Ancient mantle lithosphere beneath the Khanka Massif in Russian Far-East: in situ Re-Os evidence.Terra Nova, Vol. 27, 4, pp. 277-284.RussiaGeochronology
DS201512-1984
2015
Pearson, N.J.Wang, K-L., Prikhodo, V., O'Reilly, S.Y., Griffin, W.L., Pearson, N.J., Kovach, V., Iizuka, Y., Chien, Y-H.Ancient mantle lithosphere beneath the Khanka massif in the Russian Far East: in situ Re-Os evidence.Terra Nova, Vol. 27, 4, pp. 277-284.RussiaGeochronology

Abstract: The Os-isotope compositions of sulphides in mantle xenoliths hosted by Late Miocene alkali basalts from the Sviyaginsky volcano, Russian Far East, reveal the presence of Archaean-Proterozoic subcontinental lithospheric mantle beneath the Khanka massif. Their TMA and TRD model ages reveal similar peaks at 1.1 and 0.8 Ga suggesting later thermotectonic events in the subcontinental lithospheric mantle, whereas TRD model ages range back to 2.8 ± 0.5 (2s) Ga. The events recognized in the subcontinental lithospheric mantle are consistent with those recorded in the crust of the Khanka massif. The sulphide Os-isotope data show that the subcontinental lithospheric mantle beneath the Khanka massif had formed at least by the Mesoproterozoic, and was subsequently metasomatized by juvenile crustal-growth events related to the evolution of the Altaids. The Khanka massif is further proposed to have tectonic affinity to the Siberia Craton and should originate from it accordingly.
DS201603-0381
2016
Pearson, N.J.Griffin, W.L., Gain, S.E.M., Adams, D., Huang, J-X., Saunders, M.,Toledo, V., Pearson, N.J., O'Reilly, S.Y.Heaven on Earth: tistarite ( Ti203) and other nebular phases in corundum aggregates from Mt. Carmel volcanic rocks.Israel Geological Society, pp. 85-86. abstractEurope, IsraelMoissanite

Abstract: This ending talk, focused on the ongoing cooperative research of Prof. Griffin and his team at Macquarie University and Shefa Yamim, since January 2014, highlighting unique corundum species characteristics. Preliminary results of this research were presented in the IGS Annual Meeting of 2015, whereas this year Prof. Griffin has shared innovative findings only microscopically tracked within titanium-rich corundum aggregates. One of the more abundant minerals is Tistarite (Ti2O3), previously known only as a single grain in a primitive type of meteorite (!). An article has been submitted to a scientific journal detailing this first terrestrial occurrence. Several other minerals are common in meteorites, but unknown or extremely rare on Earth. About half of these minerals are unknown to science, and will be described as new minerals in the scientific literature. The first of these is a Titanium-Aluminium-Zirconium oxide, informally known as TAZ; it will be submitted to the International Mineralogical Association for recognition as a new mineral, ShefaTAZite. Using state of the art technologies such as Thermal Ionisation Mass Spectrometry (TIMS) and Electron Microscopy Facility (EMF) that has three scanning electron microscopes, all with EBSD capability, and a transmission electron microscope - Prof. Griffin revealed spectacular imagery of minerals and rare compounds associated with titanium rich corundum aggregates.
DS201603-0382
2016
Pearson, N.J.Griffin, W.L., Gain, S.E.M., Adams, D., Toledo, V., Pearson, N.J., O'Reilly, S.Y.Deep-Earth methane, mantle dynamics and mineral exploration: insights from northern Israel, southern Tibet and Kamchatka.Israel Geological Society, pp. 87-88. abstractEurope, Israel, TibetMoissanite
DS201603-0407
2016
Pearson, N.J.O'Reilly, S.Y., Griffin, W.L., Pearson, N.J.The role of the deep lithosphere in metallogeny.Israel Geological Society, pp. 144-145. abstractMantleSCLM - geodynamics

Abstract: This talk shortly reviewed geological and geochemical mechanisms of the deep lithosphere, a layer composed of the Earth's crust and uppermost mantle at a depth range of 100-150km below the surface. Definition of these processes at depth, reflects on surface recovery of gem and heavy minerals, of which metallic minerals were stressed out. Prof. O'reilley has also referred to Shefa Yamim's exploration area in northern Israel where the eruption of gem-bearing volcanic rocks appears to be related to a major lithospheric suture (the Dead Sea Transform) and related faulting. The Dead Sea Transform is a 1000km plate boundary stretching out from Turkey in the north to Eilat Bay in the south. As such, it is a preferred pathway for magma emplacement crystalizing in volcanic bodies that are being surveyed by Shefa Yamim as Primary Sources for gem and heavy minerals.
DS201604-0597
2016
Pearson, N.J.Castilo-Oliver, M., Gali, S., Melgarejo, J.C., Griffin, W.L., Belousova, E., Pearson, N.J., Watangua, M., O'Reilly, S.Y.Trace element geochemistry and U-Pb dating of perovskite in kimberlites of the Lunda Norte province ( NE Angola): petrogenetic and tectonic implications.Chemical Geology, Vol. 426, pp. 118-134.Africa, AngolaGeochronology

Abstract: Perovskite (CaTiO3) has become a very useful mineral for dating kimberlite eruptions, as well as for constraining the compositional evolution of a kimberlitic magma and its source. Despite the undeniable potential of such an approach, no similar study had been done in Angola, the fourth largest diamond producer in Africa. Here we present the first work of in situ U-Pb geochronology and Sr-Nd isotope analyses of perovskite in six Angolan kimberlites, supported by a detailed petrographic and geochemical study of their perovskite populations. Four types of perovskite were identified, differing in texture, major- and trace-element composition, zoning patterns, type of alteration and the presence or absence of inclusions. Primary groundmass perovskite is classified either as anhedral, Na-, Nb- and LREE-poor perovskite (Ia); or euhedral, strongly zoned, Na-, Nb- and LREE-rich perovskite (Ib). Secondary perovskite occurs as reaction rims on ilmenite (IIa) or as high Nb (up to 10.6 wt% Nb2O5) perovskite rims on primary perovskite (IIb). The occurrence of these four types within the Mulepe kimberlites is interpreted as an evidence of a complex, multi-stage process that involved mingling of compositionally different melts. U-Pb dating of these perovskites yielded Lower Cretaceous ages for four of the studied kimberlites: Mulepe 1 (116.2 ± 6.5 Ma), Mulepe 2 (123.0 ± 3.6 Ma), Calonda (119.5 ± 4.3 Ma) and Cat115 (133 ± 10 Ma). Kimberlite magmatism occurred in NE Angola likely due to reactivation of deep-seated translithospheric faults (> 300 km) during the break-up of Gondwana. Sr-Nd isotope analyses of four of these kimberlites indicate that they are Group I kimberlites, which is consistent with the petrological observations.
DS201605-0819
2016
Pearson, N.J.Castillo-Oliver, M., Gali, S., Melgarejo, J.C., Griffin, W.L., Belousova, E., Pearson, N.J., Watangua, M., O'Reilly, S.Y.Trace element geochemistry and U-Pb dating of perovskite in kimberlites of the Lunda Norte province ( NE Angola): petrogenetic and tectonic implications.Chemical Geology, Vol. 426, pp. 118-134.Africa, AngolaDeposit - Alto Cuilo

Abstract: Perovskite (CaTiO3) has become a very usefulmineral for dating kimberlite eruptions, aswell as for constraining the compositional evolution of a kimberlitic magma and its source. Despite the undeniable potential of such an approach, no similar study had been done in Angola, the fourth largest diamond producer in Africa. Here we present the firstwork of in situ U-Pb geochronology and Sr-Ndisotope analyses of perovskite in six Angolan kimberlites, supported by a detailed petrographic and geochemical study of their perovskite populations. Four types of perovskitewere identified, differing in texture,major- and trace-element composition, zoning patterns, type of alteration and the presence or absence of inclusions. Primary groundmass perovskite is classified either as anhedral, Na-, Nb- and LREE-poor perovskite (Ia); or euhedral, strongly zoned, Na-, Nb- and LREE-rich perovskite (Ib). Secondary perovskite occurs as reaction rims on ilmenite (IIa) or as high Nb (up to 10.6 wt% Nb2O5) perovskite rims on primary perovskite (IIb). The occurrence of these four types within the Mulepe kimberlites is interpreted as an evidence of a complex, multi-stage process that involved mingling of compositionally different melts. U-Pb dating of these perovskites yielded Lower Cretaceous ages for four of the studied kimberlites: Mulepe 1 (116.2±6.5Ma),Mulepe 2 (123.0±3.6Ma), Calonda (119.5±4.3 Ma) and Cat115 (133±10Ma). Kimberlite magmatism occurred in NE Angola likely due to reactivation of deep-seated translithospheric faults (N300 km) during the break-up of Gondwana. Sr-Nd isotope analyses of four of these kimberlites indicate that they are Group I kimberlites, which is consistent with the petrological observations.
DS201606-1090
2016
Pearson, N.J.Griffin, W.L., Afonso, J.C., Belousova, E.A., Gain, S.E., Gong, X-H., Gonzalez-Jiminez, J.M., Howell, D., Huang, J-X., McGowan, N., Pearson, N.J., Satsukawa, T., Shi R., Williams, P., Xiong, Q., Yang, J-S., Zhang, M., O'Reilly, S.Y.Mantle recycling: transition zone metamorphism of Tibetan ophiolitic peridotites and its tectonic implications.Journal of Petrology, in press available, 30p.Asia, China, TibetPeridotite

Abstract: Large peridotite massifs are scattered along the 1500?km length of the Yarlung-Zangbo Suture Zone (southern Tibet, China), the major suture between Asia and Greater India. Diamonds occur in the peridotites and chromitites of several massifs, together with an extensive suite of trace phases that indicate extremely low fO2 (SiC, nitrides, carbides, native elements) and/or ultrahigh pressures (UHP) (diamond, TiO2 II, coesite, possible stishovite). New physical and isotopic (C, N) studies of the diamonds indicate that they are natural, crystallized in a disequilibrium, high-T environment, and spent only a short time at mantle temperatures before exhumation and cooling. These constraints are difficult to reconcile with previous models for the history of the diamond-bearing rocks. Possible evidence for metamorphism in or near the upper part of the Transition Zone includes the following: (1) chromite (in disseminated, nodular and massive chromitites) containing exsolved pyroxenes and coesite, suggesting inversion from a high-P polymorph of chromite; (2) microstructural studies suggesting that the chromitites recrystallized from fine-grained, highly deformed mixtures of wadsleyite and an octahedral polymorph of chromite; (3) a new cubic Mg-silicate, with the space group of ringwoodite but an inverse-spinel structure (all Si in octahedral coordination); (4) harzburgites with coarsely vermicular symplectites of opx + Cr-Al spinel ± cpx; reconstructions suggest that these are the breakdown products of majoritic garnets, with estimated minimum pressures to?>?13?GPa. Evidence for a shallow pre-metamorphic origin for the chromitites and peridotites includes the following: (1) trace-element data showing that the chromitites are typical of suprasubduction-zone (SSZ) chromitites formed by magma mixing or mingling, consistent with Hf-isotope data from magmatic (375?Ma) zircons in the chromitites; (2) the composition of the new cubic Mg-silicate, which suggests a low-P origin as antigorite, subsequently dehydrated; (3) the peridotites themselves, which carry the trace element signature of metasomatism in an SSZ environment, a signature that must have been imposed before the incorporation of the UHP and low-fO2 phases. A proposed P-T-t path involves the original formation of chromitites in mantle-wedge harzburgites, subduction of these harzburgites at c. 375?Ma, residence in the upper Transition Zone for >200 Myr, and rapid exhumation at c. 170-150?Ma or 130-120?Ma. Os-isotope data suggest that the subducted mantle consisted of previously depleted subcontinental lithosphere, dragged down by a subducting oceanic slab. Thermomechanical modeling shows that roll-back of a (much later) subducting slab would produce a high-velocity channelized upwelling that could exhume the buoyant harzburgites (and their chromitites) from the Transition Zone in?
DS201606-1093
2015
Pearson, N.J.Howell, D., Griffin, W.L., Yang, J., Gain, S., Stern, R.A., Huang, J-X., Jacob, D.E., Xu, X., Stokes, A.J., O'Reilly, S.Y., Pearson, N.J.Diamonds in ophiolites: contamination or a new diamond growth environment?Earth and Planetary Science Letters, Vol. 430, pp. 284-295.Asia, TibetLuobusa Massif Type Iib

Abstract: For more than 20 years, the reported occurrence of diamonds in the chromites and peridotites of the Luobusa massif in Tibet (a complex described as an ophiolite) has been widely ignored by the diamond research community. This skepticism has persisted because the diamonds are similar in many respects to high-pressure high-temperature (HPHT) synthetic/industrial diamonds (grown from metal solvents), and the finding previously has not been independently replicated. We present a detailed examination of the Luobusa diamonds (recovered from both peridotites and chromitites), including morphology, size, color, impurity characteristics (by infrared spectroscopy), internal growth structures, trace-element patterns, and C and N isotopes. A detailed comparison with synthetic industrial diamonds shows many similarities. Cubo-octahedral morphology, yellow color due to unaggregated nitrogen (C centres only, Type Ib), metal-alloy inclusions and highly negative View the MathML sourcedC13 values are present in both sets of diamonds. The Tibetan diamonds (n=3n=3) show an exceptionally large range in View the MathML sourcedN15 (-5.6 to +28.7‰+28.7‰) within individual crystals, and inconsistent fractionation between {111} and {100} growth sectors. This in contrast to large synthetic HPHT diamonds grown by the temperature gradient method, which have with View the MathML sourcedN15=0‰ in {111} sectors and +30‰+30‰ in {100} sectors, as reported in the literature. This comparison is limited by the small sample set combined with the fact the diamonds probably grew by different processes. However, the Tibetan diamonds do have generally higher concentrations and different ratios of trace elements; most inclusions are a NiMnCo alloy, but there are also some small REE-rich phases never seen in HPHT synthetics. These characteristics indicate that the Tibetan diamonds grew in contact with a C-saturated Ni-Mn-Co-rich melt in a highly reduced environment. The stable isotopes indicate a major subduction-related contribution to the chemical environment. The unaggregated nitrogen, combined with the lack of evidence for resorption or plastic deformation, suggests a short (geologically speaking) residence in the mantle. Previously published models to explain the occurrence of the diamonds, and other phases indicative of highly reduced conditions and very high pressures, have failed to take into account the characteristics of the diamonds and the implications for their formation. For these diamonds to be seriously considered as the result of a natural growth environment requires a new understanding of mantle conditions that could produce them.
DS201610-1865
2016
Pearson, N.J.Griffin, W.L., Gain, S.E.M., Adams, D.T., Huang, J-X., Saunders, M., Toledo, V., Pearson, N.J., O'Reilly, S.Y.First terrestrial occurrence of tistarite ( Ti2O3): ultra-low oxygen fugacity in the upper mantle beneath Mount Carmel, Israel.Geology, Vol. 44, 10, pp. 815-818.Europe, IsraelMoissanite

Abstract: The minimum oxygen fugacity (fO2) of Earth's upper mantle probably is controlled by metal saturation, as defined by the iron-wüstite (IW) buffer reaction (FeO ? Fe + O). However, the widespread occurrence of moissanite (SiC) in kimberlites, and a suite of super-reduced minerals (SiC, alloys, native elements) in peridotites in Tibet and the Polar Urals (Russia), suggest that more reducing conditions (fO2 = 6-8 log units below IW) must occur locally in the mantle. We describe pockets of melt trapped in aggregates of corundum crystals ejected from Cretaceous volcanoes in northern Israel which contain high-temperature mineral assemblages requiring extremely low fO2 (IW < -10). One abundant phase is tistarite (Ti2O3), previously known as a single grain in the Allende carbonaceous chondrite (Mexico) and believed to have formed during the early evolution of the solar nebula. It is associated with other reduced phases usually found in meteorites. The development of super-reducing conditions in Earth's upper mantle may reflect the introduction of CH4 + H2 fluids from the deep mantle, specifically related to deep-seated volcanic plumbing systems at plate boundaries.
DS201610-1872
2016
Pearson, N.J.Huang, J-X., Xiang, Y., An, Y., Griffin, W.L., Greau, Y., Xie, L., Pearson, N.J., Yu, H., O'Reilly, S.Y.Magnesium and oxygen isotopes in Roberts Victor eclogites.Chemical Geology, Vol. 438, pp. 73-83.Africa, South AfricaDeposit - Roberts Victor

Abstract: Magnesium and oxygen are critical elements in the solid Earth and hydrosphere. A better understanding of the combined behavior of Mg and O isotopes will refine their use as a tracer of geochemical processes and Earth evolution. In this study, the Mg-isotope compositions of garnet and omphacite separated from well-characterized xenolithic eclogites from the Roberts Victor kimberlite pipe (South Africa) have been measured by solution multi-collector ICP-MS. The reconstructed whole-rock d26Mg values of Type I (metasomatized) eclogites range from - 0.61‰ to - 0.20‰ (Type IA) and from - 0.60‰ to - 0.30‰ (Type IB) (mean - 0.43‰ ± 0.12‰), while d26Mg of Type IIA (fresh, least metasomatized) eclogites ranges from - 1.09‰ to - 0.17‰ (mean - 0.69‰ ± 0.41‰); a Type IIB (fresh, least metasomatized) has d26Mg of - 0.37‰. Oxygen-isotope compositions of garnet were analyzed in situ by SIMS (CAMECA 1280) and cross-checked by laser fluorination. Garnets have d18O of 6.53‰ to 9.08‰ in Type IA, 6.14‰ to 6.65‰ in Type IB, and 2.34‰ to 2.91‰ in Type IIB. The variation of d26Mg and d18O in Type IA and IB eclogites is consistent with the previously proposed model for the evolution of these samples, based on major and trace elements and radiogenic isotopes. In this model, the protoliths (Type II eclogites) were metasomatized by carbonatitic to kimberlitic melts/fluids to produce first Type IA eclogites and then Type IB. Metasomatism has changed the O-isotope compositions, but the Mg-isotope compositions of Type IA are mainly controlled by the protoliths; those of Type IB eclogites reflect mixing between the protoliths and the kimberlitic melt/fluid. The combination of a large range of d26Mg and low d18O in Type II eclogites cannot be explained easily by seawater alteration of oceanic crust, interaction of carbonate/silicate sediments with oceanic crust, or partial melting of mafic rocks.
DS201701-0035
2016
Pearson, N.J.Tretiakova, I.G., Belousova, E.A., Malkovets, V.G., Griffin, W.L., Piazolo, S., Pearson, N.J., O'Reilly, S.Y., Nishido, H.Recurrent magmatic activity on a lithosphere scale structure: crystallization and deformation in kimberlitic zircons.Gondwana Research, Vol. 42, pp. 126-132.RussiaDeposit - Nubinskaya

Abstract: Kimberlites are not only the most economically important source of diamonds; they also carry unique information encapsulated in rock fragments entrained as the magma traverses the whole thickness of the lithosphere. The Nurbinskaya pipe in the Siberian kimberlite province (Russia) is one of several intruded along the Vilyui Rift, a major terrane boundary. The pipe contains three populations of mantle-derived zircon xenocrysts: Archean (mean age 2709 ± 9 Ma), Devonian (mean age 371 ± 2.3 Ma), and a subset of grains with evidence of brittle deformation and rehealing, and a range of ages between 370 and 450 Ma. The Hf-isotope, O-isotope and trace-element signatures of the last group provide a link between the Archean and Devonian events, indicating at least three episodes of magmatic activity and zircon crystallization in the lithosphere beneath the pipe. The emplacement of the Nurbinskaya pipe ca 370 Ma ago was only the youngest activity in a magma plumbing system that has been periodically reactivated over at least 2.7 billion years, controlled by the lithosphere-scale structure of the Vilyui Rift.
DS201702-0254
2017
Pearson, N.J.Xu, B., Griffin, W.L., Xiong, Q., Hou, Z-Q, O'Reilly, S.Y., Guo, Z., Pearson, N.J., Greau, Y., Yang, Z-M., Zheng, Y-C.Ultrapotassic rocks and xenoliths from South Tibet: contrasting styles of interaction between lithospheric mantle and asthenosphere during continental collision.Geology, Vol. 45, 1, pp. 51-54.China, TibetUPR - metasomatism

Abstract: Widespread Miocene (24-8 Ma) ultrapotassic rocks and their entrained xenoliths provide information on the composition, structure, and thermal state of the sub-continental lithospheric mantle in southern Tibet during the India-Asia continental collision. The ultrapotassic rocks along the Lhasa block delineate two distinct lithospheric domains with different histories of depletion and enrichment. The eastern ultrapotassic rocks (89°E-92°E) reveal a depleted, young, and fertile lithospheric mantle (87Sr/86Srt = 0.704-0.707 [t is eruption time]; Hf depleted-mantle model age [TDM] = 377-653 Ma). The western ultrapotassic rocks (79°E-89°E) and their peridotite xenoliths (81°E) reflect a refractory harzburgitic mantle refertilized by ancient metasomatism (lavas: 87Sr/86Srt = 0.714-0.734; peridotites: 87Sr/86Srt = 0.709-0.716). These data integrated with seismic tomography suggest that upwelling asthenosphere was diverted away from the deep continental root beneath the western Lhasa block, but rose to shallower depths beneath a thinner lithosphere in the eastern part. Heating of the lithospheric mantle by the rising asthenosphere ultimately generated the ultrapotassic rocks with regionally distinct geochemical signatures reflecting the different nature of the lithospheric mantle.
DS201706-1094
2017
Pearson, N.J.Lu, J-G, Xiong, Q., Griffin, W.L., Zheng, J-P., Huang, J-X., O'Reilly, S.Y., Satsuskawa, T., Pearson, N.J.Uplift of the southeastern Australian lithosphere: thermal tectonic evolution of garnet pyroxenite xenoliths from western Victoria.Geological Society of America, SPE 526 pp. 27-48.Australiageothermometry

Abstract: Detailed petrography, microstructure, and geochemistry of garnet pyroxenite xenoliths in Holocene basanite tuffs from maars at Lakes Bullenmerri and Gnotuk (western Victoria, southeastern Australia) have been used to track their igneous and metamorphic history, enabling the reconstruction of the thermal-tectonic evolution of the lithospheric mantle. The exsolution of orthopyroxene and garnet and rare spinel, plagioclase, and ilmenite from complex clinopyroxene megacrysts suggests that the xenoliths originally were clinopyroxene-dominant cumulates associated with minor garnet, orthopyroxene, or spinel. The compositions of exsolved phases and their host clinopyroxene were reintegrated using measured modal proportions to show that the primary clinopyroxene was enriched in Al2O3 (5.53-13.63 wt%) and crystallized at ~1300-1500 °C and 16-30 kbar. These cumulates then underwent extensive exsolution, recrystallization, and reaction during cooling, and finally equilibrated at ~950-1100 °C and 12-18 kbar before entrainment in the basanites. Rare earth element (REE) thermobarometry of garnets and coexisting clinopyroxenes preserves evidence of an intermediate stage (1032 °C and 21 kbar). These results imply that the protoliths of the garnet pyroxenite formed at a range of depths from ~50 to 100 km, and then during or shortly after cooling, they were tectonically emplaced to higher levels (~40-60 km; i.e., uplifted by at least 10-20 km) along the prevailing geotherm. This uplift may have been connected with lithosphere-scale faulting during the Paleozoic orogeny, or during Mesozoic-Cenozoic rifting of eastern Australia.
DS201708-1576
2017
Pearson, N.J.Lu, J-G., Xiong, Q., Griffin, W.L., Zheng, J-P., Huang, J-X., O'Reilly, S.Y., Satsukawa, T., Pearson, N.J.Uplift of southeastern Australian lithosphere: thermal tectonic evolution of garnet pyroxenite xenoliths from western Victoria.Geological Society of London, Chapter 2, pp. 27-48.Australia, Victoriaxenoliths

Abstract: Detailed petrography, microstructure, and geochemistry of garnet pyroxenite xenoliths in Holocene basanite tuffs from maars at Lakes Bullenmerri and Gnotuk (western Victoria, southeastern Australia) have been used to track their igneous and metamorphic history, enabling the reconstruction of the thermal-tectonic evolution of the lithospheric mantle. The exsolution of orthopyroxene and garnet and rare spinel, plagioclase, and ilmenite from complex clinopyroxene megacrysts suggests that the xenoliths originally were clinopyroxene-dominant cumulates associated with minor garnet, orthopyroxene, or spinel. The compositions of exsolved phases and their host clinopyroxene were reintegrated using measured modal proportions to show that the primary clinopyroxene was enriched in Al2O3 (5.53–13.63 wt%) and crystallized at ~1300–1500 °C and 16–30 kbar. These cumulates then underwent extensive exsolution, recrystallization, and reaction during cooling, and finally equilibrated at ~950–1100 °C and 12–18 kba
DS201710-2280
2017
Pearson, N.J.Xiong, Q., Griffin, W.L., Huang, J-X., Gain, S.E.M., Toledo, V., Pearson, N.J., O'Reilly, S.Y.Super reduced assemblages in "ophiolitic" chromitites and peridotites: the view from Mount Carmel.European Journal of Mineralogy, Vol. 29, 4, pp. 557-570.Europe, Israelmineralogy

Abstract: Ultrahigh-pressure (UHP) materials (e.g., diamond, high-pressure polymorph of chromite) and super-reduced (SuR) phases (e.g., carbides, nitrides, silicides and native metals) have been identified in chromitites and peridotites of the Tibetan and Polar-Urals ophiolites. These unusual assemblages suggest previously unrecognized fluid- or melt-related processes in the Earth’s mantle. However, the origin of the SuR phases, and in particular their relationships with the UHP materials in the ophiolites, are still enigmatic. Studies of a recently recognized SuR mineral system from Cretaceous volcanics on Mt Carmel, Israel, suggest an alternative genesis for the ophiolitic SuR phases. The Mt Carmel SuR mineral system (associated with Ti-rich corundum xenocrysts) appears to reflect the local interaction of mantle-derived CH4 ± H2 fluids with basaltic magmas in the shallow lithosphere (depths of ~30-100 km). These interactions produced desilication of the magma, supersaturation in Al2O3 leading to rapid growth of corundum, and phase assemblages requiring local oxygen fugacity (fO2) gradually dropping to ~11 log units below the iron-wüstite (IW) buffer. The strong similarities between this system and the SuR phases and associated Ti-rich corundum in the Tibetan and Polar-Urals ophiolites suggest that the ophiolitic SuR suite probably formed by local influx of CH4 ± H2 fluids within previously subducted peridotites (and included chromitites) during their rapid exhumation from the deep upper mantle to lithospheric levels. In the final stages of their ascent, the recycled peridotites and chromitites were overprinted by a shallow magmatic system similar to that observed at Mt Carmel, producing most of the SuR phases and eventually preserving them within the Tibetan and Polar-Urals ophiolites.
DS201711-2506
2017
Pearson, N.J.Castillo-Oliver, M., Melgarejo, J.C., Gali, S., Pervov, V., Goncalves, A.O., Griffin, W.L., Pearson, N.J., O'Reilly, S.Y.Use and misuse of Mg- and Mn- rich ilmenite in diamond exploration: a petrographic and trace element approach. Congo-Kasai cratonLithos, Vol. 292-293, pp. 348-363.Africa, Angoladeposit - CAT115, Tchiuzo

Abstract: Magnesian ilmenite is a common kimberlite indicator mineral, although its use in diamond exploration is still controversial. Complex crystallisation and replacement processes have been invoked to explain the wide compositional and textural ranges of ilmenite found in kimberlites. This work aims to shed light on these processes, as well as their implications for diamond exploration. Petrographic studies were combined for the first time with both major- and trace-element analyses to characterise the ilmenite populations found in xenoliths and xenocrysts in two Angolan kimberlites (Congo-Kasai craton). A multi-stage model describes the evolution of ilmenite in these pipes involving: i) crystallisation of ferric and Mg-rich ilmenite either as metasomatic phases or as megacrysts, both in crustal and in metasomatised mantle domains; ii) kimberlite entrainment and xenolith disaggregation producing at least two populations of ilmenite nodules differing in composition; iii) interaction of both types with the kimberlitic magma during eruption, leading to widespread replacement by Mg-rich ilmenite along grain boundaries and fractures. This process produced similar major-element compositions in ilmenites regardless of their primary (i.e., pre-kimberlitic) origin, although the original enrichment in HFSE (Zr, Hf, Ta, Nb) observed in Fe3 +-rich xenocrysts is preserved. Finally (iv) formation of secondary Mn-ilmenite by interaction with a fluid of carbonatitic affinity or by infiltration of a late hydrothermal fluid, followed in some cases by subsolidus alteration in an oxidising environment. The complexities of ilmenite genesis may lead to misinterpretation of the diamond potential of a kimberlite during the exploration stage if textural and trace-element information is disregarded. Secondary Mg-enrichment of ilmenite xenocrysts is common and is unrelated to reducing conditions that could favour diamond formation/preservation in the mantle. Similarly, Mn-rich ilmenite should be disregarded as a diamond indicator mineral, unless textural studies can prove its primary origin.
DS201902-0287
2019
Pearson, N.J.Kourim, F., Beinlich, A., Wang, K.L., Michibayashi, K., O'Reilly, S.Y., Pearson, N.J.Feedback of mantle metasomatism on olivine micro-fabric and seismic properties of the deep lithosphere. Lithos, Vol. 328, pp. 43-57.Asia, Taiwanmetasomatism

Abstract: The interaction of hydrous fluids and melts with dry rocks of the lithospheric mantle inevitably modifies their viscoelastic and chemical properties due to the formation of compositionally distinct secondary phases. In addition, melt percolation and the associated metasomatic alteration of mantle rocks may also facilitate modification of the pre-existing rock texture and olivine crystallographic preferred orientation (CPO) and thus seismic properties. Here we explore the relationship between mantle metasomatism, deformation and seismic anisotropy using subduction-related mantle xenoliths from the Penghu Islands, western Taiwan. The investigated xenoliths have equilibrated at upper lithospheric mantle conditions (879?°C to 1127?°C) based on pyroxene geothermometry and show distinct variations in clinopyroxene chemical composition, texture and olivine CPO allowing for the classification of two distinct groups. Group 1 xenoliths contain rare earth element (REE) depleted clinopyroxene, show a porphyroclastic texture and olivine grains are mostly characterized by [100]-axial pattern symmetries. In contrast, REE-enriched clinopyroxene from Group 2 xenoliths occur in a fine-grained equigranular texture and coexisting olivine frequently displays [010]-axial pattern symmetries. The clinopyroxene compositions are indicative of cryptic and modal to stealth metasomatic alteration of Group 1 and Group 2 xenoliths, respectively. Furthermore, the observed olivine [100]-axial pattern of Group 1 xenoliths reflects deformation by dislocation creep at high temperature, low pressure and dry conditions, whereas olivine [010]-axial patterns of Group 2 xenoliths imply activation of olivine [001] glide planes along preferentially wet (010) grain boundaries. This correlation indicates that the variation in olivine CPO symmetry from [100]- to [010]-axial pattern in Penghu xenoliths results from deformation and intra-crystalline recovery by subgrain rotation during metasomatic alteration induced by melt percolation. The microstructural observations and olivine CPO combined with petrological and geochemical data suggest that Group 1 xenoliths preserve microstructural and chemical characteristics of an old, probably Proterozoic lithosphere, while Group 2 xenoliths record localized Miocene deformation associated with wall-rock heating and metasomatism related to melt circulation. Furthermore, the observed transition of olivine CPO from [100]-axial pattern to [010]-axial pattern by deformation in the presence of variable melt fractions and associated metasomatic alteration can be inferred to modify the physical properties of mantle rocks.
DS201905-1052
2019
Pearson, N.J.Kourim, F., Beinlich, A., Wang, K-L., Michibayashi, K., O'Reilly, S.Y., Pearson, N.J.Feedback of mantle metasomatism on olivine micro-fabric and seismic properties of the deep lithosphere.Lithos, Vol. 328-329, pp. 43-57.Asia, Taiwan, Penghu Islandsmetasomatism

Abstract: The interaction of hydrous fluids and melts with dry rocks of the lithospheric mantle inevitably modifies their viscoelastic and chemical properties due to the formation of compositionally distinct secondary phases. In addition, melt percolation and the associated metasomatic alteration of mantle rocks may also facilitate modification of the pre-existing rock texture and olivine crystallographic preferred orientation (CPO) and thus seismic properties. Here we explore the relationship between mantle metasomatism, deformation and seismic anisotropy using subduction-related mantle xenoliths from the Penghu Islands, western Taiwan. The investigated xenoliths have equilibrated at upper lithospheric mantle conditions (879?°C to 1127?°C) based on pyroxene geothermometry and show distinct variations in clinopyroxene chemical composition, texture and olivine CPO allowing for the classification of two distinct groups. Group 1 xenoliths contain rare earth element (REE) depleted clinopyroxene, show a porphyroclastic texture and olivine grains are mostly characterized by [100]-axial pattern symmetries. In contrast, REE-enriched clinopyroxene from Group 2 xenoliths occur in a fine-grained equigranular texture and coexisting olivine frequently displays [010]-axial pattern symmetries. The clinopyroxene compositions are indicative of cryptic and modal to stealth metasomatic alteration of Group 1 and Group 2 xenoliths, respectively. Furthermore, the observed olivine [100]-axial pattern of Group 1 xenoliths reflects deformation by dislocation creep at high temperature, low pressure and dry conditions, whereas olivine [010]-axial patterns of Group 2 xenoliths imply activation of olivine [001] glide planes along preferentially wet (010) grain boundaries. This correlation indicates that the variation in olivine CPO symmetry from [100]- to [010]-axial pattern in Penghu xenoliths results from deformation and intra-crystalline recovery by subgrain rotation during metasomatic alteration induced by melt percolation. The microstructural observations and olivine CPO combined with petrological and geochemical data suggest that Group 1 xenoliths preserve microstructural and chemical characteristics of an old, probably Proterozoic lithosphere, while Group 2 xenoliths record localized Miocene deformation associated with wall-rock heating and metasomatism related to melt circulation. Furthermore, the observed transition of olivine CPO from [100]-axial pattern to [010]-axial pattern by deformation in the presence of variable melt fractions and associated metasomatic alteration can be inferred to modify the physical properties of mantle rocks.
DS201911-2544
2019
Pearson, N.J.Malkovets, V.G., Rezvukhin, D.I., Griffin, W.L., Tretiakova, I.G., Pearson, N.J., Gibsher, A.A., Belousova, E.A., Zedgenizov, D.A., O'Reilly, S.Y.Re-Os dating of sulfide inclusions in Cr-pyropes from the Upper Muna kimberlites.Goldschmidt2019, 1p. AbstractRussiadeposit - Upper Muna

Abstract: Archean cratons are underlain by highly depleted subcontinental lithospheric mantle (SCLM). However, there are extensive evidences that Archean SCLM has been extensively refertilized by metasomatic processes, with the addition of Fe, Ca, and Al to depleted protoliths. The distribution of sub-calcic Cr-rich garnets in the SCLM beneath the Siberian craton suggests (1) sub-calcic garnets and diamonds are metasomatic phases in the cratonic SCLM; (2) the distribution of both phases is laterally heterogeneous on relatively small scales and related to ancient structural controls [1]. Re-Os isotopic compositions of twenty six sulfide inclusions in lherzolitic Cr-pyropes from Upper Muna kimberlites have been determined by laser ablation MCICPMS. Most analysed sulfides (~92%) have very low Re/Os ratios (<0.07), and their Re-depletion ages (TRD) form three major peaks: 3.4-2.8, 2.2-1.8 and 1.4-1.2 Ga (±0.03 Ga, mean 2s analytical uncertainty). One sulfide give the oldest TRD age at 4 Ga. Our data suggest that refertilization of the highly depleted SCLM and the introduction of Cr-pyrope garnet occurred in several episodes. The oldest age of ca 4 Ga indicate on the beginning of the formation of the depleted SCLM of the Siberian Craton in Hadean time [2].
DS1859-0021
1809
Pearson, R.Hutton, C., Shaw, G., Pearson, R.A Description of the Diamond Mines As It Was Presented by The Earl Marshal of England to the Royal Society.Phil. Transactions Royal Society of London., Vol. 2, FROM 1672-1683, No. 136, PP. 405-411.India, Golconda, Borneo, Minas GeraisHistory
DS1991-1318
1991
Pearson, R.C.Pearson, R.C.Maps showing mineral resource assessment for placer gold and silver DillonQuad.Idaho and MontanaUnited States Geological Survey (USGS) Map, No. I-1803-F, 1: 250, 000 $ 3.10Idaho, MontanaPlacers, Map
DS1900-0793
1909
Pearson, S.Pearson, S.American Diamonds. #2South African Mining Journal, Vol. 7, PT. 1, JUNE 12TH. P. 412.United States, Gulf Coast, Arkansas, Pennsylvania, Appalachia, KentuckyDiamond Occurrences
DS1910-0079
1910
Pearson, S.Pearson, S.Origin of Diamonds of German Southwest AfricaMining Engineering Journal of South Africa, Vol. 7, PT. 2, No. 365, MARCH 5TH. P. 680.Southwest Africa, NamibiaDiamond Genesis
DS201212-0361
2012
Pearson, S.Kjarsgaard, B.A., Mather, D.G., Pearson, S., Jackson, D., Crabtree, D., Creighton, S.CR-diopside and Cr-pyrope xenocryst thermobarometry revisited: applications to lithosphere studies and diamond exploration.10th. International Kimberlite Conference Feb. 6-11, Bangalore India, AbstractCanadaGeobarometry
DS1982-0211
1982
Pearson, W.N.D.Franklin, J.M., Pearson, W.N.D.Metallogeny of the Keweenawan (mid Continent) Rift Zone in The Lake Superior Region.Geological Association of Canada (GAC), Vol. 7, P. 50. (abstract.).GlobalMid-continent
DS1996-0934
1996
Pease, T.C.McLemore, V.T., Lueth, V.W., Pease, T.C., Guilinger, J.R.Petrology and mineral resources of the Wind River laccolith, CornudasMountains, New Mexico and TexasCanadian Mineralogist, Vol. 34, pt. 2, April pp. 335-348.New Mexico, TexasAlkaline rocks
DS2003-1052
2003
Pease, V.Pease, V.Rodinia's Baltica: internal structure and marginsGeological Society of America, Annual Meeting Nov. 2-5, Abstracts p.343.Scandinavia, Poland, Ukraine, BalticaTectonics
DS200412-1512
2003
Pease, V.Pease, V.Rodinia's Baltica: internal structure and margins.Geological Society of America, Annual Meeting Nov. 2-5, Abstracts p.343.Europe, Scandinavia, Baltic ShieldTectonics
DS200512-0321
2005
Pease, V.Gee, D.G., Pease, V.The Neoproterozoic Timanide Orogen of eastern Baltica.Geological Society of London, Memoir M0030 160p.Baltic Shield, Norway, Finland, RussiaBook - East European Craton, subduction
DS200812-0237
2008
Pease, V.Condie, K.C., Pease, V.When did plate tectonics begin on Earth?Geological Society of America Special Paper, 440, 290p. $ 85.00MantleBook - tectonics
DS200812-0871
2008
Pease, V.Pease, V., Percival, J., Smithies, H., Stevens, G., Van Kramendonk, M.When did plate tectonics begin? Evidence from the orogenic record.Geological Society of America Special Paper, 440, pp. 199-228.MantleTectonics
DS1989-1187
1989
Peat MarwickPeat MarwickThe Canadian exploration incentive program (CEIP) and the new flow through share regimePeat Marwick, 2p. brief summary Database # 17611CanadaEconomics, CEIP flow through
DS1988-0294
1988
Peate, D.Hawkesworth, C.J., Mantovani, M., Peate, D.Lithospheric remobilization during Parana CFB magmatismJournal of Petrology, Special Volume 1988- Oceanic and Continental, pp. 205-224Brazil, Paraguay, ArgentinaMantle, Chemistry
DS200612-1062
2006
Peate, D.Peate, D., Kerr, A.Plumes and large igneous provinces.Goldschmidt Conference 16th. Annual, S4-08 theme abstract 1/8p. goldschmidt2006.orgMantleHotspots, plumes
DS1989-1298
1989
Peate, D.W.Rogers, N.W., Ellam, R.M., Peate, D.W., Hawkesworth, C.J.Potassic mafic rocks from the Virunga and the Karoo and the composition Of the subcontinental mantleNew Mexico Bureau of Mines Bulletin., Continental Magmatism Abstract Volume, Held, Bulletin. No. 131, p. 225 Abstract held June 25-July 1Central AfricaTectonics, Rift
DS1993-1209
1993
Peate, D.W.Peate, D.W., Hawkesworth, C.J, Mantovani, M.SM.Chemical stratigraphy of the Parana lavas (South America): classification of magma types and their spatial distributionBulletin Volcanology, Vol. 55, pp. 119-139South AmericaFlood basalts, Geochemistry
DS1995-1453
1995
Peate, D.W.Pearce, J.A., Peate, D.W.Tectonic implications of the composition of volcanic arc magmasAnnual Review of Earth Planetary Sciences, Vol. 23, pp. 251-286MantleTectonics, Magmas - arc
DS1996-1090
1996
Peate, D.W.Peate, D.W., Hawkesworth, C.J.Lithospheric to asthenospheric transition in low Ti flood basalts From southern Parana, BrasilChemical Geology, Vol. 127, No. 1-3, Jan. 10, pp. 1-24BrazilBasalts, Xenoliths, Geochemistry
DS2000-0503
2000
Peate, D.W.Kirstein, L.A., Peate, D.W., Mantovani, M.S.M.Early Cretaceous basaltic and rhyolitic magmatism in southern Uruguay: associated opening South AtlanticJournal of Petrology, Vol. 41, No. 9, Sept. pp. 1413-38.Uruguay, South AmericaMagmatism
DS2003-1053
2003
Peate, D.W.Peate, D.W., Techer, O.Pb isotope evidence for contributions from different Iceland mantle components toLithos, Vol. 67, No. 1-2, March pp. 39-52.IcelandGeochornology - Blooseville Kyst area, Iceland plume
DS200412-1513
2004
Peate, D.W.Peate, D.W., Baker, J.A., Breddam, K., Waight, T.E., Skovgaard, A.C., Stecher, O., Prestvik, T., JonassonPb isotope heterogeneity of the mantle beneath Iceland.Geochimica et Cosmochimica Acta, 13th Goldschmidt Conference held Copenhagen Denmark, Vol. 68, 11 Supp. July, ABSTRACT p.A569.Europe, IcelandGeochronology
DS200512-0833
2005
Peate, D.W.Peate, D.W., Hawkesworth, C.J.U series disequilibria: insights into mantle melting and the timescales of magma differentiation.Reviews of Geophysics, Vol. 43, 1, March 31, RG 1003MantleMelt, metasomatism
DS200712-0824
2006
Peate, D.W.Peate, D.W., Breddam, K., Baker, J.A., Kurz, M., Grassineau, N., Barker, A.K.Compositional features of enriched Icelandic mantle components.Geochimica et Cosmochimica Acta, In press availableEurope, IcelandGeochemistry
DS201012-0571
2010
Peats, J.Peats, J., Stachel, T., Stern, R., Muehlenbachs, K., Armstrong, J.Aviat diamonds as a window into the deep lithospheric mantle beneath the northern Churchill province.38th. Geoscience Forum Northwest Territories, Abstract pp.118-119.Canada, Northwest Territories, Melville PeninsulaGeochronology - nitrogen, CI
DS201212-0547
2012
Peats, J.Peats, J., Stachel, T., Ster, R.A., Muehlenbachs, K., Armstrong, J.Aviat diamonds: a window into the deep lithospheric mantle beneath the Northern Churchill Province, Melville Peninsula, Canada.Canadian Mineralogist, Vol. 50, 3, June pp. 611-624.Canada, Nunavut, Melville PeninsulaDeposit - Aviat
DS1998-1141
1998
Pebesma, E.J.Pebesma, E.J., Wesseling, C.G.GSTAT: a program for geostatistical modelling, prediction and simulationComputers and Geosciences, Vol.24, No. 1, pp. 17-31GlobalGeostatistics, Kriging, Computer - program, GSTAT.
DS200812-0345
2008
PeccerilloFerrnado, S., Frezzotti, M.L., Neumann, De Astis, Peccerillo, Dereje, Gezahegn, TeklewoldComposition and thermal structure of the lithosphere beneath the Ethiopian plateau: evidence from mantle xenoliths in basanites, Injibara Lake Tana Province.Mineralogy and Petrology, Vol. 93, 1-2, pp. 47-78.Africa, EthiopiaBasanites, Foidites
DS1985-0521
1985
Peccerillo, A.Peccerillo, A., Giampiero, P.Primary Potassic Magmas in the Roman Province: Condition Of genesis and Geodynamic Implications.Geological Association of Canada (GAC)., Vol. 10, P. A47, (abstract.).ItalyBlank
DS1987-0221
1987
Peccerillo, A.Francalanci, L., Peccerillo, A., Poli, G.Partition coefficients for minerals in potassium alkaline rocks: dat a from Roman province (Central Italy)Geochemical Journal, Vol. 21, No. 1, pp. 1-10ItalyAlkaline rocks, Analyses
DS1988-0537
1988
Peccerillo, A.Peccerillo, A., Poli, G., Serri, G.Petrogenesis of oreniditic and kamafugitic rocks from central ItalyCanadian Mineralogist, Vol. 26, No. 1, March pp. 23-44ItalyBlank
DS1989-0287
1989
Peccerillo, A.Conticelli, S., Peccerillo, A.Petrological significance of high-pressure ultramafic xenoliths from ultrapotassic rocks of central Italy #1New Mexico Bureau of Mines Bulletin., Continental Magmatism Abstract, Bulletin. No. 131, p. 58. AbstractItalyXenoliths
DS1989-1188
1989
Peccerillo, A.Peccerillo, A., Conticelli, S.Lamproitic to Roman type ultrapotassic magmatism In central Italy; petrological, geochemical and isotopicvariationsNew Mexico Bureau of Mines Bulletin., Continental Magmatism Abstract Volume, Held, Bulletin. No. 131, p. 211. AbstractItalyLamproite
DS1990-0356
1990
Peccerillo, A.Conticelli, S., Peccerillo, A.Petrological significance of high-pressure ultramafic xenoliths from ultrapotassic rocks of Central Italy #2Lithos, Vol. 24, No. 4, August pp. 305-322ItalyUltrapotassic rocks, Petrology, Xenoliths
DS1990-1167
1990
Peccerillo, A.Peccerillo, A., Conticelli, S.Petrology and geochemistry of high pressure ultramafic xenoliths from ultrapotassic rocks of central ItalyTerra, Abstracts of International Workshop Orogenic Lherzolites and Mantle Processes, Vol. 2, December abstracts p. 139ItalyAlkaline -ultrapotassic, Lherzolites, Harzburgites
DS1992-0296
1992
Peccerillo, A.Conticelli, S., Peccerillo, A.Petrology and geochemistry of potassic and ultrapotassic volcanism In central Italy -petrogenesis and inferences on the evolution of the mantlesourcesLithos, Vol. 28, No. 3-6. November pp. 221-240ItalyPetrology, geochemistry, Ultrapotassic
DS1993-1210
1993
Peccerillo, A.Peccerillo, A.Potassic and ultrapotassic rocks: compositional characteristics, petrogenesis and geologic significance.Episodes, Vol. 15, No. 4, December 1992, pp. 243-251.GlobalPetrology, Potassic rocks
DS1994-0508
1994
Peccerillo, A.Federico, M., Peccerillo, A., et al.Mineralization and geochem. study granular xenoliths from Alban Hillsvolcano, Italy: an evolutionary processes in potassic magma.Contr. Mineralogy and Petrology, Vol. 116, No. 3, pp. 384-401.ItalyAlkaline rocks, Xenoliths
DS1994-1350
1994
Peccerillo, A.Peccerillo, A.calc alkaline to ultrapotassic magmatism: constraints on mantle type of metasomatism and meltingInternational Symposium Upper Mantle, Aug. 14-19, 1994, pp. 100-102.ItalyAlkaline rocks, Metasomatism
DS1995-1466
1995
Peccerillo, A.Peccerillo, A., Ferraro, C., Gezaegn, Y.Petrogenesis of peralkaline acid magmas along the main Ethiopian RiftGeological Society Africa 10th. Conference Oct. Nairobi, p. 117. Abstract.GlobalAlkaline rocks, Petrology
DS1998-1142
1998
Peccerillo, A.Peccerillo, A.Relationships between ultrapotassic and carbonate rich volcanic rocks central Italy: petrogenetic, geodynamicLithos, Vol. 43, No. 4, Sept. pp. 267-ItalyAlkaline rocks
DS1999-0546
1999
Peccerillo, A.Peccerillo, A.Multiple mantle metasomatism in central southern Italy: geochemicaleffects, timing and geodynamic implicationsGeology, Vol. 27, No. 4, Apr pp. 315-8.ItalyLamproites, Magmatism, Metasomatism