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SDLRC - Scientific Articles all years by Author - St+


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 - St+
Posted/
Published
AuthorTitleSourceRegionKeywords
DS1900-0625
1908
St Louis TimesSt Louis TimesDiamonds in Alaska; September, 1908St. Louis Times, SEPT. 28TH.United States, AlaskaDiamond Occurrence
DS1991-1650
1991
St Seymour, K.St Seymour, K., Kiddie, A., Wares, R.Basalts and gabbros of the Labrador trough-remnants of a Proterozoic failedocean?Neues Jahrbuch fnr Mineralogie Monat, No. 6, pp. 271-280Quebec, Labrador, UngavaBasalts, Tectonics
DS1950-0304
1956
St. clair, J.Q.St. clair, J.Q.Report on the Arkansaw Diamond PropertyCompany Report., 15P. UNPUBL.United States, Gulf Coast, Arkansas, PennsylvaniaEvaluation, Methods, Mining, Prospectus
DS1920-0414
1928
St. clair, S.Weller, S., St. clair, S.Geology of the St. Genevieve County, MissouriMissouri Bureau of Geology And Mines, SER. 2, Vol. 22, 352P.GlobalKimberlite, Central States, Alnoite
DS1860-0773
1892
St. George, G.St. George, G.Among the African Diamond Mines. #5Jewellers Circular Keystone, Vol. 25, No. 4, AUG. 24TH. P. 22.Africa, South AfricaAlluvial placers
DS1860-0815
1893
St. george, G.St. george, G.Among the African Diamond Mines. #8 Hansens WarrentonJewellers Circular Keystone, Vol. 26, No. 3, Feb. 15TH. P. 11.Africa, South AfricaAlluvial placers
DS1860-0858
1894
St. george, G.St. george, G.Among the African Diamond Mines. #6Jewellers Circular Keystone, Vol. 28, No. 10, APRIL 11TH. PP. 7-8.Africa, South AfricaAlluvial placers
DS1860-0908
1895
St. george, G.St. george, G.Among the African Diamond Mines. #6Jewellers Circular Keystone, VOL 30, No. 23, JULY 10TH. P. 9.Africa, South AfricaAlluvial placers
DS1860-0909
1895
St. george, G.St. george, G.Among the African Diamond Mines. #1Jewellers Circular Keystone, Vol. 30, No. 19, JUNE 12TH. P. 7.Africa, South Africa, Orange Free StateAlluvial placers
DS1860-0910
1895
St. george, G.St. george, G.Among the African Diamond Mines. #2Jewellers Circular Keystone, Vol. 30, No. 7, MARCH 20TH. PP. 7-8.Africa, South Africa, Orange Free StateDiamonds Notable
DS1860-0959
1896
St. george, G.St. george, G.Among the African Diamond Mines. #4Jewellers Circular Keystone, Vol. 32, No. 8, MARCH 25TH. P. 7.Africa, South AfricaAlluvial placers
DS1860-0960
1896
St. george, G.St. george, G.Among the African Diamond Mines. #7Jewellers Circular Keystone, Vol. 33, No. 8, SEPT. 23RD. PP. 7, 9.Africa, South AfricaAlluvial placers
DS1860-1048
1898
St. george, G.St. george, G.Among the African Diamond Mines. #3Jewellers Circular Keystone, Vol. 35, No. 24, Jan. 12TH. P. 7.Africa, South Africa, TransvaalHistory
DS1960-1215
1969
St. george, G.St. george, G.Diamonds; Van Rees Press, 1969Van Rees Press, New York, PP. 182-198.RussiaDiamond Occurrences
DS1982-0286
1982
St. joe bonaparte pty. ltd., AQUITAINE MINE.Ingebritsen, R.H., St. joe bonaparte pty. ltd., AQUITAINE MINE.El 2528 Grass Plains Nt Final Report 1980-1982Northern Territory Geological Survey Open File Report, No. CR.82/309, 8P.Australia, Northern TerritoryProspecting, Geophysics
DS1991-1613
1991
St. Jorre, L. deSmith, D.G.W., St. Jorre, L. de, Reed, S.J.B., Long, J.V.P.Zonally metamictized and other zircons from Thor Lake, NorthwestTerritoriesCanadian Mineralogist, Vol. 29, No. 2, June pp. 301-310Northwest TerritoriesRare earths, Deposit -Thor Lake
DS1984-0704
1984
St. louis, R.M.St. louis, R.M.Geochemistry of the platinum group elements in the Tulameenultramaficcomplex, British ColumbiaMsc. Thesis, University of Alberta, 127pBritish ColumbiaGeochemistry, Diatreme
DS1900-0098
1902
St. Louis GlobeSt. Louis GlobeIndiana Man Discovered Valuable Stone in Morgan CountySt. Louis Globe Democrat., MAY 20TH.United States, Indiana, Great LakesDiamond Occurrence
DS1860-0737
1892
St. Louis Globe DemocratSt. Louis Globe DemocratDiamonds in NebraskaSt. Louis Globe Democrat., Jan. 3RD.United States, Nebraska, Central StatesDiamond Occurrence
DS1900-0102
1902
St. Louis RepublicSt. Louis RepublicDiamonds Are SapphiresSt. Louis Republic., Jan. 26TH. ALSO : BOSTON EVENING TRANSCRIPT, Jan. 26TH.United States, Montana, Rocky Mountains, FergusDiamond Occurrence
DS2003-0361
2003
St. Onge, D.A.Dyke, A.S., St. Onge, D.A., Savelle, J.M.Deglaciation of southwestern Victoria Island and adjacent Arctic mainland, NunavutGeological Survey of Canada Map, No. 2027A, 1: 500,000 $ 20.NunavutGeomorphology
DS2002-1434
2002
St. Onge, M.Scott, D.J., Stern, R.A., St. Onge, M., McMullen, S.U Pb geochronology of detrital zircons in metasedimentary rocks from southern BaffinCanadian Journal of Earth Science, Vol.39,5, May, pp.611-623.Quebec, Labrador, Baffin IslandGeophysics - ESCOOT, Tectonics - Laurentia
DS1991-1651
1991
St. Onge, M.R.St. Onge, M.R., Lucas, S.B.Evolution of regional metamorphism in the Cape Smith Thrust Belt, northernQuebec, :interaction of tectonic and thermal processesJournal of Metamorphic Geology, Vol. 9, No. 5, September pp. 515-534Quebec, Labrador, UngavaMetamorphism, Cape Smith
DS1992-0963
1992
St. Onge, M.R.Lucas, S.B., St. Onge, M.R., Parrish, R.R.Long lived continent ocean interaction in the Early Proterozoic UngavaOrogen, northern Quebec, Canada.Geology, Vol. 20, Feb. pp. 113-6.Quebec, LabradorCape Smith Thrust Belt, Orogeny
DS1992-1463
1992
St. Onge, M.R.St. Onge, M.R., Lucas, S.B.New insight on crustal structure and tectonic history of the Ungava Kovic Bay and Cap WoltenholmeGeological Survey of Canada (GSC) Paper, No. 92-1C, pp. 31-41.QuebecTectonics
DS1992-1464
1992
St. Onge, M.R.St. Onge, M.R., Lucas, S.B., Parrish, R.R.Terrane accretion in the internal zone of the Ungava Orogen Pt. 1 and Pt.2.Canadian Journal of Earth Sciences, Vol. 29, pp. 746-64; 765-82.Labrador, Ungava, QuebecTectonics, structure, tectonostratigraphic, metamorphic
DS1995-1121
1995
St. Onge, M.R.Lucas, S.B., St. Onge, M.R.Syn tectonic magmatism and the development of compositional layering, Ungava Orogen (Northern Quebec)Journal of Structural Geology, Vol. 17, No. 4, pp. 475-491Quebec, UngavaArchean Superior, Paleoproterozoic, Tectonics
DS1996-1359
1996
St. Onge, M.R.St. Onge, M.R., Lucas, S.B.Paleoproterozoic orogenic beltsGeological Survey of Canada, LeCheminant ed, OF 3228, pp. 17-24.CanadaOrogeny -Torngat, New Quebec, Ungava, Trans Hudson, Wopmay, Taltson-Thelon
DS1998-0900
1998
St. Onge, M.R.Lucas, S.B., St. Onge, M.R.Geology of the Precambrian Superior and Grenville Provinces and Precambrian fossils in North America.Geological Survey of Canada (GSC) DNAG, Vol. 7, pp. 13-270.Ontario, Quebec, Labrador, Baffin Island, Manitoba, SaskatchewanRegional geology - not specific to diamonds, Superior Province
DS1998-1460
1998
St. Onge, M.R.Theriault, R.J., Scott, D.J., St. Onge, M.R.neodymium isotopic framework of the intermediate structural levels of eastern Trans-Hudson Orogen, Baffin Island.Geological Society of America (GSA) Annual Meeting, abstract. only, p.A110.Northwest Territories, Baffin Island, LabradorTectonics, Trans Hudson Orogen
DS1999-0703
1999
St. Onge, M.R.St. Onge, M.R., Lucas, S.B., Scott, D.J., Wodicka, N.Upper and lower plate juxtaposition, deformation and metamorphism during crustal convergence, Trans HudsonPrecambrian Research, Vol. 93, No. 1, Jan. pp. 5-26.GlobalTectonics, Trans Hudson Orogen
DS2001-1114
2001
St. Onge, M.R.St. Onge, M.R., Corrigan, D., Dredge, L., Scott, D.J.An overview of the multidisciplinary central Baffin Project29th. Yellowknife Geoscience Forum, Nov. 21-23, abstract p. 82-3.Northwest Territories, NunavutGeology - not specific to diamonds
DS2001-1115
2001
St. Onge, M.R.St. Onge, M.R., Scott, D.J., Corrigan, D.Geology, central Baffin Island, NunavutGeological Survey of Canada (GSC) Open File, D3996, 1 CD, $ 130.Northwest Territories, Nunavut, Baffin IslandGeology
DS2001-1116
2001
St. Onge, M.R.St. Onge, M.R., Scott, D.J., Wodicka, N.Terrane boundaries within Trans Hudson Orogen Quebec - Baffin segment. Changing structural and metamorphic...Precambrian Research, Vol. 107, No. 1-2, Mar. 30, pp. 75-92.Quebec, Ungava, Baffin IslandForeland to hinterland, Trans Hudson Orogeny
DS2001-1153
2001
St. Onge, M.R.Theriault, R.J., St. Onge, M.R., Scott, D.J.neodymium isotopic and geochemical signature of the Paleoproterozoic Trans HudsonOrogen, implications forPrecambrian Research, Vol. 108, No. 1-2, May 1, pp. 113-138.Northwest Territories, Baffin IslandEvolutin of eastern Laurentia, Geochronology, geochemistry
DS2003-1323
2003
St. Onge, M.R.St. Onge, M.R., Wodicka, N., Scott, D.J., Corrigan, D., Carmichael, D.M.Thermal architecture of a continent-continent collision zone: a Superior to Rae CratonGeological Association of Canada Annual Meeting, Abstract onlyQuebecGeothermometry
DS2003-1494
2003
St. Onge, M.R.Wodicka, N., St. Onge, M.R., Corrigan, D., Scott, D.J.Tectonothermal evolution of Archean basement and Paleoproterozoic cover in centralGeological Association of Canada Annual Meeting, Abstract onlyNunavut, Baffin IslandGeothermometry
DS201706-1077
2017
St. Onge, M.R.Harrison, J.C., St. Onge, M.R., Paul, D., Brodaric, B.A new geological map and map database for Canada north of 60.GAC annual meeting, 1p. AbstractCanadamap
DS201706-1105
2017
St. Onge, M.R.St. Onge, M.R., Harrison, J.C., Paul, D., Tella, S., Brent, T.A., Jauer, C.D., MacleanTectonic map of Arctic Canada (TeMAC): a first derivative product from Canada in 3-D geological compilation work.GAC annual meeting, 1p. AbstractCanadatectonics
DS1860-1064
1899
St. Paul Minneapolis GlobeSt. Paul Minneapolis GlobeDiamonds in Wisconsin. #1St. Paul Minneapolis Globe, SEPT. 10TH.United States, Great Lakes, WisconsinDiamond Occurrence
DS1860-1068
1899
St. Paul Minneapolis GlobeSt. Paul Minneapolis GlobeDiamonds found in 1899St. Paul Minneapolis Globe, SEPT. 10TH.United States, Great Lakes, WisconsinDiamond Occurrence
DS1998-1395
1998
St. Pierre, M.St. Pierre, M., Wynne, P.J., Counts, B.Paleomagnetisation of kimberlites on the BHP/Dia Met diamond project7th International Kimberlite Conference Abstract, pp. 871-73.Northwest TerritoriesPaleomagnetics, Deposit - Kaola, Beaver, Jay, Caribou, Kaska, Misery, L.
DS1999-0704
1999
St. Pierre, M.St. Pierre, M.Diamonds in the Northwest Territories. Geophysical characteristics of the BHP/Dia Met kimberlite.Congres de L'Association Geol. Geophys., du Quebec, pp. 171-80.Northwest TerritoriesGeophysics - magnetics
DS1999-0705
1999
St. Pierre, M.St. Pierre, M.Geophysical characteristics of the BHP Dia Met kimberlites, northwest Territories CanadaGeological Association of Canada (GAC) Short Course Geophysics in, Vol. 14, pp. 63-72.Northwest TerritoriesGeophysics, Grizzly, Leslie, Point Lake
DS2000-0921
2000
St. Pierre, M.St. Pierre, M.An exploration review of Tahera Corporation core properties28th. Yellowknife Geoscience Forum, p.78-9.abstractNorthwest TerritoriesExploration - history, Deposit - Jericho
DS1988-0385
1988
St. Seymour, K.Kumarapeli, S., St. Seymour, K., Pintson, H., Hasselgren, E.volcanism on the passive margin of Laurentia: an early Palezoic analogue of Cretaceous volcanism on the northeastern American marginCanadian Journal of Earth Sciences, Vol. 25, No. 11, November pp. 1824-1833Quebec, Labrador, UngavaAllochthons, volcanism.
DS1991-1652
1991
St. Seymour, K.St. Seymour, K., Kiddie, A., Wares, R.Basalts and gabbros of the Labrador Trough: remnants of a Proterozoic failed ocean?Neues Jahrb. fur Mineralogie, No. 6, pp. 271-280Quebec, Labrador, UngavaProterozoic, Trough
DS1995-1815
1995
St. Seymour, K.St. Seymour, K., Kumarapili, P.S.Geochemistry of the Grenville dyke swarm: role of plume source mantle in magma genesis.Contributions to Mineralogy and Petrology, Vol. 120, No. 1, pp. 29-41.OntarioGeochemistry dykes, Grenville dyke swarm
DS200512-0957
2005
St.George, G.M.Sears, J.W., St.George, G.M., Winne, J.C.Continental rift systems and anorogenic magmatism.Lithos, Vol. 80, 1-4, March pp. 147-154.Rift, Gondwana, Laurentia, plume
DS201212-0379
2012
St.O'Neill, H.Kovacs, I., Green, D.H., Rosenthal, A., Hermann, J., St.O'Neill, H., Hibberson, W.O., Udvardi, B.An experimental study of water in nominally anhydrous minerals in the upper mantle near the water saturated solidus.Journal of Petrology, Vol. 53, 10, pp. 2067-2093.MantleWater content
DS201312-0118
2013
St.O'Neill, H.Campbell, I.H., St.O'Neill, H.Evidence against a chondritic Earth.Goldschmidt 2013, AbstractMantleGeochemistry
DS200412-0495
2003
St.Onge, D.A.Dyke, A.S., St.Onge, D.A., Savelle, J.M.Deglaciation of southwestern Victoria Island and adjacent Arctic mainland, Nunavut, NWT.Geological Survey of Canada Map, No. 2027A, 1: 500,000 $ 20.Canada, NunavutMap Geomorphology
DS200512-0193
2005
St.Onge, M.Corrigan, D., St.Onge, M., Pehrsson, S.Paleproterozoic growth of continental lithosphere: a perspective from Laurentia in Canada.GAC Annual Meeting Halifax May 15-19, Abstract 1p.Canada, NunavutCraton, tectonics
DS201312-0563
2013
St.Onge, M.Machado, G., Bilodeau, C., Takpanie, R., St.Onge, M., Rayner, N., Skipton, D., From, R., MacKay, C., Young, M., Creason, G., Braden, Z.Regional bedrock mapping, Hall Peninsula, Nunavut.Geoscience Forum 40 NWT, abstract only p. 26Canada, NunavutMapping
DS2001-1117
2001
St.Onge, M.R.St.Onge, M.R., Scott, D.J., Corrigan, Wodicka, De KempThe fundamental asymmetry of a continent - continent collision zone: a Superior to Rae Craton transect.Geological Association of Canada (GAC) Annual Meeting Abstracts, Vol. 26, p. 146.abstract.Quebec, Baffin IslandTrans Hudson orogen, Tectonics
DS2002-1534
2002
St.Onge, M.R.St.Onge, M.R., Scott, D.J., Wodicka, N.Review of crustal architecture and evolution in the Ungava Peninsula - Baffin Island area: connection to the Lithoprobe ESCOOT transect.Canadian Journal of Earth Science, Vol.39,5, May, pp.589-610.Quebec, Labrador, Baffin IslandGeophysics - ESCOOT, Tectonics
DS200412-1903
2003
St.Onge, M.R.St.Onge, M.R., Wodicka, N., Scott, D.J., Corrigan, D., Carmichael, D.M., Dubach, K., Berniolles, F., Begin, N.Thermal architecture of a continent-continent collision zone: a Superior to Rae Craton transect of Trans-Hudson Orogen ( Quebec-Geological Association of Canada Annual Meeting, Abstract onlyCanada, QuebecGeothermometry
DS200412-2139
2003
St.Onge, M.R.Wodicka, N., St.Onge, M.R., Corrigan, D., Scott, D.J.Tectonothermal evolution of Archean basement and Paleoproterozoic cover in central Baffin Island, Nunavut: constraints from U PbGeological Association of Canada Annual Meeting, Abstract onlyCanada, Nunavut, Baffin IslandGeothermometry
DS200512-1037
2005
St.Onge, M.R.St.Onge, M.R., Wodicka, N.The Trans Hudson Orogen of North America and the Himalayan Karakoram Tibetan Orogen of Asia: structural and thermal evolution of the lower and upper plates.GAC Annual Meeting Halifax May 15-19, Abstract 1p.Canada, Nunavut, Saskatchewan, AlbertaTectonics, geothermometry
DS200612-1357
2006
St.Onge, M.R.St.Onge, M.R.Geology, Cape Smith Belt and adjacent domains, Ungava Peninsula, Quebec-Nunavut.Geological Survey of Canada Open File, No. 4930, 1:300,000 CD $ 20.00Canada, Quebec, NunavutGeology
DS200612-1358
2006
St.Onge, M.R.St.Onge, M.R., Jackson, G.D., Henderson, I.Geology, Baffin Island south of 70 N and east of 80 W.Geological Survey of Canada, No. 4931, 1 CD $ 9.10Canada, NunavutBedrock data
DS200612-1359
2006
St.Onge, M.R.St.Onge, M.R., Searle, M.P., Wodicka, N.Trans Hudson Orogen of North America and Himalaya Karakoram Tibetan Orogen of Asia: structural and thermal characteristics of the lower and upper plates.Tectonics, Vol. 25, 4, TC4006Canada, AsiaGeothermometry
DS200712-1031
2007
St.Onge, M.R.St.Onge, M.R., Wodicka, N., Ijewliw, O.Polymetamorphic evolution of the Trans-Hudson Orogen, Baffin Island, Canada: integration of petrological, structural and geochronological data.Journal of Petrology, Vol. 48, 2, Feb., pp. 271-302.Canada, Nunavut, Baffin IslandTectonics
DS200912-0727
2009
St.Onge, M.R.St.Onge, M.R., Van Gool, A.M., Garde, A.A., Scott, D.J.Correlation of Archean and paleoproterozoic units between northeastern Canada and western Greenland: constraining the pre-collisional upper plate accretionary historyGeological Society of London, Special Publication Earth Accretionary systems in Space and Time, No. 318, pp. 193-235.Canada, Ontario, Europe, GreenlandTrans-Hudson Orogen
DS201605-0836
2016
Stabbert, W.Fouchee, A., Stabbert, W.Technological advances of Longi-Multotec high intensity rare earth magnetic seperators improving DMS media circuits.Diamonds Still Sparkling SAIMM 2016 Conference, Mar. 14-17, pp. 153-158.TechnologyDMS - applied
DS1988-0271
1988
Stabel, A.Griffin, W.L., O'Reilly, S.Y., Stabel, A.Mantle metasomatism beneath western Victoria, Australia: III sotopicgeochemistry of chromium diopside lherzolites and aluminium augite pyroxenitesGeochimica et Cosmochimica Acta, Vol. 52, No. 2, February pp. 449-460AustraliaMetasomatism, Mantle
DS1988-0525
1988
Stabel, A.O'Reilly, S.Y., Griffin, W.L., Stabel, A.Evolution of Phanerozoic Eastern Australian Lithosphere: isotopic evidence for magmatic and tectonicunderplatingJournal of Petrology, Special Volume 1988- Oceanic and Continental, pp. 89-108AustraliaTectonics
DS2003-1084
2003
Stabel, L.Z.Pla Cid, J., Nardi, L.V., Stabel, L.Z., Conceicao, R.V., Balzetti, N.M.High pressure minerals in mafic microgranular enclaves: evidence for co-minglingContributions to Mineralogy and Petrology, Vol. 145, 4, pp. 444-459.MantleMagmatism
DS200412-1555
2003
Stabel, L.Z.Pla Cid, J., Nardi, L.V., Stabel, L.Z., Conceicao, R.V., Balzetti, N.M.High pressure minerals in mafic microgranular enclaves: evidence for co-mingling between lamprophyric and syenitic magmas at manContributions to Mineralogy and Petrology, Vol. 145, 4, pp. 444-459.MantleMagmatism
DS201502-0109
2014
Stacey, A.Stacy, J., Stacey, A.Perceptions of the impact of board members' individual perspectives on the social and environmental performance of companies. ( Based on SA and not junior companies).Journal of the South African Institute of Mining and Metallurgy, Vol. 114, Nov. pp. 957-969.Africa, South AfricaCSR
DS202010-1844
2020
Stacey, A.Genish, H., Ganesan, K., Stacey, A., Prawer, S., Rosenbluh, M.Effect of radiation damage on the quantum optical properties of nitrogen vacancies in diamond.Diamond & Related Materials, Vol. 109, 108049, 6p. PdfMantlenitrogen

Abstract: Single crystal diamond (<5?ppm nitrogen) containing native NV centers with coherence time of 150?µs was irradiated with 2?MeV alpha particles, with doses ranging from 1012 ion/cm2 to 1015 ion/cm2. The effect of ion damage on the coherence time of NV centers was studied using optically detected magnetic resonance and supplemented by fluorescence and Raman microscopy. A cross-sectional geometry was employed so that the NV coherence time could be measured as a function of increasing defect concentration along the ion track. Surprisingly, although the ODMR contrast was found to decrease with increasing ion induced vacancy concentration, the measured decoherence time remained undiminished at 150us despite the estimated vacancy concentration reaching a value of 40?ppm at the end of range. These results suggest that ion induced damage in the form of an increase in vacancy concentration does not necessarily result in a significant increase in the density of the background spin bath.
DS1999-0706
1999
Stacey, C.H.B.Stacey, F.D., Stacey, C.H.B.Gravitational energy of core evolution: implications for thermal history and geodynamo power.Physical Earth and Planetary Interiors, Vol. 110, pp. 83-93.MantleDensity - pressure relationship
DS1999-0706
1999
Stacey, F.D.Stacey, F.D., Stacey, C.H.B.Gravitational energy of core evolution: implications for thermal history and geodynamo power.Physical Earth and Planetary Interiors, Vol. 110, pp. 83-93.MantleDensity - pressure relationship
DS2001-1118
2001
Stacey, F.D.Stacey, F.D.Finite strain, thermodynamics and the Earth's corePhysics of the Earth and Planetary Interiors, Vol. 128, No. 1-4, Dec. 10, pp. 179-83.MantleCore-mantle
DS2001-1119
2001
Stacey, F.D.Stacey, F.D., Isaak, D.G.Compositional constraints on the equation of state and thermal properties of the lower mantle.Geophys. Journal of International, Vol. 146, No. 1, pp. 143-54.MantleGeothermometry
DS200412-1904
2004
Stacey, F.D.Stacey, F.D., Davis, P.M.High pressure equations of state with applications to the lower mantle and core.Physics of the Earth and Planetary Interiors, Vol. 142, 3-4, pp. 137-184.MantleUHP
DS200512-0113
2005
StachelBrenker, F.E., Vincze, L., Velemans, Nasdala, Stachel, Vollmer, Kersten, Somogyi, Adams, Joswig, HarrisDetection of a Ca rich lithology in the Earth's deep ( >300km) convecting mantle.Earth and Planetary Science Letters, Vol. 236, 3-4, pp. 579-587.Africa, GuineaKankan, diamond inclusions, spectroscopy
DS201112-0454
2011
StachelHowell, 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
DS200512-1073
2005
Stachel, R.Tappert, R., Stachel, R.Subducting oceanic crust: the source of deep diamonds.Geology, Vol. 33, 7, July, pp. 565-568.Africa, South AfricaJagersfontein, majorite, diamond inclusions, Eu anomalies
DS200812-0249
2009
Stachel, S.Creighton, S., Stachel, S., Matveev, S., Hofer, H., McCammon, C., Luth, R.W.Oxidation of the Kaapvaal lithospheric mantle driven by metasomatism.Contributions to Mineralogy and Petrology, Vol. 157, pp. 491-504.Africa, South AfricaMetasomatism, Kimberley
DS1991-1653
1991
Stachel, T.Stachel, T., Lorenz, V., Smith, C.B., Jaques, A.L.Volcanology and geochemistry of the Ellendale lamproite field, WesternAustraliaProceedings of Fifth International Kimberlite Conference held Araxa June 1991, Servico Geologico do Brasil (CPRM) Special, pp. 392-394AustraliaPetrogenesis, olivine lamproites, Leucite lamproites
DS1993-1521
1993
Stachel, T.Stachel, T.Spinels from the Ellendale olivine lamproites (Western Australia)Significance for diamond distribution and emplacement history.Neues Jahrbuch Miner. Abh., Vol. 165, No. 2, pp. 155-167.AustraliaLamproites, mineralogy, Deposit -Ellendale
DS1994-1680
1994
Stachel, T.Stachel, T., Lorenz, V., Smith, C.B., Jaques, A.L.Evolution of four individual lamproite pipes, Ellendale volcanic field(Western Australia).Proceedings of Fifth International Kimberlite Conference, Vol. 1, pp. 177-194.AustraliaLamproite, Deposit -Ellendale
DS1995-1110
1995
Stachel, T.Lorenz, V., Kurzlaukis, S., Stachel, T., Brey, StanistreetVolcanology of the diatreme rich carbonatitic Gross Brukkaros volcanicfield and of the near by Gibeon K.Proceedings of the Sixth International Kimberlite Conference Abstracts, pp. 333-335.NamibiaCarbonatite, Deposit -Gross Brukkaros, Gibeon
DS1995-1816
1995
Stachel, T.Stachel, T., Brey, G., Lorenz, V.Carbonatite magmatism and fenitization of the epiclastic caldera fill at gross Brukkaros (Namibia).Bulletin. Volcanology, Vol. 57, pp. 185-196.NamibiaCarbonatite, Deposit -Gros Brukkaros
DS1995-1817
1995
Stachel, T.Stachel, T., Harris, J.W., Cartigny, P.Diamonds and their syngenetic mineral inclusions from the 2 Ga Birimiandeposits, Ghana, West Africa.Proceedings of the Sixth International Kimberlite Conference Abstracts, pp. 578-580.GhanaDiamond inclusions, Birimian Supergroup
DS1997-1096
1997
Stachel, T.Stachel, T., Harris, J.W.Syngenetic inclusions in diamond from the Birim Field, (Ghana) a deepContributions to Mineralogy and Petrology, Vol. 127, No. 4, pp. 336-352.GhanaDiamond inclusions, Deposit - Birim field
DS1997-1097
1997
Stachel, T.Stachel, T., Harris, J.W.Diamond precipitation and mantle metasomatism - evidence from the trace element chemistry of silicate..Contributions to Mineralogy and Petrology, Vol. 129, pp. 143-154.Ghana, South AfricaDiamond inclusions - silicate, Deposit - Akwatia, Roberts Victor
DS1998-0514
1998
Stachel, T.Girnis, A.V., Stachel, T., Brey, G., Harris, J., PhilipInternally consistent geothermobarometers for garnet harzburgites7th International Kimberlite Conference Abstract, pp. 253-5.GlobalGeothermometry, Garnet harzburgite compositions
DS1998-1396
1998
Stachel, T.Stachel, T., Harris, J.W., Brey, G.P.Rare and unusual mineral inclusions in diamonds from Mwadui, TanzaniaContributions to Mineralogy and Petrology, Vol. 132, No. 1, pp. 34-47.TanzaniaDiamond inclusions, Deposit - Mwadui
DS1998-1397
1998
Stachel, T.Stachel, T., Harris, J.W., Brey, G.P.Inclusions in diamonds from Mwadui- chemical mush in the source7th International Kimberlite Conference Abstract, pp. 859-61.TanzaniaMineral inclusions, Deposit - Mwadui
DS1998-1398
1998
Stachel, T.Stachel, T., Viljoen, K.S., Harris, J.W.Metasomatic processes in lherzolitic and harzburgitic domains of diamondiferous lithospheric mantle: rare earth elements (REE).Earth and Planetary Science Letters, Vol. 159, No. 1-2, June 15, pp. 1-12.MantleGarnets - xenoliths, Diamond inclusions
DS1998-1399
1998
Stachel, T.Stachel, T., Viljoen, K.S., Harris, J.W., Brey, G.P.rare earth elements (REE) patterms of garnets from diamonds and Diamondiferous geochemical signatures7th International Kimberlite Conference Abstract, pp. 862-4.South Africa, GhanaDiamond source, Deposit - Roberts Victor, BiriM.
DS1999-0707
1999
Stachel, T.Stachel, T., Harris, J.W., Brey, G.P.rare earth elements (REE) patterns of peridotitic and eclogitic inclusions in diamonds from Mwadui ( Tanzania).7th International Kimberlite Conference Nixon, Vol. 2, pp. 829-35.TanzaniaDiamond - inclusions, geochemistry, lherzolite garnet, Deposit - Mwadui
DS2000-0922
2000
Stachel, T.Stachel, T., Brey, G.P., Harris, J.W.Kankan diamonds I. from the lithosphere down to the transition zoneContributions to Mineralogy and Petrology, Vol. 140, No. 1, pp. 1-15.GuineaDiamond genesis, Deposit - Kankan
DS2000-0923
2000
Stachel, T.Stachel, T., Harris, J.W., Joswig, W.Kankan diamonds II. Lower mantle inclusion paragenesesContributions to Mineralogy and Petrology, Vol. 140, No. 1, pp. 16-27.GuineaDiamond genesis, Deposit - Kankan
DS2001-0451
2001
Stachel, T.Harris, J.W., Stachel, T., Cartigny, P.Diamond - the ultimate mantle mineralInstitute of Mining and Metallurgy (IMM) Transactions. Durham Meeting absts., Vol. 110, p. B45-6. abstractGlobalDiamond - genesis brief
DS2001-1120
2001
Stachel, T.Stachel, T.Diamonds from the asthenosphere and the transition zoneEur. Jour. Min., Vol. 13, No. 5, pp. 883-92.MantleDiamond - genesis
DS2001-1121
2001
Stachel, T.Stachel, T., Harris, J.W., Tappert, R.Inclusions in diamonds from the PAnd a kimberlite29th. Yellowknife Geoscience Forum, Nov. 21-23, abstract p. 80.Northwest TerritoriesDiamond - inclusions, Deposit - Panda
DS2001-1122
2001
Stachel, T.Stachel, T., Harris, J.W., Tappert, R., Brey, G.P.Peridotitic inclusions in diamonds from the Slave and Kaapvaal cratons - afirst comparison.Slave-Kaapvaal Workshop, Sept. Ottawa, 4p. abstractNorthwest Territories, South AfricaDiamond - inclusions, Geochemistry - major and trace elements Panda
DS2002-0084
2002
Stachel, T.Aulbach, S., Stachel, T., Vijoen, K., Brey, G., HarrisEclogitic and websteritic diamond sources beneath the Limpopo Belt - is slab melting the link?Contribution to Mineralogy and Petrology, Vol.143, 1, Feb.pp.56-70.South AfricaDiamond - inclusions, mineralogy, Secondary Ion Mass Spectrometry, Deposit - Venetia
DS2002-0203
2002
Stachel, T.Brenker, F.E., Stachel, T., Harris, J.W.Exhumation of lower mantle inclusions in diamond: ATEM investigation of retrograde phase transitions, reactionEarth and Planetary Science Letters, Vol.198,1-2,pp.1-9., Vol.198,1-2,pp.1-9.MantleMineralogy - diamond inclusions
DS2002-0204
2002
Stachel, T.Brenker, F.E., Stachel, T., Harris, J.W.Exhumation of lower mantle inclusions in diamond: ATEM investigation of retrograde phase transitions, reactionEarth and Planetary Science Letters, Vol.198,1-2,pp.1-9., Vol.198,1-2,pp.1-9.MantleMineralogy - diamond inclusions
DS2002-1535
2002
Stachel, T.Stachel, T.Peridotitic and eclogitic diamond sources and their bearing on the evolution of subcratonic lithosphere.University of Western Ontario, SEG Student Chapter, March 8, pp. 31-35. abstractMantleCratonic lithosphere - trace element data, model
DS2002-1536
2002
Stachel, T.Stachel, T., Haris, J.W., Aulbach, S., deines, P.Kankan diamonds III: delta 13 C and nitrogen characteristics of deep diamondsContributions to Mineralogy and Petrology, Vol. 142, No. 4, pp. 465-75.GuineaGeochronology, Deposit - Kankan
DS2002-1537
2002
Stachel, T.Stachel, T., Harris, J.W., McCammon, C.Inclusions in ultra deep diamonds - tracers of ancient slabs?18th. International Mineralogical Association Sept. 1-6, Edinburgh, abstract p.74.MantleUHP mineralogy
DS2002-1538
2002
Stachel, T.Stachel, T., Tappert, R., Harris, J.W.PAnd a diamonds: a window into the deep lithosphere beneath the central SlaveGac/mac Annual Meeting, Saskatoon, Abstract Volume, P.112., p.112.Northwest TerritoriesGeochronology, Diamond - inclusions
DS2002-1539
2002
Stachel, T.Stachel, T., Tappert, R., Harris, J.W.PAnd a diamonds: a window into the deep lithosphere beneath the central SlaveGac/mac Annual Meeting, Saskatoon, Abstract Volume, P.112., p.112.Northwest TerritoriesGeochronology, Diamond - inclusions
DS2002-1579
2002
Stachel, T.Tappert, R., Stachel, T., Harris, J.W., Brey, G.P.Composition of mineral inclusions from Brazilian diamondsGac/mac Annual Meeting, Saskatoon, Abstract Volume, P.116., p.116.BrazilAlluvials, Deposit - Aranapolis, Canastra
DS2002-1580
2002
Stachel, T.Tappert, R., Stachel, T., Harris, J.W., Brey, G.P.Composition of mineral inclusions from Brazilian diamondsGac/mac Annual Meeting, Saskatoon, Abstract Volume, P.116., p.116.BrazilAlluvials, Deposit - Aranapolis, Canastra
DS2003-0157
2003
Stachel, T.Brenker, F.E., Stachel, T., Harris, J.W.TEM analysis of inclusions in diamonds from the lower mantle and transition zone8ikc, Www.venuewest.com/8ikc/program.htm, Session 3, POSTER abstractGuineaDiamonds - inclusions
DS2003-0158
2003
Stachel, T.Brey, G.P., Bulatov, V., Girnis, A., Harris, J., Stachel, T.Ferropericlase - a lower mantle phase in the upper mantle8 Ikc Www.venuewest.com/8ikc/program.htm, Session 6, AbstractGuineaMantle petrology
DS2003-0224
2003
Stachel, T.Cartigny, P., Stachel, T., Harris, J.W., Javoy, M.C and N stable isotope characteristics of diamonds from Namibia8 Ikc Www.venuewest.com/8ikc/program.htm, Session 2, AbstractNamibiaEclogites, diamonds, Geochronology
DS2003-0795
2003
Stachel, T.Leost, I., Stachel, T., Brey, G.P., Harris, J.W., Ryabchikov, I.D.Diamond formation and source carbonation: mineral associations in diamonds fromContributions to Mineralogy and Petrology, Vol. 145, 1, pp. 15-24.NamibiaDiamond genesis
DS2003-0797
2003
Stachel, T.Leost, J., Stachel, T., Brey, G.P., Harris, J.W., Ryabichikov, I.D.Diamond formation and source carbonation: mineral associations in diamonds fromContribution to Mineralogy and Petrology, NamibiaDiamond mineralogy, morphology, genesis
DS2003-1248
2003
Stachel, T.Seitz, H.M., Brey, G.P., Stachel, T., Harris, J.W.Li abundances in inclusions in diamonds from the upper and lower mantleChemical Geology, Vol. 201, 3-4, Nov. 28, pp. 307-318.MantleEclogites, peridotites, diamond
DS2003-1249
2003
Stachel, T.Seitz, H.M., Brey, G.P., Stachel, T., Harris, J.W.Lithium abundances in inclusions in diamonds from the upper and lower mantle8ikc, Www.venuewest.com/8ikc/program.htm, Session 4, POSTER abstractMantleMantle geochemistry, Diamond - inclusions
DS2003-1324
2003
Stachel, T.Stachel, T., Aulbavh, S., Brey, G.P., Harris, J.W., Leost, I., Tappert, R., ViljoenDiamond formation and mantle metasomatism: a trace element perspective8 Ikc Www.venuewest.com/8ikc/program.htm, Session 3, AbstractGlobalDiamonds, database REE 135 peridotite garnet inclusions, Review - genesis
DS2003-1325
2003
Stachel, T.Stachel, T., Harris, J.W., Tappert, R., Brey, G.P.Peridotitic diamonds from the Slave and the Kaapvaal cratons similarities andLithos, Vol. 71, 2-4, pp. 489-503.South Africa, Northwest Territories, NunavutMineral chemistry
DS2003-1359
2003
Stachel, T.Tappert, R., Stachel, T., Harris, J.W., Brey, G.P.Mineral inclusions in diamonds from the PAnd a kimberlite, Slave Province, Canada8ikc, Www.venuewest.com/8ikc/program.htm, Session 3, POSTER abstractNorthwest TerritoriesDiamonds - inclusions, Deposit - Panda
DS200412-0090
2004
Stachel, T.Banas, A., Stachel, T., McCandless, T.E.Diamonds from the K252, K11 and K 19 kimberlites, Buffalo Head Hills, Alberta Canada.Geological Association of Canada Abstract Volume, May 12-14, SS14-10 p. 269.abstractCanada, AlbertaDiamond inclusions, morphology
DS200412-0205
2003
Stachel, T.Brey, G.P., Bulatov, V., Girnis, A., Harris, J., Stachel, T.Ferropericlase - a lower mantle phase in the upper mantle.8 IKC Program, Session 6, AbstractAfrica, GuineaMantle petrology
DS200412-0206
2004
Stachel, T.Brey, G.P., Bulatov, V., Girnis, A., Harris, J.W., Stachel, T.Ferropericlase - a lower mantle phase in the upper mantle.Lithos, Vol. 77, 1-4, Sept. pp. 655-663.South America, BrazilUHP, diamond inclusions, olivine, San Luiz
DS200412-0292
2003
Stachel, T.Cartigny, P., Stachel, T., Harris, J.W., Javoy, M.C and N stable isotope characteristics of diamonds from Namibia.8 IKC Program, Session 2, AbstractAfrica, NamibiaEclogite, diamonds, geochronology
DS200412-0293
2004
Stachel, T.Cartigny, P., Stachel, T., Harris, J.W., Javoy, M.Constraining diamond metasomatic growth using C - and N stable isotopes: examples from Namibia.Lithos, Vol. 77, 1-4, Sept. pp. 359-373.Africa, NamibiaPlacers, alluvials, Nitrogen, metasomatism
DS200412-0784
2003
Stachel, T.Hanrahan, M., Stachel,T., Brey, G.P., Lahaye, Y.Garnet peridotite xenoliths from the Koffiefontein mine, South Africa.8 IKC Program, Session 6, POSTER abstractAfrica, South AfricaMantle petrology Deposit - Koffiefontein
DS200412-0798
2004
Stachel, T.Harris, J.W., Stachel, T., Leost, I., Brey, G.P.Peridotitic diamonds from Namibia: constraints on the composition and evolution of their mantle source.Lithos, Vol. 77, 1-4, Sept. pp. 209-223.Africa, NamibiaPlacer, alluvials, diamond inclusions, metasomatism,REE
DS200412-0933
1999
Stachel, T.Joswig, W., Stachel, T., Harris, J.W., Baur, W.H., Brey, G.P.New Ca silicate inclusions in diamonds - tracers from the lower mantle.Earth and Planetary Science Letters, Vol. 173, pp. 1-6.TechnologyDiamond inclusions
DS200412-1116
2003
Stachel, T.Leost, I., Stachel, T., Brey, G.P., Harris, J.W., Ryabchikov, I.D.Diamond formation and source carbonation: mineral associations in diamonds from Namibia.Contributions to Mineralogy and Petrology, Vol. 145, 1, pp. 15-24.Africa, NamibiaDiamond genesis
DS200412-1248
2004
Stachel, T.Matveev, S., Creighton, S., Stachel, T.The hydrogen content of olivine - a new tool for diamond exploration.Geological Association of Canada Abstract Volume, May 12-14, SS14-04 p. 263.abstractCanada, Northwest Territories, Africa, South AfricaSpectroscopy
DS200412-1259
2004
Stachel, T.McCammon, C.A., Stachel, T., Harris, J.W.Iron oxidation state in lower mantle mineral assemblages. Part 1.Earth and Planetary Science Letters, Vol. 222, 2, pp. 423-434.MantleMineral chemistry
DS200412-1406
2003
Stachel, T.Nasdala, L., Brenker, F.E., Glinnemann, J., Hofmeister, W., Gasparik, T., Harris, J.W., Stachel, T., Reese, I.Spectroscopic 2D tomography: residual pressure and strain around mineral inclusions in diamonds.European Journal of Mineralogy, Vol.15, 6, pp. 931-36.TechnologyTechnology - tomography inclusions
DS200412-1905
2004
Stachel, T.Stachel, T., Aulbach, S., Brey, G.P., Harris, J.W., Leost, I., Tappert, R., Vijoen, K.S.The trace element composition of silicate inclusions in diamonds: a review.Lithos, Vol. 77, 1-4, Sept. pp. 1-19.MantleDiamond inclusion, REE, metasomatism, lithosphere, garn
DS200412-1906
2003
Stachel, T.Stachel, T., Aulbavh, S., Brey, G.P., Harris, J.W., Leost, I., Tappert, R., Viljoen, K.S.Diamond formation and mantle metasomatism: a trace element perspective.8 IKC Program, Session 3, AbstractTechnologyDiamonds, database REE 135 peridotite garnet inclusions Review - genesis
DS200412-1907
1992
Stachel, T.Stachel, T., Brey, G.The olivine and leucite lamproite pipes of the Ellendale volcanic field ( Western Australia).Zeitschrift der Deutschen Gesellschaft fur Geowissenschaften , Vol. 143, pp. 133-158.AustraliaPetrology
DS200412-1908
1995
Stachel, T.Stachel, T., Brey, G., Stanistreet, I.Gross Brukkaros (Namibia) - petrography and geochemistry of the intra-caldera sediments and their magmatic components.Communications of the Geological Survey of Namibia 1993/1994, pp. 23-42.Africa, NamibiaGeochemistry
DS200412-1909
1997
Stachel, T.Stachel, T., Harris, J.W.Syngenetic inclusions in diamond from the Birim Field, ( Ghana) - a deep peridotitic profile with a history of depletion and re-Contributions to Mineralogy and Petrology, Vol. 127, pp. 336-352.Africa, GhanaDiamond inclusions
DS200412-1910
2003
Stachel, T.Stachel, T., Harris, J.W., Tappert, R., Brey, G.P.Peridotitic diamonds from the Slave and the Kaapvaal cratons similarities and differences based on a preliminary dat a set.Lithos, Vol. 71, 2-4, pp. 489-503.Africa, South Africa, Northwest Territories, NunavutMineral chemistry
DS200412-1911
1994
Stachel, T.Stachel, T., Lorenz, V., Stanistreet, I.Gross Brukkaros (Namibia) - an enigmatic crater fill reinterpreted as due to Cretaceous caldera evolution.Bulletin of Volcanology, Vol. 56, pp. 386-397.Africa, NamibiaStratigraphy
DS200412-1912
2004
Stachel, T.Stachel, T., Vijoen, K.S., McDada, P., Harris, J.W.Survival of diamonds during major tectonothermal events - peridotitic inclusions in diamonds from Orapa and Jwaneng.Geological Association of Canada Abstract Volume, May 12-14, SS14-13 p. 272.abstractAfrica, BotswanaGeochemistry - major element
DS200412-1913
2004
Stachel, T.Stachel, T., Viljoen, K.S., McDade,P.,Harris, J.W.Diamondiferous lithospheric roots along the western margin of the Kalahari Craton - the peridotitic inclusion suites in diamondsContributions to Mineralogy and Petrology, Vol. 147, 1, pp. 32-47.Africa, BotswanaDiamond genesis, Orapa, Jwaneng deposits
DS200412-1964
2004
Stachel, T.Tappert, R., Stachel, T., Harris, J.W., Brey, G.P., Ludwig, T.Messingers from the sublithospheric mantle: diamonds and their mineral inclusions from the Jagersfontein kimberlite ( South AfriGeological Association of Canada Abstract Volume, May 12-14, SS14-11 p. 270.abstractAfrica, South AfricaDiamond inclusions, morphology
DS200512-0063
2004
Stachel, T.Banas, A., Stachel, T., Muehlenbachs, K., McCandless, T.E.Origin of diamonds from the K252, K91 and K11 kimberlites, Buffalo Head Hills, Alberta, Canada.32nd Yellowknife Geoscience Forum, Nov. 16-18, p.3-4. (talk)Canada, AlbertaDiamond morphology, genesis
DS200512-0593
2005
Stachel, T.Kurszlaukis, S., Walker, E.C., Stachel, T.Deep mantle derived diamond bearing Archean volcanogenic rocks from Wawa Ontario.GAC Annual Meeting Halifax May 15-19, Abstract 1p.Canada, Ontario, WawaDeeper mantle sources
DS200512-0709
2004
Stachel, T.McLean, H., Banas, A., Creighton, S., Whiteford, S., Luth, R., Stachel, T.Garnet xenocrysts from the Diavik mine - composition, paragenesis and color.32nd Yellowknife Geoscience Forum, Nov. 16-18, p.49-50. (talk)Canada, Northwest TerritoriesGarnet mineralogy
DS200512-1038
2004
Stachel, T.Stachel, T., Blackburn, L., Kurszlaukis, S., Barton, E., Walker, E.C.Diamonds from the Cristal and genesis volcanics, Wawa Ontario.32nd Yellowknife Geoscience Forum, Nov. 16-18, p.74-75. (talk)Canada, Ontario, WawaDiamond inclusions
DS200512-1039
2005
Stachel, T.Stachel, T., Brey, G.P., Harris, J.W.Inclusions in sublithospheric diamonds: glimpses of deep Earth.Elements, Vol. 1, 2, March pp. 73-79.MantleDiamond inclusion, majorite, perovskite, subduction
DS200512-1040
2005
Stachel, T.Stachel, T., Kurzlaukis, S., Walker, E.C.Archean diamonds from the Wawa area of Ontario (Canada).GAC Annual Meeting Halifax May 15-19, Abstract 1p.Canada, Ontario, WawaGenesi, Cristal, diamond morphology
DS200512-1074
2005
Stachel, T.Tappert, R., Stachel, T., Harris, J.W., Shimizu, N., Brey, G.P.Mineral inclusions in diamonds from the PAnd a kimberlite, Slave Province, Canada.European Journal of Mineralogy, Vol. 17, 3, pp. 423-440.Canada, Northwest TerritoriesMineralogy - Panda
DS200612-0288
2006
Stachel, T.Creighton, S., Stachel, T., Luth, R.W.Carbon speciation and mantle metasomatism.Geochimica et Cosmochimica Acta, Vol. 70, 18, p. 117. abstract only.MantleMetasomatism
DS200612-0874
2005
Stachel, T.Mateev, S., Stachel, T.FTIR spectroscopy of kimberlitic olivine: a new tool in diamond exploration.32ndYellowknife Geoscience Forum, p. 44 abstractTechnologySpectroscopy
DS200612-0881
2006
Stachel, T.Matveev, S., Creighton, S., Stachel, T.OH in peridotitic olivines entrained in kimberlitic magma.Geochimica et Cosmochimica Acta, Vol. 70, 18, p. 24. abstract only.MantleMagmatism - olivine mineral chemistry
DS200612-1360
2006
Stachel, T.Stachel, T., Cartigny, P., Jaques, L.The deepest lithosphere and beyond: diamonds and related research, a session in honour of Jeff Harris.Goldschmidt Conference 16th. Annual, S5-01 theme abstract 1/8p. goldschmidt2006.orgMantleDiamond Inclusions
DS200612-1361
2006
Stachel, T.Stachel, T., Creighton, S., McLean, H., Donnelly, C.L., Whiteford, S., Luth, R.W.Diamondiferous microxenoliths from the Diavik diamond mine ( Canada): lherzolite hosts for harzburgitic diamonds?Geochimica et Cosmochimica Acta, Vol. 70, 18, p. 56. abstract only.Canada, Northwest TerritoriesDeposit - Diavik, xenolith mineral chemistry
DS200612-1362
2006
Stachel, T.Stachel, T., Paulen, R., Prior, G., Micea, C., Cubbing, M., McConnell, GlennDiamond exploration in western sedimentary basin ( glacial processes, till sampling, geophysics)Calgary Mining Forum, April 28 Short Course # 3, NOTICE only meg.calgary.ab.caCanada, AlbertaExploration - program
DS200612-1412
2006
Stachel, T.Tappert, R., Stachel, T., Harris, J.W., Muehlenbachs, K., Brey, G.P.Placer diamonds from Brazil: indicators of the composition of the Earth's mantle and the distance to their kimberlitic sources.Economic Geology, Vol. 101, 2, pp. 543-470.South America, Brazil, Mato Grosso, Roraima, Minas GeraisDiamond morphology, inclusions
DS200612-1413
2005
Stachel, T.Tappert, R., Stachel, T., Harris, J.W., Muehlenbachs, K., Ludwig, T., Brey, G.P.Diamonds from Jagersfontein (South Africa): messengers from the sublithopheric mantle.Contributions to Mineralogy and Petrology, Vol. 150, 5, pp. 505-522.Africa, South AfricaDiamond inclusions
DS200612-1414
2006
Stachel, T.Tappert, R., Stachel, T., Muehlenbachs, K., Harris, J.W., Brey, G.P.Alluvial diamonds from Brazil: where and what are their sources?Geochimica et Cosmochimica Acta, Vol. 70, 18, p. 4. abstract onlySouth America, BrazilDiamond genesis
DS200712-0040
2007
Stachel, T.Aulbach, S., Shirey, S.B., Stachel, T., Harris, J.W.Proterozoic diamond formation at the Kaapvaal craton edge: Re-Os of Jagersfontein sulfide inclusions.Plates, Plumes, and Paradigms, 1p. abstract p. A44.Africa, South AfricaDiamond genesis
DS200712-0050
2007
Stachel, T.Banas, A., Stachel, T., Muehlenbachs, K., McCandless, T.E.Diamonds from the Buffalo Head Hills, Alberta: formation in a non-conventional setting.Lithos, Vol. 93, 1-2, pp. 199-213.Canada, AlbertaDeposit - Buffalo Head Hills area
DS200712-0185
2006
Stachel, T.Chislett, K., Crieghton, S., Stachel, T., Whiteford, S.Garnet peridotite microxenoliths from A154, Diavik diamond mines.34th Yellowknife Geoscience Forum, p. 68-69. abstractCanada, Northwest TerritoriesDiavik - geology
DS200712-0207
2007
Stachel, T.Creighton, S., Luth, R.W., Stachel, T., Eichenberg, D., Whiteford, S.Oxidation states of the lithospheric mantle beneath the Central Slave Craton.Geological Association of Canada, Gac-Mac Yellowknife 2007, May 23-25, Volume 32, 1 pg. abstract p.18,19.Canada, Northwest TerritoriesDeposit - Diavik
DS200712-0208
2006
Stachel, T.Creighton, S., Stachel, T.An empirical chromite classification for diamond exploration.34th Yellowknife Geoscience Forum, p. 74-75. abstractTechnologyChromite database - spinel
DS200712-0209
2006
Stachel, T.Creighton, S., Stachel, T., McLean, H., Donnelly, C., Whiteford, S., Luth, R.W.Diamondiferous peridotite microxenoliths from the Diavik diamond mine: a challenge to the G10 paradigm in diamond exploration?34th Yellowknife Geoscience Forum, p. 13. abstractCanada, Northwest TerritoriesGeology - Diavik
DS200712-0265
2007
Stachel, T.Donnelly, C.L., Stachel, T., Creighton, S., Muehlenbachs, K., Whiteford, S.Diamonds and their mineral inclusions from A154 South pipe mine, Northwest Territories, Canada.Lithos, Vol. 98, 1-4, pp. 160-176.Canada, Northwest TerritoriesDeposit - A154
DS200712-0414
2007
Stachel, T.Harris, J., Stachel, T.Damtshaa versus Orapa: a mineralogical comparison of inclusion bearing diamonds from new and old Botswana mines.Geological Association of Canada, Gac-Mac Yellowknife 2007, May 23-25, Volume 32, 1 pg. abstract p.37-38.Africa, BotswanaMineral chemistry
DS200712-0697
2007
Stachel, T.Mateev, S., Stachel, T.Does kimberlitic magma degas at the MOHO?Geological Association of Canada, Gac-Mac Yellowknife 2007, May 23-25, Volume 32, 1 pg. abstract p.54.Canada, Northwest TerritoriesA154 Diavik, Grizzly Elati FTIR
DS200712-0699
2006
Stachel, T.Matveev, S., Stachel, T.Unleashing olivine's potential as a first class kimberlite indicator mineral through FTIR spectroscopy.34th Yellowknife Geoscience Forum, p. 90. abstractTechnologyDatabase - olivine, nickel content
DS200712-0700
2007
Stachel, T.Matveev, S., Stachel, T.OH in mantle olivine: experiment vs nature.Plates, Plumes, and Paradigms, 1p. abstract p. A638.MantleOlivine
DS200712-0701
2007
Stachel, T.Matveev, S., Stachel, T.FTIR spectroscopy of OH in olivine: a new tool in kimberlite exploration.Geochimica et Cosmochimica Acta, Vol. 71, pp. 5528-5543,Canada, Northwest Territories, SaskatchewanSpectroscopy
DS200712-0702
2007
Stachel, T.Matveev, S., Stachel, T.FTIR spectroscopy of OH in olivine- a new tool in kimberlite exploration.Geochimica et Cosmochimica Acta, In press, availableTechnologySpectroscopy
DS200712-0709
2007
Stachel, T.McLean, H., Banas, A., Creighton, S., Whiteford, S., Luth, R.W., Stachel, T.Garnet xenocrysts from the Diavik mine, NWT, Canada: composition colour and paragenesis.Canadian Mineralogist, Vol. 45, 5, Oct. pp. 1131-1145.Canada, Northwest TerritoriesDeposit - Diavik
DS200812-0059
2008
Stachel, T.Aulbach, S., Creaser, R.A.,Heaman, L.M., Simonetti, S.S., Griffin, W.L., Stachel, T.Sulfides, diamonds and eclogites: their link to peridotites and Slave Craton hydrothermal evolution.Goldschmidt Conference 2008, Abstract p.A36.Canada, Northwest TerritoriesDeposit - A 154, geochronology
DS200812-0062
2009
Stachel, T.Aulbach, S., Shirey, S.B., Stachel, T., Creighton, S., Muehlenbachs, K., Harris, J.W.Diamond formation episodes at the southern margin of the Kaapvaal Craton: Re-Os systematics of sulfide inclusions from the Jagersfontein mine.Contributions to Mineralogy and Petrology, Vol. 157, pp. 525-540.Africa, South AfricaDeposit - Jagersfontein
DS200812-0250
2007
Stachel, T.Creighton, S., Stachel, T., McLean, H., Muehlenbachs, K., Simonett, A., Eichenberg, D., Luth, R.Diamondiferous peridotitic microxenoliths from the Diavik diamond mine, NT.Contributions to Mineralogy and Petrology, Vol.155, 5, pp. 541-554.Canada, Northwest TerritoriesDeposit - Diavik, mineral inclusions, chemistry
DS200812-0492
2007
Stachel, T.Hunt, L., Stachel, T., McCandless, T.A study on diamonds and their mineral inclusions from the Renard kimberlites, Quebec. Stornoway35th. Yellowknife Geoscience Forum, Abstracts only p. 25-26.Canada, QuebecDiamond inclusions - Renard
DS200812-0493
2008
Stachel, T.Hunt, L., Stachel, T., Simonetti, T., Armstrong, J., McCandless, T.E.Microxenoliths from the Renard kimberlites, Quebec.Northwest Territories Geoscience Office, p. 35-36. abstractCanada, QuebecBrief overview - Stornoway
DS200812-0516
2007
Stachel, T.Janson, G., Muehlenbachs, K., Stachel, T., Eichenberg, D.Cyclic growth conditions for Diavik diamonds? Insights from carbon isotopes.35th. Yellowknife Geoscience Forum, Abstracts only p. 28.Canada, Northwest TerritoriesDiamond morphology - Diavik
DS200812-0517
2008
Stachel, T.Janson, G.F., Muehlenbachs, K., Stachel, T., Eichenber, D.Microscale variations in D13 C evidence for growth of coated Diavik diamonds from kimberlite derived fluid.Northwest Territories Geoscience Office, p. 38. abstractCanada, Northwest TerritoriesDeposit - Diavik
DS200812-0524
2007
Stachel, T.Johnson, A., Stachel, T., Creighton, S.,Naher, U.Peridotite xenoliths from the Monument Property, Slave Craton, NWT, Canada. SouthernEra35th. Yellowknife Geoscience Forum, Abstracts only p. 29.Canada, Northwest TerritoriesMineralogy
DS200812-0724
2008
Stachel, T.Matveev, S., Stachel, T.Differences in FTIR spectra measured in olivines derived from depleted and metasomatised sections of the Earth's mantle.Goldschmidt Conference 2008, Abstract p.A606.Africa, South Africa, Canada, OntarioDeposit - Finsch, Victor
DS200812-1110
2008
Stachel, T.Stachel, T., Harris, J.W.The origin of cratonic diamonds - constraints from mineral inclusions.Ore Geology Reviews , 83p.GlobalMineral inclusions - review
DS200912-0018
2009
Stachel, T.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
DS200912-0031
2009
Stachel, T.Banas, A., Stachel, T., Phillips, D., Shimizu, N., Viljoen, K.S., Harris, J.W.Ancient metasomatism recorded by ultra-depleted garnet inclusions in diamonds from De Beers Pool, South Africa.Lithos, In press availableAfrica, South AfricaDeposit - DeBeers Pool
DS200912-0099
2009
Stachel, T.Cartigny, P., Farquar, J., Thomassot, E., Harris, J.W., Wing, B., Masterson, A., McKeegan, K., Stachel, T.A mantle origin for Paleoarchean peridotite diamonds from the PAnd a kimberlite, Slave Province: evidence from 13C, 15N and 34,34S stable isotope systematics.Lithos, In press - available 38p.Canada, Northwest TerritoriesDeposit - Panda
DS200912-0135
2009
Stachel, T.Creighton, S.,Stachel, T., Matveev, S., Hofer, H., McCammon, C., Luth, R.W.Oxidation of the Kaapvaal lithospheric mantle driven by metasomatism.Contributions to Mineralogy and Petrology, Vol. 157, 4, pp. 491-504.Africa, South AfricaMetasomatism
DS200912-0137
2009
Stachel, T.Creighton, S., Stachel, T., Eichenberg, D., Luth, R.W.Oxidation state of the lithospheric mantle beneath Diavik diamond mine, central Slave craton, NWT, Canada.Contributions to Mineralogy and Petrology, in press available 13p.Canada, Northwest TerritoriesDeposit - Diavik
DS200912-0138
2009
Stachel, T.Creighton, S., Stachel, T., Eichenberg, D., Luth, R.W.Oxidation state of the lithospheric mantle beneath Diavik diamond mine, central Slave craton, NWT, Canada.Mineralogy and Petrology, in press available format 13p.Canada, Northwest TerritoriesDeposit - Diavik
DS200912-0321
2009
Stachel, T.Hunt, L., Stachel, T., Armstrong, J.Trace element systematics of microxenoliths and xenocrysts from the Renard kimberlites, Quebec.37th. Annual Yellowknife Geoscience Forum, Abstracts p. 26.Canada, QuebecGeothermometry
DS200912-0322
2009
Stachel, T.Hunt, L., Stachel, T., Armstrong, J.P., Simonetti, A.The Diamondiferous lithospheric mantle underlying the eastern Superior Craton: evidence from mantle xenoliths from the Renard kimberlite, Quebec.GAC/MAC/AGU Meeting held May 23-27 Toronto, Abstract onlyCanada, QuebecDeposit - Renard
DS200912-0323
2009
Stachel, T.Hunt, L., Stachel, T., Morton, R., Grutter, H., Creaser, R.A.The Carolin a kimberlite, Brazil - insights into an unconventional diamond deposit.Lithos, In press available 39p.South America, BrazilDeposit - Carolina
DS200912-0339
2009
Stachel, T.Johnson, C., Stachel, T., Muehlenbachs, K., Armstrong, J.The micro-/macro diamond relationship: a preliminary case study on diamonds from Artemisia kimberlite ( northern Slave Craton), Canada.37th. Annual Yellowknife Geoscience Forum, Abstracts p. 74-75.Canada, Nunavut, Coronation Gulfmicrodiamonds
DS200912-0472
2009
Stachel, T.Marcheggiani-Croden, V., Hunt, L., Stachel, T., Muehlenbachs, K., Eichenberg, D.Diavik boart - unrelated to gem diamond and fibrous coats?37th. Annual Yellowknife Geoscience Forum, Abstracts p. 81-2.Canada, Northwest TerritoriesBoart diamond
DS200912-0481
2009
Stachel, T.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
DS200912-0483
2009
Stachel, T.Matveev, S., Stachel,T.Evaluation of diamond potential using FTIR spectroscopy of xenocrystic olivine.Lithos, In press available, 18p.Africa, Ghana, Canada, Northwest TerritoriesDeposit - Birim, Diavik
DS200912-0699
2009
Stachel, T.Smart, K.A., Chacko, T., Heaman, L.M., Stachel, T., Muehlenbachs, K.Multiple origins of eclogitic diamonds from the Jericho kimberlite, Nunavut.37th. Annual Yellowknife Geoscience Forum, Abstracts p. 58-59.Canada, NunavutDiamond genesis
DS200912-0728
2009
Stachel, T.Stachel, T.Diamond treasures from the Canadian vault.PDAC 2009, 1p. abstractCanada, Northwest Territories, Ontario, QuebecCraton
DS200912-0729
2009
Stachel, T.Stachel, T., Harris, J.W.Formation of diamond in the Earth's mantle.Journal of Physics Condensed Matter, in press ( August)MantleDiamond genesis
DS200912-0730
2009
Stachel, T.Stachel, T., Harris, J.W., Muehlenbachs, K.Sources of carbon in inclusion bearing diamonds.Lithos, In press available 65p.TechnologyDiamond inclusions
DS200912-0748
2009
Stachel, T.Tappert, R., Foden, J., Stachel, T., Muehlenbacher, K., Tappert, M., Wills, K.Deep mantle diamonds from South Australia: a record of Pacific subduction at the Gondwanan margin.Geology, Vol. 37, 1, pp. 43-46.Australia, South AustraliaDiamond genesis
DS200912-0749
2009
Stachel, T.Tappert, R., Foden, J., Stachel, T., Muehlenbachs, K., Tappert, M., Wills, K.The diamonds of South Australia.Lithos, In press available 49p.AustraliaDiamond inclusions
DS201012-0024
2009
Stachel, T.Aulbach, S., Stachel, T., Craeser, R.A., Heaman, L.M., Shirey, S.B., MUehlenbachs, K., Eichenberg, D., HarrisSulphide survival and diamond genesis during formation and evolution of Archean subcontinental lithosphere: a comparison between the Slave and Kaapvaal cratons.Lithos, Vol. 112 S pp. 747-757.Canada, AfricaGeochronology
DS201012-0025
2010
Stachel, T.Aulbach, S., Stachel, T., Heaman, L., creaser, R., Shirey, S.Formation of cratonic subcontinental lithospheric mantle from hybrid plume sources.Goldschmidt 2010 abstracts, abstractMantleSubduction
DS201012-0026
2010
Stachel, T.Aulbach, S., Stachel, T., Heaman, L.M., Creaser, R.A., Shirey, S.B.Formation of cratonic subcontinental lithospheric mantle and complementary komatiite from hybrid plume sources.Contributions to Mineralogy and Petrology, In press available, 14p.Canada, Northwest TerritoriesPeridotitic sulphide inclusions in diamonds - SCLM
DS201012-0130
2010
Stachel, T.Creighton, S., Stachel, T., Eichenberg, D., Luth, R.W.Oxidation state of the lithospheric mantle beneath Diavik diamond mine, central Slave Craton, NWT, Canada.Contributions to Mineralogy and Petrology, Vol. 159, 5, pp. 645-659.Canada, Northwest TerritoriesDeposit - Diavik
DS201012-0146
2009
Stachel, T.Deines, P., Stachel, T., Harris, J.W.Systematic regional variations in diamond carbon isotopic composition and inclusion chemistry beneath the Orapa kimberlite cluster, in Botswana.Lithos, Vol. 112 S pp. 776-784,Africa, BotswanaDeposit - Orapa
DS201012-0268
2009
Stachel, T.Harris, J., Stachel, T.Professor Peter Deines ( 1936-2009). Tribute.Lithos, Vol. 112 S p. 775.Tribute to Deines
DS201012-0298
2010
Stachel, T.Hunt, L., Stachel, T., Armstrong, J.Evolution of SCLM beneath the Renard kimberlites, SE Superior Craton: an integrated study of diamonds, xenoliths and xenocrysts.Goldschmidt 2010 abstracts, abstractCanada, QuebecDeposit - Renard
DS201012-0301
2010
Stachel, T.Ickert, R., Stern, R., Stachel, T.MC Hr Sims oxygen isotope analysis of ferropericlase inclusions in diamond.Goldschmidt 2010 abstracts, abstractTechnologyDiamond morphology
DS201012-0328
2010
Stachel, T.Johnson, C.N., Stern, R., Stachel, T., Muehlenbachs, K., Armstrong, J.The micro/macro diamond relationship: a case study from the Artemisia kimberlite northern Slave Craton ( Nunavut, Canada).38th. Geoscience Forum Northwest Territories, Abstract p. 52.Canada, NunavutDeposit - Artemisia
DS201012-0571
2010
Stachel, T.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
DS201012-0720
2010
Stachel, T.Smart, K., Chacko, T., Heaman, L., Stachel, T., Muehlenbachs, K.13 C depleted diamonds in Jericho eclogites: diamond formation from ancient subducted organic matter.Goldschmidt 2010 abstracts, abstractCanada, NunavutDeposit - Jericho
DS201012-0749
2010
Stachel, T.Stachel, T.Formation of diamond in the lithospheric mantle.International Mineralogical Association meeting August Budapest, AbstractMantleDiamond genesis
DS201112-0044
2011
Stachel, T.Aulbach, S., Stachel, T., Heaman, L.H., Carlson, J.A.Microxenoliths from the Slave Craton: archives of diamond formation along fluid conduits.Lithos, Vol. 126, pp. 419-434.Canada, Northwest TerritoriesEclogite, subduction, metasomatism, Ekati
DS201112-0045
2011
Stachel, T.Aulbach, S., Stachel, T., Heaman, L.M., Creaser, R.A., Shirey, S.B.Formation of cratonic subcontinental lithospheric mantle and complementary komatiite from hybrid plume sources.Contributions to Mineralogy and Petrology, Vol. 161, 6, pp. 947-960.MantleHotspots
DS201112-0046
2011
Stachel, T.Aulbach, S., Stachel, T., Heaman, L.M., Creaser, R.A.,Thomassot, E., Shirey, S.B.C and S transfer in subduction zones: insight from diamonds.Goldschmidt Conference 2011, abstract p.462.Canada, Northwest TerritoriesDiavik, Ekati
DS201112-0739
2011
Stachel, T.Nichols, K., Stachel, T., Hunt, L., McLean, H.A study on websterites from the Diavik diamond mine, Slave Craton, Canada.Yellowknife Geoscience Forum Abstracts for 2011, Poster abstract p. 114-115.Canada, Northwest TerritoriesGarnet mineralogy
DS201112-0862
2011
Stachel, T.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
DS201112-0974
2011
Stachel, T.Smart, K.A., Chacko, T., Stachel, T., Muehlenbachs, K., Stern, R.A., Heaman, L.M.Diamond growth from oxidized carbon sources beneath the Northern Slave Craton, Canada: A delta 13 C-N study of eclogite hosted diamonds from the Jericho kimberlite.Geochimica et Cosmochimica Acta, Vol. 75, pp. 6027-6047.Canada, NunavutJericho - diamond morphology
DS201112-0975
2011
Stachel, T.Smart, K.A., Chacko, T., Stachel, T., Stern, R.A., Muehlenbachs, K.Formation of diamond from oxidized fluids/melts: delta 13 C-N SIMS study of an eclogitic diamond from the Jericho kimberlite, Canada.Goldschmidt Conference 2011, abstract p.1894.Canada, NunavutDeposit - Jericho
DS201112-0995
2011
Stachel, T.Stachel, T.Diamonds and cratons - does the relationship hold for Canadian deposits?GIA International Symposium 2011, Gems & Gemology, Summer abstract p. 112-114.CanadaCraton history
DS201212-0040
2012
Stachel, T.Aulbach, S., Stachel, T., Heaman, L.M., Creaser, R.A., Seitz, H.M., Shirey, S.B.Diamond formation in the slab and mantle wedge: examples from the Slave Craton.10th. International Kimberlite Conference Feb. 6-11, Bangalore India, AbstractCanada, Northwest TerritoriesDiamond genesis
DS201212-0041
2012
Stachel, T.Aulbach, S., Stachel, T., Seitz, H-M., Brey, G.P.Chalcophile and siderophile elements in sulphide inclusions in eclogitic diamonds and metal cycling in a Paleoproterozoic subduction zone.Geochimica et Cosmochimica Acta, Vol 93, Sept. 15, pp. 278-299.Canada, Northwest TerritoriesDeposit - Diavik
DS201212-0152
2012
Stachel, T.De Hoog, J.C.M., Stachel, T.Trace element geochemistry of olivine inclusions in diamonds from Akwatia, Ghana: implications for diamond paragenesis and mantle processes.emc2012 @ uni-frankfurt.de, 1p. AbstractAfrica, GhanaDeposit - Akwatia
DS201212-0310
2012
Stachel, T.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
DS201212-0318
2012
Stachel, T.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
DS201212-0319
2012
Stachel, T.Hunt, L., Marcheggliani-Croden, V., Stachel, T., Muehlenbachs, K., Eichenberg, D.Polycrystalline and fibrous diamonds from the Diavik mine, Canada.10th. International Kimberlite Conference Held Bangalore India Feb. 6-11, Poster abstractCanada, Northwest TerritoriesDeposit - Diavik
DS201212-0320
2012
Stachel, T.Hunt, L., Stachel, T., Grutter, H., Armstrong, J., McCandless, T.E., Simonetti, A., Tappe, S.Small mantle fragments from the Renard kimberlites, Quebec: powerful recorders of mantle lithosphere formation and modification beneath the eastern Superior Craton.Journal of Petrology, Vol. 53, 8, pp. 1597-1635.Canada, QuebecDeposit - Renard
DS201212-0321
2012
Stachel, T.Hunt, L., Stachel, T., McCandless, T.E., Armstrong, J., Muelenbachs, K.Diamonds and their mineral inclusions from the Renard kimberlites in Quebec.Lithos, in press availableCanada, QuebecDeposit - Renard
DS201212-0340
2012
Stachel, T.Johnson, C.N., Stachel, T., Muehlenbachs, K., Stern, R.A., Armstrong, J.P., EIMFThe micro/macro diamond relationship: a case study from the Artemisia kimberlite ( northern Slave Craton), Canada.Lithos, Vol. 148, pp. 86-97.Canada, Northwest TerritoriesDeposit - Artemisia
DS201212-0423
2012
Stachel, T.Lu, T.,Chen, H., Qiu, Z., Zhang, J., Wei, R., Ke, J., Sunagawa, I.,Stern, R., Stachel, T.Multiple core growth structure and nitrogen abundances of diamond crystals from Shandong and Liaoning kimberlite pipes, China.European Journal of Mineralogy, Vol. 24, 4, pp. 651-656.ChinaDeposit - Shandong, Liaonging
DS201212-0462
2012
Stachel, T.Melton, G., Stachel, T., Stern, R., Harris, J., Carlson, J.The micro and macrodiamond relationship at the PAnd a kimberlite (Ekati mine) Canada.GEM 2012, PPT. 19p.Canada, Northwest TerritoriesMicrodiamonds
DS201212-0463
2012
Stachel, T.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
DS201212-0537
2012
Stachel, T.Palot, M., Cartigny, P., Harris, J.W., Kaminsky, F.V., Stachel, T.Evidence for deep mantle convection and primordial heterogeneity from nitrogen and carbon isotopes in diamond.Earth and Planetary Science Letters, Vol. 357-358, pp. 179-193.South America, Brazil, Africa, GuineaDeposit - Juina, Kankan
DS201212-0538
2012
Stachel, T.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
DS201212-0547
2012
Stachel, T.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
DS201212-0604
2012
Stachel, T.Rubanova, E.V., Griffin, W.L., Plazoloa, S., O'Reilley, S.Y., Stachel, T., Sten, R., Birniec, A.C.Geochemistry and microstructure of diamondites.10th. International Kimberlite Conference Held Bangalore India Feb. 6-11, Poster abstractTechnologyDiamondites
DS201212-0668
2012
Stachel, T.Smart, K.A., Chacko, T., Stachel, T., Tappe, S., Muehlenbachs, K., Ickert, R.B., Stern, R.A.Jericho eclogite formation revealed by diamond inclusions: oceanic origin without crustal signature?10th. International Kimberlite Conference Feb. 6-11, Bangalore India, AbstractCanada, NunavutDeposit - Jericho
DS201212-0669
2012
Stachel, T.Smart, K.A., Chacko, T., Stachel, T., Tappe, S., Stern, R.A., Ickert, R.B.Eclogite formation beneath the northern Slave Craton constrained by diamond inclusions: oceanic lithosphere origin without a crustal signature.Earth and Planetary Science Letters, Vol. 319-320, pp. 165-177.Canada, Northwest TerritoriesDiamond inclusions
DS201212-0672
2012
Stachel, T.Smit, K.V., Stachel, T., Seller, M.Constraints on composition of possible diamond bearing lithosphere as sampled by the Victor kimberlite.10th. International Kimberlite Conference Feb. 6-11, Bangalore India, AbstractCanada, Ontario, AttawapiskatDeposit - Victor
DS201312-0404
2013
Stachel, T.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
DS201312-0405
2013
Stachel, T.Hua, C., Zhili, Q., Taijin, L., Stern, R., Stachel, T., Yuan, S., Jian, Z., Jie, K., Shyu, P., Shecai, Q.Variations in carbon isotopic composition in the subcontinental lithospheric mantle beneath the Yangtze and North Chin a cratons; evidence from in-situ analysis of diamonds using SIMS.Chinese Science Bulletin, Vol. 58, 1, pp. 99-107ChinaCraton
DS201312-0406
2015
Stachel, T.Howell, D., Stern, R.A., Griffin, W.L., Southworth, R., Mikhail, S., Stachel, T.Nitrogen isotope systematics and origins of mixed-habit diamonds.Geochimica et Cosmochimica Acta, Vol. 157, pp. 1-12.Africa, South AfricaDeposit - Roberst Victor
DS201312-0410
2013
Stachel, T.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
Stachel, T.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
DS201312-0415
2013
Stachel, T.Ickert, R.B., Stachel, T., Stern, R.A., Harris, J.W.Diamond from recycled crustal carbon documented by coupled delta 18 O-delta 13 C measurements of diamonds and their inclusions.Earth and Planetary Science Letters, Vol. 364, pp. 85-97.MantleDiamond inclusions
DS201312-0516
2013
Stachel, T.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
DS201312-0598
2013
Stachel, T.Melton, G.L., Stachel, T., Stern, R.A., Carlson, J., Harris, J.W.Micro and macro diamond characteristics from the PAnd a kimberlite.Geoscience Forum 40 NWT, abstract only p. 29Canada, Northwest TerritoriesDeposit - Panda
DS201312-0599
2013
Stachel, T.Melton, G.L., Stachel, T., Stern, R.A., Carlson, J., Harris, J.W.Infrared spectral and carbon isotopic characteristics of micro- and macro diamonds from the PAnd a kimberlite, Central Slave Craton, Canada).Lithos, Vol. 177, pp. 110-119.Canada, Northwest TerritoriesDeposit - Panda
DS201312-0645
2013
Stachel, T.Nichols, K., Stachel, T., Pell, J., Mate, D.Diamond sources beneath the Hall Peninsula, Nunavut: a preliminary assessment based on micro-diamonds.Geoscience Forum 40 NWT, Poster abstract only p. 64Canada, Nunavut, Baffin IslandDeposit - Chidliak
DS201312-0646
2013
Stachel, T.Nichols, K., Stachel, T., Stern, R.A., Pell, J., Mate, D.Diamond sources beneath the Hall Peninsula, Nunavut: a preliminary assessment based on micro-diamonds.GAC-MAC 2013 SS4: Diamond: from birth in the mantle to emplacement in kimberlite, abstract onlyCanada, Nunavut, Hall PeninsulaMicrodiamonds
DS201312-0647
2013
Stachel, T.Nichols, K.M.A., Stachel, T., Pell, J.A., Mate, D.J.Diamond sources beneath the Hall Peninsula, Baffin Island, Nunavut: preliminary assessment based on microdiamonds.Canada-Nunavut Geoscience Summary of Activities 2012, pp. 113-120.Canada, Nunavut, Baffin IslandDeposit - Chidliak
DS201312-0676
2013
Stachel, T.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
Stachel, T.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
Stachel, T.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
DS201312-0838
2013
Stachel, T.Smit, K.V., Stachel, T., Creaser, R.A., Ickert, R.B., Dufrane, S.A., Stern, R.A., Seller, M.Origin of eclogite and pyroxenite xenoliths from the Victor kimberlite, Canada, and implications for Superior Craton formation.Geochimica et Cosmochimica Acta, Vol. 125, pp. 308-337.Canada, OntarioDeposit - Victor
DS201312-0878
2013
Stachel, T.Stachel, T.Diamond formation and mantle f02GEM Diamond Workshop Feb. 21-22, Noted onlyMantleDiamond genesis
DS201312-0879
2013
Stachel, T.Stachel, T., Harris, J.W., Hunt, L., Muehlenbachs, K., and EIMFDiamonds from the Argyle lamproite ( Western Australia): different from any other mine?GAC-MAC 2013 SS4: Diamond: from birth in the mantle to emplacement in kimberlite, abstract onlyAustraliaDeposit - Argyle
DS201312-0966
2013
Stachel, T.Wescott, P., Nichols, K., Stachel, T., Muehlenbachs, K., Kong, J.Infrared spectroscopy and carbon isotopic analyses of Victor mine diamonds.2013 Yellowknife Geoscience Forum Abstracts, p. 82-83.Canada, OntarioDeposit - Victor
DS201412-0086
2014
Stachel, T.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
Stachel, T.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
DS201412-0532
2014
Stachel, T.Luth, R., Stachel, T.The buffering capacity of cratonic mantle peridotite: implications for the formation of diamond.Geological Society of America Conference Vancouver Oct. 19-22, 1p. AbstractTechnologyDiamond formation - CHO fluids
DS201412-0533
2014
Stachel, T.Luth, R.W., Stachel, T.The buffering capacity of lithospheric mantle: implications for diamond formation.Contributions to Mineralogy and Petrology, Vol. 168, 5, pp. 1083-MantleDiamond genesis
DS201412-0656
2014
Stachel, T.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
Stachel, T.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
DS201412-0685
2014
Stachel, T.Petts, D., Stern, R., Stachel, T., Chacko, T., Heaman, L.A nitrogen isotope fractionation factor between diamond and fluid derived from detailed SIMS analysis of an eclogitic diamond.Goldschmidt Conference 2014, 1p. AbstractTechnologyGeochronology
DS201412-0844
2014
Stachel, T.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
DS201412-0845
2014
Stachel, T.Smit, K.V., Stachel, T., Creaser, R.A., Ickert, R.B., DuFrane, S.A., Stern, R.A., Seller, M.Origin of eclogite and pyroxenite xenoliths from the Victor kimberlite, Canada, and implications for Superior craton formation.Geochimica et Cosmochimica Acta, Vol. 125, pp. 308-337.Canada, Ontario, AttawapiskatDeposit - Victor
DS201412-0846
2014
Stachel, T.Smit, K.V., Stachel, T., Stern, R.A.Diamonds in the Attawapiskat area of the Superior craton ( Canada): evidence for a major diamond forming event younger than 1.1 Ga.Contributions to Mineralogy and Petrology, in press availableCanada, Ontario, AttawapiskatNitrogen aggregation
DS201412-0880
2014
Stachel, T.Stachel, T.The mantle source of Argyle diamonds.ima2014.co.za, AbstractAustraliaDeposit - Argyle
DS201412-0881
2014
Stachel, T.Stachel, T., Stern, R.A., Petts, D., Nichols, K., Chacko, T.SIMS application to diamond research.Geological Society of America Conference Vancouver Oct. 19-22, 1p. AbstractTechnologyDiamond growth
DS201504-0206
2015
Stachel, T.Luth, R.W., Stachel, T.The buffering capacity of lithospheric mantle: implications for diamond formation.Contributions to Mineralogy and Petrology, Vol 168, 12p.MantleOxygen barometry
DS201504-0223
2015
Stachel, T.Stachel, T., Luth, R.W.Diamond formation - where, when and how?Lithos, Vol. 220-223, pp. 200-220.MantleDiamond inclusion, redox, geobarometry
DS201507-0316
2015
Stachel, T.Ickert, R.B., Stachel, T., Stern, R.A., Harris, J.W.Extreme 18O-enrichment in majorite constrains a crustal origin of transition zone diamonds.Geochemical Perspectives Letters, 1, pp. 65-74.Africa, South AfricaDeposit - Jagersfontein
DS201511-1846
2012
Stachel, T.Johnson, C.N., Stachel, T., Muehlenbachs, K., Stern, R.A., Armstrong, J.P.The micro/macro diamond relationship: a case study from the Artemisia kimberlite ( Northern Slave Craton) Canada.Lithos, Vol. 148, pp. 86-97. Available pdfCanada, Northwest TerritoriesMicrodiamonds - responses

Abstract: Size frequency distributions are the principal tool for predicting the macro-diamond grade of new kimberlite discoveries, based on micro-diamonds (i.e., diamond = 0.5 mm) recovered from small exploration samples. Lognormal size frequency distributions – as observed for the Artemisia kimberlite (Slave Craton, Canada) – suggest a common source for micro- and macro-diamonds recovered from single samples, an implication that has never been conclusively tested. We analyzed 209 diamonds between 0.2 and 2 mm in size from the Artemisia kimberlite for their carbon isotopic compositions and nitrogen characteristics to determine the nature of the micro-/macro-diamond relationship.-Despite overall similarity in the d13C distributions of micro- and macro-diamonds – both are bimodal with peaks in classes - 5.0 to - 4.5‰ and - 3.5 to - 3.0‰ – rare diamonds with d13C between - 14.2 and - 24.5‰ of presumed eclogitic origin are restricted to macro-diamonds, whereas positive values are only observed for micro-diamonds. In addition, a shift in main mode and median value in d13C of about +1‰ is observed for micro- relative to macro-diamonds. Fundamental differences between micro- and macro-diamonds at Artemisia were revealed through the analysis of nitrogen concentrations: 68% of micro-diamonds are Type II (“nitrogen free”) versus 21% of macro-diamonds, and only 19% of micro-diamonds have nitrogen contents > 100 atomic ppm versus 43% of macro-diamonds. Similarly, the presence of a detectable hydrogen related peak (at 3107 cm- 1) increases from 40% for micro-diamonds to 94% for macro-diamonds.-Previous studies on diamond populations from individual deposits have documented that single batches of ascending kimberlite or lamproite magma sample multiple diamond subpopulations formed during distinct growth events in compositionally variable sources and at various depth levels. The Artemisia data clearly show that even over a fairly narrow size interval, spanning the micro- to macro-diamond transition, the specific diamond subpopulations present and their relative proportions may vary significantly with diamond size. At Artemisia, we conclude that the observed lognormal size distribution is not a reflection of an entirely common origin of micro- and macro-diamonds.
DS201512-1926
2015
Stachel, T.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.
DS201512-1972
2015
Stachel, T.Stachel, T., Luth, R.W.Diamond formation in Earth's mantle.43rd Annual Yellowknife Geoscience Forum Abstracts, abstract p. 98.MantleDiamond genesis

Abstract: Studies of mineral inclusions in diamond have conclusively established that the principal diamond substrates in Earth's mantle are peridotitic (about 2/3) and eclogitic (about 1/3) domains located at 140-200 km depth in the subcratonic lithosphere. There, the formation of the dominant harzburgitic diamond association generally occurred under subsolidus (melt-absent) conditions. In eclogitic and lherzolitic substrates, however, diamond grew in the presence of a melt, with relatively rare exceptions relating to formation from strongly reducing fluids or at relatively low pressure (<50 kbar) and temperature (<1050°C). Complex internal growth structures indicate that in many instances, diamond formation did not occur in a single short lived event. The observed close agreement of radiometric ages involving different isotope systems and inclusion minerals for diamonds from individual occurrences, however, cannot be coincidental and implies that the temporal extent of individual diamond growth events is contained within the uncertainty of the age dates. Diamond formed through most of Earth's history, from the Paleoarchean to at least the Mesozoic. Diamond forming episodes occur on regional to global scales in response to tectonothermal events such as suturing, subduction and plume impact. Individual diamond forming episodes may be associated with particular substrates, with harzburgitic paragenesis diamonds generally yielding Paleoarchean (3.6-3.2 Ga) ages and lherzolitic paragenesis diamonds forming mostly in the Paleoproterozoic at ~2 Ga. Peridotitic diamond growth, however, continued through Earth's history, with the youngest age date being ~90 Ma. Formation of diamonds hosted by eclogite is documented from the Mesoarchean to the Neoproterozoic (2.9 and 0.6 Ga) and may well continue up to the present. Multiple lines of evidence suggest that formation of fibrous diamonds and diamond coats often is penecontemporaneous to kimberlite magmatism and hence, for the Central Slave, may even extent into the Tertiary. When it comes to the actual process(es) driving the precipitation of diamond, our knowledge is much less complete. Diamond grows during the infiltration of carbon-bearing fluids or melts into a suitable substrate. But what exactly is the diamond forming reaction that occurs there? The conventional view that redox reactions between percolating fluids/melts and wall rocks are nature's diamond recipe is inconsistent with both the low redox capacity of lithospheric mantle and the occurrence of large diamonds. Based on thermodynamic modeling, we instead propose that isochemical cooling or ascent of carbon-bearing fluids is a key mechanism of diamond formation. It operates particularly efficiently in chemically depleted mantle rocks (harzburgite), where a high melting temperature precludes dilution of the infiltrating fluid (see above), thereby explaining the long observed close association between diamond and harzburgitic garnet.
DS201601-0028
2016
Stachel, T.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.
DS201602-0219
2016
Stachel, T.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.
DS201602-0231
2016
Stachel, T.Petts, D.C., Stachel, T., Stern, R.A., Hunt, L., Fomradas, G.Multiple carbon and nitrogen sources associated with the parental mantle fluids of fibrous diamonds from Diavik, Canada revealed by SIMS microanalysis.Contributions to Mineralogy and Petrology, Vol. 171, 15p.Canada, Northwest TerritoriesDeposit - Diavik

Abstract: Fibrous diamonds are often interpreted as direct precipitates of primary carbonate-bearing fluids in the lithospheric mantle, sourced directly from common reservoirs of “mantle” carbon and nitrogen. Here we have examined fibrous growth layers in five diamonds (as three rims or “coats” and two whole-crystal cuboids) from the Diavik Diamond Mine, Canada, using in situ C- and N-isotope and N-abundance measurements to investigate the origin and evolution of their parental fluids, and in particular, to test for isotopic variability within a suite of fibrous diamonds. High-resolution growth structure information was gleaned from cathodoluminescence (CL) imaging and, in combination with the isotopic data, was used to assess the nature of the transition from gem to fibrous growth in the coated diamonds. The two cuboids are characterized by fine concentric bands of fibrous and/or milky opaque diamond, with one sample (S1719) having intermittent gem-like growth layers that are transparent and colourless. The three coated diamonds comprise octahedral gem cores mantled by massive or weakly zoned fibrous rims, with sharp and well-defined gem-fibrous boundaries. For the two cuboid samples, d 13C and d 15N values were -7.7 to -3.2 ‰ (mean -6.3 ± 1.3 ‰; 1 SD; n = 84) and -5.6 to -2.1 ‰ (mean -4.0 ± 0.8 ‰; 1 SD; n = 48), respectively. The three fibrous rims have combined d 13C values of -8.3 to -4.8 ‰ (mean -6.9 ± 0.7 ‰; 1 SD; n = 113) and d 15N values of -3.8 to -1.9 ‰ (mean -2.7 ± 0.4 ‰; 1 SD; n = 43). N-abundances of the combined cuboid-fibrous rim dataset range from 339 to 1714 at. ppm. The gem cores have d 13C and d 15N values of -5.4 to -3.5 ‰ and -17.7 to +4.5 ‰, respectively, and N-abundances of 480 to 1699 at. ppm. Broadly uniform C- and N-isotope compositions were observed in each of the gem cores (variations of ~<1 ‰ for carbon and ~<3 ‰ for nitrogen). This limited C- and N- isotope variability implies that the gem cores formed from separate pulses of fluid that remained isotopically uniform throughout the duration of growth. Significant isotopic and abundance differences were observed between the gem and fibrous growth zones, including in one detailed isotopic profile d 13C and d 15N offsets of ~-2.4 and ~-3.7 ‰, respectively, and a ~230 at. ppm increase in N-abundance. Combined with the well-defined gem-fibrous boundaries in plane light and CL, these sharp isotopic differences indicate separate parental fluid histories. Notably, in the combined fibrous diamond dataset prominent C- and N-isotope differences between the whole-crystal cuboid and fibrous rim data were observed, including a consistent ~1.3 ‰ offset in d 15N values between the two growth types. This bimodal N-isotope distribution is interpreted as formation from separate parental fluids, associated with distinct nitrogen sources. The bimodal N-isotope distribution could also be explained by differences in N-speciation between the respective parental fluids, which would largely be controlled by the oxidation state of the fibrous rim and cuboid growth environments (i.e., N2 vs. NH4 + or NH3). We also note that this C- and N-isotope variability could indicate temporal changes to the source(s) of the respective parental fluids, such that each stage of fibrous diamond growth reflects the emplacement of separate pulses of proto-kimberlitic fluid—from distinct carbon and nitrogen sources, and/or with varying N-species—into the lithospheric mantle.
DS201604-0596
2016
Stachel, T.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
DS201604-0599
2016
Stachel, T.Czas, J., Stachel, T., Morton, R.Diamond genesis and evolution of the FALC area of Saskatchewan Craton.GAC MAC Meeting Special Session SS11: Cratons, kimberlites and diamonds., abstract 1/4p.Canada, SaskatchewanFort a la Corne area
DS201604-0616
2016
Stachel, T.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
Stachel, T.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.
DS201604-0631
2016
Stachel, T.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
DS201604-0634
2016
Stachel, T.Tan, J.S., Stachel, T., Morton, R.Diamonds from the Konawaruk River, Guyana.GAC MAC Meeting Special Session SS11: Cratons, kimberlites and diamonds., abstract 1/4p.South America, GuyanaKonawaruk area
DS201606-1094
2015
Stachel, T.Howell, D., Stern, R.A., Griffin, W.L., Southworth, R., Mikhail, S., Stachel, T.Nitrogen isotope systematics and origins of mixed habit diamonds.Geochimica et Cosmochimica Acta, Vol. 157, pp. 1-12.TechnologyDiamond morphology

Abstract: Nitrogen isotope values from mantle diamonds are a commonly used tracer in the quest to track volatiles within the Earth’s mantle through deep time. Interpretations of this isotope data are valid so long as stable isotope fractionation processes in the mantle are understood. The fractionation of nitrogen isotopes between {1 1 1} and {1 0 0} growth sectors is well documented for high-pressure high-temperature (HPHT) synthetic diamonds, but there is little data on whether it also occurs in natural mixed-habit diamonds. We present 91 in-situ nitrogen isotope (d15N) measurements, along with carbon isotope (d13C) values and nitrogen abundances [N], obtained from three mixed-habit diamonds by secondary ion mass spectrometry (SIMS). While the well-documented enrichment of nitrogen concentrations in octahedral sectors compared to contemporaneous cuboid sectors is observed, a similarly clear disparity is not obvious in the d15N data. Whereas HPHT synthetic diamonds exhibit 15N enrichment in the {1 0 0} sectors by ~+30‰, the mixed-habit diamonds studied here show enrichment of the octahedral sectors in 15N by only 0.4-1‰. This major difference between HPHT synthetic and natural mixed-habit diamonds is proposed to be the result of different physical properties of the growth interfaces. The smooth interfaces of the octahedral sectors are the same in both types of crystal, but the outermost atoms on the smooth cube interfaces of an HPHT synthetic diamond behave differently to those on the rough cuboid interfaces of the natural mixed-habit diamonds, resulting in different d15N values. Both the d13C (average of ~-8.7‰) and d15N (average of ~0‰) data show only minor offsets from the typical mantle values (d13C = -5 ± 3‰, d15N = -5 ± 4‰). This may indicate diamond formation from a mantle derived fluid/melt containing a minor subducted component (lowering d13C values and elevating d15N) or relate to moderate degrees of isotopic fractionation of a pure mantle fluid/melt by prior diamond precipitation. The homogeneous nature of both the carbon and nitrogen isotopic compositions of all three diamonds, however, documents continuous and unlimited supply of diamond forming fluid/melt, with a constant composition. Such homogenous isotopic compositions exclude fluid mixing or isotopic fractionation close to the site of diamond formation and preclude distinguishing between these two processes based on diamond analyses alone.
DS201607-1288
2016
Stachel, T.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
Stachel, T.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
Stachel, T.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.
DS201609-1721
2016
Stachel, T.Hogberg, K., Stachel, T., Stern, R.A.Carbon and nitrogen isotope systematics in diamond: different sensitivities to isotopic fractionation or a decoupled origin?Lithos, In press available 15p.Canada, Nunavut, Baffin IslandDeposit - Chidliak

Abstract: Using stable isotope data obtained on multiple aliquots of diamonds from worldwide sources, it has been argued that carbon and nitrogen in diamond are decoupled. Here we re-investigate the carbon-nitrogen relationship based on the most comprehensive microbeam data set to date of stable isotopes and nitrogen concentrations in diamonds (n = 94) from a single locality. Our diamond samples, derived from two kimberlites in the Chidliak Field (NE Canada), show large variability in d13C (- 28.4 ‰ to - 1.1‰, mode at - 5.8‰), d15N (- 5.8 to + 18.8‰, mode at - 3.0‰) and nitrogen contents ([N]; 3800 to less than 1 at.ppm). In combination, cathodoluminescence imaging and microbeam analyses reveal that the diamonds grew from multiple fluid pulses, with at least one major hiatus documented in some samples that was associated with a resorption event and an abrupt change from low d13C and [N] to mantle-like d13C and high [N]. Overall, d13C appears to be uncorrelated to d15N and [N] on both the inter- and intra-diamond levels. Co-variations of d15N-log[N], however, result in at least two parallel, negatively correlated linear arrays, which are also present on the level of the individual diamonds falling on these two trends. These arrays emerge from the two principal data clusters, are characterized by slightly negative and slightly positive d15N (about - 3 and + 2‰, respectively) and variable but overall high [N]. Using published values for the diamond-fluid nitrogen isotope fractionation factor and nitrogen partition coefficient, these trends are perfectly reproduced by a Rayleigh fractionation model. Overall, three key elements are identified in the formation of the diamond suite studied: (1.) a low d13C and low [N] component that possibly is directly associated with an eclogitic diamond substrate or introduced during an early stage fluid event. (2.) Repeated influx of a variably nitrogen-rich mantle fluid (mildly negative d13C and d15N). (3.) In waning stages of influx, availability of the mantle-type fluid at the site of diamond growth became limited, leading to Rayleigh fractionation. These fractionation trends are clearly depicted by d15N-[N] but are not detected when examining co-variation diagrams involving d13C. Also on the level of individual diamonds, large (= 5‰) variations in d15N are associated with d13C values that typically are constant within analytical uncertainty. The much smaller isotope fractionation factor for carbon (considering carbonate- or methane-rich fluids as possible carbon sources) compared to nitrogen leads to an approximately one order of magnitude lower sensitivity of d13C values to Rayleigh fractionation processes (i.e. during fractionation, a 1‰ change in d13C is associated with a 10‰ change in d15N). As a consequence, even minor heterogeneity in the primary isotopic composition of diamond forming carbon (e.g., due to addition of minor subducted carbon) will completely blur any possible co-variations with d15N or [N]. We suggest this strong difference in isotope effects for C and N to be the likely cause of observations of an apparently decoupled behaviour of carbon and nitrogen isotopes in diamond.
DS201610-1871
2016
Stachel, T.Hogberg, K.,Stachel, T., Stern, R.A.Carbon and nitrogen isotope systematics in diamond: different sensitivities to isotopic fractionation or a decoupled origin?Lithos, in press available 15p.Canada, NunavutDeposit - Chidliak

Abstract: Using stable isotope data obtained on multiple aliquots of diamonds from worldwide sources, it has been argued that carbon and nitrogen in diamond are decoupled. Here we re-investigate the carbon-nitrogen relationship based on the most comprehensive microbeam data set to date of stable isotopes and nitrogen concentrations in diamonds (n = 94) from a single locality. Our diamond samples, derived from two kimberlites in the Chidliak Field (NE Canada), show large variability in d13C (- 28.4 ‰ to - 1.1‰, mode at - 5.8‰), d15N (- 5.8 to + 18.8‰, mode at - 3.0‰) and nitrogen contents ([N]; 3800 to less than 1 at.ppm). In combination, cathodoluminescence imaging and microbeam analyses reveal that the diamonds grew from multiple fluid pulses, with at least one major hiatus documented in some samples that was associated with a resorption event and an abrupt change from low d13C and [N] to mantle-like d13C and high [N]. Overall, d13C appears to be uncorrelated to d15N and [N] on both the inter- and intra-diamond levels. Co-variations of d15N-log[N], however, result in at least two parallel, negatively correlated linear arrays, which are also present on the level of the individual diamonds falling on these two trends. These arrays emerge from the two principal data clusters, are characterized by slightly negative and slightly positive d15N (about - 3 and + 2‰, respectively) and variable but overall high [N]. Using published values for the diamond-fluid nitrogen isotope fractionation factor and nitrogen partition coefficient, these trends are perfectly reproduced by a Rayleigh fractionation model. Overall, three key elements are identified in the formation of the diamond suite studied: (1.) a low d13C and low [N] component that possibly is directly associated with an eclogitic diamond substrate or introduced during an early stage fluid event. (2.) Repeated influx of a variably nitrogen-rich mantle fluid (mildly negative d13C and d15N). (3.) In waning stages of influx, availability of the mantle-type fluid at the site of diamond growth became limited, leading to Rayleigh fractionation. These fractionation trends are clearly depicted by d15N-[N] but are not detected when examining co-variation diagrams involving d13C. Also on the level of individual diamonds, large (= 5‰) variations in d15N are associated with d13C values that typically are constant within analytical uncertainty. The much smaller isotope fractionation factor for carbon (considering carbonate- or methane-rich fluids as possible carbon sources) compared to nitrogen leads to an approximately one order of magnitude lower sensitivity of d13C values to Rayleigh fractionation processes (i.e. during fractionation, a 1‰ change in d13C is associated with a 10‰ change in d15N). As a consequence, even minor heterogeneity in the primary isotopic composition of diamond forming carbon (e.g., due to addition of minor subducted carbon) will completely blur any possible co-variations with d15N or [N]. We suggest this strong difference in isotope effects for C and N to be the likely cause of observations of an apparently decoupled behaviour of carbon and nitrogen isotopes in diamond.
DS201705-0875
2017
Stachel, T.Smit, K.V., Stachel, T., Stern, R.A., Shirey, S.B., Steele, A.Diamond formation through isochemical cooling of CHO fluids vs redox buffering: examples from Marange peridotitic and Zimmi eclogitic diamonds.European Geosciences Union General Assembly 2017, Vienna April 23-28, 1p. 9187 AbstractAfrica, Zimbabwe, Sierra LeoneDeposit - Marange, Zimmi

Abstract: Traditional models for diamond formation within the lithospheric mantle invoke either carbonate reduction or methane oxidation. Both these mechanisms require some oxygen exchange with the surrounding wall-rock at the site of diamond precipitation. However, peridotite does not have sufficient buffering capacity to allow for diamond formation via these traditional models and instead peridotitic diamonds may form through isochemical cooling of H 2 O-rich CHO fluids [1]. Marange mixed-habit diamonds from eastern Zimbabwe provide the first natural confirmation of this new diamond growth model [2]. Although Marange diamonds do not contain any silicate or sulphide inclusions, they contain Ni-N-vacancy complexes detected through photoluminescence (PL) spectroscopy that suggest the source fluids equilibrated in the Ni-rich depleted peridotitic lithosphere. Cuboid sectors also contain abundant micro-inclusions of CH 4 , the first direct observation of reduced CH 4-rich fluids that are thought to percolate through the lithospheric mantle [2]. In fluid inclusion-free diamonds, core-to-rim trends in d 13 C and N content are used to infer the speciation of the diamond-forming fluid. Core to rim trends of increasing d 13 C with decreasing N content are interpreted as diamond growth from oxidized CO 2-or carbonate-bearing fluids. Diamond growth from reduced species should show the opposite trends-decreasing d 13 C from core to rim with decreasing N content. Within the CH 4-bearing growth sectors of Marange diamonds, however, such a 'reduced' trend is not observed. Rather, d 13 C increases from core to rim within a homogeneously grown zone [2]. These contradictory observations can be explained through either mixing between CH 4-and CO 2-rich end-members of hydrous fluids [2] or through closed system precipitation from an already mixed CH 4-CO 2 H 2 O-maximum fluid with XCO 2 (CO 2 /[CO 2 +CH 4 ]) between 0.3 and 0.7 [3]. These results demonstrate that Marange diamonds precipitated from cooling CH 4-CO 2-bearing hydrous fluids rather than through redox buffering. As this growth mechanism applies to both the fluid-rich cuboid and gem-like octahedral sectors of Marange diamonds, a non-redox model for diamond formation from mixed CH 4-CO 2 fluids is indicated for a wider range of gem-quality peridotitic diamonds. Indeed, at the redox conditions of global diamond-bearing lithospheric mantle (FMQ-2 to-4; [4]), CHO fluids are strongly water-dominated and contain both CH 4 and CO 2 as dominant carbon species [5]. By contrast diamond formation in eclogitic assemblages, through either redox buffering or cooling of carbon-bearing fluids, is not as well constrained. Zimmi diamonds from the West African craton have eclogitic sulphide inclusions (with low Ni and high Re/Os) and formed at 650 Ma, overlapping with the timing of subduction [6]. In one Zimmi diamond, a core to rim trend of decreasing d 13 C (-23.4 to-24.5 %¸) and N content is indicative of formation from reduced C 2 H 6 /CH 4-rich fluids, likely derived from oceanic crust recycled during Neoproterozoic subduction. Unlike mixed CH 4-CO 2 fluids near the water maximum, isochemical cooling or ascent of such reduced CHO fluids is not effficient at diamond precipitation. Furthermore, measurable carbon isotopic variations in diamond are not predicted in this model and therefore cannot be reconciled with the ~1 internal variation seen. Consequently, this Zimmi eclogitic diamond likely formed through redox buffering of reduced subduction-related fluids, infiltrating into sulphide-bearing eclogite.
DS201707-1372
2017
Stachel, T.Stachel, T., Chack, T., Luth, R.W.Carbon isotopoe fractionation during diamond growth in depleted peridotite: counterintuitive insights from modeling water-maximum CHO fluids as multi-compnent systems.Earth and Planetary Science Letters, Vol. 473, pp. 44-51.Africa, Zimbabwedeposit - Marange

Abstract: Because of the inability of depleted cratonic peridotites to effectively buffer oxygen fugacities when infiltrated by CHO or carbonatitic fluids, it has been proposed recently (Luth and Stachel, 2014) that diamond formation in peridotites typically does not occur by rock-buffered redox reactions as previously thought but by an oxygen-conserving reaction in which minor coexisting CH4 and CO2 components in a water-rich fluid react to form diamond (CO2 + CH4 = 2C + 2H2O). In such fluid-buffered systems, carbon isotope fractionation during diamond precipitation occurs in the presence of two dominant fluid carbon species. Carbon isotope modelling of diamond precipitation from mixed CH4CH4- and CO2-bearing fluids reveals unexpected fundamental differences relative to diamond crystallization from a single carbon fluid species: (1) irrespective of which carbon fluid species (CH4 or CO2) is dominant in the initial fluid, diamond formation is invariably associated with progressive minor (<1‰) enrichment of diamond in 13C as crystallization proceeds. This is in contrast to diamond precipitation by rock-buffered redox processes from a fluid containing only a single carbon species, which can result in either progressive 13C enrichment (CO2 or carbonate fluids) or View the MathML sourceC13 depletion (CH4 fluids) in the diamond. (2) Fluid speciation is the key factor controlling diamond d13Cd13C values; as XCO2 (XCO2 = CO2/[CO2 + CH4]) in the initial fluid increases from 0.1 to 0.9 (corresponding to an increase in fO2fO2 of 0.8 log units), the carbon isotope composition of the first-precipitated diamond decreases by 3.7‰. The tight mode in d13C of -5 ±1‰-5 ±1‰ for diamonds worldwide places strict constraints on the dominant range of XCO2 in water-rich fluids responsible for diamond formation. Specifically, precipitation of diamonds with d13C values in the range -4 to -6‰ from mantle-derived fluids with an average d13C value of -5‰ (derived from evidence not related to diamonds) requires that diamond-forming fluids were relatively reduced and had methane as the dominant carbon species (XCO2 = 0.1–0.5). Application of our model to a recently published set of in-situ carbon isotope analyses for peridotitic diamonds from Marange, Zimbabwe (Smit et al., 2016), which contain CH4 fluid inclusions, allows us to perfectly match the observed co-variations in d13Cd13C, d15Nd15N and N content and at the same time explain the previously counter-intuitive observation of progressive View the MathML sourceC13 enrichment in diamonds that appear to have grown from a fluid with methane as the dominant carbon species. Similarly, the almost complete absence in the published record of progressive View the MathML sourceC13 depletion trends within diamonds likely reflects ubiquitous precipitation from CH4- and CO2-bearing water-rich fluids, rather than diamond formation exclusively by carbonate-bearing and CH4-free oxidized fluids or melts.
DS201708-1771
2017
Stachel, T.Stachel, T.The Victor diamond mine ( Superior craton, Canada) - A new paradigm for exploration in unconventional settings.11th. International Kimberlite Conference, OralCanada, Ontario, Attawapiskatdeposit - Victor
DS201709-2014
2017
Stachel, T.Kiseeva, E.S., Vasiukov, D.M., Wood, B.J., McCammon, C., Stachel, T., Chumakov, A., Dubrovinsky, L.Oxidation state of majoritic garnet inclusions in diamond.Goldschmidt Conference, abstract 1p.Africa, South Africadeposit, Jagersfontein

Abstract: Diamond inclusions are the only samples from the mantle transition zone (410-660 km) and the lower mantle. Majoritic garnet is a rare inclusion, limited to pressures of ~8-20 Gpa with Si content being indicative of depth of re-equilibration. These garnet inclusions can therefore provide information on properties of the transition zone such as oxidation state. In this study, we used Synchrotron Mössbauer Source (SMS) to determine the ferric-ferrous ratios of 13 small (30 to 100 micrometers diameter) majoritic inclusions in diamonds from Jagersfontein. The studied inclusions have pyroxenitic affinities [1], with compositions intermediate between typical peridotite and eclogite. They contain 4.62-11.2 wt% CaO, 0.03-0.34 wt% Cr2O3 and Mg# of 0.65-0.81. Minimum pressures for their equilibration using Beyer and Frost [2] barometer are between 8 and 18 GPa with at least 4 of these inclusions being formed in the transition zone. The Fe3+/Fetotal ratios in the garnets increase from 0.08±0.01 to 0.30±0.03 with increasing pressure. These values define a clear extension of the trend apparent in the data from peridotite xenoliths crystallised at lower pressures. Thermodynamic calculations suggest that these high ferric contents correspond to oxygen fugacities above the FeFeO (IW) buffer, which means that the high Fe3+ contents were not generated by disproportionation of Fe2+ to Fe3+ and Fe0 . It is more likely that carbonate was the oxidising agent responsible for generating the high Fe3+ of these garnets.
DS201709-2058
2017
Stachel, T.Stachel, T., Harris, J.W., Hunt, L., Muehlenbachs, K., Kobussen, A., EIMFArgyle diamonds - how subduction along the Kimberley Craton edge generated the World's biggest diamond deposit.Economic Geology, 50p. By permission of authorAustraliadeposit - Argyle

Abstract: Based on the mineral inclusion content, diamonds from the Argyle Mine, Western Australia, derive primarily (~90%) from eclogitic sources with a minor peridotitic contribution from both harzburgitic and lherzolitic lithologies. The eclogitic inclusions cover a large compositional range and show in part unusually high concentrations of mantle incompatible elements (P, Ti, Na and K). Coherent trends in major elements (e.g., of Ti or Na versus Mg-number) suggest that the eclogitic diamond source was created by a single process, namely igneous fractionation. Calculated bulk rock REEN patterns match a section of oceanic crust reaching from lavas and sheeted dykes to upper gabbros. Positive Eu anomalies for garnet and clinopyroxene, with calculated bulk rock REEN patterns similar to upper (non-layered) gabbros, are strong evidence for plagioclase accumulation, which is characteristic for the gabbroic portions of oceanic crust. Linking previously published oxygen isotope analyses of eclogitic garnet inclusions with their major element composition reveals a correlation between d18O (mean of +7.2‰) and Na content, consistent with coupled 18O and Na enrichment during low temperature alteration of oceanic crust. The carbon isotopic composition of Argyle eclogitic diamonds forms a normal distribution around a d13C value of -11‰, indicative of mixing and homogenization of mantle and crustal (organic matter) derived carbon prior to diamond precipitation. Previously published noble gas data on Argyle diamonds support this two component model. Inclusion and nitrogen-in-diamond based thermometry indicate an unusually hot origin of the eclogitic diamond suite, indicative of derivation from the lowermost 25 km (about 180-205 km depth) of the local lithospheric mantle. This is consistent with emplacement of an oceanic protolith during subduction along the Kimberley Craton margin, likely during the Halls Creek Orogeny (about 1.85 Ga). For Argyle eclogitic diamonds the relationship between the rate of platelet degradation and mantle residence temperature indicates that both temperature and strain play an important role in this process. Therefore, ubiquitous platelet degradation and plastic deformation of Argyle diamonds are consistent with derivation from a high temperature environment (softening the diamond lattice) close to the lithosphere-asthenosphere boundary (inducing strain). In combination, the Argyle data set represents a uniquely strong case for a subduction origin of an eclogitic diamond source followed by mixing of mantle and crustal components during diamond formation. Some lherzolitic inclusions show a similarity in incompatible element enrichments (elevated P, Na and K) to the eclogitic suite. The presence of a mildly majoritic lherzolitic garnet further supports a link to eclogitic diamond formation, as very similar majoritic components were found in two eclogitic garnet inclusions. The carbon isotopic composition of peridotitic diamonds shows a mode between -5 to -4 ‰ and a tail extending towards the eclogitic mode (-11 ‰). This suggests the presence of multiple generations of peridotitic diamonds, with indications for an origin linked to the eclogitic suite being restricted to diamonds of lherzolitic paragenesis. Argyle diamonds – how subduction along the Kimberley Craton edge generated the world's biggest diamond deposit.
DS201802-0241
2018
Stachel, T.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.
DS201804-0743
2018
Stachel, T.Stachel, T.Formation of diamond in Earth's mantle.4th International Diamond School: Diamonds, Geology, Gemology and Exploration Bressanone Italy Jan. 29-Feb. 2nd., pp. 43-44. abstractMantlediamond inclusions
DS201805-0934
2018
Stachel, T.Aulbach, S., Creaser, R.A., Stachel, T., Kong, J.Diamond ages from Victor ( Superior craton): intra-mantle cycling of volatiles ( C.N.S) during supercontinent reorganisation.Earth Planetary Science Letters, Vol. 490, pp. 77-87.Canada, Ontariodeposit - Victor

Abstract: The central Superior Craton hosts both the diamondiferous 1.1 Ga Kyle Lake and Jurassic Attawapiskat kimberlites. A major thermal event related to the Midcontinent Rift at ca. 1.1 Ga induced an elevated geothermal gradient that largely destroyed an older generation of diamonds, raising the question of when, and how, the diamond inventory beneath Attawapiskat was formed. We determined Re-Os isotope systematics of sulphides included in diamonds from Victor by isotope dilution negative thermal ionisation mass spectrometry in order to obtain insights into the age and nature of the diamond source in the context of regional tectonothermal evolution. Regression of the peridotitic inclusion data (n = 14 of 16) yields a 718 ± 49 Ma age, with an initial 187Os/188Os ratio of 0.1177 ± 0.0016, i.e. depleted at the time of formation (?Os -3.7 ± 1.3). Consequently, Re depletion model ages calculated for these samples are systematically overestimated. Given that reported 187Os/188Os in olivine from Attawapiskat xenoliths varies strongly (0.1012-0.1821), the low and nearly identical initial Os of sulphide inclusions combined with their high 187Re/188Os (median 0.34) suggest metasomatic formation from a mixed source. This was likely facilitated by percolation of amounts of melt sufficient to homogenise Os, (re)crystallise sulphide and (co)precipitate diamond; that is, the sulphide inclusions and their diamond host are synchronous if not syngenetic. The ~720 Ma age corresponds to rifting beyond the northern craton margin during Rodinia break-up. This suggests mobilisation of volatiles (C, N, S) and Os due to attendant mantle stretching and metasomatism by initially oxidising and S-undersaturated melts, which ultimately produced lherzolitic diamonds with high N contents compared to older Kyle Lake diamonds. Thus, some rift-influenced settings are prospective with respect to diamond formation. They are also important sites of hidden, intra-lithospheric volatile redistribution that can be revealed by diamond studies. Later emplacement of the Attawapiskat kimberlites, linking the carbon cycle to the surface, was associated with renewed disturbance during passage of the Great Meteor Hotspot. Lherzolitic diamond formation from oxidising small-volume melts may be the expression of an early and deep stage of the lithospheric conditioning required for the successful eruption of kimberlites, which complements the late and shallow emplacement of volatile-rich metasomes after upward displacement of a redox freezing front.
DS201806-1255
2018
Stachel, T.Stachel, T., Banas, A., Aulbach, S., Smit, K.V., Wescott, P., Chinn, I.L.The Victor mine ( Superior Craton, Canada): Neoproterozoic lherzolitic diamonds from a thermally-modified cratonic root.Mineralogy and Petrology, in press available, 12p.Canada, Ontario, Attawapiskatdeposit - Victor

Abstract: The Jurassic Victor kimberlite (Attawapiskat Field) was emplaced into an area of the central Superior Craton that was affected by a lithosphere-scale thermal event at ~1.1 Ga. Victor diamonds formed ca. 400 million years after this event, in a lithospheric mantle characterized by an unusually cool model geotherm (37-38 mW/m2; Hasterok and Chapman 2011). The bulk of Victor diamonds derives from a thin (<10 km thick) layer that is located at about 180 km depth and represents lherzolitic substrates (for 85% of diamonds). Geothermobarometric calculations (average pressure and temperature at the 1 sigma level are 57?±?2 kbar and 1129?±?16 °C) coupled with typical fluid metasomatism-associated trace element patterns for garnet inclusions indicate diamond precipitation under sub-solidus (lherzolite + H2O) conditions. This conclusion links the presence of a diamond-rich lherzolitic layer in the lithospheric mantle, just above the depth where ascending melts would freeze, to the unusually low paleogeotherm beneath Attawapiskat, because along an average cratonic geotherm (40 mW/m2) lherzolite in the presence of hydrous fluid would melt at depths >140 km.
DS201807-1482
2018
Stachel, T.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.
DS201807-1518
2018
Stachel, T.Navon, O., Stachel, T., Stern, R.A., Harris, J.W.Carbon and nitrogen systematics in nitrogen-rich, ultradeep diamonds from Sao Luiz, Brazil.Mineralogy and Petrology, 10.1007/ s710-018-0576 -9, 10p.South America, Brazildeposit - Sao Luiz

Abstract: Three diamonds from Sao Luiz, Brazil carrying nano- and micro-inclusions of molecular d-N2 that exsolved at the base of the transition zone were studied for their C and N isotopic composition and the concentration of N utilizing SIMS. The diamonds are individually uniform in their C isotopic composition and most spot analyses yield d13C values of -3.2?±?0.1‰ (ON-SLZ-390) and?-?4.7?±?0.1‰ (ON-SLZ-391 and 392). Only a few analyses deviate from these tight ranges and all fall within the main mantle range of -5?±?3‰. Most of the N isotope analyses also have typical mantle d15N values (-6.6?±?0.4‰, -3.6?±?0.5‰ and?-?4.1?±?0.6‰ for ON-SLZ-390, 391 and 392, respectively) and are associated with high N concentrations of 800-1250 atomic ppm. However, some N isotopic ratios, associated with low N concentrations (<400 ppm) and narrow zones with bright luminescence are distinctly above the average, reaching positive d15N values. These sharp fluctuations cannot be attributed to fractionation. They may reflect arrival of new small pulses of melt or fluid that evolved under different conditions. Alternatively, they may result from fractionation between different growth directions, so that distinct d15N values and N concentrations may form during diamond growth from a single melt/fluid. Other more continuous variations, in the core of ON-SLZ-390 or the rim of ON-SLZ-392 may be the result of Rayleigh fractionation or mixing.
DS201808-1750
2018
Stachel, T.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
DS201808-1769
2018
Stachel, T.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
Stachel, T.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.
DS201809-2044
2018
Stachel, T.Jacob, D.E., Stern, R.A., Stachel, T., Piazolo, S.Polycrystalline diamonds and their mantle derived mineral and fluid intergrowths. (Aggregates, framesites, boart, diamondite)Goldschmidt Conference, 1p. AbstractAfrica, South Africadeposit - Venetia

Abstract: Polycrystalline diamond aggregates (framesites, boart, diamondite) are an understudied variety of mantle diamond, but can make up 20% of the production in some Group I kimberlites. Their polycrystalline nature indicates rapid precipitation from carbon-oversaturated fluids and individual PDAs often contain a chemically heterogeneous suite of websteritic and pyroxenitic inclusions and minerals intimately intergrown with the diamond crystals. Geochemical and microstructural evidence suggests that fluid-driven redox reactions with lithospheric material occurring episodically over millions of years play a major role in freezing carbon in the subcratonic lithosphere (Jacob et al., 2000; 2016; Mikhail et al., 2014). A suite of 39 samples from the Venetia kimberlite pipe in South Africa allows a more detailed look at the diamondforming fluids. 13C values in the diamonds measured by secondary ion mass spectrometry range from +2 to -28 and cover the entire range for PDA from the literature. Nitrogen concentrations are mostly very low (less than 100 at ppm), but reach up to 2660 at ppm in individual samples. These high nitrogen concentrations in concert with mostly positive 15N values of up to +17 and some very negative 3C values suggest crustal material as the source of the nitrogen and the carbon. However, detailed analysis of the sample provides evidence for a more complex growth history followed by alteration. Individual diamond crystals show complex growth zonations by cathodoluminescence imaging that can be related with the carbon and nitrogen isotopic compositions and points to growth incorporating several pulses of carbon-nitrogen fluid with distinct isotopic compositions. Most of these growth events show decoupled carbon and nitrogen systematics. In addition, EBSD identifies deformation and recrystallization and nitrogen aggregation states range from pure IaA to pure IaB, supporting a heterogeneous and episodic growth history.
DS201809-2079
2018
Stachel, T.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.
DS201812-2777
2018
Stachel, T.Aulbach, S., Heaman, L.M., Stachel, T.Diavik deposit: The diamondiferous mantle root beneath the central Slave craton.Society of Economic Geology Geoscience and Exploration of the Argyle, Bunder, Diavik, and Murowa Diamond Deposits, Special Publication no. 20, pp.319-342.Canada, Northwest Territoriesdeposit - Diavik
DS201812-2786
2018
Stachel, T.Bulbuc, K.M., Galarneau, M., Stachel, T., Stern, R.A., Kong, J., Chinn, I.Contrasting growth conditions for sulphide-and garnet-included diamonds from the Victor mine ( Ontario).2018 Yellowknife Geoscience Forum , p. 97-98. abstractCanada, Ontario, Attawapiskatdeposit - Victor

Abstract: The Victor Diamond Mine, located in the Attawapiskat kimberlite field (Superior Craton), is known for its exceptional diamond quality. Here we study the chemical environment of formation of Victor diamonds. We imaged eight sulphide-included diamond plates from Victor using cathodoluminescence (CL). Then, along core-rim transects, we measured nitrogen content and aggregation state utilizing Fourier Transform Infrared (FTIR) spectroscopy, and the stable isotope compositions of carbon (d13C) and nitrogen (d15N), using a multi-collector ion microprobe (MC-SIMS). We compare the internal growth features and chemical characteristics of these sulphide inclusion-bearing diamonds with similar data on garnet inclusion-bearing diamonds from Victor (BSc thesis Galarneau). Using this information, possible fractionation processes during diamond precipitation are considered and inferences on the speciation of the diamond forming fluid(s) are explored. Sulphide inclusion-bearing diamonds show much greater overall complexity in their internal growth features than garnet inclusion-bearing diamonds. Two of the sulphide-included samples have cores that represent an older generation of diamond growth. Compared to garnet inclusion-bearing diamonds, the sulphide-included diamonds show very little intra-sample variation in both carbon and nitrogen isotopic composition; the inter-sample variations in carbon isotopic composition, however, are higher than in garnet included diamonds. For sulphide-included diamonds, d13C ranges from -3.4 to -17.5 and d15N ranges from -0.2 to -9.2. Garnet inclusion-bearing diamonds showed d13C values ranging from -4.6 to -6.0 and d15N ranging from -2.8 to -10.8. The observation of some 13C depleted samples indicates that, unlike the lherzolitic garnet inclusion-bearing diamonds, the sulphide inclusion-bearing diamonds are likely both peridotitic and eclogitic in origin. The total range in N content across sulphide inclusion-bearing diamonds was 2 to 981 at ppm, similar to the garnet-included samples with a range of 5 to 944 at ppm. The very limited variations in carbon and nitrogen isotopic signatures across growth layers indicate that sulphide-included Victor diamonds grew at comparatively high fluid:rock ratios. This is contrasted by the garnet inclusion-bearing diamonds that commonly show the effects of Rayleigh fractionation and hence grew under fluid-limited conditions.
DS201812-2818
2018
Stachel, T.Hunt, L., Stachel, T., Stern, R.A., Creighton, S.Diavik deposit: Diamonds from the Diavik mine: from formation through mantle residence to emplacement.Society of Economic Geology Geoscience and Exploration of the Argyle, Bunder, Diavik, and Murowa Diamond Deposits, Special Publication no. 20, pp. 343-358.Canada, Northwest Territoriesdeposit - Diavik
DS201812-2831
2018
Stachel, T.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.
DS201812-2867
2018
Stachel, T.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
Stachel, T.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
Stachel, T.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.
DS201812-2887
2018
Stachel, T.Stachel, T., Harris, J.W., Hunt, L., Muehlenbachs, K., Kobussen, A.F., Edinburgh Ion Micro-Probe facilityArgyle deposit: Argyle diamonds: how subduction along the Kimberley craton edge generated the world's biggest diamond deposit.Society of Economic Geology Geoscience and Exploration of the Argyle, Bunder, Diavik, and Murowa Diamond Deposits, Special Publication no. 20, pp. 145-168.Australia, western Australiadeposit - Argyle
DS201901-0081
2018
Stachel, T.Stachel, T., Luth, R.W., Navon, O.Diamond precipitation from high-density CHO fluids.Gems & Gemology, Sixth International Gemological Symposium Vol. 54, 3, 1p. Abstract p. 271-2.Globaldiamond inclusions

Abstract: Through research on inclusions in diamonds over the past 50 years, a detailed picture has emerged of the mineralogical and chemical composition of diamond substrates in Earth’s mantle and of the pressure-temperature conditions during diamond formation. The exact diamond-forming processes, however, are still a subject of debate. One approach to constrain diamond-forming processes is through model calculations that aim to obtain the speciation and the carbon content of carbon-hydrogen-oxygen (CHO) fluids at particular O/(O+H) ratios and pressure-temperature conditions (using GFluid of Zhang and Duan, 2010, or other thermodynamic models of fluids). The predictions of such model calculations can then be tested against carbon and nitrogen stable isotopes and nitrogen content fractionation models, based on in situ analyses across homogenously grown diamond growth layers. Based on this approach, Luth and Stachel (2014) proposed that diamond precipitation occurs predominantly from cooling or ascending CHO fluids, composed of water with minor amounts of CO2 and CH4 (which in response to decreasing temperature may react to form diamond: CO2+ CH4 ? 2C + 2H2O). The second approach focuses on constraining the diamondforming medium by studying submicrometer fluid inclusions in fibrous-clouded and, more recently, gem diamonds. Such studies established the presence of four compositional end members of inclusions: hydrous-saline, hydrous-silicic, high-Mg carbonatitic, and low-Mg carbonatitic (e.g., Navon et al., 1988; Weiss et al., 2009). Although these fluid inclusions only depict the state of the diamond-forming medium after formation, they nevertheless provide unique insights into the major and trace-element composition of such fluids that otherwise could not be obtained. The apparent dichotomy between the two approaches—models for pure CHO fluids and actual observation of impure fluids (socalled high-density fluids) in clouded and fibrous diamonds—relates to the observation that in high-pressure and high-temperature experiments close to the melting temperature of mantle rocks, hydrous fluids contain 10–50% dissolved solid components (e.g., Kessel et al., 2015). Although at this stage the impurity content in natural CHO fluids cannot be included in numerical models, the findings for clouded and fibrous diamonds are not in conflict with the isochemical diamond precipitation model. Specifically, the fact that observed high-density inclusions are often carbonate bearing is not in conflict with the relatively reducing redox conditions associated with the O/(O+H) ratios of modeled diamond-forming CHO fluids. The model for the minimum redox stability of carbonate - bearing melts of Stagno and Frost (2010) permits fluid carbonate contents of up to about 30% at such redox conditions. Although additional data need to be obtained to build a thermodynamic model for CHO fluids with dissolved silicates and to better characterize the major and trace-element composition of high-density CHO fluids in equilibrium with typical diamond substrates (the rock types peridotite and eclogite), we already see sufficient evidence to suggest that the two approaches described above are converging to a unified model of isochemical diamond precipitation from cooling or ascending high-density CHO fluids.
DS201902-0285
2018
Stachel, T.Kiseeva, E.S., Vasiukov, D.M., Wood, B.J., McCammon, C., Stachel, T., Bykov, M., Bykova, E., Chumakov, A., Cerantola, V., Harris, J.W., Dubrovinsky, L.Oxidized iron in garnets from the mantle transition zone.Nature Geoscience, Vol. 11, pp. 144-147. Africa, South Africadeposit - Jagersfontein

Abstract: The oxidation state of iron in Earth’s mantle is well known to depths of approximately 200?km, but has not been characterized in samples from the lowermost upper mantle (200-410?km depth) or the transition zone (410-660?km depth). Natural samples from the deep (>200?km) mantle are extremely rare, and are usually only found as inclusions in diamonds. Here we use synchrotron Mössbauer source spectroscopy complemented by single-crystal X-ray diffraction to measure the oxidation state of Fe in inclusions of ultra-high pressure majoritic garnet in diamond. The garnets show a pronounced increase in oxidation state with depth, with Fe3+/(Fe3++ Fe2+) increasing from 0.08 at approximately 240?km depth to 0.30 at approximately 500?km depth. The latter majorites, which come from pyroxenitic bulk compositions, are twice as rich in Fe3+ as the most oxidized garnets from the shallow mantle. Corresponding oxygen fugacities are above the upper stability limit of Fe metal. This implies that the increase in oxidation state is unconnected to disproportionation of Fe2+ to Fe3+ plus Fe0. Instead, the Fe3+ increase with depth is consistent with the hypothesis that carbonated fluids or melts are the oxidizing agents responsible for the high Fe3+ contents of the inclusions.
DS201902-0288
2019
Stachel, T.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
Stachel, T.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.
DS201905-1026
2019
Stachel, T.Dsmit, K.V., Stachel, T., Luth, R.W., Stern, R.A.Evaluating mechanisms for eclogitic diamond growth: an example from Zimmi Neoproterozoic diamonds ( West African Craton).Chemical Geology, doi.org/10,1016/j.chem geo.2019.04.014 37p.Africa, Sierra Leonedeposit - Zimmi

Abstract: Here we present SIMS data for a suite of Zimmi sulphide-bearing diamonds that allow us to evaluate the origin and redox-controlled speciation of diamond-forming fluids for these Neoproterozoic eclogitic diamonds. Low d13C values below -15‰ in three diamonds result from fluids that originated as carbon in the oceanic crust, and was recycled into the diamond-stable subcratonic lithospheric mantle beneath Zimmi during subduction. d13C values between -6.7 and -8.3‰ in two diamonds are within the range for mantle-derived carbon and could reflect input from mantle fluids, serpentinised peridotite, or homogenised abiogenic and/or biogenic carbon (low d13C values) and carbonates (high d13C values) in the oceanic crust. Diamond formation processes in eclogitic assemblages are not well constrained and could occur through redox exchange reactions with the host rock, cooling/depressurisation of CHO fluids or during H2O-loss from CHO fluids. In one Zimmi diamond studied here, a core to rim trend of decreasing d13C (-23.4 to -24.5‰) and decreasing [N] is indicative of formation from reduced CH4-bearing fluids. Unlike mixed CH4-CO2 fluids near the water maximum, isochemical diamond precipitation from such reduced CHO fluids will only occur during depressurisation (ascent) and should not produce coherent fractionation trends in single diamonds that reside at constant depth (pressure). Furthermore, due to a low relative proportion of the total carbon in the fluid being precipitated, measurable carbon isotopic variations in diamond are not predicted in this model and therefore cannot be reconciled with the 1‰ internal core-to- rim variation. Consequently, this Zimmi eclogitic diamond showing a coherent trend in d13C and [N] likely formed through oxidation of methane by the host eclogite, although the mineralogical evidence for this process is currently lacking.
DS201906-1314
2019
Stachel, T.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.
DS201908-1802
2019
Stachel, T.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.
DS201910-2252
2019
Stachel, T.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.
DS201912-2775
2019
Stachel, T.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
Stachel, T.Czas, J., Pearson, D.G., Stachel, T., Kjarsgaard, B.A., Read, G.H.A Paleoproterozoic diamond bearing lithospheric mantle root beneath the Archean Sask craton, Canada.Lithos, DOI:10.1016/ j.lithos.2019.105301Canada, Saskatchewandiamond genesis

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.
DS202002-0176
2019
Stachel, T.De Hoog, J.C.M., Stachel, T., Harris, J.W.Trace element geochemistry of diamond hosted olivine inclusions from the Akwatia mine, West African Craton: implications for diamond paragenesis and geothermobarometry.Contributions to Mineralogy and Petrology, Vol. 174, (12) doi: 10.1007/s00410-019-1634-yAfrica, Ghanadeposit - Akwatia

Abstract: Trace-element concentrations in olivine and coexisting garnets included in diamonds from the Akwatia Mine (Ghana, West African Craton) were measured to show that olivine can provide similar information about equilibration temperature, diamond paragenesis and mantle processes as garnet. Trace-element systematics can be used to distinguish harzburgitic olivines from lherzolite ones: if Ca/Al ratios of olivine are below the mantle lherzolite trend (Ca/Al??300 µg/g Ca or?>?60 µg/g Na are lherzolitic. Conventional geothermobarometry indicates that Akwatia diamonds formed and resided close to a 39 mW/m2 conductive geotherm. A similar value can be derived from Al in olivine geothermometry, with TAl-ol ranging from 1020 to 1325 °C. Ni in garnet temperatures is on average somewhat higher (TNi-grt?=?1115-1335 °C) and the correlation between the two thermometers is weak, which may be not only due to the large uncertainties in the calibrations, but also due to disequilibrium between inclusions from the same diamond. Calcium in olivine should not be used as a geothermobarometer for harzburgitic olivines, and often gives unrealistic P-T estimates for lherzolitic olivine as well. Diamond-hosted olivine inclusions indicate growth in an extremely depleted (low Ti, Ca, Na, high Cr#) environment with no residual clinopyroxene. They are distinct from olivines from mantle xenoliths which show higher, more variable Ti contents and lower Cr#. Hence, most olivine inclusions in Akwatia diamonds escaped the refertilisation processes that have affected most mantle xenoliths. Lherzolitic inclusions are probably the result of refertilisation after undergoing high-degree melting first. Trivalent cations appear to behave differently in harzburgitic diamond-hosted olivine inclusions than lherzolitic inclusions and olivine from mantle xenoliths. Some divalent chromium is predicted to be present in most olivine inclusions, which may explain high concentrations up to 0.16 wt% Cr2O3 observed in some diamond inclusions. Strong heterogeneity of Cr, V and Al in several inclusions may also result in apparent high Cr contents, and is probably due to late-stage processes during exhumation. However, in general, diamond-hosted olivine inclusions have lower Cr and V than expected compared to mantle xenoliths. Reduced Na activity in depleted harzburgites limits the uptake of Cr, V and Sc via Na-M3+ exchange. In contrast, Al partitioning in harzburgites is not significantly reduced compared to lherzolites, presumably due to uptake of Al in olivine by Al-Al exchange.
DS202002-0199
2020
Stachel, T.Lai, M.Y., Breeding, C.M., Stachel, T., Stern, R.A.Spectroscopic features of natural and HPHT treated yellow diamonds. EkatiDiamonds & Related Materials, Vol. 101, 107642, 8p. PdfCanada, Northwest Territoriesdeposit - Ekati

Abstract: High pressure high temperature (HPHT) treatment has long been applied in the gem trade for changing the body colour of diamonds. The identification of HPHT-treated diamonds is a field of on-going research in gemological laboratories, as different parameters of treatment will result in either the creation or the destruction of a variety of lattice defects in diamonds. Some features that exist in treated diamonds can also be found in natural diamonds, and consequently must not be employed for the separation of treated and natural diamonds. In this research, we investigated the properties of 11 natural yellow diamonds (directly obtained from the Ekati Diamond Mine to ensure that they are untreated) before and after HPHT treatment, conducted at a temperature of 2100 °C and a pressure of 6 GPa for 10 min. We report spectroscopic data and fluorescence characteristics, collected using PL mapping, FTIR mapping and fluorescence imaging showing the distribution of lattice defects and internal growth structures. PL mapping indicates SiV defects exist in one of the nitrogen-rich natural diamonds prior to treatment. Silicon-related defects can also be created by HPHT treatment, and they seem to show a relationship with pre-existing NV- centres. SIMS analysis was conducted to confirm the presence of silicon in these diamonds. The increase in the hydrogen-related infrared absorption peak at 3107 cm-1 (VN3H) is very strong in some diamonds that do not form B-centres during treatment. NVH was observed in our HPHT-treated natural diamonds, so it is possible that this strong increase in VN3H suppresses the aggregation of A- to B-centres as the newly formed A-centres were captured by NVH lattice defects to form VN3H. HPHT-altered and HPHT-induced platelet peaks are different from their natural counterparts in peak width and shape. Strong green fluorescence over a large area of a diamond, which is linked to relatively high concentration of H3 centres, was produced after HPHT treatment. We are confident that the unusual platelet peaks and strong emission of H3 centres are reliable indicators for HPHT-treated diamonds as they are not observed in untreated natural diamonds.
DS202003-0347
2020
Stachel, T.Lai, M.Y., Stachel, T., Breeding, C.M., Stern, R.A.Yellow diamonds with colourless cores - evidence for episodic diamond growth beneath Chidliak and Ekati mine, Canada.Mineralogy and Petrology, in press available 13p. PdfCanada, Northwest Territoriesdeposit - Chidliak, Ekati

Abstract: Yellow diamonds from the CH-7 (Chidliak) and the Misery (Ekati Mine) kimberlites in northern Canada are characterised for their nitrogen characteristics, visible light absorption, internal growth textures, and carbon isotope compositions. The diamonds are generally nitrogen-rich, with median N contents of 1230 (CH-7) and 1030 at.ppm (Misery). Normally a rare feature in natural diamonds, single substitutional nitrogen (C centres) and related features are detected in infrared absorption spectra of 64% of the studied diamonds from CH-7 and 87% from Misery and are considered as the major factor responsible for their yellow colouration. Episodically grown diamonds, characterised by colourless cores containing some nitrogen in the fully aggregated form (B centres) and yellow outer layers containing C centres, occur at both localities. Carbon isotope compositions and N contents also are significantly different in such core and rim zones, documenting growth during at least two temporally distinct events and involving different diamond forming fluids. Based on their nitrogen characteristics, both the yellow diamonds and yellow rims must have crystallized in close temporal proximity (<<1 Ma) to kimberlite activity at CH-7 and Misery.
DS202004-0519
2020
Stachel, T.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.
DS202007-1123
2020
Stachel, T.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
DS202008-1423
2020
Stachel, T.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
Stachel, T.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.
DS202009-1635
2020
Stachel, T.Koemets, I., Satta, N., Marquardt, H., Kiseeva, E.S., Kurnosov, A., Stachel, T., Harris, J.W., Dubrovinsky, L.Elastic properties of majorite garnet inclusions in diamonds and the seismic signature of pyroxenites in the Earth's upper mantle.American Mineralogist, Vol. 105, pp. 984-991. pdfMantlediamond inclusions

Abstract: Majoritic garnet has been predicted to be a major component of peridotite and eclogite in Earth's deep upper mantle (>250 km) and transition zone. The investigation of mineral inclusions in diamond confirms this prediction, but there is reported evidence of other majorite-bearing lithologies, intermediate between peridotitic and eclogitic, present in the mantle transition zone. If these lithologies are derived from olivine-free pyroxenites, then at mantle transition zone pressures majorite may form monomineralic or almost monomineralic garnetite layers. Since majoritic garnet is presumably the seismically fastest major phase in the lowermost upper mantle, the existence of such majorite layers might produce a detectable seismic signature. However, a test of this hypothesis is hampered by the absence of sound wave velocity measurements of majoritic garnets with relevant chemical compositions, since previous measurements have been mostly limited to synthetic majorite samples with relatively simple compositions. In an attempt to evaluate the seismic signature of a pyroxenitic garnet layer, we measured the sound wave velocities of three natural majoritic garnet inclusions in diamond by Brillouin spectroscopy at ambient conditions. The chosen natural garnets derive from depths between 220 and 470 km and are plausible candidates to have formed at the interface between peridotite and carbonated eclogite. They contain elevated amounts (12-30%) of ferric iron, possibly produced during redox reactions that form diamond from carbonate. Based on our data, we model the velocity and seismic impedance contrasts between a possible pyroxenitic garnet layer and the surrounding peridotitic mantle. For a mineral assemblage that would be stable at a depth of 350 km, the median formation depth of our samples, we found velocities in pyroxenite at ambient conditions to be higher by 1.9(6)% for shear waves and 3.3(5)% for compressional waves compared to peridotite (numbers in parentheses refer to uncertainties in the last given digit), and by 1.3(13)% for shear waves and 2.4(10)% for compressional waves compared to eclogite. As a result of increased density in the pyroxenitic layer, expected seismic impedance contrasts across the interface between the monomineralic majorite layer and the adjacent rocks are about 5-6% at the majorite-eclogite-interface and 10-12% at the majoriteperidotite-boundary. Given a large enough thickness of the garnetite layer, velocity and impedance differences of this magnitude could become seismologically detectable.
DS202010-1872
2020
Stachel, T.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.
DS202105-0781
2021
Stachel, T.Pamato, M.G., Novella, D., Jacobs, D.E., Oliveira, B., Pearson, D.G., Greene, S., Alfonso, J.C., Favero, M., Stachel, T., Alvaro, M., Nestola, F.Protogenetic sulfide inclusions in diamonds date the diamond formation event using Re-Os isotopes. Victor, JerichoGeology , Vol. 49, 4, 5p. Canada, Ontario, Nunavutdiamond inclusions

Abstract: Sulfides are the most abundant inclusions in diamonds and a key tool for dating diamond formation via Re-Os isotopic analyses. The manner in which fluids invade the continental lithospheric mantle and the time scale at which they equilibrate with preexisting (protogenetic) sulfides are poorly understood yet essential factors to understanding diamond formation and the validity of isotopic ages. We investigated a suite of sulfide-bearing diamonds from two Canadian cratons to test the robustness of Re-Os in sulfide for dating diamond formation. Single-crystal X-ray diffraction (XRD) allowed determination of the original monosulfide solid-solution (Mss) composition stable in the mantle, indicating subsolidus conditions of encapsulation, and providing crystallographic evidence supporting a protogenetic origin of the inclusions. The results, coupled with a diffusion model, indicate Re-Os isotope equilibration is sufficiently fast in sulfide inclusions with typical grain size, at mantle temperatures, for the system to be reset by the diamond-forming event. This confirms that even if protogenetic, the Re-Os isochrons defined by these minerals likely reflect the ages of diamond formation, and this result highlights the power of this system to date the timing of fluid migration in mantle lithosphere.
DS2003-0549
2003
Stachel. T.Hanrahan, M., Stachel. T., Brey, G.P., Lahaye, Y.Garnet peridotite xenoliths from the Koffiefontein mine, South Africa8 Ikc Www.venuewest.com/8ikc/program.htm, Session 6, POSTER abstractSouth AfricaDeposit - Koffiefontein
DS201705-0870
2017
Stachel. T.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
DS201707-1362
2017
Stachnik, J.Schulte-Pelkum, V., Mahan, K., Shen, W., Stachnik, J.The distribution and composition of high velocity lower crust across the continental US: comparison of seismic and xenolith dat a and implications for lithospheric dynamics and history.Tectonics, in press availableUnited Statesgeophysics

Abstract: The magnetotelluric component of the EarthScope USArray program has covered over 35% of the continental United States. Resistivity tomography models derived from these data image lithospheric structure and provide constraints on the distribution of fluids and melt within the lithosphere. We present a three-dimensional resistivity model of the northwestern United States which provides new insight into the tectonic assembly of western North America from the Archean to present. Comparison with seismic tomography models reveals regions of correlated and anti-correlated resistivity and velocity that help identify thermal and compositional variations within the lithosphere. Recent (Neogene) tectonic features reflected in the model include the subducting Juan de Fuca–Gorda plate which can be traced beneath the forearc to more than 100 km depth, high lithospheric conductivity along the Snake River Plain, and pronounced lower-crustal and upper-mantle conductivity beneath the Basin and Range. The latter is abruptly terminated to the northwest by the Klamath–Blue Mountains Lineament, which we interpret as an important structure during and since the Mesozoic assembly of the region. This boundary is interpreted to separate hot extended lithosphere from colder, less extended lithosphere. The western edge of Proterozoic North America, as indicated by the Cretaceous initial 87Sr/86Sr = 0.706 contour, is clearly reflected in the resistivity model. We further image an Archean crustal block (“Pend Oreille block”) straddling the Washington/Idaho border, which we speculate separated from the Archean Medicine Hat block in the Proterozoic. Finally, in the modern Cascades forearc, the geometry and internal structure of the Eocene Siletz terrane is reflected in the resistivity model. The apparent eastern edge of the Siletz terrane under the Cascades arc suggests that pre-Tertiary rocks fill the Washington and Oregon back-arc.
DS200412-1914
2004
Stachnik, J.C.Stachnik, J.C., Abers, G.C., Christensen, D.H.Seismic attenuation and mantle wedge temperatures in the Alaska subduction zone.Journal of Geophysical Research, Vol. 109, B10, B10405 10.1029/2004 JBO3018United States, AlaskaGeophysics - seismics, geothermometry
DS201312-0360
2013
Stachnik, J.C.Hansen, S.M., Dueker, K.G., Stachnik, J.C., Aster, R.C., Karlstrom, K.E.A rootless rockies support and lithospheric structure of the Colorado Rocky Mountains inferred from CREST and TA seismic data.Geochemistry, Geophysics, Geosystems: G3, Vol. 14, 8, pp. 2670-2695.United StatesGeophysics - seismics
DS1995-1818
1995
Stack, B.Stack, B.Encyclopedia of tunnelling, mining and drilling equipmentMuden Publishing Co, GlobalBook -ad, Drilling, mining equipment review
DS200512-0849
2005
Stackhouse, S.Petford, N., Yuen, D., Rushmer, T.,Brodholt, J., Stackhouse, S.Shear induced material transfer across the core mantle boundary aided by the post perovskite phase transition.Earth Planets and Space, Vol. 57, 5, pp. 459-464.MantleMineralogy
DS200612-1543
2005
Stackhouse, S.Wookey, J., Stackhouse, S., Kendall, J.M., Brodholt, J., Price, G.D.Efficacy of the post perovskite phase as an explanation for lowermost mantle seismic properties.Nature, No. 7070, Dec. 15, pp. 1004-1007.MantlePetrology
DS201112-0693
2011
Stackhouse, S.Miyagi, L., Kanitpanyacharoen, W., Stackhouse, S., Wenk, H-R.The enigma of post perovskite anisotropy: deformation versus transformation textures.Physics and Chemistry of Minerals, Vol. 38, 9, pp. 665-678.MantleD layer - core mantle boundary
DS201312-0946
2013
Stackhouse, S.Walker, A.M., Ammann, M.W., Stackhouse, S., Wookey, J., Bordholdt, J.P., Dobson, D.Anisotropy: a cause of heat flux variation at the CMB?Goldschmidt 2013, 1p. AbstractMantlePerovskite
DS201502-0109
2014
Stacy, J.Stacy, J., Stacey, A.Perceptions of the impact of board members' individual perspectives on the social and environmental performance of companies. ( Based on SA and not junior companies).Journal of the South African Institute of Mining and Metallurgy, Vol. 114, Nov. pp. 957-969.Africa, South AfricaCSR
DS201212-0012
2012
Stadler, G.Alistic, L., Gurnis, M., Stadler, G., Burstedde, C., Ghattas, O.Multi scale dynamics and rheology of mantle flow with plates.Journal of Geophysical Research, Vol. 117, B10 B10402MantleTectonics
DS201312-0113
2013
Stadler, G.Burstedde, C., Stadler,G., Alisic, L., Wilcox, L.C., Tan, E.,Gurnis, M., Ghattas, O.Large scale adaptive mantle convection simulation.Geophysical Journal International, Vol. 192, no. 3, pp. 889-906.MantleConvection
DS2001-1123
2001
Stadler, R.Stadler, R., Ulmer, P.Phase relations of a serpentine composition between 5 and 14 GPa: significance of clinohumite and phase E.Contributions to Mineralogy and Petrology, Vol. 140, No. 6, pp. 670-79.MantleTransition zone - E as water carriers
DS1987-0364
1987
Stadnik, E.V.Komogorova, L.G., Stadnik, E.V., Federov, V.I.Phytogeochemical investigations in contours of kimberlite bodies. (Russian)Doklady Academy of Sciences Akademy Nauk SSSR, (Russian), Vol. 297, No. 2, pp. 468-470RussiaBlank
DS1987-0711
1987
Stadnik, V.A.Stadnik, V.A.Use of vein calcites for the prospecting of rare earthcarbonatites.(Russian)Geokhim. Rudoobraz., (Russian), Vol. 15, pp. 84-88RussiaBlank
DS1988-0635
1988
Stadnik, V.A.Shramenko, I.F., Stadnik, V.A., Kostyuchenko, N.G., Kotko, A.G.Rare elements in carbonate rocks of the Western part of theUkrainianshield.(Russian)Doklady Academy of Sciences Nauk Ukr., SSSR, (Russian), Ser. B., Geol. Khim. Biol. No. 2, pp. 31-34RussiaCarbonatite
DS1989-1444
1989
Stadnik, V.A.Stadnik, V.A., Shramenko, I.F.Carbonatites of the Malotersyansk alkali massif (USSR) (Russian)Geokhim. Rudoobraz., (in Russian), Vol. 17, pp. 57-61RussiaCarbonatite, Minettes
DS1989-0822
1989
Stadnik, Ye.V.Komogorova, L.G., Stadnik, Ye.V., Federov, V.I.Phytogeochemical surveys within kimberlite bodiesDoklady Academy of Science USSR, Earth Science Section, Vol. 297, No. 1-6, pp. 184-185RussiaUdachanaya, Dalnyaya, Zarnitsa, biochemistry, kimberlite fields, Geochemistry -dispersion
DS201705-0879
2017
Staebler, G.A.Staebler, G.A., Mitchell, C.Lands Immemorial.lithographie.org, No. 19, pp. 4-9.IndiaBook - history
DS1900-0276
1904
Stafford, O.F.Stafford, O.F.The Mineral Resources and Mineral Industry of Oregon for 190University OREGON Bulletin., N.S. Vol. 1, No. 4, 112P.United States, Oregon, Rocky MountainsGemstones
DS1994-1681
1994
Stagg, A.K.Stagg, A.K., Hammond, D.R.Environmental site assessments in the acquisition of industrial mineralassetsAmerican Institute of Mining, Metallurgical, and Petroleum Engineers (AIME) Preprint, Meeting held Albuquerque Feb. 14-17th, No. 94-75, 8pUnited StatesMining -environmental, Industrials
DS2002-1540
2002
Stagg, A.K.Stagg, A.K.The appraisal of mining enterprises - understanding and meeting the challengesFifth Joint Advanced Business Valuation Conference American Society of, Oct. 24-26, Orlando, Fla. 4p.United StatesEconomics - valuation, Standards, types of properties
DS200412-1379
2004
Stagg, H.M.J.Muller, R.D., Gaina, C., Struckmeyer, H.I.M., Stagg, H.M.J., Symonds, P.A.Formation and evolution of Australian passive margins: implications for locating the boundary between continental and oceanic crHillis, R.R., Muller, R.D. Evolution and dynamics of the Australian Plate, Geological Society America Memoir, No. 372, pp. 223-244.AustraliaTectonics
DS1975-0872
1978
Stagman, J.G.Stagman, J.G., Harrison, N.M., Broderick, T.J., Stocklmayer, V.An Outline of the Geology of RhodesiaRhodesia Geological Survey, Bulletin. No. 80, 126P.ZimbabweGeology, Kimberley
DS201012-0750
2010
Stagno, V.Stagno, V., Frost, D.J.Carbon speciation in the asthenosphere: experimental measurements of the redox conditions at which carbonate bearing melts coexist with graphite or diamond in peridotite assemblages.Earth and Planetary Science Letters, Vol. 300, 1-2, Nov. 15, pp. 72-84.MantlePeridotite, assemblages
DS201112-0996
2011
Stagno, V.Stagno, V., McCammon, C.A., Frost, D.J.High pressure calibration of the oxygen fugacity recorded by garnet bearing peridotites.Goldschmidt Conference 2011, abstract p.1928.MantleGraphite/diamond in peridotite mantle
DS201212-0701
2012
Stagno, V.Stagno, V., Fei, Y., McCammon, C.A., Frost, D.J.Redox equilibration temperatures within eclogite assemblages as function of pressure and temperature: implications for the deep carbon cycle.emc2012 @ uni-frankfurt.de, 1p. AbstractMantleRedox
DS201312-0282
2013
Stagno, V.Frost, D.J., Stagno, V., McCammon, C.A., Fei, Y.The stability of carbonate melt in eclogite rocks with respect to oxygen fugacity. Diamond formation.Goldschmidt 2013, AbstractMantleRedox
DS201412-0882
2014
Stagno, V.Stagno, V., Sverjensky, D., Sharar, A.Diamonds, carbonate melts and carbon-bearing aqueous fluids in eclogites. Goldschmidt Conference 2014, 1p. AbstractMantleEclogite
DS201503-0179
2015
Stagno, V.Stagno, V., Frost, D.J., McCammon, C.A., Mohseni, H., Fei, Y.The oxygen fugacity at which graphite or diamond forms from carbonate bearing melts in eclogitic rocks.Contributions to Mineralogy and Petrology, Vol. 169, 18p.TechnologyRedox, carbonatite, geobarometry
DS201609-1702
2016
Stagno, V.Aulbach, S., Stagno, V.Evidence for a reducing Archean ambient mantle and its effects on the carbon cycle.Geology, Vol. 44, 9, pp. 751-754.MantleRedox state

Abstract: Chemical reduction-oxidation mechanisms within mantle rocks link to the terrestrial carbon cycle by influencing the depth at which magmas can form, their composition, and ultimately the chemistry of gases released into the atmosphere. The oxidation state of the uppermost mantle has been widely accepted to be unchanged over the past 3800 m.y., based on the abundance of redox-sensitive elements in greenstone belt-associated samples of different ages. However, the redox signal in those rocks may have been obscured by their complex origins and emplacement on continental margins. In contrast, the source and processes occurring during decompression melting at spreading ridges are relatively well constrained. We retrieve primary redox conditions from metamorphosed mid-oceanic ridge basalts (MORBs) and picrites of various ages (ca. 3000-550 Ma), using V/Sc as a broad redox proxy. Average V/Sc values for Proterozoic suites (7.0 ± 1.4, 2s, n = 6) are similar to those of modern MORB (6.8 ± 1.6), whereas Archean suites have lower V/Sc (5.2 ± 0.4, n = 5). The lower Archean V/Sc is interpreted to reflect both deeper melt extraction from the uppermost mantle, which becomes more reduced with depth, and an intrinsically lower redox state. The pressure-corrected oxygen fugacity (expressed relative to the fayalite-magnetite-quartz buffer, ?FMQ, at 1 GPa) of Archean sample suites (?FMQ -1.19 ± 0.33, 2s) is significantly lower than that of post-Archean sample suites, including MORB (?FMQ -0.26 ± 0.44). Our results imply that the reducing Archean atmosphere was in equilibrium with Earth's mantle, and further suggest that magmatic gases crossed the threshold that allowed a build-up in atmospheric O2 levels ca. 3000 Ma, accompanied by the first "whiffs" of oxygen in sediments of that age.
DS201610-1842
2016
Stagno, V.Aubach, S., Stagno, V.Evidence for a reducing Archean ambient mantle and its effects on the carbon cycle.Geology, Vol. 44, 9, pp. 751-754.MantleRedox

Abstract: Chemical reduction-oxidation mechanisms within mantle rocks link to the terrestrial carbon cycle by influencing the depth at which magmas can form, their composition, and ultimately the chemistry of gases released into the atmosphere. The oxidation state of the uppermost mantle has been widely accepted to be unchanged over the past 3800 m.y., based on the abundance of redox-sensitive elements in greenstone belt-associated samples of different ages. However, the redox signal in those rocks may have been obscured by their complex origins and emplacement on continental margins. In contrast, the source and processes occurring during decompression melting at spreading ridges are relatively well constrained. We retrieve primary redox conditions from metamorphosed mid-oceanic ridge basalts (MORBs) and picrites of various ages (ca. 3000-550 Ma), using V/Sc as a broad redox proxy. Average V/Sc values for Proterozoic suites (7.0 ± 1.4, 2s, n = 6) are similar to those of modern MORB (6.8 ± 1.6), whereas Archean suites have lower V/Sc (5.2 ± 0.4, n = 5). The lower Archean V/Sc is interpreted to reflect both deeper melt extraction from the uppermost mantle, which becomes more reduced with depth, and an intrinsically lower redox state. The pressure-corrected oxygen fugacity (expressed relative to the fayalite-magnetite-quartz buffer, ?FMQ, at 1 GPa) of Archean sample suites (?FMQ -1.19 ± 0.33, 2s) is significantly lower than that of post-Archean sample suites, including MORB (?FMQ -0.26 ± 0.44). Our results imply that the reducing Archean atmosphere was in equilibrium with Earth's mantle, and further suggest that magmatic gases crossed the threshold that allowed a build-up in atmospheric O2 levels ca. 3000 Ma, accompanied by the first "whiffs" of oxygen in sediments of that age.
DS201612-2318
2016
Stagno, V.Lustrino, M., Agostini, S., Chalal, Y., Fedele, L., Stagno, V., Colombi, F., Bouguerra, A.Exotic lamproites or normal ultrapotassic rocks? The Late Miocene volcanic rocks from Kef Hahouner, NE Algeria, in the frame of the circum-Mediterranean lamproites.Journal of Volcanology and Geothermal Research, in press available 15p.Africa, AlgeriaLamproite

Abstract: The late Miocene (11-9 Ma) volcanic rocks of Kef Hahouner, ~ 40 km NE of Constantine (NE Algeria), are commonly classified as lamproites in literature. However, these rocks are characterized by an anhydrous paragenesis with plagioclase and Mg-rich olivine phenocrysts, set in a groundmass made up of feldspars, pyroxenes and opaque minerals. Thus, we classify the Kef Hahouner rocks as ultrapotassic shoshonites and latites, having K2O > 3 wt.%, K2O/Na2O > 2.5, MgO > 3-4 wt.%, SiO2 < 55-57 wt.% and SiO2/K2O < 15. All the investigated samples show primitive mantle-normalized multi-element patterns typical of orogenic (arc-type) magmas, i.e. enriched in LILE (e.g. Cs, Rb and Ba) and LREE (e.g. La/Yb = 37-59) with respect to the HFSE, peaks at Pb and troughs at Nb and Ta. Initial isotopic ratios are in the range of 87Sr/86Sr = 0.70874-0.70961, 143Nd/144Nd = 0.51222-0.51223, 206Pb/204Pb = 18.54-18.60, 207Pb/204Pb = 15.62-15.70 and 208Pb/204Pb = 38.88-39.16. The Kef Hahouner volcanic rocks show multi-element patterns similar to the other circum-Mediterranean lamproites and extreme Sr, Nd and Pb isotopic compositions. Nevertheless, the abundant plagioclase, the presence of Al-rich augite coupled with high Al2O3 whole rock compositions (9.6-21.4 wt.%), and the absence of phlogopite are all at inconsistent with the definition of lamproite. We reviewed the rocks classified as lamproites worldwide, and found that many of these rocks, as for the Kef Hahouner samples, should be actually defined as "normal" potassic to ultrapotassic volcanic rocks. Even the grouping of lamproites into "orogenic" and "anorogenic" types appears questionable.
DS201709-1970
2017
Stagno, V.Caruso, M., Stagno, V.The Transition from carbonatitic to carbonate silicate magmas in carbonated elogitic rocks as function of pressure, temperature and oxygen fugacity.Goldschmidt Conference, abstract 1p.Mantlecarbonatite

Abstract: The deep carbon cycle and the origin of carbonatitic melts into the Earth’s mantle have been studied through the effect of CO2 on phase equilibria within carbonated eclogitic assemblage in the last decades. However the effect of temperature (T), pressure (P) and oxygen fugacity (fO2) on the melt composition remains unclear. This study aims to determine the melt composition of CO2-rich melts at fO2 buffered by the C/carbonate equilibrium as function of P and T. Experiments were performed using the Voggenreiter 840 t, Walker-type multi anvil press available at HP/HT Lab at National Institute of Geophysics and Volcanology (INGV) in Rome. The starting material employed for all the experiments is a mixture of synthetic omphacitic glass, quartz, dolomite and graphite representative of the Dolomite-CoesiteDiopside-Graphite buffering assemblage [DCDG; 1], doped with ilmenite and rutile and ~3 wt% iridium used as redox sensor to monitorate the oxygen fugacity during the experiment. The recovered quenched samples were polished for textural and chemical analysis of the mineral phases using Field emission scanning electron microscope and electron microprobe at the INGV. Preliminary results were combined with previous published data [2], and the determined fo2 compared with thermodynamic predictions. The obtained data show that at 800°C run product consists of a subsolidus mineral assemblage representative of the DCDG mineral assemblage. With increasing temperature, a carbonatitic melt forms with 1-5 wt% SiO2 at 900 °C, then evolves to a carbonate-silicate melt with 25 wt% SiO2 at 1100 °C, and to a silicate melt with ~32 wt% SiO2 at 1200 °C. Preliminary results demonstrate that magmas with compositions from carbonatitic to carbonate-silicate (hybrid) melts can form within less than 1 log unit of fO2 by redox melting of elemental carbon-bearing eclogite rocks.
DS201709-2059
2017
Stagno, V.Stagno, V., Kono, Y., Greaux, S., Kebukawa, Y., Stopponi, V., Scarlato, P., Lustrino, M., Irifune, T.From carbon in meteorites to carbonatite rocks on Earth.Goldschmidt Conference, abstract 1p.Globalcarbonatite

Abstract: The composition of the early Earth’s atmosphere is believed to result from significant magma outgassing during the Archaean eon. It has been widely debated whether the oxygen fugacity (fo2) of the Earth’s mantle has remained constant over the last ~3.8 Ga to levels where volatiles were mostly in their mobile form [1,2], or whether the mantle has experienced a gradual increase of its redox state [3]. Both hypotheses raise fundamental questions on the effect of composition of the early Earth’s accreting material, the origin and availability of primordial carbon in Earth’s interior, and the migration rate of CO2-rich magmas. In addition, the occurrence in nature of carbonatites (or silicate-carbonatitic rocks), diamonds and carbides indicate a dominant control of the mantle redox state on the volatile speciation over time and, maybe, on mechanisms of their formation, reaction and migration through the silicate mantle. A recent model has been developed that combines both experimental results on the fo2 of preserved carbonaceous chondrites at high pressure and thermodynamic predictions of the the temporal variation of the mantle redox state, with the CO2-bearing magmas that could form in the early asthenospheric mantle. Since any variation in melt composition is expected to cause significant changes in the physical properties (e.g., viscosity and density), the migration rate of these magmas has been determined using recent in situ viscosity data on CO2-rich melts with the falling sphere technique. Our results allow determining the composition of CO2- bearing magmas as function of the increasing mantle redox state over time, and the mechanisms and rate for exchange of carbon between mantle reservoirs.
DS201812-2888
2018
Stagno, V.Stagno, V., Stopponi, V., Kono, Y., Manning, C.E., Irifune, T.Experimenal determination of the viscosity of Na2CO3 melt between 1.7 and 4.6 Gpa at 1200-1700 C: implications for the rheology of carbonatite magmas in the Earth's upper mantle.Chemical Geology, Vol. 501, pp. 19-25.Mantlecarbonatite

Abstract: Knowledge of the rheology of molten materials at high pressure and temperature is required to understand magma mobility and ascent rate at conditions of the Earth's interior. We determined the viscosity of nominally anhydrous sodium carbonate (Na2CO3), an analogue and ubiquitous component of natural carbonatitic magmas, by the in situ “falling sphere” technique at 1.7, 2.4 and 4.6?GPa, at 1200 to 1700?°C, using the Paris-Edinburgh press. We find that the viscosity of liquid Na2CO3 is between 0.0028?±?0.0001?Pa•s and 0.0073?±?0.0001?Pa•s in the investigated pressure-temperature range. Combination of our results with those from recent experimental studies indicate a negligible dependence on pressure from 1?atm to 4.6?GPa, and a small compositional dependence between molten alkali metal-bearing and alkaline earth metal-bearing carbonates. Based on our results, the viscosity of Na2CO3 is consistent with available viscosity data of both molten calcite (determined at high pressure and temperature) and Na2CO3 at ambient pressure. Molten Na2CO3 is a valid experimental analogue for study of the rheology of natural and/or synthetic near-solidus carbonatitic melts. Estimated values of the mobility and ascent velocity of carbonatitic melts at upper conditions are between 70 and 300?g?cm-3•Pa-1•s-1 and 330-1450?m•year-1, respectively, when using recently proposed densities for carbonatitic melts. The relatively slow migration rate allows magma-rock interaction over time causing seismic anomalies and chemical redox exchange.
DS201902-0323
2019
Stagno, V.Stagno, V.Carbon, carbides, carbonates and carbonatitic melts in the Earth's interior.Researchgate preprint, 10.31223/ofs.io/uh5c8 40p. PdfMantlecarbonatite

Abstract: Over the last decades, many experimental studies have focused on the effect of CO2 on phase equilibria and melting behavior of synthetic eclogite and peridotite rocks as function of pressure and temperature. These studies have been of fundamental importance to understanding the origin of carbonated magmas varying in composition from carbonatitic to kimberlitic. The occurrence of diamonds in natural rocks is a further evidence of the presence of (reduced) carbon in the Earth’s interior. The oxygenation of the Earth’s interior (i.e. its redox state) through time has strongly influenced the speciation of carbon from the mantle to mantle-derived magmas and, in turn, to the released volcanic gases to the atmosphere. This paper explains how the knowledge of the oxygen fugacity recorded by mantle rocks and determined through the use of appropriate oxy-thermobarometers allows modeling the speciation of carbon in the mantle, its mobilization in the asthenospheric mantle by redox partial melting, and its sequestration and storage during subduction by redox freezing processes. The effect of a gradual increase of the mantle fo2 on the mobilization of C is here discussed along with the main variables affecting its transport by subduction down to the mantle.
DS201904-0784
2018
Stagno, V.Stagno, V.Carbon, carbides, carbonates and carbonatitic melts in the Earth's interior.Journal of the Geological Society of London, Vol. 176, pp. 375-387.Globalcarbonatite

Abstract: Over the last decades, many experimental studies have focused on the effect of CO2 on phase equilibria and melting behavior of synthetic eclogite and peridotite rocks as function of pressure and temperature. These studies have been of fundamental importance to understanding the origin of carbonated magmas varying in composition from carbonatitic to kimberlitic. The occurrence of diamonds in natural rocks is a further evidence of the presence of (reduced) carbon in the Earth’s interior. The oxygenation of the Earth’s interior (i.e. its redox state) through time has strongly influenced the speciation of carbon from the mantle to mantle-derived magmas and, in turn, to the released volcanic gases to the atmosphere. This paper explains how the knowledge of the oxygen fugacity recorded by mantle rocks and determined through the use of appropriate oxy-thermobarometers allows modeling the speciation of carbon in the mantle, its mobilization in the asthenospheric mantle by redox partial melting, and its sequestration and storage during subduction by redox freezing processes. The effect of a gradual increase of the mantle fo2 on the mobilization of C is here discussed along with the main variables affecting its transport by subduction down to the mantle.
DS202004-0534
2020
Stagno, V.Stagno, V., Stopponi, V., Kono, Y., D'Arco, A., Lupi, S., Romano, C., Poe, B.T., Foustoukos, D.J., Scarlato, P., Manning, C.E.The viscosity and atomic structure of volatile bearing melililititic melts at high pressure and temperature and the transport of deep carbon.Minerals MDPI, Vol. 10, 267 doi: 10.23390/min10030267 14p. PdfMantleMelililite, carbon

Abstract: Understanding the viscosity of mantle-derived magmas is needed to model their migration mechanisms and ascent rate from the source rock to the surface. High pressure-temperature experimental data are now available on the viscosity of synthetic melts, pure carbonatitic to carbonate-silicate compositions, anhydrous basalts, dacites and rhyolites. However, the viscosity of volatile-bearing melilititic melts, among the most plausible carriers of deep carbon, has not been investigated. In this study, we experimentally determined the viscosity of synthetic liquids with ~31 and ~39 wt% SiO2, 1.60 and 1.42 wt% CO2 and 5.7 and 1 wt% H2O, respectively, at pressures from 1 to 4.7 GPa and temperatures between 1265 and 1755 °C, using the falling-sphere technique combined with in situ X-ray radiography. Our results show viscosities between 0.1044 and 2.1221 Pa•s, with a clear dependence on temperature and SiO2 content. The atomic structure of both melt compositions was also determined at high pressure and temperature, using in situ multi-angle energy-dispersive X-ray diffraction supported by ex situ microFTIR and microRaman spectroscopic measurements. Our results yield evidence that the T-T and T-O (T = Si,Al) interatomic distances of ultrabasic melts are higher than those for basaltic melts known from similar recent studies. Based on our experimental data, melilititic melts are expected to migrate at a rate ~from 2 to 57 km•yr-1 in the present-day or the Archaean mantle, respectively.
DS202009-1606
2020
Stagno, V.Anzolini, C., Marquardt, K., Stagno, V., Nestola, F.Evidence for complex iron oxides in the deep mantle from FeNi(Cu) inclusions in superdeep diamondsProceedings of the National Academy of Sciences, pnas.org/cgi/doi.10.1073 /pnas.2004269117 7p. PdfMantlediamond inclusions

Abstract: The recent discovery in high-pressure experiments of compounds stable to 24-26 GPa with Fe4O5, Fe5O6, Fe7O9, and Fe9O11 stoichiometry has raised questions about their existence within the Earth’s mantle. Incorporating both ferric and ferrous iron in their structures, these oxides if present within the Earth could also provide insight into diamond-forming processes at depth in the planet. Here we report the discovery of metallic particles, dominantly of FeNi (Fe0.71Ni0.24Cu0.05), in close spatial relation with nearly pure magnetite grains from a so-called superdeep diamond from the Earth’s mantle. The microstructural relation of magnetite within a ferropericlase (Mg0.60Fe0.40)O matrix suggests exsolution of the former. Taking into account the bulk chemistry reconstructed from the FeNi(Cu) alloy, we propose that it formed by decomposition of a complex metal M oxide (M4O5) with a stoichiometry of (Fe3+2.15Fe2+1.59Ni2+0.17Cu+0.04)S = 3.95O5. We further suggest a possible link between this phase and variably oxidized ferropericlase that is commonly trapped in superdeep diamond. The observation of FeNi(Cu) metal in relation to magnetite exsolved from ferropericlase is interpreted as arising from a multistage process that starts from diamond encapsulation of ferropericlase followed by decompression and cooling under oxidized conditions, leading to the formation of complex oxides such as Fe4O5 that subsequently decompose at shallower P-T conditions.
DS202009-1667
2020
Stagno, V.Stagno, V., Fei, Y.The redox boundaries of Earth's interiors.Elements, Vol. 16, 3, pp. 167-172.Mantleredox

Abstract: he interior of the Earth is an important reservoir for elements that are chemically bound in minerals, melts, and gases. Analyses of the proportions of redox-sensitive elements in ancient and contemporary natural rocks provide information on the temporal redox evolution of our planet. Natural inclusions trapped in diamonds, xenoliths, and erupted magmas provide unique windows into the redox conditions of the deep Earth, and reveal evidence for heterogeneities in the mantle’s oxidation state. By examining the natural rock record, we assess how redox boundaries in the deep Earth have controlled elemental cycling and what effects these boundaries have had on the temporal and chemical evolution of oxygen fugacity in the Earth’s interior and atmosphere.
DS202012-2234
2020
Stagno, V.Mikhailenko, D.S., Stagno, V., Korsakov, A.V., Andreozzi, G.B., Marras, G., Cerantola, V., Malygina, E.V.Redox state determination of eclogite xenoliths from Udachnaya kimberlite pipe ( Siberian craton), with some implications for the graphite/diamond formation.Contributions to Mineralogy and Petrology, Vol. 175, 107, 17p. PdfRussiadeposit - Udachnaya

Abstract: The formation of diamonds within eclogitic rocks has been widely linked to the fate of carbon during subduction and, therefore, referred to conditions of pressure, temperature, and oxygen fugacity (fo2). Mantle-derived eclogite xenoliths from Udachnaya kimberlite pipes represent a unique window to investigate the formation of carbon-free, graphite-diamond-bearing and diamond-bearing rocks from the Siberian craton. With this aim, we exploited oxy-thermobarometers to retrieve information on the P-T-fo2 at which mantle eclogites from the Siberian craton equilibrated along with elemental carbon. The chemical analyses of coupled garnet and omphacitic clinopyroxene were integrated with data on their iron oxidation state, determined both by conventional and synchrotron 57Fe Mössbauer spectroscopy. The calculated fo2s largely vary for each suite of eclogite samples from 0.10 to - 2.43 log units (?FMQ) for C-free eclogites, from - 0.01 to - 2.91 (?FMQ) for graphite-diamond-bearing eclogites, and from - 2.08 to - 3.58 log units (?FMQ) for diamond-bearing eclogites. All eclogite samples mostly fall in the fo2 range typical of diamond coexisting with CO2-rich water-bearing melts and gaseous fluids, with diamondiferous eclogites being more reduced at fo2 conditions where circulating fluids can include some methane. When uncertainties on the calculated fo2 are taken into account, all samples essentially fall within the stability field of diamonds coexisting with CO2-bearing melts. Therefore, our results provide evidence of the potential role of CO2-bearing melts as growth medium on the formation of coexisting diamond and graphite in mantle eclogites during subduction of the oceanic crust.
DS202103-0411
2018
Stagno, V.Stagno, V.Carbon, carbides, carbonates and carbonatitic melts in the Earth's interiors. *** NOTE DATEresearchgate, doi:10.31223/ osf.io/uhSc8 40p. PdfMantlecarbonatite

Abstract: Over recent decades, many experimental studies have focused on the effect of CO2 on phase equilibria and melting behaviour of synthetic eclogites and peridotites as a function of pressure and temperature. These studies have been of fundamental importance to understanding the origin of carbonated magmas varying in composition from carbonatitic to kimberlitic. The occurrence of diamonds in natural rocks is further evidence of the presence of (reduced) carbon in the Earth's interior. The oxygenation of the Earth's interior (i.e. its redox state) through time has strongly influenced the speciation of carbon from the mantle to mantle-derived magmas and, in turn, to the volcanic gases released to the atmosphere. This paper explains how the knowledge of the oxygen fugacity recorded by mantle rocks and determined through the use of appropriate oxy-thermobarometers allows modelling of the speciation of carbon in the mantle, its mobilization in the asthenospheric mantle by redox partial melting, and its sequestration and storage during subduction by redox freezing processes. The effect of a gradual increase of the mantle fO2 on the mobilization of C is here discussed along with the main variables affecting its transport by subduction into the mantle.
DS2003-1250
2003
Stahel, T.Seitz, H-M., Brey, G.P., Stahel, T., Harris, J.W.Li abundances in inclusions in diamonds from the upper and lower mantleChemical Geology, Vol. 201, 3-4, Nov. 28, pp. 307-318.MantleBlank
DS200412-1784
2003
Stahel, T.Seitz, H-M., Brey, G.P., Stahel, T., Harris, J.W.Li abundances in inclusions in diamonds from the upper and lower mantle.Chemical Geology, Vol. 201, 3-4, Nov. 28, pp. 307-318.MantleDiamond inclusions, eclogites, peridotites, websterite.
DS2000-0322
2000
Stahl, A.Geiger, C.A., Stahl, A., Rossman, G.R.Single crystal IR and UV VIS spectroscopic measurements on transition metal bearing pyrope: incorporation...European Journal of Mineralogy, Vol. 12, pp. 259-71.GlobalPyrope mineralogy - hydroxide in garnet, Spectroscopy - pyrope
DS1900-0221
1903
Stahl, A.F.Stahl, A.F.Diamanten Producktion in der Kapkolonie, 1883-1901Deut. Handelsarchiv. (berlin), Africa, South AfricaEconomics
DS1995-0773
1995
Stahl, S.Hausel, W.D., Stahl, S.The Great Diamond Hoax of 1872Wyoming Geol. Association Field Conference Guidebook, pp. 13-28.ColoradoHistory -diamond hoax 1872
DS1995-0482
1995
Staillard, R.F.Edmond. J.M., Palmer, M.R., Staillard, R.F.The fluvial geochemistry and denudation rate of the Guyana shield inVenezuela, Colombia and Brasil.Geochimica et Cosmochimica Acta, Vol. 59, No. 16, August 1, pp. 3301-3326.Venezuela, Colombia, BrazilGeochemistry, Geomorphology
DS1990-0685
1990
Stainstreet, I.G.Henry, G., Clendenin, C.W., Stainstreet, I.G., Maiden, K.J.Multiple detachment model for the early rifting stAge of Late Proterozoic Damara orogen in NamibiaGeology, Vol. 18, No. 1, January pp. 67-71Southwest Africa, NamibiaTectonics, Damara orogen
DS1990-0477
1990
Stal, A.N.Fodor, R.V., Stal, A.N., Mukasa, S.B., McKee, E.H.Petrology, isotope characteristics, and K-Ar ages Of the Maranhao, Northern Brasil, Mesozoic basaltprovinceContributions to Mineralogy and Petrology, Vol. 104, No. 5, pp. 555-567BrazilBasalt, Maranhao
DS1998-1400
1998
Stalder, R.Stalder, R., Foley, S.F., Brey, G., Horn, I.Mineral aqueous fluid partitioning of trace elements at 900 1200 C and 3.0- 5.7 GPa: garnet, clinopyroxeneGeochimica et Cosmochimica Acta, Vol. 62, No. 10, pp. 1781-1801.MantleMetasomatism, Petrology - experimental
DS1998-1401
1998
Stalder, R.Stalder, R., Foley, S.F., Brey, G.P., Forsythe, HornFirst results from a new experimental technique to determine fluid/solidtrace element partition coeffic.Neues Jahrbuch fnr Mineralogie Abh., Vol. 172, No. 1, pp. 117-132.GlobalPetrology - experimental, Diamond aggregates
DS2001-1124
2001
Stalder, R.Stalder, R., Ulmer, P., Gunther, D.high pressure fluids in the system MgO SiO2H2 under upper mantle conditionsContributions to Mineralogy and Petrology, Vol. 140, No. 5, pp. 607-18.MantlePressure
DS201112-1019
2011
Stalder, R.Sundvall, R., Stalder, R.Water in upper mantle pyroxene megacrysts and xenocrysts: a survey study.American Mineralogist, Vol. 96, 8-9, pp. 1215-1227.Africa, Lesotho, United States, ColoradoMineral chemistry
DS201508-0377
2015
Stalder, R.Tappert, M.C., Rivard, B., Fulop, A., Rogge, D., Feng, J., Tappert, R., Stalder, R.Characterizing kimberlite dilution by crustal rocks at the Snap Lake diamond mine ( Northwest Territories, Canada) using SWIR ( 1.90-2.36 um) and LWIR ( 8.1-11.1um) hypersprectal imagery collected from drill core.Economic Geology, Vol. 110, 6, Sept-Oct. pp. 1375-1387.Canada, Northwest TerritoriesDeposit - Snap Lake
DS201511-1878
2015
Stalder, R.Schmadicke, E., Gose, J., Reinhardt, J., Will, T.M., Stalder, R.Garnet in cratonic and non-cratonic mantle and lower crustal xenoliths from southern Africa: composition, water in corporation and geodynamic constraints.Precambrian Research, Vol. 270, pp. 285-299.Africa, South Africa, Lesotho, NamibiaKaapvaal craton, Rehoboth Terrane

Abstract: Garnets from kimberlite-hosted mantle and a few xenoliths from the lower crust were investigated for water, major, minor, and trace elements. Xenoliths from the mantle comprise pyroxenite, eclogite, alkremite, and peridotite, and crustal xenoliths are mafic high-pressure granulites. Samples from South Africa, Lesotho, and Namibia comprise two principal settings, Kaapvaal Craton (‘on craton’) and Rehoboth terrane (‘off craton’). The composition of garnet depends on rock type but is unrelated to the setting, except for Ti and Cr. In garnets from ‘off craton’ mantle xenoliths, Ti positively correlates with Cr whereas those from ‘on craton’ samples reveal a negative correlation between both elements. Rare earth element patterns indicative of a metasomatic overprint are observed in garnets from both settings, especially in eclogitic garnet. Water contents in garnet are low and range from <1 to about 40 ppm. No setting-related difference occurs, but a weak correlation between water and rock type exists. Water contents in garnets from eclogite and mafic granulite are lower than those in pyroxenite, alkremite, and peridotite. All garnets are water under-saturated, i.e. they do not contain the maximum amount of water that can be accommodated in the mineral structure. Cratonic and non-cratonic samples also show the same characteristics in the infrared (IR) absorption spectra. An absorption band at 3650 cm-1 is typical for most mantle garnets. Bands at 3520 and 3570 cm-1 are present only in TiO2-rich garnets from the Rehoboth terrane and are ascribed to a Ti-related hydrogen substitution. A number of garnets, especially from the Kaapvaal Craton, contain molecular water in addition to structural water. Molecular water is inhomogeneously distributed at grain scale pointing to local interaction with fluid and to disequilibrium at grain scale. These garnets consistently reveal either submicroscopic hydrous phases or additional IR bands at 3630 and 3610-3600 cm-1 caused by structural water. Both features do not occur in garnets in which molecular water is absent. The observations imply (i) relatively late introduction of fluid, at least in cases where hydrous phases formed, and (ii) a relatively dry environment because only water-deficient garnets are able to incorporate additional structural water. Most importantly, they imply (iii) that the low water contents are primary and not due to water loss during upward transport. This late water influx is not responsible for the metasomatic overprint indicated by garnet REE patterns. The results of this study suggest dry conditions in the lithosphere, including mantle and crustal sections of both the Kaapvaal Craton (‘on craton’) and the Rehoboth terrane (‘off craton’). If the low water contents contributed to the stabilization of the Kaapvaal cratonic root (Peslier et al., 2010) the same should apply to the Rehoboth lithosphere where the same variety of rock types occurs. The extremely low water contents in eclogite relative to pyroxenite may be explained by an oceanic crust origin of the eclogites. Subduction and partial melting would cause depletion of water and incompatible elements. The pyroxenites formed by crystal accumulation in the mantle and did not suffer melt depletion. Such a difference in origin can be reconciled with the low Ti contents in eclogitic garnet and the high Ti contents in pyroxenitic garnet.
DS201809-2022
2018
Stalder, R.Frigo, C., Stalder, R., Ludwig, T.OH defects in coesite and stishovite during ultrahigh-pressure metamorphism of continental crust. Dora Maira, Kochetav massifsPhysics and Chemistry of Minerals, dor.org/10.1007/ d00269-018-0987-5 13p.Russia, Kazakhstan, Alpscoesite, UHP

Abstract: The high-pressure silica polymorphs coesite and stishovite were synthesized under water-saturated conditions from a natural granitic composition doped with Li and B. Experiments were performed in a Multi-Anvil apparatus between 4 and 9.1 GPa and 900 and 950 °C, based on the conditions of a subducting continental crust as realistic for the ultrahigh-pressure metamorphic units Dora Maira and Kochetav massifs. Run products consisted of coesite/stishovite?+?kyanite?±?phengite?±?omphacite, and quench material. The synthesized silica polymorphs were successively analyzed by infrared spectroscopy, electron microprobe, and Secondary-Ion Mass Spectrometry (SIMS). No hydrous defects were observed in coesite synthesized at 4 GPa and 900 °C, whereas coesite grown at higher pressures revealed a triplet of infrared absorptions bands at 3575, 3523, and 3459 cm-?1, two minor bands at 3535 and 3502 cm-?1, and a small band at 3300 cm-?1 that was only visible at 7.7 GPa. The total amount of Al was charge-balanced by H and the other monovalent cations. However, the band triplet could not be associated with AlOH defects, while the band doublet was inferred to BOH defects and the small band probably corresponded to interstitial H. Stishovite displayed one dominant band at 3116 cm-?1 with a shoulder at 3170 cm-?1, and a minor band at 2665 cm-?1, probably all associated with AlOH defects. BOH defects were not observed in stishovite, and LiOH defects were neither observed in coesite nor stishovite, probably because of preferentially partition of Li in other phases such as omphacite. The total amount of defect protons increased with pressure and with metal impurity concentrations. The general increase in OH defects in silica polymorphs with increasing pressure (this study) contrasted the negative pressure trend of OH in quartz observed previously from the same starting material, and revealed an incorporation minimum of OH in silica polymorphs around the quartz/coesite phase transition.
DS201903-0510
2019
Stalder, R.Frigo, C., Stalder, R., Ludwig, T.OH defects in coesite and stishovite during ultrahigh-pressure metamorphism of continental crust. Dora Massif, KochetavPhysics and Chemistry of Minerals, Vol. 46, pp. 77-89.Russia, Europe, AlpsUHP

Abstract: The high-pressure silica polymorphs coesite and stishovite were synthesized under water-saturated conditions from a natural granitic composition doped with Li and B. Experiments were performed in a Multi-Anvil apparatus between 4 and 9.1 GPa and 900 and 950 °C, based on the conditions of a subducting continental crust as realistic for the ultrahigh-pressure metamorphic units Dora Maira and Kochetav massifs. Run products consisted of coesite/stishovite?+?kyanite?±?phengite?±?omphacite, and quench material. The synthesized silica polymorphs were successively analyzed by infrared spectroscopy, electron microprobe, and Secondary-Ion Mass Spectrometry (SIMS). No hydrous defects were observed in coesite synthesized at 4 GPa and 900 °C, whereas coesite grown at higher pressures revealed a triplet of infrared absorptions bands at 3575, 3523, and 3459 cm-?1, two minor bands at 3535 and 3502 cm-?1, and a small band at 3300 cm-?1 that was only visible at 7.7 GPa. The total amount of Al was charge-balanced by H and the other monovalent cations. However, the band triplet could not be associated with AlOH defects, while the band doublet was inferred to BOH defects and the small band probably corresponded to interstitial H. Stishovite displayed one dominant band at 3116 cm-?1 with a shoulder at 3170 cm-?1, and a minor band at 2665 cm-?1, probably all associated with AlOH defects. BOH defects were not observed in stishovite, and LiOH defects were neither observed in coesite nor stishovite, probably because of preferentially partition of Li in other phases such as omphacite. The total amount of defect protons increased with pressure and with metal impurity concentrations. The general increase in OH defects in silica polymorphs with increasing pressure (this study) contrasted the negative pressure trend of OH in quartz observed previously from the same starting material, and revealed an incorporation minimum of OH in silica polymorphs around the quartz/coesite phase transition.
DS200412-0407
2004
Stalker, K.das Gupta, R., Stalker, K., Withers, A.C., Hirschmann, M.M.The transition from carbonate rich to silicate rich melts in eclogite: partial melting experiments of carbonated eclogite at 3 GLithos, ABSTRACTS only, Vol. 73, p. S23. abstractTechnologyEclogite
DS200612-0308
2006
Stalker, K.Das Gupta, R., Hirschmann, M.M., Stalker, K.Immiscible transition from carbonate rich to silicate rich melts in the 3 GPa melting interval of eclogite + CO2 and genesis of silica undersaturated Oceanic lavas.Journal of Petrology, Vol. 47, 4, April pp. 647-671.Mantle, Oceanic IslandCarbonatite, eclogites
DS1992-1750
1992
Stam, J.M.T.Zijl, W., Stam, J.M.T.Modeling permeability in imperfectly layered porous media. 1. derivation of block scale permeability tensor for thin grid blocksMathematical Geology, Vol. 24, No. 8, November pp. 865-884GlobalGeostatistics, Grid blocks
DS201708-1772
2017
Stamm, N.Stamm, N.The petrology and mineralogy of the kimberlite blow in Letseng la Terae: implications for its parental magma.11th. International Kimberlite Conference, PosterAfrica, Lesothodeposit - Letseng la terae
DS201709-2060
2017
Stamm, N.Stamm, N., Schmidt, M.W.Asthenospheric kimberlites: volatile contents and bulk compositions at 7 Gpa.Earth and Planetary Science Letters, Vol. 474, pp. 309-321.Canada, Nunavutdeposit - Jericho

Abstract: During ascent, kimberlites react with the lithospheric mantle, entrain and assimilate xenolithic material, loose volatiles and suffer from syn- and post-magmatic alteration. Consequently, kimberlite rocks deviate heavily from their primary melt. Experiments at 7 GPa, 1300–1480?°C, 10–30 wt% CO2 and 0.46 wt% H2O on a proposed primitive composition from the Jericho kimberlite show that saturation with a lherzolitic mineral assemblage occurs only at 1300–1350?°C for a carbonatitic melt with <8 wt% SiO2 and >35 wt% CO2. At asthenospheric temperatures of >1400?°C, where the Jericho melt stays kimberlitic, this composition saturates only in low-Ca pyroxene, garnet and partly olivine. We hence forced the primitive Jericho kimberlite into multiple saturation with a lherzolitic assemblage by adding a compound peridotite. Saturation in olivine, low- and high-Ca pyroxene and garnet was obtained at 1400–1650 °C (7 GPa), melts are kimberlitic with 18–29 wt% SiO2 + Al2O3, 22.1–24.6 wt% MgO, 15–27 wt% CO2 and 0.4–7.1 wt% H2O; with a trade-off of H2O vs. CO2 and temperature. Melts in equilibrium with high-Ca pyroxene with typical mantle compositions have =2.5 wt% Na2O, much higher than the commonly proposed 0.1–0.2 wt%. The experiments allow for a model of kimberlite origin in the convective upper mantle, which only requires mantle upwelling that causes melting at the depth where elemental carbon (in metal, diamond or carbide) converts to CO2 (at ~250 km). If primary melts leading to kimberlites contain a few wt% H2O, then adiabatic temperatures of 1400–1500?°C would yield asthenospheric mantle melts that are kimberlitic (>18 wt% SiO2 + Al2O3) but not carbonatitic (<10 wt% SiO2 + Al2O3) in composition, carbonatites only forming 100–200?°C below the adiabat. These kimberlites represent small melt fractions concentrating CO2 and H2O and then acquire part of their chemical signature by assimilation/fractionation during ascent in the subcratonic lithosphere.
DS201810-2381
2018
Stamm, N.Stamm, N., Schmidt. M.W., Szymanowski, D., von Quadt, A., Mohapi, T., Fourie, A.Primary petrology, mineralogy and age of the Letseng-la-Terae kimberlite ( Lesotho), southern Africa) and parental magmas of Group 1 kimberlites.Contributions to Mineralogy and Petrology, Vol. 173, pp. 76- doi.org/10.1007/ s00410-018-1502-1Africa, Lesothodeposit - Letseng

Abstract: The Letšeng-la-Terae kimberlite (Lesotho), famous for its large high-value diamonds, has five distinct phases that are mined in a Main and a Satellite pipe. These diatreme phases are heavily altered but parts of a directly adjacent kimberlite blow are exceptionally fresh. The blow groundmass consists of preserved primary olivine with Fo86-88, chromite, magnesio-ulvöspinel and magnetite, perovskite, monticellite, occasional Sr-rich carbonate, phlogopite, apatite, calcite and serpentine. The bulk composition of the groundmass, extracted by micro-drilling, yields 24-26 wt% SiO2, 20-21 wt% MgO, 16-19 wt% CaO and 1.9-2.1 wt% K2O, the latter being retained in phlogopite. Without a proper mineral host, groundmass Na2O is only 0.09-0.16 wt%. However, Na-rich K-richterite observed in orthopyroxene coronae allows to reconstruct a parent melt Na2O content of 3.5-5 wt%, an amount similar to that of highly undersaturated primitive ocean island basanites. The groundmass contains 10-12 wt% CO2, H2O is estimated to 4-5 wt%, but volatiles and alkalis were considerably reduced by degassing. Mg# of 77.9 and 530 ppm Ni are in equilibrium with olivine phenocrysts, characterize the parent melt and are not due to olivine fractionation. 87Sr/86Sr(i)?=?0.703602-0.703656, 143Nd/144Nd(i)?=?0.512660 and 176Hf/177Hf(i)?=?0.282677-0.282679 indicate that the Letšeng kimberlite originates from the convective upper mantle. U-Pb dating of groundmass perovskite reveals an emplacement age of 85.5?±?0.3 (2s) Ma, which is significantly younger than previously proposed for the Letšeng kimberlite.
DS201012-0469
2010
Stammer, J.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
DS200912-0304
2009
Stammer, J.G.Hoal, K., Appleby, S.K., Stammer, J.G.Understanding garnet variability: application of geometallurgy to diamonds and exploration.GAC/MAC/AGU Meeting held May 23-27 Toronto, Abstract onlyTechnologyGarnet chemistry
DS200912-0305
2009
Stammer, J.G.Hoal, K.O., Appleby, S.K., Stammer, J.G., Palmer, C.SEM based quantitative mineralogical analysis of peridotite, kimberlite and concentrate.Lithos, In press - available 20pAfrica, South Africa, Lesotho, BotswanaDeposit - Premier/Cullinan, Letseng, Ngamiland
DS1992-1465
1992
Stammler, K.Stammler, K., Kind, R., Petesen, N., Kosarev, G., Vinnik, L., LiuThe upper mantle discontinuities: correlated or anticorrelated?Geophysical Research Letters, Vol. 19, No. 15, August 3, pp. 1563-1566MantleDiscontinuity, Structure
DS201212-0755
2012
Stampfil, G.Verad, C., Hochard, C., Stampfil, G.Non-random distribution of euler poles: is plate tectonics subject to rotational effects?Terra Nova, in press availableMantleTectonics
DS2003-1432
2003
Stampfli, G.M.Von Raumer, J.F., Stampfli, G.M., Bussy, F.Gondwana derived microcontinents - the constituents of the Variscan and AlpineTectonophysics, Vol. 365, 1-4, pp.7-22.EuropeOrogenesis
DS2003-1433
2003
Stampfli, G.M.Von Raumer, J.F., Stampfli, G.M., Bussy, F.Gondwana derived microcontinents - the constituents of the Variscan and AlpineTectonophysics, Vol. 365, 1-4, pp. 7-22.Tectonics
DS200412-2064
2003
Stampfli, G.M.Von Raumer, J.F., Stampfli, G.M., Bussy, F.Gondwana derived microcontinents - the constituents of the Variscan and Alpine collisional orogens.Tectonophysics, Vol. 365, 1-4, pp.7-22.EuropeOrogenesis
DS201012-0751
2010
Stamps, D.S.Stamps, D.S., Flesch, L.M., Calais, E.Lithospheric bouyancy forces in Africa from a thin sheet approach.International Journal of Earth Sciences, Vol. 99, 7, pp. 1525-1533.AfricaGeophysics - seismics
DS201808-1790
2017
Stan, C.V.Stan, C.V., Obannon, E.F., Dobrzhinetskaya, L.F., Tamura, N.Polytypism in natural SiC using Laue microdiffraction.Acta Crystallographia, A70, 1p. abstractEurope, Israelmoissanite

Abstract: Silicon carbide (SiC, moissanite) is a common industrial material that is rarely found in terrestrial rocks and meteorites. It has been found to adopt over 300 different crystal structures, most of which are polytypic: they consist of alternating layers of Si and C, with only small stacking faults or shears distinguishing them from one another. In nature, only a few polytypes of SiC have been found, primarily a cubic zincblende type (3C-SiC), several hexagonal wurtzite types (4H-SiC and 6H-SiC), and a rhombohedral type (15R-SiC). Our natural silicon carbide sample is from a Miocene tuff (Yizre’el Valley, Israel) related to interplate alkaline basalt volcanism. Three SiC grains with native silicon and metal silicide inclusions were analyzed using Raman spectroscopy and synchrotron Laue X-ray microdiffraction accompanied by mapping at a 5-8 um resolution. SiC is found to crystallize in only the 4H and 6H polytypes. Due to the crystal orientation of the grains, as well as the significant difference in the c-axis length (~10 vs. ~15 um in 4H and 6H respectively), we were able to unambiguously assign polytypes to each diffraction pattern. Each grain contains large areas where one polytype dominates as a single crystal. In some cases, multiple stacking faults and misoriented polycrystalline aggregates of SiC occur at the 4H/6H interface. In other cases we see intercalation of the 4H and 6H crystals throughout the diffracting volume without a significant change in their crystallographic axes orientation, pointing to a possibly incommensurate crystal structure. Stress and strain are also mapped for all three grains, showing a slight (< 2 ppt) compressive strain in the y direction of all three grains, and a tensile strain in the x and z directions. In the SiC-2 grain, a mostly single-crystalline Si inclusion was found, with an exposed surface diameter of ~30 um. We examine residual strain in Si by both Laue X-ray diffraction and Raman spectroscopy, and find results to generally agree between the two measurements.
DS202004-0535
2020
Stan, C.V.Stan, C.V., O'Bannon III, E.F., Mukhin, P., Tamura, N., Dobrzhinetskaya, L.X-ray laue microdiffraction and raman spectroscopic investigation of natural silicon and moissanite.Minerals MDPI, Vol. 10, 10030204 12p. PdfGlobalmoissanite

Abstract: Moissanite, SiC, is an uncommon accessory mineral that forms under low oxygen fugacity. Here, we analyze natural SiC from a Miocene tuff-sandstone using synchrotron Laue microdiffraction and Raman spectroscopy, in order to better understand the SiC phases and formation physics. The studied crystals of SiC consist of 4H- and 6H-SiC domains, formed from either, continuous growth or, in one case, intergrown, together with native Si. The native Si is polycrystalline, with a large crystal size relative to the analytical beam dimensions (>1-2 µm). We find that the intergrown region shows low distortion or dislocation density in SiC, but these features are comparatively high in Si. The distortion/deformation observed in Si may have been caused by a mismatch in the coefficients of thermal expansion of the two materials. Raman spectroscopic measurements are discussed in combination with our Laue microdiffraction results. Our results suggest that these SiC grains likely grew from an igneous melt.
DS1992-1466
1992
Stanaway, K.J.Stanaway, K.J.Heavy mineral placersMining Engineering, Vol. 44, No. 4, April pp. 352-358GlobalAlluvials, trap, bed, rutile, ilmenite, Placers - general not specific to diamonds
DS201312-0880
2012
Stanaway, K.J.Stanaway, K.J.Ten placer deposit models from five sedimentary environments.Applied Earth Science Transactions Institute of Mining and Metallurgy, Vol. 121, 1, pp. 43-51.TechnologyAlluvials, deposits, not specific to diamonds
DS1860-0093
1870
Standard and MailStandard and MailDiary of a Recent Trip to the Diamondiferous Region Near Pniel.Standard And Mail, JUNE 9TH.Africa, South AfricaHistory
DS200612-1310
2006
Standish, J.Sims, K., Standish, J.Integrated studies of MORB petrogenesis: sources, melting processes, and timescales.Goldschmidt Conference 16th. Annual, S4-06 theme abstract 1/8p. goldschmidt2006.orgMantleGeochemistry
DS200612-0468
2006
StanevichGladkochub, D.P., Wingate, M.T.D., Pisarevsky, S.A., Donskaya, T.V., Mazukababzov, Ponomarchuk, StanevichMafic intrusions in southwestern Siberia and implications for a Neoproterozoic connection with Laurentia.Precambrian Research, Vol. 147, 3-4, July 5, pp. 260-278.Russia, CanadaMagmatism
DS200612-0469
2006
StanevichGladkochub, D.P., Wingate, M.T.D., Pisarevsky, S.A., Donskaya, T.V., Mazukabzov, Ponomarchuk, StanevichMafic intrusions in southwestern Siberia and implications for a Neoproterozoic connection with Laurentia.Precambrian Research, In press, availableRussia, SiberiaGeochronology, Biryusa, magmatism
DS200612-0467
2006
Stanevich, A.Gladkochub, D., Pisarevsky, S., Donskaya, L., Mazukabzov, A., Stanevich, A., Sklyarov, E.Siberian Craton and its evolution in terms of Rodinia hypothesis.Episodes, Vol. 29, 3, pp. 169-174.Russia, SiberiaCraton, genesis
DS200712-0363
2007
Stanevich, A.M.Gladkochub, D.P., Donskaya, T.V., Mazukabzov, A.M., Stanevich, A.M., Sklyarov, E.V., Ponomarchuk, V.A.Signature of Precambrian extension events in the southern Siberian Craton.Russian Geology and Geophysics, Vol. 48, pp. 17-31.RussiaDike swarm, rifting, Rodinia
DS200812-0413
2008
Stanevich, A.M.Gladkochub, D.P., Sklyarov, E.V., Donskaya, T.V., Stanevich, A.M., Mazukabzov, A.M.A period of global uncertainty ( Blank spot) in the Precambrian history of the southern Siberian Craton and the problem of the transproterozoic supercontinent.Doklady Earth Sciences, Vol. 421, 1, pp. 774-778.Russia, SiberiaTectonics
DS1860-0776
1893
Stanford, E.Stanford, E.The Diamond Industry of South Africa #2London: E. Stanford., 25P.Africa, South AfricaKimberley, History, Production, Mining Economics
DS1860-0816
1893
Stanford, E.Stanford, E.The Diamond Industry of South Africa #1London: E. Stanford., 17P.Africa, South AfricaHistory
DS1860-0920
1896
Stanford, E.Stanford, E.The Diamond Industry of South Africa (1896)London: E. Stanford., 17P. And mapAfrica, South Africa, Kimberley AreaDiamond Occurrence
DS1993-1360
1993
Stange, S.Sachs, P.M., Stange, S.Fast assimilation of xenoliths in magmasJournal of Geophysical Research, Vol. 98, No. B 11, November 10, pp. 19, 741-754.MantleMagma, Xenoliths
DS1993-1361
1993
Stange, S.Sachs, P.M., Stange, S.Fast assimilation of xenoliths in magmasJournal of Geophysical Research, Vol. 98, No. B 11, Nov. 10, pp. 19, 741-754MantleXenoliths, Magma
DS1998-0634
1998
Stangl, R.Hollnack, D., Stangl, R.The seismicity related to the southern part of the Kenya RiftJournal of African Earth Sciences, Vol. 26, No. 3, Apr. pp. 477-95.KenyaGeophysics - seismics, Tectonics
DS1995-1110
1995
StanistreetLorenz, V., Kurzlaukis, S., Stachel, T., Brey, StanistreetVolcanology of the diatreme rich carbonatitic Gross Brukkaros volcanicfield and of the near by Gibeon K.Proceedings of the Sixth International Kimberlite Conference Abstracts, pp. 333-335.NamibiaCarbonatite, Deposit -Gross Brukkaros, Gibeon
DS1998-0639
1998
StanistreetHolzforster, F., Stollhofen, H., Lorenz, StanistreetThe Waterberg Basin in central Namibia: transfer fault activity during early South Atlantic rift evolution.Journal of African Earth Sciences, Vol. 27, 1A, p. 116. AbstractNamibiaTectonics
DS200412-1908
1995
Stanistreet, I.Stachel, T., Brey, G., Stanistreet, I.Gross Brukkaros (Namibia) - petrography and geochemistry of the intra-caldera sediments and their magmatic components.Communications of the Geological Survey of Namibia 1993/1994, pp. 23-42.Africa, NamibiaGeochemistry
DS200412-1911
1994
Stanistreet, I.Stachel, T., Lorenz, V., Stanistreet, I.Gross Brukkaros (Namibia) - an enigmatic crater fill reinterpreted as due to Cretaceous caldera evolution.Bulletin of Volcanology, Vol. 56, pp. 386-397.Africa, NamibiaStratigraphy
DS1986-0544
1986
Stanistreet, I.G.McCarthy, T.S., Charlesworth, E.G., Stanistreet, I.G.Post Transvaal structural features of the northern portion of the Witwatersrand BasinEconomic Geology Research Unit, Circular No. 191, 21pSouth AfricaStructure, Basin
DS1991-0937
1991
Stanistreet, I.G.Kukla, P.A., Stanistreet, I.G.Record of the Damaran Khomas Hochland accretionary prism in centralNamibia: refutation of an ensialic origin of a late Proterozoic orogenic beltGeology, Vol. 19, No. 5, May pp. 473-476NamibiaTectonics, Damara belt
DS1991-1654
1991
Stanistreet, I.G.Stanistreet, I.G., Kukla, P.A., Henry, G.Sedimentary basinal responses to a Late Precambrian Wilson Cycle: the Damara Orogen and Nama Foreland, NamibiaJournal of African Earth Sciences, Vol. 13, No. 1, pp. 141-156Namibia, Southwest AfricaOrogeny, Wilson Cycle
DS1994-0840
1994
Stanistreet, I.G.Jasper, M.J.U., Charlesworth, E.G., Stanistreet, I.G.Effects of oceanic closure and continental collision along Gariep belt LateProt./early Paleo Damara OrogenEconomic Geology Research Unit, Wits, No. 282, 34pSouth AfricaProterozoic, Damara Orogen
DS1995-0880
1995
Stanistreet, I.G.Jasper, M.J.U., Stanistreet, I.G., Charlesworth, E.G.Recognition of inversion tectonics within the Pan African Gariep Belt, Damara Orogen in southern NamibiaEconomic Research Unit University of Witwatersrand, No. 285, 15pNamibiaTectonics, Gariep Belt
DS1995-0881
1995
Stanistreet, I.G.Jasper, M.J.U., Stanistreet, I.G., Charlesworth, E.G.Recognition of inversion tectonics within the Pan African Gariep belt(Damara Orogen) in southern NamibiaEcon. Res. Unit, University of Witwatersrand, No. 285, 15p.NamibiaTectonics, Gariep Belt area
DS2002-0669
2002
Stankiewicz, J.Harvey, J.D., De Wit, M.J., Stankiewicz, J., DoucoureStructural variations of the crust in the southwestern Cape, deduced from seismic receiver functions.South Africa Journal of Geology, Vol. 104, pp. 231-42.South AfricaKaapvaal Craton, Tectonics
DS2002-1541
2002
Stankiewicz, J.Stankiewicz, J., Chevrot, S., Van der Hilst, R.D., De Wit, M.J.Crustal thickness, discontinuity depth and upper mantle structure beneath southern Africa: constraints from body wave conversions.Physics of the Earth and Planetary Interiors, Vol. 130, No. 3-4, pp. 235-51.South AfricaGeophysics - seismics, Tectonics
DS200512-1041
2005
Stankiewicz, J.Stankiewicz, J., De Wit, M.J.River networks of southern Africa: scaling laws governing their geometry and deviations from scaling.Geochemistry, Geophysics, Geosystems: G3, In pressAfrica, South Africa, BotswanaGeomorphology, drainage
DS200812-0668
2007
Stankiewicz, J.Lindeque, A.S., Ryberg, T., Stankiewicz, J., Weber, M.H., De Wit, M.J.Deep crustal seismic reflection experiment across the Southern Karoo Basin, South Africa.South African Journal of Geology, Vol. 110, 2-3, Sept. pp. 419-438.Africa, South AfricaGeophysics - seismics
DS200812-1111
2008
Stankiewicz, J.Stankiewicz, J., Parsiegla, N., Ryberg, T., Gohl, K., Weckhmann, U., Trumball, R., Weber, M.Crustal structure of the southern margin of the African continent: results from geophysical experiments.Journal of Geophysical Research, Vol. 113, B005612.AfricaGeophysics - seismics
DS200812-1112
2007
Stankiewicz, J.Stankiewicz, J., Ryberg, T., Schulze, A., Lindeque, A., Weber, M.H., De Wit, M.Initial results from wide angle seismic refraction lines in the southern Cape.South African Journal of Geology, Vol. 110, 2-3, Sept. pp. 407-418.Africa, South AfricaGeophysics - seismics
DS200912-0731
2008
Stankiewicz, J.Stankiewicz, J., Parsiegle, N., Ryberg, T., Gohl, K., Weckmann, U., Trumball, R., Weber, M.Crustal structure of the southern margin of the African continent: results from geophysical experiments.Journal of Geophysical Research, Vol. 113, B10, B10313AfricaTectonics
DS1981-0395
1981
Stankovskiy, A.F.Stankovskiy, A.F., Verichev, YE.M., et al.New Type of Vendian Igneous Activity in the Northern Part Of the Russian PlatformDoklady Academy of Science USSR, Earth Science Section., Vol. 247, No. 1-6, PP. 93-96.RussiaKimberlite
DS1982-0574
1982
Stankovskiy, A.F.Sobolev, V.K., Stankovskiy, A.F.Carbonate Inclusions in Chrome Spinnellids from Kimberlite Sheets.Doklady Academy of Science USSR, Earth Science Section., Vol. 251, No. 6, PP. 140-141.RussiaXenoliths, Mineralogy
DS201112-0812
2011
StanleyPolyakova, E.A., Chakhmouradian, A.R., Siidra ,Britvin, Petrov, Spratt, Williams, Stanley, ZaitsevFluorine, yttrium and lanthanide rich cerianite from carbonatitic rocks of the Kerimasi volcano and surrounding explosion craters, Gregory Rift.Peralk-Carb 2011, workshop held Tubingen Germany June 16-18, PosterAfrica, TanzaniaCarbonatite
DS201201-0861
2011
StanleyZaitsev, A.N., Chakmouradian, A.R., Sidra, O.I., Spratt, J., Williams, Stanley, Petrov, Britvin, PolyakaFlourine , yttrium and lanthaide rich cerianite (Ce) from carbonatitic rocks of the Kerimasi volcano and surrounding explosive craters Gregory Rift Tanzania.Mineralogical Magazine, Vol. 75, 6, pp. 2813-2822.Africa, TanzaniaCarbonatite
DS2000-0523
2000
Stanley, C.Kopylova, M.G., Russell, K., Stanley, C., Cookenboo, H.Garnet from chromium and Calcium saturated mantle implications for diamond exploration.Journal of Geochem. Exp., Vol. 69-70, pp.183-99.South Africa, Colorado Plateau, Northwest TerritoriesCraton - garnet mineralogy, Deposit - Jericho
DS201707-1373
2017
Stanley, C.Stanley, C.Lithogeochemical classification of igneous rocks using Streckeisen ternary diagrams.Geochemistry: Exploration, Environment, Analysis, Vol. 17, 2, pp. 63-91.Technologyclassification

Abstract: Mineral deposit models strategically guide exploration. The lithologies from which these models are built have genetic connotations. Thus, rock classification must be accurate to ensure that mineral exploration is effective and successful. Rock classification is based on mineral proportions, and these are commonly determined by: (1) visual inspection, which is subject to large errors; (2) point counting, which is tedious and time-consuming; (3) image analysis of stained slabs or polished thin sections, which is expensive and constrained by the availability of appropriate stains; and (4) image analysis of spectrometric data, which is expensive. These features make rock classification difficult and undermine its quality, thereby negatively impacting geological conclusions and mineral exploration results. A novel alternative procedure for igneous rock classification involves using whole rock lithogeochemical data for classification on Streckeisen ternary diagrams. This approach employs several calculations that transform: (1) mass-based element concentrations (the original lithogeochemical data produced by the laboratory) sequentially into (2) unstandardized (do not sum to unity) molar element numbers; (3) unstandardized molar mineral numbers; (4) unstandardized volume mineral numbers; and finally (5) standardized (closed; sum to unity) volume mineral concentrations that estimate the mineral modes in rocks. These mineral mode estimates can then be plotted on (projected onto) Streckeisen ternary diagrams, to classify the rocks in the normal manner. This new approach has advantages over conventional classification strategies, in that it is relatively inexpensive, adaptable to all forms of igneous rocks, quantitative, accurate, and precise. Required petrographic information necessary to conduct such a classification includes only knowledge of chemical formulae of the ‘essential’ mineral assemblage. Essential minerals are, here, considered those minerals having concentrations exceeding 5% in 5% of the rocks under consideration. This criterion allows this lithogeochemical classification procedure to be applicable to a wide variety of igneous rocks. This lithogeochemical classification procedure has additional applications beyond the classification of plutonic igneous rocks. For example, if an essential mineral assemblage can be identified or hypothesized, classification of felsic or mafic volcanic rocks can also be achieved. Additionally, an essential mineral assemblage does not have to consist exclusively of igneous minerals. As a result, conversion from molar element numbers to molar mineral numbers can be undertaken using many mineral assemblages. This allows analogous lithogeochemical classification to be undertaken for almost any rock type (e.g. clastic sedimentary rocks, using the calculated proportions of quartz, feldspar, and clay minerals). Consequently, lithogeochemical calculation of the essential mineral modes in rocks can be used to establish mineral zoning maps in space or time, allowing exploration geoscientists to create down-hole logs depicting hydrothermal alteration mineral abundances, or surface maps of hydrothermal alteration zones on a mineral property. To demonstrate this new procedure, results from classifications of metaluminous, peraluminous, and alkaline felsic plutonic and volcanic rocks, and mafic and ultramafic plutonic and volcanic rocks are compared with mineral modes acquired by independent means (visual estimates, point counts, image analysis, spectrometry). These case studies demonstrate that the proposed lithogeochemical classification procedure is as or more accurate than conventional classification methods. Furthermore, because lithogeochemical samples are far larger, and thus more representative than the surfaces used to estimate mineral modes by conventional means, this lithogeochemical classification procedure is also far more precise. The resulting classification is thus especially effective when working with fine-grained rocks where mineral identification and volume estimation is difficult.
DS200712-1212
2007
Stanley, C.J.Zaccarini, F., Thalhammer, O.A.R., Princivalle, F., Lenaz, D., Stanley, C.J., Garuti, G.Djerfisherite in the Guli dunite complex, Polar Siberia: a primary or metasomatic phase?Canadian Mineralogist, Vol. 45, 5, Oct. pp. 1201-1211.RussiaMetasomatism
DS200912-0845
2009
Stanley, C.J.Yusupov, R.G., Stanley, C.J., Welch, M.D., Spratt, J., Cressey, G., Rusmsey, M.S., Seltmann, R., IgamberdievMavlyanovite, Mn5813: a new mineral species from a lamproite diatreme, Chatkal Ridge, Uzbekistan.Mineralogical Magazine, Vol. 73, 1, Feb. pp. 43-50.RussiaLamproite mineralogy
DS1989-1445
1989
Stanley, C.R.Stanley, C.R., Russell, J.K.PEARCE.PLOT: a turbo Pascal program for the analysis of rock compositions with Pearce element ratio diagramsComputers and Geosciences, Vol. 15, No. 6, pp. 905-926GlobalComputer, Program -PEARCE.PLOT.
DS1989-1446
1989
Stanley, C.R.Stanley, C.R., Smee, B.W.A test in pattern recognition: defining anomalous patterns in surficial samples which exhibit severe nugget effects-IIExplore (association Of Exploration Geochemists Newsletter), No. 65, April pp. 12, 14GlobalGeochemistry, Nugget effect
DS1990-1281
1990
Stanley, C.R.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
DS1990-1282
1990
Stanley, C.R.Russell, J.K., Stanley, C.R.A theoretical basis for the development and use of chemical variationdiagramsGeochim. et Cosmochim Acta, Vol. 54, pp. 2419-2431GlobalPetrology- igneous, Geochemistry
DS1993-1522
1993
Stanley, C.R.Stanley, C.R.Effects of non-conserved denonminators on Pearce element ratio diagramsMathematical Geology, Vol. 25, No. 8, November pp. 1049-1070GlobalGeostatistics, Geochemistry
DS1998-1402
1998
Stanley, C.R.Stanley, C.R.NUGGETL PC software to calculate parameters for samples and elements affected by the nugget effect.The Canadian Institute of Mining, Metallurgy and Petroleum (CIM) Paper, 20p.AustraliaSampling, size fraction analysis, Deposit - Argyle ( one example only pp. 14-16.)
DS2003-1326
2003
Stanley, C.R.Stanley, C.R.THPLOT.M: a MATLAB function to implement generalized Thompson Howarth errorComputers and Geosciences, Vol. 29, 2, pp. 225-37.GlobalComputer - program
DS200412-1915
2003
Stanley, C.R.Stanley, C.R.THPLOT.M: a MATLAB function to implement generalized Thompson Howarth error analyis using replicate data.Computers & Geosciences, Vol. 29, 2, pp. 225-37.TechnologyComputer - program
DS200612-1363
2006
Stanley, C.R.Stanley, C.R.Numerical transformation of geochemical dat a: 1. maximizing geochemical contrast to facilitate information extraction and improve dat a presentation.Geochemistry, Vol. 6, 3-4, pp. 69-78.TechnologyGeochemistry - program not specific to diamonds
DS200612-1364
2006
Stanley, C.R.Stanley, C.R.Numerical transformation of geochemical dat a: 2. stabilizing measurement error to facilitate dat a interpretation.Geochemistry, Vol. 6, 3-4, pp. 79-96.TechnologyGeochemistry - program not specific to diamonds
DS200712-1032
2007
Stanley, C.R.Stanley, C.R., Murphy, D.M.K.Documenting the chemical, physical and thermodynamic changes associated with all possible geochemical reactions in rocks using Gale vector space:JerichoGeological Association of Canada, Gac-Mac Yellowknife 2007, May 23-25, Volume 32, 1 pg. abstract p.78-79.Canada, NunavutOlivine, serpentinization
DS200812-1113
2008
Stanley, C.R.Stanley, C.R., Lawie, D.Thompson-Howarth error analysis: unbiased alternatives to the large sample method for assessing non-normally distributed measurement error in geochemical samples.Geochemistry, Exploration, Environment Analysis, Vol. 8, pp. 173-182.TechnologySampling - Not specific to diamonds
DS200812-1114
2008
Stanley, C.R.Stanley, C.R., Noble, R.R.P.Quantitative assessment of the success of geochemical exploration techniques using minimum probablity methods.Geochemistry, Exploration, Environment Analysis, Vol. 8, pp. 115-127.TechnologySampling - Not specific to diamonds
DS201012-0752
2009
Stanley, C.R.Stanley, C.R.Geochemical, mineralogical and lithological disposal methods in glacial till: physical process constraints and application in mineral exploration.Geological Association of Canada Short Course, No. 18, pp. 35-48.Canada, Northwest TerritoriesGeomorphology
DS201012-0753
2010
Stanley, C.R.Stanley, C.R., O'Driscoll, N., Ranjan, P.Determining the magnitude of true analytical error in geochemical analysis.Geochemistry: Exploration, Environment, Analysis, Vol. 10, 4, pp. 355-364.TechnologyGeochemistry - not specific to diamonds
DS1993-1386
1993
Stanley, D.A.Scheiner, B.J., Stanley, D.A., Karr, C.L.Emerging computer techniques for the minerals industrySociety for Mining, Metallurgy and Exploration (SME), American Institute of Mining, Metallurgical, and Petroleum Engineers (AIME) Publication, 400p. approx. $ 65.00GlobalBook -table of contents, Computer techniques
DS200612-1365
2006
Stanley, G.Stanley, G.Exploration - the Wall Street perspective.SEG 2006 Conference, Wealth Creation in the Minerals Industry, May 14-16, Keystone Colorado USA, Abtract Volume p. 93-95. ( 3p.)GlobalEconomics - valuations
DS200712-1033
2007
Stanley, G.Stanley, G.Putting exploration into Wall street's perspective.SEG Newsletter, No. 68, January pp. 1, 10-17.GlobalEconomics- exploration valuation, spending, resources
DS201412-0006
2014
Stanley, J.Alvarez-Valero, A.M., Jagoutz, O., Stanley, J., Manthei, C., Ali Moukadiri, A., Piasecki, A.Crustal attenuation as a tracer for the emplacement of the Beni Bousera ultramafic massif ( Betico-Rifean belt).Geological Society of America Bulletin, Vol. 126, no. 11/12, pp. 1614-1624.Africa, MoroccoBeniBoussera
DS201705-0880
2017
Stanley, J.Stanley, J., Flowers, R.Dating kimberlite emplacement with zircon and perovskite ( U-Th) /He geochronology.European Geosciences Union General Assembly 2017, Vienna April 23-28, 1p. 18924 AbstractAfricaGeochronology

Abstract: Kimberlites provide rich information about the composition and evolution of cratonic lithosphere. Accurate geochronology of these eruptions is key for discerning spatiotemporal trends in lithospheric evolution, but kimberlites can sometimes be difficult to date with available methods. We explored whether (U-Th)/He dating of zircon and perovskite can serve as reliable techniques for determining kimberlite emplacement ages. We obtained zircon and/or perovskite (U-Th)/He (ZHe, PHe) dates from 16 southern African kimberlites. Most samples with abundant zircon yielded reproducible ZHe dates (=15% dispersion) that are in good agreement with published eruption ages. The majority of dated zircons were xenocrystic. Zircons with reproducible dates were fully reset during eruption or resided at temperatures above the ZHe closure temperature prior to entrainment in the kimberlite magma. Not dating hazy and radiation damaged grains can help avoid anomalous results for more shallowly sourced zircons that underwent incomplete damage annealing and/or partial He loss during the eruptive process. All seven kimberlites dated with PHe yielded reproducible (=15% dispersion) and reasonable results. We conducted two preliminary perovskite 4He diffusion experiments, which suggest a PHe closure temperature of >300°C. Perovskite in kimberlites is unlikely to be xenocrystic and its relatively high temperature sensitivity suggests that PHe dates will typically record emplacement rather than postemplacement processes. ZHe and PHe geochronology can effectively date kimberlite emplacement and provide useful complements to existing techniques.
DS201412-0883
2013
Stanley, J.R.Stanley, J.R., Flowers, R.M., Bell, D.R.Kimberlite ( U-Th) He dating links surface erosion with lithospheric heating, thinning, and metasomatism in the southern African Plateau.Geology, Vol. 4, pp. 1243-1246.AfricaGeochronology
DS202003-0363
2020
Stanley, J.R.Stanley, J.R., Flowers, R.M.Mesozoic denudation history of the lower Orange River and eastward migration of erosion across the southern African plateau.Lithosphere, in press available 14p. PdfAfrica, South Africageochronology

Abstract: Topographic uplift of the southern African Plateau is commonly attributed to mantle causes, but the links between mantle processes, uplift, and erosion patterns are not necessarily straightforward. We acquired apatite (U-Th)/He (AHe) dates from eight kimberlite and basement samples from the lower reaches of the large westward-draining Orange River system with the goal of evaluating the roles of lithospheric modification and river incision on the erosion history here. Average AHe dates range from 79 to 118 Ma and thermal history models suggest that most samples are consistent with a main erosion phase at ca. 120-100 Ma, with some variability across the region indicating a complex erosion history. Major erosion overlaps with the timing of strong lithospheric thermochemical modification as recorded in xenoliths from the studied kimberlites, but the denudation pattern does not mimic the northward progression of lithospheric alteration across the study region. We attribute this area’s denudation history to a combination of mantle effects, rifting, establishment of the Orange River outlet at its current location, and later faulting. When considering these results with other kimberlite-derived surface histories from an ~1000-km-long E-W transect across the plateau, an eastward-younging trend in denudation is evident. The interplay of mantle processes and the shape of the large, west-draining Orange River basin likely control this first order-pattern.
DS1985-0125
1985
Stanley, M.Collins, A.T., Stanley, M.Absorption and luminescence studies of synthetic diamond in which the nitrogen has been aggregatedJournal of Physics D. Applied physics, Vol. 18, No. 12, Dec. 14, pp. 2537-2545GlobalDiamond Morphology
DS1987-0112
1987
Stanley, M.Collins, A.T., Stanley, M., Woods, G.S.Nitrogen isotope effects in synthetic diamondsJournal of Physics D. Applied physics, Vol. 20, No. 7, July 14, pp. 969-974GlobalSynthetic diamond, luminescense, Petrology
DS1997-0897
1997
Stanley, M.Pell, J.A., Stanley, M., Relf, C.Archean carbonatite bearing alkaline complexes, Slave structural northwest Territories.Geological Association of Canada (GAC) Abstracts, POSTER.Northwest TerritoriesCarbonatite, Slave Structural province
DS202103-0412
2021
Stanley, S.Stanley, S.Subduction may recycle less water than thought.Eos, 102, doi.org/10.1029 /2021EO154530Mantlesubduction

Abstract: When one tectonic plate dives beneath another at a subduction zone, it recycles huge amounts of water and other chemicals into Earth’s mantle. The sinking plate carries seawater trapped in sediments and crust or chemically bound in minerals like serpentine. Later release of this water in the mantle contributes to key geological processes, such as earthquakes and the formation of volcano-feeding magma. By volume, the largest portion of a subducting plate is its bottom layer, which comprises upper mantle material. Estimates of the amount of water in downgoing slabs of upper mantle vary widely: Some suggest that worldwide, subduction zones have swallowed more than two oceans’ worth of water in the past 540 million years. However, new research by Miller et al. suggests that water transport at the Middle America Trench subduction zone is an order of magnitude less than previously estimated. As a plate approaches a subduction zone, it bends downward, causing faults to form. Models and earlier observations have suggested that this bending and faulting allow seawater to infiltrate into the upper mantle, where it fills cracks in fault zones, reacts with olivine to produce serpentine, and is later carried deeper into the subduction zone. Previous estimates of how much water reaches the upper mantle along bending faults have relied on measurements of the speed of seismic waves as they pass through a subducting plate. However, those measurements and estimates could not discern whether the upper mantle layer is uniformly hydrated or whether water is confined to bending fault zones. To address that limitation, the new study accounted for seismic anisotropy characterizing how the speed of seismic waves depends on the direction they travel through a material. The researchers used data collected by seafloor seismometers to measure seismic anisotropy along the Middle America Trench near Nicaragua, which enabled a much more detailed picture of upper mantle hydration. The data revealed that in the region studied, water storage in the upper mantle is limited to serpentinized fault zones that thin rapidly with depth, suggesting that fault dynamics and serpentinization reaction kinetics prevent seawater from hydrating the mantle between bending faults. New estimates of water transport that incorporate this finding are an order of magnitude lower than previous estimates for the Middle America Trench. Because the same processes occur at other subduction zones, the researchers report that far less water may be transported worldwide than previously estimated. (Journal of Geophysical Research: Solid Earth, https://doi.org/10.1029/2020JB020982, 2021)
DS200512-1042
2005
Stanley, W.Stanley, W.Background to the Liberia and Sierra Leone implosions.Geojournal, Vol. 61, 1, pp. 69-78.Africa, Liberia, Sierra LeoneHistory
DS200512-1043
2005
Stanley, W.Stanley, W.Background to the Liberia and Sierra Leone implosions.Geojournal, Vol. 61, 1, pp. 69-78.Africa, Liberia, Sierra LeoneHistory
DS1995-0476
1995
Stanley, W.D.Eberhardt-Phillips, D., Stanley, W.D., et al.Surface seismic and electrical methods to detect fluids related tofaultingJournal of Geophysical Research, Vol. 100, No. B 7, July 10, pp. 12, 919-12, 936GlobalGeophysics -seismics, Fluids -faulting
DS1996-1201
1996
Stanley, W.D.Rodrigues, B.D., Stanley, W.D., Williams, J.M.Axial structures within the Reelfoot Rift delineated with magnetotelluricsurveys.United States Geological Survey (USGS) Prof. Paper, No. 1538-K, 30p.Michigan, Wisconsin, Arkansas, MidcontinentGeophysics - magnetotellurics, Tectonics, structure
DS1995-1564
1995
Stanonis, F.L.Rene, R.M., Stanonis, F.L.Reflection seismic profiling of the Wabash Valley fault system in the Illinois Basin.United States Geological Survey (USGS) Prof. paper, No. 1538- O, 33p.Midcontinent, IllinoisGeophysics - seismics
DS1970-0830
1973
Stansfield, G.Stansfield, G.The Geology Around Dukwe and Tlalamabele, Central District Botswana.Botswana Geological Survey, DISTRICT MEMOIR, No. 1.BotswanaGeology
DS1920-0171
1923
Stansfield, J.Stansfield, J.Extensions of the Montregian Petrographic Province to West And Northwest.Geology Magazine., Vol. 60, PP. 433-453.Canada, QuebecBlank
DS201908-1790
2019
Stanstreet, I.Lu, K., Hanafy, S., Stanstreet, I., Schuster, G.Seismic imaging of the Olduvai Basin, Tanzania.Paleogeography, Paleoclimatology, Paleoecology, 10.1016/j.palaeo .2019.109246Africa, Tanzaniageophysics - seismic

Abstract: A 5.6-km-long line of refraction and reflection seismic data spanning the Pliocene-Pleistocene fill of the Olduvai Basin, Tanzania is presented. The line is oriented along a northwest-southeast profile through the position of Olduvai Gorge Coring Project (OGCP) Borehole 2A. Our aims are to (1) delineate the geometry of the basin floor by tracing bedrock topography of the metaquartzitic and gneissic basement, (2) map synsedimentary normal faults and trace individual strata at depth, and (3) provide context for the sequence observed in OGCP cores. Results with refraction tomography and poststack migration show that the maximum basin depth is around 405?m (±25?m) in the deepest portion, which quadruples the thickness of the basin-fill previously known from outcrops. Variations in seismic velocities show the positions of lower density lake claystones and higher density well-cemented sedimentary sequences. The Bed I Basalt lava is a prominent marker in the refraction seismic results. Bottom-most sediments are dated to >2.2?Ma near where Borehole 2A bottoms out at the depth of 245?m. However, the seismic line shows that the basin-fill reaches a maximum stratigraphic thickness of around 380?m deep at Borehole 2A, in the western basin where the subsidence was greatest. This further suggests that potential hominin palaeoenvironments were available and preserved within the basin-fill possibly as far back as around 4?Ma, applying a temporal extrapolation using the average sediment accretion rate.
DS200812-0162
2008
Staostin, V.A.I.A.Burnistrov, A.A.A.A., Staostin, V.A.I.A., Sakya, D.A.R.A.Tectonic aspects of the evolution of ore potential of carbonatite and kimberlite magmatism.Doklady Earth Sciences, Vol. 418, 1, pp. 19-23.MantleMagmatism
DS1994-1164
1994
Stapel, C.Meijer, de, R.J., Tanczos, I.C., Stapel, C.Radiometric techniques in heavy mineral exploration and exploitationExploration and Mining Geology, Vol. 3, No. 4, Oct. pp. 389-98GlobalHeavy sands, Radiometric mapping
DS1997-0259
1997
Stapel, C.De Meijer, R.J., Stapel, C., Jones, D.G., Roberts..Improved and new uses of natural radiactivity n mineral exploration andprocessingExploration and Mining Geology, Vol. 6, No. 1, pp. 105-117GlobalCoast - sediments, heavy minerals, Technology - radioactivity
DS1999-0680
1999
Staples, R.K.Smallwood, J.R., Staples, R.K., White, R.Crust generated above the Iceland mantle plume: from continental rift to oceanic spreading center.Journal of Geophysical Research, Vol. 104, No. B10, Oct. 10, pp. 22885-902.GlobalMantle plume, Tectonics
DS1997-1098
1997
Stapleton, J.Stapleton, J., Land, B.A.Metallic and industrial mineral assessment report, lamprophyres of Peace River District, ashes ...Alberta Geological Survey, MIN 19970006AlbertaExploration - assessment, TUL Petroleums Ltd.
DS1995-1819
1995
Stapleton, M.J.Stapleton, M.J.Metallic and industrial mineral assessment report in support of the Peace diamond project and iron and gold.Alberta Geological Survey, MIN 19950019AlbertaExploration - assessment, Tul Petroleum, Tri Union Resources Ltd.
DS1996-1360
1996
Stapleton, M.J.Stapleton, M.J.Will Peace River release her wealth of minerals to us?Calgary Mining Forum Fifth Held April 11, 12., p. 9. abstractAlbertaNews item, Diamond overview
DS1998-1403
1998
Stapleton, M.J.Stapleton, M.J., Land, P.Metallic and industrial mineral assessment report on the West River diamond indicator geochemistryAlberta Geological Survey, MIN 19980014, pt.3.AlbertaExploration - assessment, Hawk Hills Magnetic Anomaly, TUL Petroleums
DS1999-0708
1999
Stapleton, M.J.Stapleton, M.J., Land, P.Exploration of the West Peace River diamond indicator mineral trendAlberta Geological Survey, MIN 19990025AlbertaExploration - assessment, New Claymore Resources Ltd.
DS1999-0709
1999
Stapleton, M.J.Stapleton, M.J., Land, P.Exploration of thew West Peace River diamond indicator mineral trendAlberta Geological Survey, MIN 19990025AlbertaExploration - assessment, New Claymore Resources Ltd.
DS2002-1542
2002
Starchenko, S.V.Starchenko, S.V., Stepanov, A.A.Heat sources and fluxes in the Earth's mantleDoklady Earth Sciences, Vol. 384, 4, May-June pp. 438-41.MantleHot spots, plumes
DS201312-0723
2012
Starchenko, S.V.Pushkarev, Y.D., Starchenko, S.V.Hypothesis of the eroding protocore: new view on the nature of the geomagnetic field.Vladykin, N.V. ed. Deep seated magmatism, its sources and plumes, Russian Academy of Sciences, pp. 104-109.MantleGeomagnetics
DS200712-0261
2007
StarchevichDobtresov, V.Y., Psakhe, S.G., Popov, V.L., Shilko, E.V., Granin, Timofeev,Astafurov, Dimaki, StarchevichIce cover of Lake Baikal as a model for studying tectonic processes in the Earth's crust.Doklady Earth Sciences, Vol. 413, 2, pp. 155-159.RussiaGeomorphology
DS201712-2686
2017
Starikova, A.E.Gladkochub, D.P., Donskaya, T.V., Sklyarov, E.V., Kotov, A.B., Vladykin, N.V., Pisarevsky, S.A., Larin, A.M., Salnikova, E.B., Saveleva, V.B., Sharygin, V.V., Starikova, A.E., Tolmacheva, E.V., Velikoslavinsky, S.D., Mazukabzov, A.M., Bazarova, E.P., KovaThe unique Katugin rare metal deposit ( southern Siberia): constraints on age and genesis.Ore Geology Reviews, in press available, 18p.Russia, Siberiadeposit - Katugin

Abstract: We report new geological, mineralogical, geochemical and geochronological data about the Katugin Ta-Nb-Y-Zr (REE) deposit, which is located in the Kalar Ridge of Eastern Siberia (the southern part of the Siberian Craton). All these data support a magmatic origin of the Katugin rare-metal deposit rather than the previously proposed metasomatic fault-related origin. Our research has proved the genetic relation between ores of the Katugin deposit and granites of the Katugin complex. We have studied granites of the eastern segment of the Eastern Katugin massif, including arfvedsonite, aegirine-arfvedsonite and aegirine granites. These granites belong to the peralkaline type. They are characterized by high alkali content (up to 11.8?wt% Na2O?+?K2O), extremely high iron content (FeO*/(FeO*?+?MgO)?=?0.96-1.00), very high content of most incompatible elements - Rb, Y, Zr, Hf, Ta, Nb, Th, U, REEs (except for Eu) and F, and low concentrations of CaO, MgO, P2O5, Ba, and Sr. They demonstrate negative and CHUR-close eNd(t) values of 0.0…-1.9. We suggest that basaltic magmas of OIB type (possibly with some the crustal contamination) represent a dominant part of the granitic source. Moreover, the fluorine-enriched fluid phases could provide an additional source of the fluorine. We conclude that most of the mineralization of the Katugin ore deposit occurred during the magmatic stage of the alkaline granitic source melt. The results of detailed mineralogical studies suggest three major types of ores in the Katugin deposit: Zr mineralization, Ta-Nb-REE mineralization and aluminum fluoride mineralization. Most of the ore minerals crystallized from the silicate melt during the magmatic stage. The accessory cryolites in granites crystallized from the magmatic silicate melt enriched in fluorine. However, cryolites in large veins and lens-like bodies crystallized in the latest stage from the fluorine enriched melt. The zircons from the ores in the aegirine-arfvedsonite granite have been dated at 2055?±?7?Ma. This age is close to the previously published 2066?±?6?Ma zircon age of the aegirine-arfvedsonite granites, suggesting that the formation of the Katugin rare-metal deposit is genetically related to the formation of peralkaline granites. We conclude that Katugin rare-metal granites are anorogenic. They can be related to a Paleoproterozoic (~2.05?Ga) mantle plume. As there is no evidence of the 2.05?Ga mantle plume in other areas of southern Siberia, we suggest that the Katugin mineralization occurred on the distant allochtonous terrane, which has been accreted to Siberian Craton later.
DS202104-0601
2021
Starikova, A.E.Prokopyev, I.R., Doroshkevich, A.G., Zhumadilova, D.V., Starikova, A.E., Nugumanova, Ya.N., Vladykin, N.V.Petrogenesis of Zr-Nb ( REE) carbonatites from the Arbarastakh complex ( Aldan Shield, Russia): mineralogy and inclusion data.Ore Geology Reviews, Vol. 131, 104042, 15p. Pdf.Russiadeposit - Arbarastakh

Abstract: The Arbarastakh Neoproterozoic ultramafic carbonatite complex is located in the southwestern part of the Siberian Craton (Aldan Shield) and contains ore-bearing Zr-Nb (REE) carbonatites and phoscorites. Carbonatites are mainly represented by calcite and silicocarbonatite varieties. The primary minerals composing the carbonatites are calcite and dolomite, as well as phlogopite, clinopyroxene, fluorapatite, amphibole, fluorite, K-feldspar and feldspathoids. Olivine (forsterite), Ti-magnetite, apatite, phlogopite, calcite, dolomite and the minor spinel group minerals form the primary phoscorites. The ore-bearing Zr-Nb mineral assemblages of the phoscorites and carbonatites include accessory zircon, zirconolite, perovskite, pyrochlore and baddeleyite. The Ba-Sr-REE hydrothermal mineralisation consists of ancylite-(Ce), bastnaesite-(Ce) and burbankite, as well as barite-celestite, strontianite, barytocalcite, and rare Cu-Fe sulphides. The silicocarbonatites and carbonatites formed in multiple stages from a single alkaline Ca-Na-K-silicocarbonatite melt, while the phoscorites are products of differentiation of the carbonatitic melt and were crystallised from an Fe-rich phosphate-carbonate melt at temperatures of more than 720 °C. The silicate-phosphate-carbonate melts were responsible for the Zr-Nb mineralisation of the carbonatites at temperatures of more than 540-575 °C; the hydrothermal REE-bearing mineral assemblages crystallised from saline (60-70 wt%) carbonatitic fluids of Na-Ca-Mg-F-carbonate composition at a minimum temperature range of 350-300 °C. The Ca-Sr-carbonate as well as the Na-hydro-carbonate fluids were responsible for the Ba-Sr-REE mineralisation of the phoscorites at ~500-480 and 450-430 °C.
DS1994-1682
1994
Staritskii, Y.G.Staritskii, Y.G., Kochin, G.G.Ore types of metallic and non-metallic mineral deposits in the cover of the Russian PlatformGeology of Ore Deposits, Vol. 36, No. 2, pp. 124-133RussiaMetallogeny
DS1996-1361
1996
Staritskii, Yu.G.Staritskii, Yu.G., Kochkin, G.B., Yanova, E.O.Regularities of spatial distribution of the major minerals in the Russian Platform coverGeology of Ore Deposits, Vol. 38, No. 1, pp. 66-77RussiaModels, genesis, Uranium, Rare earths
DS201801-0068
2017
Stark, J.C.Stark, J.C., Wang, X-C., Denyszyn, S.W., Li, Z-X., Rasmusson, B., Zi, J-W., Sheppard, S., Liu, Y.Newly identified 1.89 Ga mafic dyke swarm in the Archean Yilgarn craton, Western Australia suggests a connection to India.Precambrian Research, in press available 47p.Australia, Indiacraton - Yilgarn

Abstract: The Archean Yilgarn Craton in Western Australia is intruded by numerous mafic dykes of varying orientations, which are poorly exposed but discernible in aeromagnetic maps. Previous studies have identified two craton-wide dyke swarms, the 2408?Ma Widgiemooltha and the 1210?Ma Marnda Moorn Large Igneous Provinces (LIP), as well as limited occurrences of the 1075?Ma Warakurna LIP in the northern part of the craton. We report here a newly identified NW-trending mafic dyke swarm in southwestern Yilgarn Craton dated at 1888?±?9?Ma with ID-TIMS U-Pb method on baddeleyite from a single dyke and at 1858?±?54?Ma, 1881?±?37 and 1911?±?42?Ma with in situ SHRIMP U-Pb on baddeleyite from three dykes. Preliminary interpretation of aeromagnetic data indicates that the dykes form a linear swarm several hundred kilometers long, truncated by the Darling Fault in the west. This newly named Boonadgin dyke swarm is synchronous with post-orogenic extension and deposition of granular iron formations in the Earaheedy basin in the Capricorn Orogen and its emplacement may be associated with far field stresses. Emplacement of the dykes may also be related to initial stages of rifting and formation of the intracratonic Barren Basin in the Albany-Fraser Orogen, where the regional extensional setting prevailed for the following 300?million years. Recent studies and new paleomagnetic evidence raise the possibility that the dykes could be part of the coeval 1890?Ma Bastar-Cuddapah LIP in India. Globally, the Boonadgin dyke swarm is synchronous with a major orogenic episode and records of intracratonic mafic magmatism on many other Precambrian cratons.
DS201811-2609
2018
Stark, J.C.Stark, J.C., Wilde, S.A., Soderlund, U., Li, Z-X., Rasmussen, B., Zi, J-W.First evidence of Archean mafic dykes at 2.62 Ga in the Yilgarn Craton, Western Australia: links to cratonisation and the Zimbabwe craton.Precambrian Research, Vol. 317, pp. 1-13.Australia, Africa, Zimbabwecraton

Abstract: The Archean Yilgarn Craton in Western Australia hosts at least five generations of Proterozoic mafic dykes, the oldest previously identified dykes belonging to the ca. 2408-2401?Ma Widgiemooltha Supersuite. We report here the first known Archean mafic dyke dated at 2615?±?6?Ma by the ID-TIMS U-Pb method on baddeleyite and at 2610?±?25?Ma using in situ SHRIMP U-Pb dating of baddeleyite. Aeromagnetic data suggest that the dyke is part of a series of NE-trending intrusions that potentially extend hundreds of kilometres in the southwestern part of the craton, here named the Yandinilling dyke swarm. Mafic magmatism at 2615?Ma was possibly related to delamination of the lower crust during the final stages of assembly and cratonisation, and was coeval with the formation of late-stage gold deposit at Boddington. Paleogeographic reconstructions suggest that the Yilgarn and Zimbabwe cratons may have been neighbours from ca. 2690?Ma to 2401?Ma and if the Zimbabwe and Kaapvaal cratons amalgamated at 2660-2610?Ma, the 2615?Ma mafic magmatism in the southwestern Yilgarn Craton may be associated with the same tectonic event that produced the ca. 2607-2604?Ma Stockford dykes in the Central Zone of the Limpopo Belt. Paleomagnetic evidence and a similar tectonothermal evolution, including coeval low-pressure high-temperature metamorphism, voluminous magmatism, and emplacement of mafic dykes, support a configuration where the northern part of the Zimbabwe Craton was adjacent to the western margin of the Yilgarn Craton during the Neoarchean. Worldwide, reliably dated mafic dykes of this age have so far been reported from the Yilgarn Craton, the Limpopo Belt and the São Francisco Craton.
DS1995-1820
1995
Stark, J.T.Stark, J.T.In search of the East Continental Rift Complex: evidence and conclusionsBasement Tectonics 10, held Minnesota Aug 92, pp. 103-106.MidcontinentTectonics, Structure
DS1992-0367
1992
Stark, K.B.Dirlam, D.M., Misiorowski, E.B., Tozer, M., Stark, K.B., BassettGem wealth of TanzaniaGems and Gemology, Vol. 28, No. 2, Summer pp. 80-103TanzaniaDiamonds -all gem stones as well, Excellent article, photographs, historical coverage
DS1993-1523
1993
Stark, P.B.Stark, P.B.Toward tubular tomographyJournal of Geophysical Research, Vol. 98, No. B5, May 10, pp. 8095-8106GlobalTomography
DS2002-0577
2002
Stark, R.Gitelson, A.A., Stark, R., Grits, U., et al.Vegetation and soil lines in visible spectral space: a concept and technique for remote estimation of vegetation fraction.International Journal of Remote Sensing, Vol.23,No.13, July 20, pp. 2537-62.GlobalRemote sensing - not specific to diamonds, Techniques
DS1992-1467
1992
Stark, T.J.Stark, T.J.In search of the east continent rift complex: evidence and conclusionsGeological Society of America (GSA) Abstracts with programs, 1992 Annual, Vol. 24, No. 7, abstract p. A364MidcontinentTectonics, Rifting
DS2001-0255
2001
Starkey, J.Diniz de Costa, R., Starkey, J.PhotoLin: a program to identify and analyze linear structures in aerial photographs, satellite images mapsComputers and Geosciences, Vol. 27, No. 5, pp. 527-48.GlobalComputer - PhotoLin
DS200712-1034
2007
Starkey, N.Starkey, N., Stuart, F.M., Ellam, R.M., Fitton, J.G., Basu, S., Larsen, L.M.No role for discrete, depleted high 3 He/4He mantle.Plates, Plumes, and Paradigms, 1p. abstract p. A967.Canada, Nunavut, Baffin Island, Europe, GreenlandPicrite
DS200812-1115
2008
Starkey, N.Staurt, F.M., Basu, S., Ellam, R., Fitton, G., Starkey, N.Is there a hidden primordial 3He rich reservoir in the deep Earth?Goldschmidt Conference 2008, Abstract p.A908.Europe, Iceland, Canada, Baffin IslandChemistry - basalts
DS200912-0221
2009
Starkey, N.Fitton, G., Starkey, N.Hotspots and large igneous provinces: excess mantle temperature or mantle fertility?Goldschmidt Conference 2009, p. A382 Abstract.MantlePlume
DS200912-0143
2009
Starkey, N.A.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
Starkey, N.A.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
DS200912-0732
2009
Starkey, N.A.Starkey, N.A., Stuart, F.M., Ellam, R.M., Fitton, J.G., Basu, S., Laresen, L.M.Helium isotopes in early Iceland plume picrites: constraints on the composition of high 3he/4He mantle.Earth and Planetary Science Letters, Vol. 277, 1-2, pp. 91-100.MantlePicrite
DS201212-0702
2012
Starkey, N.A.Starkey, N.A., Fitton, J.G., Stuart, F.M., Larsen, L.M.As commodity, is it diamond's time to shine?The New York Times Magazine, April 14, 1p.GlobalDiamond backed exchange traded fund
DS201610-1870
2016
Starkey, N.A.Herzberg, C., Vidito, C., Starkey, N.A.Nickel cobalt contents of olivine record origins of mantle peridotite and related rocks.American Mineralogist, Vol. 101, pp. 1952-1966.MantlePeridotite

Abstract: Olivine is distinguished from all other minerals in providing a remarkable chemical narrative about magmatic processes that occurred in Earth’s crust, mantle, and core over the entire age of Earth history. Olivines in mantle peridotite have Ni contents and Mg numbers that were largely produced by equilibrium crystallization in an early turbulently convecting magma ocean; subsequent stages of partial melting operated to slightly elevate Ni and Mg number in residual olivines. Olivines from Archean komatiites from the Abitibi greenstone belt have Ni contents and Mg numbers that are consistent with an extensively melted peridotite source at great depths in the mantle. Olivines from basaltic oceanic crust, the Icelandic mantle plume and other Phanerozoic occurrences have compositions that record magma chamber crystallization, recharge, mixing, and partial melting. Olivines from the present-day Icelandic mantle plume have compositions that are consistent the melting of a peridotite source; unlike Hawaii, the melting of recycled crust as a distinct pyroxenite lithology is not evident in the olivine chemistry of Iceland. Paleocene picrites from Baffin Island and West Greenland from the ancient Icelandic plume have olivines with Ni contents that are consistent with either Ni-rich peridotite that formed by core-mantle interaction or by low-pressure crystallization of hot and deep magmas. In general, hot magma oceans, mantle plumes, and ambient mantle magmatism form in ways that are captured by the compositions of the olivine crystals that they contain.
DS201603-0422
2015
Starkey, R.E.Starkey, R.E., Faithfull, J.The history and occurrence of "Buxton Diamonds".Journal of the Russell Society, Vol. 18, pp. 24-45.Europe, United KingdomHistory

Abstract: The presence of quartz crystals in t he soils around Buxton has been known for centuries, and at one time theses so-called 'Buxton Diamonds' were, from published sources, apparently realtively abundant, and well-knwn to both visitors and to commentators. However, few specimens survive in museum collections, and there is considerable confusion in published accounts as to what exactly constitutes a 'Buxton Diamond'. No satisfactory description or explanation of their origin r occurrence has hitherto been published. Attractive specimens of quartz and amethyst are known from various occurrences in the Peak District, associated with igneous rocks, but these are not true 'Buxton Diamonds' . This paper presents the history of 'Buxton Diamonds', and confirms the occurrence of these, sometime highly attractive, crystals of quartz in the limestone of Diamond Hill and the surrounding area.
DS1989-1447
1989
Starling, A.Starling, A., Gilligan, J.M., Carter, A.H.C., Foster, R.P.Experimental evidence for very low solubility of rareearth elements inCO2 rich fluids at mantle conditions #2Nature, Vol.340, No. 6231, July 27, pp. 298-300GlobalRare earth, Mantle
DS1990-1409
1990
Starmer, I.C.Starmer, I.C., Smalley, P.C.rubidium-strontium (Rb-Sr) systematics of a Gardar-age layered alkaline monzonite suite in southern Norway: a discussionJournal of Geology, Vol. 98, No. 1, pp. 119-127. Discussion and replyNorwayAlkaline rocks, Gardar age Complex
DS1990-1410
1990
Starmer, I.C.Starmer, I.C., Smalley, P.C.rubidium-strontium (Rb-Sr) systematics of a Gardar age layered alkaline monzonite suite in southern NorwayJournal of Geology, Vol. 98, No. 1, January pp. 119-125NorwayAlkaline rocks, Geochronology
DS1996-1362
1996
Starmer, I.C.Starmer, I.C.Oblique terrane assembly in the late Paleoproterozoic during the Labradorian Gothian Orogeny in southern Scandianvia.Journal of Geology, Vol. 104, pp. 341-50.Norway, Ungava, LabradorTectonics, Subduction
DS1940-0133
1946
Starnes, X.B.Starnes, X.B.Exploration for Fluorite ,crittenden and Livingston Counties, Kentucky.United States Bureau of Mines Report INV., No. 3943, PP. 2-40.GlobalKimberlite, Western Kentucky, Central States
DS1950-0046
1950
Starnes, X.B.Starnes, X.B.Investigations of the Fluorite Deposits of the Dike and Eaton Veins, Crittenden County, Kentucky.United States Bureau of Mines Report INV., No. 4645, 21P.GlobalKimberlite, Western Kentucky, Central States
DS200712-1044
2006
Starostenko, V.Stephenson, R.A., Yegorova, T., Brunet, M.F., Stovba, S., Wilson, M., Starostenko, V., Saintot, A., Kusznir, N.Late Paleozoic intra- and pericratonic basins on the East European Craton and its margins.Geological Society of London Memoir, No. 32, pp. 463-480.Europe, Baltic ShieldCraton
DS1996-1363
1996
Starostenko, V.I.Starostenko, V.I., Danilenko, V.A., et al.A fully dynamic model of continental rifting applied to syn rift Evolution of sedimentary basinsTectonophysics, Vol. 268, No. 1-4, Dec. 31, pp. 211-220RussiaTectonics, Basin
DS201510-1797
2015
Starostenko, V.I.Pashkevich, I.K., Savchenko, A.S., Starostenko, V.I., Sharov, N.V.A three dimensional geophysical model of the Earth's crust in the central part of the Karelian Craton.Doklady Earth Sciences, Vol. 463, 2, pp. 808-812.RussiaGeophysics
DS1999-0323
1999
Starostin, V.I.Ignatov, P.A., Starostin, V.I., Shtein, Ya. I.Impact strain in sedimentary rocks hosting Diamondiferous kimberlites in Malaya Botuoba and NakynMoscow University of Geol. Bulletin., Vol. 54, No. 6, pp. 31-7.Russia, SiberiaStructure, petrology, Deposit - Malaya Botuoba, Nakyn
DS1996-1364
1996
Starotsin, V.I.Starotsin, V.I.The major geologico metallogenic periods in the evolution of the earthMoscow University of Bulletin, Vol. 51, No. 4, pp. 16-22RussiaMetallogeny
DS1994-1683
1994
Starr, R.Starr, R.Legal aspects of natural resources projects in the Commonwealth of Independent States (CIS)Natural Resources forum, Vol. 18, No. 1, February pp. 63-68.Russia, Commonwealth of Independent States (CIS)Legal, Overview
DS1994-1684
1994
Starr, R.Starr, R.Legal aspects of natural resource projects in the Commonwealth of Independent States (CIS)Natural Resources forum, Vol. 18, No. 1, pp. 63-68Russia, Commonwealth of Independent States (CIS), RussiaLegal, Mining
DS2001-1145
2001
StasiukSweet, A.R., Stasiuk, McIntyre, Dolby, Hamblin, KiviStratigraphy of the eroded sedimentary cover recorded by xenoliths and crater fill sediments associated....29th. Yellowknife Geoscience Forum, Nov. 21-23, abstract p. 86-7.Northwest TerritoriesStratigraphy, Lac de Gras field
DS1995-1821
1995
Stasiuk, L.D.Stasiuk, L.D., Nassichuk, W.W.Thermal history and petrology of wood and other organic inclusions In kimberlite pipes at Lac de Gras.Geological Survey of Canada, Paper 1995-B, pp. 115-124.Northwest TerritoriesThermal history, Lac de Gras area kimberlite pipes
DS1996-1365
1996
Stasiuk, L.D.Stasiuk, L.D., Nassichuk, W.W.Thermal dat a from petrographic analysis of organic matter in kimberlitepipes, Lac de Gras.Geological Survey of Canada, LeCheminant ed, OF 3228, pp. 147-149.Northwest TerritoriesReflectance data, Thermal history, Lac de Gras area
DS1998-1404
1998
Stasiuk, L.D.Stasiuk, L.D., Lockhart, G.D., Nassichuk, W.W., CarlsonKimberlite emplacement temperatures derived from the thermal history of organic matter, Lac de Gras.7th International Kimberlite Conference Abstract, pp. 865-7.Northwest TerritoriesHuminites, diatreme facies, Deposit - Hawk, Point Lake, Gazelle, Caribou W.
DS1999-0710
1999
Stasiuk, L.D.Stasiuk, L.D., Lockhart, G.D., Nassiuk, W., Carlson, J.Thermal maturity evaluation of dispersed organic matter inclusions From kimberlite pipes, Lac de Gras.International Journal of Coal. Geol., Vol. 40, No. 1, Jan. pp. 1-25.Northwest TerritoriesOrganic inclusions, Deposit - Lac de Gras pipes
DS2000-0924
2000
Stasiuk, L.D.Stasiuk, L.D., Nassichuk, W.W., Lockhart, G.D., CarlsonThermal maturity, evaluation of organic matter from kimberlite pipes: discriminating therml zones in...Geological Association of Canada (GAC)/Mineralogical Association of Canada (MAC) 2000, 1p. abstract.Northwest TerritoriesKimberlites - organics - brief
DS2001-1125
2001
Stasiuk, L.D.Stasiuk, L.D., Sweet, A.R., Hamblin, Issler, Dyck, KiviUpdate on multidisciplinary study of sedimentary cover sequence Lac de Gras kimberlite field.29th. Yellowknife Geoscience Forum, Nov. 21-23, abstract p. 81.Northwest TerritoriesPetrology - geochemistry, Lac de Gras field
DS2002-1543
2002
Stasiuk, L.D.Stasiuk, L.D., Sweet, A.R., Issler, D.J.Organic petrology, organic geochemistry, palynology and petrophysics dat a from Lac de Gras kimberlites and associated sedimentary rocks and xenoliths.Geological Survey of Canada Open File, No. 4272, 1 CD $ 32.50Northwest TerritoriesGeochemistry, Deposit - Lac de Gras area
DS2002-1544
2002
Stasiuk, L.D.Stasiuk, L.D., Sweet, A.R., Issler, D.R.Extent of Mesozoic sedimentary cover sequence in Lac de Gras kimberlite field, Northwest Territories.Gac/mac Annual Meeting, Saskatoon, Abstract Volume, P.113., p.113.Northwest TerritoriesGeochronology, Thermal alteration
DS2002-1545
2002
Stasiuk, L.D.Stasiuk, L.D., Sweet, A.R., Issler, D.R.Extent of Mesozoic sedimentary cover sequence in Lac de Gras kimberlite field, Northwest Territories.Gac/mac Annual Meeting, Saskatoon, Abstract Volume, P.113., p.113.Northwest TerritoriesGeochronology, Thermal alteration
DS2002-1572
2002
Stasiuk, L.D.Sweet, A.R., Stasiuk, L.D., McIntyre, D.J., Kivi, K.Characteristics of the eroded sedimentary cover inferred from organics in crater fill sediments....Gac/mac Annual Meeting, Saskatoon, Abstract Volume, P.115., p.115.Northwest TerritoriesCrater fill sediments, Deposit - Lac de Gras region
DS2002-1573
2002
Stasiuk, L.D.Sweet, A.R., Stasiuk, L.D., McIntyre, D.J., Kivi, K.Characteristics of the eroded sedimentary cover inferred from organics in crater fill sediments....Gac/mac Annual Meeting, Saskatoon, Abstract Volume, P.115., p.115.Northwest TerritoriesCrater fill sediments, Deposit - Lac de Gras region
DS2003-0538
2003
Stasiuk, L.D.Hamblin, A.P., Stasiuk, L.D., Sweet, L.D., Lockhart, G., Dyck, D.R., Jagger, K.Post kimberlite Eocene strat a in Crater Basin, Lac de Gras, Northwest Territories8ikc, Www.venuewest.com/8ikc/program.htm, Session 1 POSTER abstractNorthwest TerritoriesKimberlite geology and economics, Stratigraphy
DS2003-1327
2003
Stasiuk, L.D.Stasiuk, L.D., Sweet, A.R., Issler, D.R., Kivi, K., Lockhart, G., Dyck, D.D.Pre and post kimberlite emplacement thermal history of Cretaceous and Tertiary8ikc, Www.venuewest.com/8ikc/program.htm, Session 1 POSTER abstractNorthwest TerritoriesKimberlite geology and economics, Geothermometry
DS2003-1328
2003
Stasiuk, L.D.Stasiuk, L.D., Sweet, A.R., Issler, D.R., McIntyre, D.J.Organic petrology, organic geochemistry, palynology and petrophysics dat a from LacGeological Survey of Canada Open File, No. 4272.Northwest TerritoriesGeochemistry
DS2003-1353
2003
Stasiuk, L.D.Sweet, A.R., Stasiuk, L.D., Nassichuk, W.W., Catunneau, O., McIntrye, D.J.Paleontology and diamonds: geological environments associated with kimberlite8ikc, Www.venuewest.com/8ikc/program.htm, Session 1 POSTER abstractNorthwest TerritoriesKimberlite geology and economics, Paleontology
DS200412-1916
2003
Stasiuk, L.D.Stasiuk, L.D., Sweet, A.R., Issler, D.R., McIntyre, D.J.Organic petrology, organic geochemistry, palynology and petrophysics dat a from Lac de Gras kimberlites and associated sedimentarGeological Survey of Canada Open File, No. 4272.Canada, Northwest TerritoriesGeochemistry
DS200612-1366
2006
Stasiuk, L.D.Stasiuk, L.D., Sweet, A.R., Issler, D.R.Reconstruction of burial history of eroded Mesozoic strat a using kimberlite shale xenoliths, volcanoclastic and crater facies, Northwest Territories.International Journal of Coal Geology, Vol. 65, 1-2, pp. 129-145.Canada, Northwest TerritoriesSedimentation
DS2000-0506
2000
Stasiuk, V.Kjarsgaard, B., Wilkinson, L., Stasiuk, V., Armstrong, J.Understanding the Diamondiferous Lac de Gras kimberlite field28th. Yellowknife Geoscience Forum, p. 44-5.abstractNorthwest TerritoriesKimberlite - volcanism., GIS project
DS201312-0157
2012
Stastna, M.Chi, X., Amos, R.T., Stastna, M., Blowes, D.W., Sego, D.C., Smith, L.The Diavik waste rock project: implications of wind-induced gas transport.Applied Geochemistry, Vol. 36, pp. 246-255.Canada, Northwest TerritoriesDeposit - Diavik, environmental
DS1994-1685
1994
Stather, M.Stather, M.The origin, formation and emplacement of diamondsThe Australian Gemologist, Vol. 18, No. 11, August pp. 342-345.AustraliaDiamond genesis
DS200612-1367
2006
StatisticsStatisticsCurrent state of the industry.. one page on exploration overview expenditures Jr vs Srs, Canada's performance.Statistics, Sept. 1p.Global, CanadaExploration - expenditures
DS1990-1116
1990
Staub, M.W.Noblett, J.B., Staub, M.W.Mid-Proterozoic lamprophyre commingled with late-stage granitic dikes Of the anorogenic San Isabel batholith, Wet Mountains, ColoradoGeology, Vol. 18, No. 2, February pp. 120-123ColoradoLamprophyre, Wet Mountains area
DS200612-1488
2006
Staudacher, T.Vlastelic, I., Lewin, E., Staudacher, T.Th/U and other geochemical evidence for the Reunion plume sampling a less differentiated mantle domain.Earth and Planetary Science Letters, Vol. 248, 1-2, Aug. 15, pp. 364-378.MantleGeochemistry
DS1994-0704
1994
StaudeHanchar, J.M., Miller, C.F., Wooden, J.L., Bennett, StaudeEvidence from xenoliths for a dynamic lower crust eastern Mojave desert, California.Journal of Petrology, Vol. 35, pt. 5, pp. 1377-1415.CaliforniaXenoliths
DS2001-0392
2001
Staude, W.Goddard, I.A., Onley, P., Staude, W.The 2001 independent review of the VALMIN code (1998): a work in progressValmin 01, Mineral Asset Valuation Oct. 25-6th., pp.206-8.AustraliaEconomics - legal code, Mineral reserves, resources, valuation, exploration
DS1975-0527
1977
Stauder, W.Hildenbrand, T.G., Kane, M.F., Stauder, W.Magnetic and Gravity Anomalies in the Northern Mississippi Embayment and Their Spatial Relation to Seismicity.United States Geological Survey (USGS) miscellaneous FIELD MAP, No. MF-914, 1:1, 000, 000.GlobalMid-continent
DS1975-0629
1977
Stauder, W.Stauder, W., Kramer, M., Fischer, G., Schaeffer, S., Morrissey.Seismic Characteristics of Southeast Missouri As Indicated By a Regional Telemetered Microearthquake Array.Seismol. Soc. American Bulletin., Vol. 66, PP. 1953-1964.GlobalMid Continent
DS201112-0871
2004
StaudigelRobinson, P.T., Bai, W-J., Malpas, J., Yang, J-S., Zhou, M-F., Fang, Q-S., Hu, X-F., Cameron, StaudigelUltra high pressure minerals in the Loubasa ophiolite, Tibet and their tectonic implications.Aspects of the Tectonic evolution of China, Editors Fletcher, Ali, Aitchison, Geological Society Of America, Spec. Pub.226, pp.247-71China, TibetUHP
DS1989-0648
1989
Staudigel, H.Hoernie, K.A., Tilton, G., Le Bas, M.J., Staudigel, H.A plume origin for Fuerteventura (Canary Islands) carbonatitesEos, Vol. 70, No. 15, April 11, p. 503. (abstract.)GlobalCarbonatite
DS200812-0586
2008
Staudigel, H.Konter, J.C., Hanan, B.B., Blichert-Toft, J., Koppers, A.A.P., Plank, T., Staudigel, H.One hundred million years of mantle geochemical history suggest the retiring of mantle plumes is premature.Earth and Planetary Science Letters, Vol. 275, 3-4, pp. 285-295.MantleMagmatism
DS2002-0633
2002
Stauffer, M.Hajnal, Z., White, D., Clowes, R., Stauffer, M.3- D perspective of the western portion of the Trans Hudson Orogen in SaskatchewanGac/mac Annual Meeting, Saskatoon, Abstract Volume, P.44., p.44.SaskatchewanGeophysics - seismics
DS2002-0634
2002
Stauffer, M.Hajnal, Z., White, D., Clowes, R., Stauffer, M.3- D perspective of the western portion of the Trans Hudson Orogen in SaskatchewanGac/mac Annual Meeting, Saskatoon, Abstract Volume, P.44., p.44.SaskatchewanGeophysics - seismics
DS200512-0389
2005
Stauffer, M.Hajnal, Z., Lewry, J., White, D., Ashton, K., Clowes, R., Stauffer, M., Gyorfi, I., Takacs, E.The Saskatchewan Craton and Hearne Province margin: seismic reflection studies in the western Trans Hudson Orogen.Canadian Journal of Earth Sciences, Vol. 42, 4, April pp. 403-419.Canada, Saskatchewan, ManitobaGeophysics - Lithoprobe
DS1984-0705
1984
Stauffer, M.R.Stauffer, M.R.Manikewan: an Early Proterozoic ocean in central Canada, its igneous history and orogenic closure.Precambrian Research, Vol. 25, pp. 257-81.Saskatchewan, AlbertaTectonics
DS1987-0712
1987
Stauffer, M.R.Stauffer, M.R., Gendzwill, D.J.Fractures in the northern plains, stream patterns and the midcontinent stress field.Canadian Journal of Earth Sciences, Vol. 24, pp. 1086-97.Saskatchewan, MontanaGeophysics - seismics
DS1993-1524
1993
Stauffer, M.R.Stauffer, M.R., Lewry, J.F.Regional setting and kinematic features of the Needle Falls Shear Zone, Trans-Hudson orogenCanadian Journal of Earth Sciences, Vol. 30, No. 7, July, pp. 1338-1354SaskatchewanStructure, Trans-Hudson orogen
DS1985-0735
1985
Staufigel, H.Woener, G., Staufigel, H., Zindler, A.Isotopic Constraints on Open System Evolution of the Laacher See Magma Chamber.Earth Planet. Sci. Letters, Vol. 75, No. 1, PP. 37-49.GlobalLeucitite, Nephelinite, Basanite
DS200812-1115
2008
Staurt, F.M.Staurt, F.M., Basu, S., Ellam, R., Fitton, G., Starkey, N.Is there a hidden primordial 3He rich reservoir in the deep Earth?Goldschmidt Conference 2008, Abstract p.A908.Europe, Iceland, Canada, Baffin IslandChemistry - basalts
DS1991-1655
1991
Stavnezer, J.Stavnezer, J., and reply Reaban, M.E., Griffiths, J.A.Triple helix stabilizationNature, Vol. 351, No. 6326, June 6, p. 447GlobalStructure, Tectonics
DS1987-0713
1987
Stavskiy, A.P.Stavskiy, A.P., Berezner, O.S.Alkalic rocks of the Tas Khayakhtakh range, northeastern USSRDoklady Academy of Science USSR, Earth Science Section, Vol. 287, No. 1-6, pp. 63-66RussiaBlank
DS200512-1044
2004
Stazhevskii, S.B.Stazhevskii, S.B.Ring structures as a contribution to the genesis and stress strain state of mineral deposits.Journal of Mining Science, Vol. 40, 3, pp. 259-264.Mining - not specific to diamonds
DS200712-1035
2006
Stea, R.Stea, R., Hanchar, D., Johnson, M.Glacial mapping as an aid to diamond exploration.34th Yellowknife Geoscience Forum, p. 104. abstractCanada, NunavutTahera - till sampling
DS201012-0754
2009
Stea, R.R.Stea, R.R., Johnson, M., Hanchar, D.The geometry of kimberlite indicator mineral dispersal fans in Nunavut, Canada.Geological Association of Canada Short Course, No. 18, pp. 1-14.Canada, NunavutGeomorphology, geochemistry
DS201612-2340
2016
Stead, C.V.Stead, C.V., Tomlinson, E.L., Kamber, B.S., Babechuk, M.G., McKenna, C.A.REE determination in olivine by LA-Q-ICP-MS: an analytical strategy and applications.Geostandards and Geoanalytical Research, in press availableTechnologyREE mass fractions

Abstract: Olivine offers huge, largely untapped, potential for improving our understanding of magmatic and metasomatic processes. In particular, a wealth of information is contained in rare earth element (REE) mass fractions, which are well studied in other minerals. However, REE data for olivine are scarce, reflecting the difficulty associated with determining mass fractions in the low ng g-1 range and with controlling the effects of LREE contamination. We report an analytical procedure for measuring REEs in olivine using laser ablation quadrupole-ICP-MS that achieved limits of determination (LOD) at sub-ng g-1 levels and biases of ~ 5-10%. Empirical partition coefficients (D values) calculated using the new olivine compositions agree with experimental values, indicating that the measured REEs are structurally bound in the olivine crystal lattice, rather than residing in micro-inclusions. We conducted an initial survey of REE contents of olivine from mantle, metamorphic, magmatic and meteorite samples. REE mass fractions vary from 0.1 to double-digit ng g-1 levels. Heavy REEs vary from low mass fractions in meteoritic samples, through variably enriched peridotitic olivine to high mass fractions in magmatic olivines, with fayalitic olivines showing the highest levels. The variable enrichment in HREEs demonstrates that olivine REE patterns have petrological utility.
DS201709-2065
2017
Stead, C.V.Tomlinson, E.L., Kamber, B.C., Hoare, C.V., Stead, C.V., Ildefonse, B.An exsolution origin for Archaean mantle garnet.Goldschmidt Conference, abstract 1p.Mantlegarnet

Abstract: It is now well established that the cratonic sub-continental lithospheric mantle (SCLM) represents a residue of extensively melted fertile peridotite. The widespread occurrence of garnet in the Archaean SCLM remains a paradox because many experiments agree that garnet is exhausted beyond c. 20% melting. It has been suggested that garnet may have formed by exsolution from Al-rich orthopyroxene [1,2,3]. However, the few examples of putative garnet exsolution in cratonic samples remain exotic and have not afforded a link to garnet that occurs as distinct grains in granular harzburgite. We present crystallographic (EBSD), petrographic and chemical (SEM-EDS and LA-ICP-MS) data for an exceptionally well-preserved orthopyroxene megacryst juxtaposed against granular harzburgite. Garnet lamellae within the megacryst show crystallographic continuity and have a strong fabric relative to the host orthopyroxene, strongly indicating that the megacryst formed by exsolution. Garnet lamellae are sub-calcic Cr-pyropes with sinusoidal rare earth element patterns, while the orthopyroxene host is high-Mg enstatite; the reconstructed precursor is clinoestatite. The megacryst shows evidence for disintegrating into granular peridotite, and garnet and orthopyroxene within the granular peridotite are texturally and chemically identical to equivalent phases in the megacryst. Collectively, this evidence supports a common origin for the granular and exsolved portions of the sample. The compositions of the exsolved Cr pyrope and enstatite are typical of harzburgites and depleted lherzolites from the SCLM. Furthermore, garnet inclusions within orthopyroxene in several granular peridotites exhibit the same fabric as those in the exsolved megacryst. We hypothesise that clinoenstatite was a common phase in cratonic SCLM and that exsolution is the likely origin of many sub-calcic garnets in depleted peridotites.
DS201805-0983
2018
Stead, C.V.Tomlinson, E.L., Kamber, B.S., Hoare, B.C., Stead, C.V., Ildefonse, B.An exsolution origin for Archean mantle garnet. C-SCLM KaapvaalGeology, Vol. 46, 2, pp. 123-126.Africa, South Africacraton

Abstract: It is well established that the cratonic subcontinental lithospheric mantle (C-SCLM) represents a residue of extensively melted peridotite. The widespread occurrence of garnet in C-SCLM remains a paradox because experiments show that it should be exhausted beyond ~20% melting. It has been suggested that garnet may have formed by exsolution from Al-rich orthopyroxene; however, the few documented examples of garnet exsolution in cratonic samples are exotic and do not afford a direct link to garnet in granular harzburgite. We report crystallographic, petrographic, and chemical data for an exceptionally well preserved orthopyroxene megacryst containing garnet lamellae, juxtaposed against granular harzburgite. Garnet lamellae are homogeneously distributed within the host orthopyroxene and occur at an orientation that is unrelated to orthopyroxene cleavage, strongly indicating that they formed by exsolution. Garnet lamellae are subcalcic Cr-pyrope, and the orthopyroxene host is high-Mg enstatite; these phases equilibrated at 4.4 GPa and 975 °C. The reconstructed precursor is a high-Al enstatite that formed at higher pressure and temperature conditions of ~6 GPa and 1750 °C. The megacryst shows evidence for disintegrating into granular peridotite, and garnet and orthopyroxene within the granular peridotite are texturally and chemically identical to equivalent phases in the megacryst. Collectively, this evidence supports a common origin for the granular and exsolved portions of the sample. We hypothesize that high-Al enstatite was a common phase in the C-SCLM and that exsolution during cooling and stabilization of the C-SCLM could be the origin of most subcalcic garnets in depleted peridotites.
DS1992-0479
1992
Stead, D.Fowler, C.M.R., Stead, D., Pandit, B.I., Nisbet, E.G.Physical properties of rocks from the Trans-Hudson OrogenEos Transactions, Vol. 73, No. 14, April 7, supplement abstracts p. 322SaskatchewanLithoprobe, Geophysics -magnetics
DS201112-0997
2011
Stead, R.Steck, L.K., Behnaud, M.L., Phillips, S., Stead, R.Tomography of crustal P and S travel times across the western United States.Journal of Geophysical Research, Vol. 116, no. B 11, B11304.United StatesGeophysics - seismics
DS1988-0766
1988
Steams, R.G.Wyatt, D.E. Jr., Steams, R.G.Possible active fault zones in west Tennessee interpreted from surface lineaments and magnetic and gravity anomaliesSoutheastern Geology, Vol. 28, No. 4, May pp. 191-210GlobalStructure, Geophysics
DS1986-0484
1986
Stearn, C.W.Larsson, S.Y., Stearn, C.W.Silurian stratigraphy of the Hudson bay Lowland in QuebecCanadian Journal of Earth Sciences, Vol. 23, pp. 288-99.QuebecStratigraphy
DS1993-1549
1993
Stearn, C.W.Suchy, D.R., Stearn, C.W.Evidence of a continent wide fault system on the Attawapiskat River, Hudson Bay Platform, northern Ontario.Canadian Journal of Earth Sciences, Vol. 30, No. 8, August pp. 1668-1673.OntarioTectonics, structure, fault, Attawapiskat River area
DS1930-0043
1930
Stearn, N.H.Stearn, N.H.A Geomagnetic Survey of the Bauxite Region in Central Arkansas.Arkansaw Geological Survey Bulletin., No. 5, 16P.United States, Gulf Coast, ArkansasGeophysics
DS1930-0121
1932
Stearn, N.H.Stearn, N.H.Practical Geomagnetic Exploration With the Hotchkiss SuperdiAmerican Institute of Mining and Metallurgy. Transactions, Vol. 97, PP. 195-199.United States, Gulf Coast, Arkansas, PennsylvaniaKimberlite, Geophysics, Groundmag, Prairie Creek, Crater Of Diamonds
DS1960-1193
1969
Stearns, D.G.Puryear, S.M., Stearns, D.G.Control of Fabric of the Wells Creek Structure by Pre-existing Joints.Geological Society of America (GSA) SPECIAL PAPER., No. 121, P. 462, (abstract.).GlobalKimberlite, Western Tennessee, Cryptoexplosion, Central States
DS1960-1107
1969
Stearns, P.G.Ganster, M., Stearns, P.G.Configuration and Source of Anomalous Magnetic Field Near Gordonsville in Smith County, Tennessee.Tennessee Academy of Science Journal, Vol. 44, No. 2, P. 49, (abstract.).United States, Tennessee, Central StatesBlank
DS1960-0296
1962
Stearns, R.G.Stearns, R.G., Marcher, M.V.Late Cretaceous and Subsequent Structural Development of The Northern Mississippi Embayment Area.Geological Society of America (GSA) Bulletin., Vol. 73, PP. 1387-1394.GlobalMid-continent
DS1960-0311
1962
Stearns, R.G.Wilson, C.W.JR., Stearns, R.G.Development of the Nashville Dome, TennesseeGeological Society of America (GSA) Bulletin., Vol. 73, No. 4, PP. 481-504.Central States, Western TennesseeKimberlite, Tectonics
DS1960-0605
1965
Stearns, R.G.Stearns, R.G., Marsh, P.S.Preliminary Conclusions from a Regional Gravity Survey of The Wells Creek Basin Structure, Houston and Stewart Counties.Tennessee Academy of Science Journal, Vol. 40, No. 2, P. 67, (abstract.).GlobalKimberlite, Geophysics
DS1960-0767
1966
Stearns, R.G.Wilson, C.W. JR., Stearns, R.G.Circumferential Faulting Around Wells Creek Basin, Houston And Stewart Counties, Tennessee- a Manuscript by Safford, J.m. and Lander, D.w.t. : Circa 1895.Tennessee Academy of Science Journal, Vol. 41, No. 1, PP. 37-48.GlobalKimberlite, Western Tennessee, Central States, Cryptoexplosion
DS1960-0768
1966
Stearns, R.G.Wilson, C.W.JR., Stearns, R.G., et al.Wells Creek Basin Cryptoexplosion Structure, Stewart and Houston Counties, Tennessee... Progress Report.Geological Society of America (GSA) SPECIAL PAPER., No. 87, PP. 266-267, (abstract.).GlobalKimberlite, Western Tennessee, Cryptoexplosion, Central States
DS1960-0880
1967
Stearns, R.G.Stearns, R.G., et al.The Wells Creek Structure-tennessee: Shock Metamorphism of Natural Naterials.First Conference Greenbelt, Maryland, Monobrook Corporation., PP. 323-337.GlobalKimberlite, Western Tennessee, Cryptoexplosion, Central States
DS1975-0419
1976
Stearns, R.G.Stearns, R.G., Zurawski, A.Post-cretaceous Faulting in the Head of the Mississippi Embayment.Southeast Geol., Vol. 17, PP. 207-229.GlobalMid-continent
DS1985-0641
1985
Stearns, R.G.Stearns, R.G., Wyatt, D.E.Segmentation of Reelfoot Rift As Evidenced by Geophysics, Groundwater and Stream Lineations.Geological Society of America (GSA), Vol. 17, No. 5, MARCH P. 328.United States, MissouriMid Continent
DS1900-0408
1906
Steart, F.A.Hall, A.L., Steart, F.A.On Folding and Faulting in the Pretoria Series and the Dolomite.Geological Society of South Africa Transactions, Vol. 8, PP. 7-15.Africa, South AfricaGeology, Structure
DS1995-1822
1995
StebbinsStebbins, McMillan, DingwellStructure, dynamics and properties of silicate meltsMineralogical Society of America, Vol. 32GlobalBook -table of contents, Silicate melts
DS200712-0428
2006
Stebbins, J.F.Henderson, G.S., Calas, G., Stebbins, J.F.The structure of silicate glasses and melts.Elements, Vol. 2, 5, October pp. 269-274.TechnologyGeochemistry
DS201112-0766
2011
Stebbins, J.F.Palke, A.C., Stebbins, J.F.Variable temperature 27Al and 29Si NMR studies of synthetic forsterite and Fe bearing Dora Maira pyrope garnet: temperature dependence and mechanisms of paramagnetically shifted peaks.American Mineralogist, Vol. 96, pp. 1090-1099.Europe, ItalySpectroscopy, paramagnetic shifts
DS2003-1329
2003
Steblov, G.M.Steblov, G.M., Kogan, M.G., King, R.W., Scholz, C.H., Burgmann, R., FrolovImprint of the North American plate in Siberia revealed by GPSGeophysical Research Letters, Vol. 30, 18, 1924 DOI.1029/2003GLO17805Russia, Siberia, Northwest Territories, EurasiaGeophysics - seismics
DS200412-1917
2004
Steblov, G.M.Steblov, G.M.Interaction between lithospheric plates in northeastern Asia.Doklady Earth Sciences, Vol. 394, 2, Feb-Mar. pp. 226-229.AsiaTectonics
DS200412-1918
2003
Steblov, G.M.Steblov, G.M., Kogan, M.G., King, R.W., Scholz, C.H., Burgmann, R., Frolov, D.I.Imprint of the North American plate in Siberia revealed by GPS.Geophysical Research Letters, Vol. 30, 18, 1924 DOI.1029/2003 GLO17805Russia, Siberia, Canada, Northwest TerritoriesGeophysics - seismics
DS1982-0579
1982
Stecher, O.Stecher, O., Thy, P.Kimberlite and Lamproite Dykes, West Greenland, Implications for Melting Richterite, Phlogopite, and Clinopyroxene in Alil Enriched Mantle.Proceedings of Third International Kimberlite Conference, TERRA COGNITA, ABSTRACT VOLUME., Vol. 2, No. 3, PP. 212-213, (abstract.).GreenlandKimberlite, Geochemistry, Mineralogy
DS1982-0580
1982
Stecher, O.Stecher, O., Thy, P.Kimberlite and Lamproite Dykes West Greenland. Implications for Melting of Richterite, Phlogopite and Clinopyroxene in A Lil Enriched Mantle.Terra Cognita., Vol. 2, PP. 212-213. (abstract.).GreenlandMineral Chemistry
DS1985-0670
1985
Stecher, O.Thy, P., Stecher, O., Korstgard, J.A.Crystallization sequences in kimberlite and lamproite dikes from the Sisimuit area, central West GreenlandPreprint from author, 70pGreenlandLamproite
DS1987-0714
1987
Stecher, O.Stecher, O., Thy, P., Carlson, R.W.Subcrustal metasomatism below west Greenland: isotopic and geochemical evidence from lamproite and kimberlite dykesTerra Cognita, Conference abstracts Oceanic and Continental Lithosphere:, Vol. 7, No. 4, Autumn, abstract only p. 625GreenlandBlank
DS1987-0739
1987
Stecher, O.Thy, P., Stecher, O., Korstgard, J.A.Mineral chemistry and crystallization sequences in Kimberlite and lamproite dikes from the Sisimiut area, West GreenlandLithos, Vol. 20, pp. 391-417GreenlandMineral Chemistry, Analyses
DS2001-0105
2001
Stecher, O.Bernstein, S., Brooks, C.K., Stecher, O.Enriched component of the proto Icelandic mantle plume revealed in alkaline tertiary lavas from East GreenlandGeology, Vol. 29, No. 9, Sept. pp. 859-62.GreenlandHotspot
DS2001-0106
2001
Stecher, O.Bernstein, S., Brooks, C.K., Stecher, O.Enriched component of the proto-Icelandic mantle plume revealed in alkaline Tertiary lavas from East GreenlandGeology, Vol. 29, No. 9, Sept. pp. 859-62.GreenlandMelting, mixing, alkaline lavas, Nunatak region
DS2003-0547
2003
Stecher, O.Hanghjoi, K., Storey, M., Stecher, O.An isotope and trace element study of the East Greenland Tertiary dyke swarm:Journal of Petrology, Vol. 44, 11, Nov. pp. 2081-2112.GreenlandDyke - geochemistry
DS200412-0781
2003
Stecher, O.Hanghjoi, K., Storey, M., Stecher, O.An isotope and trace element study of the East Greenland Tertiary dyke swarm: constraints on temporal and spatial evolution duriJournal of Petrology, Vol. 44, 11, Nov. pp. 2081-2112.Europe, GreenlandDyke - geochemistry
DS200412-1513
2004
Stecher, O.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
DS200412-1932
2004
Stecher, O.Storey, M., Pedersen, A.K., Stecher, O., Bernstein, S., Larsen, H.C., Larsen, L.M., Baker, Duncan, R.A.Long lived post breakup magmatism along the East Greenland margin: evidence for shallow mantle metasomatism by the Iceland plumeGeology, Vol. 32, 2, Feb. pp. 173-176.Europe, Greenland, IcelandMagmatism
DS201112-0997
2011
Steck, L.K.Steck, L.K., Behnaud, M.L., Phillips, S., Stead, R.Tomography of crustal P and S travel times across the western United States.Journal of Geophysical Research, Vol. 116, no. B 11, B11304.United StatesGeophysics - seismics
DS200412-1998
2004
Stedra, V.Timmermann, H., Stedra, V., Gerdes, A., Noble, S.R., Parrish, R.R., Dorr, W.The problem of dating high pressure metamorphism: a U Pb isotope and geochemical study on eclogites and related rocks of the MarJournal of Petrology, Vol. 45, 7, pp. 1311-1338.Europe, Czech RepublicEclogite, UHP
DS2003-1529
2003
Steeds, J.Yeliseev, A.P., Pkhilenko, N.P., Zedgenizov, D.A., Steeds, J.Features of coated diamonds from the Snap Lake King Lake kimberlite dyke system8ikc, Www.venuewest.com/8ikc/program.htm, Session 3, POSTER abstractNorthwest TerritoriesDiamonds - inclusions, Deposit - Snap Lake, King Lake
DS200412-2181
2004
Steeds, J.W.Yelisseyev, A.P., Pokhilenko, N.P., Steeds, J.W., Zedgenizov, D.A., Afanasiev, V.P.Features of coated diamonds from the Snap Lake/King Lake kimberlite dyke, Slave Craton, Canada, as revealed by optical topographLithos, Vol. 77, 1-4, Sept. pp. 83-97.Canada, Northwest TerritoriesCoated diamonds, absorption, luminescence, nickel, nitr
DS1992-1468
1992
Steefel, C.ISteefel, C.I, Lasaga, A.C.Transport into water-rock interaction modelsGeology, Vol. 20, No. 8, August pp. 680-684GlobalFluid flow paths, Water-rock interaction
DS1987-0413
1987
Steel, E.Lewis, R.S., Ming, T., Wacker, J.F., Anders, E., Steel, E.Interstellar diamonds in meteoritesNature, Vol. 326, No. 6109, March 12, pp. 160-161GlobalMeteorites
DS201112-1098
2011
SteeleWalter, M.J., Kohn, Arajuo, Bulanova, Smith, Gaillou, Wang, Steele, ShireyDeep mantle cycling of oceanic crust: evidence from diamonds and their mineral inclusions.Science, Vol. 334, 6052, pp. 51-52.MantleDiamond inclusions
DS200612-0822
2005
Steele, A.Lindsay, J.F., Brasier, M.D., McLoughlin, N., Green, O.R., Fogel, M., Steele, A., Mertzman, S.A.The problem of deep carbon - an Archean paradox.Precambrian Research, Vol. 143,1-4, Dec. 15, pp. 1-22.AustraliaCarbon dykes, geochronology
DS201012-0214
2010
Steele, A.Gaillou, E., Post, J.E., Bassim, N.D., Zaitsev, A.M., Rose, T., Fries, M.D., Stroud, R.M., Steele, A., Butler, J.E.Spectroscopic and microscopic characterizations of color laminae in natural pink diamonds.Diamond and Related Materials, Vol. 19, 10, pp. 1207-1220.TechnologySpectroscopy
DS201112-0145
2011
Steele, A.Carmody, L., Jones, A.P., Kilburn, C., Steele, A., Bower, D.A first Raman study of fluid inclusions within xenoliths from Oldoinyo Lengai, Tanzania.Peralk-Carb 2011, workshop held Tubingen Germany June 16-18, PosterAfrica, TanzaniaCarbonatite
DS201112-0146
2011
Steele, A.Carmody, L., Jones, A.P., Kilburn, C., Steele, A., Bower, D.A first Raman study of fluid inclusions within xenoliths from Oldoinyo Lengai, Tanzania.Peralk-Carb 2011... workshop June 16-18, Tubingen, Germany, Abstract p.15-16.Africa, TanzaniaCarbonatite
DS201112-0147
2011
Steele, A.Carmody, L., Jones, A.P., Kilburn, C., Steele, A., Bower, D.A first Raman study of fluid inclusions within xenoliths from Oldoinyo Lengai, Tanzania.Peralk-Carb 2011... workshop June 16-18, Tubingen, Germany, Abstract p.15-16.Africa, TanzaniaCarbonatite
DS201312-0126
2012
Steele, A.Carmody, L., Jones, A.P., Mikhail, S., Bower, D.M., Steele, A., Lawrence, D.M., Verchovsky, A.B., Buikin, A., Taylor, L.A.Is the World's only carbonatite volcano a dry anhydrous system?Geological Society of America Annual Meeting abstract, Paper 157-2, 1/2p. AbstractAfrica, TanzaniaDeposit - Oldoinyo Lengai
DS201412-0261
2014
Steele, A.Galillou, E., Post, J.E., Steele, A., Butler, J.E.Constrains on highly strained pink diamonds by high spatial resolution FTIR and Raman mapping.Geological Society of America Conference Vancouver Oct. 19-22, 1p. AbstractTechnologyPink diamond colour
DS201612-2339
2016
Steele, A.Smit, K.V., Shirey, S.B., Stern, R.A., Steele, A., Wang, W.Diamond growth from C-H-N-O recycled fluids in the lithosphere: Evidence from CH4 micro-inclusions and dleta 13 C-Delta 15 N-N content in Marange mixed-habit diamonds.Lithos, Vol. 265, pp. 68-81.Africa, ZimbabweDeposit - Marange
DS201705-0875
2017
Steele, A.Smit, K.V., Stachel, T., Stern, R.A., Shirey, S.B., Steele, A.Diamond formation through isochemical cooling of CHO fluids vs redox buffering: examples from Marange peridotitic and Zimmi eclogitic diamonds.European Geosciences Union General Assembly 2017, Vienna April 23-28, 1p. 9187 AbstractAfrica, Zimbabwe, Sierra LeoneDeposit - Marange, Zimmi

Abstract: Traditional models for diamond formation within the lithospheric mantle invoke either carbonate reduction or methane oxidation. Both these mechanisms require some oxygen exchange with the surrounding wall-rock at the site of diamond precipitation. However, peridotite does not have sufficient buffering capacity to allow for diamond formation via these traditional models and instead peridotitic diamonds may form through isochemical cooling of H 2 O-rich CHO fluids [1]. Marange mixed-habit diamonds from eastern Zimbabwe provide the first natural confirmation of this new diamond growth model [2]. Although Marange diamonds do not contain any silicate or sulphide inclusions, they contain Ni-N-vacancy complexes detected through photoluminescence (PL) spectroscopy that suggest the source fluids equilibrated in the Ni-rich depleted peridotitic lithosphere. Cuboid sectors also contain abundant micro-inclusions of CH 4 , the first direct observation of reduced CH 4-rich fluids that are thought to percolate through the lithospheric mantle [2]. In fluid inclusion-free diamonds, core-to-rim trends in d 13 C and N content are used to infer the speciation of the diamond-forming fluid. Core to rim trends of increasing d 13 C with decreasing N content are interpreted as diamond growth from oxidized CO 2-or carbonate-bearing fluids. Diamond growth from reduced species should show the opposite trends-decreasing d 13 C from core to rim with decreasing N content. Within the CH 4-bearing growth sectors of Marange diamonds, however, such a 'reduced' trend is not observed. Rather, d 13 C increases from core to rim within a homogeneously grown zone [2]. These contradictory observations can be explained through either mixing between CH 4-and CO 2-rich end-members of hydrous fluids [2] or through closed system precipitation from an already mixed CH 4-CO 2 H 2 O-maximum fluid with XCO 2 (CO 2 /[CO 2 +CH 4 ]) between 0.3 and 0.7 [3]. These results demonstrate that Marange diamonds precipitated from cooling CH 4-CO 2-bearing hydrous fluids rather than through redox buffering. As this growth mechanism applies to both the fluid-rich cuboid and gem-like octahedral sectors of Marange diamonds, a non-redox model for diamond formation from mixed CH 4-CO 2 fluids is indicated for a wider range of gem-quality peridotitic diamonds. Indeed, at the redox conditions of global diamond-bearing lithospheric mantle (FMQ-2 to-4; [4]), CHO fluids are strongly water-dominated and contain both CH 4 and CO 2 as dominant carbon species [5]. By contrast diamond formation in eclogitic assemblages, through either redox buffering or cooling of carbon-bearing fluids, is not as well constrained. Zimmi diamonds from the West African craton have eclogitic sulphide inclusions (with low Ni and high Re/Os) and formed at 650 Ma, overlapping with the timing of subduction [6]. In one Zimmi diamond, a core to rim trend of decreasing d 13 C (-23.4 to-24.5 %¸) and N content is indicative of formation from reduced C 2 H 6 /CH 4-rich fluids, likely derived from oceanic crust recycled during Neoproterozoic subduction. Unlike mixed CH 4-CO 2 fluids near the water maximum, isochemical cooling or ascent of such reduced CHO fluids is not effficient at diamond precipitation. Furthermore, measurable carbon isotopic variations in diamond are not predicted in this model and therefore cannot be reconciled with the ~1 internal variation seen. Consequently, this Zimmi eclogitic diamond likely formed through redox buffering of reduced subduction-related fluids, infiltrating into sulphide-bearing eclogite.
DS1992-1078
1992
Steele, I.Mitchell, R.H., Steele, I.Potassium zirconium and titanium silicates and strontian cerianperovskitein lamproites from the Leucite Hills, Wyoming.Canadian Mineralogist, Vol. 30, No. 4, December pp. 1153-1160.WyomingLamproites, Leucite Hills
DS1975-0760
1978
Steele, I.M.Hervig, R.L., Smith, J.V., Steele, I.M.Mineral Chemistry of Fertile and Barren Harzburgites from The Upper Mantle Below South Africa.Geological Society of America (GSA), Vol. 10, No. 7, P. 420. (abstract.).South AfricaGeochemistry
DS1980-0171
1980
Steele, I.M.Hervig, R.L., Smith, J.V., Steele, I.M., Dawson, J.B.Fertile and Barren Aluminum- Chromium Spinel Harzburgites from the UpperEarth and Planetary Science Letters, Vol. 50, PP. 41-58.South AfricaPetrology, Probe, Mineral Chemistry
DS1980-0172
1980
Steele, I.M.Hervig, R.L., Smith, J.V., Steele, I.M., Gurney, J.J., Meyer, H.Diamonds: Minor Elements in Silicate Inclusions: Pressure Temperature Implications.Journal of Geophysical Research, Vol. 85, No. B 12, DECEMBER 10TH. PP. 6919=6929.GlobalMineralogy
DS1989-0339
1989
Steele, I.M.Dawson, J.B., Smith, J.V., Steele, I.M.Combeite (Na2.33Ca1.74 others 0.12) Si3O9 from Oldoinyo Lengai, TanzaniaJournal of Geology, Vol. 97, No. 3, May pp. 365-372TanzaniaCarbonatite, Mineralogy
DS1994-0403
1994
Steele, I.M.Dawson, J.B., Smith, J.V., Steele, I.M.Trace element distribution between co-existing perovskite, apatite and titanite from Oldoinyo Lengai.Chemical Geol., Vol. 117, pp. 285-290.TanzaniaCarbonatite, Deposit -Oldoinyo Lengai
DS1994-0404
1994
Steele, I.M.Dawson, J.B., Smith, J.V., Steele, I.M.Trace element distribution between coexisiting perovskite, apatite and titanite from Oldoinyo Lengai, Tanzania.Chemical Geology, Vol. 117, pp. 285-290.TanzaniaGeochemistry
DS1995-0399
1995
Steele, I.M.Dawson, J.B., Smith, J.V., Steele, I.M.Petrology and mineral chemistry of plutonic igneous xenoliths from carbonatite volcano, Oldoinyo Lengai.Journal of Petrology, Vol. 36, No. 3, pp. 797-826.TanzaniaCarbonatite, Deposit -Oldoinyo Lengai
DS1996-0346
1996
Steele, I.M.Dawson, J.B., Steele, I.M., Smith, J.V., Rivers, M.L.Minor and trace element chemistry of carbonates, apatites and magnetites insome African carbonatites.Mineralogical Magazine, Vol. 60, pp. 415-425.South Africa, AfricaCarbonatite, Geochemistry
DS1998-0478
1998
Steele, I.M.Gaspar, J.C., Teixeira, N.A., Steele, I.M.Cathodluminescence of Juin a diamonds7th International Kimberlite Conference Abstract, pp. 242-4.BrazilAlluvials, Deposit - Juina
DS2002-1546
2002
Steele, K. Sangster.Steele, K. Sangster.Ontario's Eastern Frontier, uranium, diamonds and cement. One page overview ofCim Toronto Branch Industrial Minerals Division Field Trip Monday October 21, 1p.Ontario, Prince Edward CountyBrief
DS1970-0722
1973
Steele, K.F.Howard, J.M., Steele, K.F., Owens, D.R.Chemically Rounded Xenoliths in an Alkalic Dike, Garland County, Arkansaw.Geological Society of America (GSA), Vol. 5, No. 3, P. 263. (abstract.).United States, Gulf Coast, Arkansas, Garland CountyPetrology
DS1975-0108
1975
Steele, K.F.Howard, J.M., Steele, K.F.Origin of the Potash Sulfur Springs Intrusive Complex, Arkansas.Geological Society of America (GSA), Vol. 7, No. 4, P. 502. (abstract.).United States, Gulf Coast, Arkansas, Garland CountyGeology
DS1975-0297
1976
Steele, K.F.Jackson, K.D., Steele, K.F.New Dat a on Some Arkansaw Igneous RocksGeological Society of America (GSA), Vol. 8, No. 1, PP. 25-26. (abstract.).United States, Gulf Coast, Arkansas, Garland CountyGeochemistry
DS1975-0420
1976
Steele, K.F.Steele, K.F., Robison, E.C.Chemical Relationships of Lamprophyre, Central ArkansawEos, Vol. 57, P. 1018. (abstract.).United States, Gulf Coast, ArkansasGeochemistry
DS1975-0604
1977
Steele, K.F.Robison, E.C., Steele, K.F., Jackson, K.C.Geochemistry of Lamprophyric Rocks, Eastern Ouachita Mountains, Arkansaw.Geological Society of America (GSA), Vol. 9, No. 1, PP. 69-70.United States, Oklahoma, Gulf Coast, Arkansas, Garland CountyPetrology, Geochemistry
DS1975-0630
1977
Steele, K.F.Steele, K.F., Robison, E.C.Chemical Weathering of Lamprophyric Rock, Central ArkansawArkansaw Academy of Science Proceedings, Vol. 31, PP. 119-121.United States, Gulf Coast, ArkansasPetrology, Geomorphology
DS1975-0647
1977
Steele, K.F.Wagner, G.H., Steele, K.F.The Chemical Composition of Carbonatite in Conway and Perry counties of Arkansaw.Arkansaw Academy of Science Proceedings, Vol. 31, PP. 121-123.United States, Gulf Coast, Arkansas, Conway County, PennsylvaniaPetrology
DS1975-1232
1979
Steele, K.F.Steele, K.F., Jackson, K.C., Van buren, W.Geochemical Comparison of Arkansaw SyeniteGeological Society of America (GSA), Vol. 11, No. 2, P. 166. (abstract.).United States, Gulf Coast, Arkansas, Garland County, Hot Spring CountyMagnet Cove, Potash Sulfur Springs, Geochemistry
DS1975-1233
1979
Steele, K.F.Steele, K.F., Wagner, G.H.Relationship of the Murfreesboro Kimberlite and Other Igneous Rocks of Arkansaw.International Kimberlite Conference SECOND Proceedings, Vol. 1, PP. 393-399.United States, Gulf Coast, Arkansas, Pennsylvania, OklahomaPetrology
DS1982-0581
1982
Steele, K.F.Steele, K.F.Uranium and Other Element Analyses of Igneous Rocks of Arkansas.National Technical Information Service, DU PONT DE NEMOURS AND CO., GJBX-129-82, DPST-8L-141-17, 14P. FICHE ONLY.United States, Gulf Coast, Arkansas, Pennsylvania, Hot Spring CountyGeochemistry
DS1983-0116
1983
Steele, K.F.Bales, J.R., Steele, K.F.A Comparison of Carbonatites at Magnet Cove and Potash Sulfur Springs, Arkansaw.Geological Society of America (GSA), Vol. 15, No. 1, P. 7, (abstract.).United States, Gulf Coast, Arkansas, Hot Spring County, Garland CountyPetrology, Geochemistry, Ijolite, Mineral Chemistry
DS1986-0696
1986
Steele, K.F.Sadeghi, A., Steele, K.F.Geochemical orientation survey for carbonatites in central ArkansawGeological Society of America, Vol. 18, No. 3, p. 263. AbstractArkansas, Hot Spring County, Garland County, GrantCarbonatite, Geochemistry
DS1989-1324
1989
Steele, K.F.Sadeghi, A., Steele, K.F.Use of stream sediment elemental enrichment factors ingeochemical exploration for carbonatite and uranium,Arkansaw,United States (US)Journal of Geochemical Exploration, Special issue - Geochemical Exploration 1987, Vol. 32, pp. 279-286ArkansasCarbonatite, Geochemistry
DS1985-0040
1985
Steele, K.G.Baker, C.L., Steele, K.G., MccleneaghanReconnaissance till sampling program Matheson Lake Abitibi areaCochranedistrictOntario Geological Survey miscellaneous Paper, No. 126, pp. 329-333OntarioSampling, Geochemistry
DS1989-1448
1989
Steele, K.G.Steele, K.G.Correlation of glacial stratigraphy between drillholes, MathesonOntarioGeological Association of Canada (GAC) Annual Meeting Program Abstracts, Vol. 14, p. A112. (abstract.)OntarioTectonics, Kapuskasing zone
DS200412-1919
2002
Steele, K.Sangster.Steele, K.Sangster.Ontario's Eastern Frontier, uranium, diamonds and cement. One page overview of stop at Picton dyke system.CIM Toronto Branch Industrial Minerals Division Field Trip Monday October 21, 1p.Canada, Ontario, Prince Edward CountyBrief
DS1991-0350
1991
Steele, L.M.Dawson, J.B., Smith, J.V., Steele, L.M.Peralkaline plutonic magmatic rocks of the carbonatite volcano OldoinyoLengaiProceedings of Fifth International Kimberlite Conference held Araxa June 1991, Servico Geologico do Brasil (CPRM) Special, pp. 69-70TanzaniaCarbonatite, Nephelinitic
DS201906-1313
2019
Steele-MacInnis, M.Lentz, D., Steele-MacInnis, M., Charlier, B.Carbonatitic to limestone syntectic decarbonation reactions in silicate magmas: CO2 oxidant enhancing IOA liquid immiscibility.GAC/MAC annual Meeting, 1p. Abstract p. 130.Mantlecarbonatites

Abstract: The formation of Iron Oxide-Apatite (IOA) systems has long been enigmatic. The compositions of both magnetite and apatite and the other component elements suggest derivation from high temperature (T) magmatic systems, with genetic models including iron oxide magmas or igneous magnetite and apatite flotation. Ideas related to the role of H2O and associated oxidative mechanisms have resurfaced from models of the late 1960s. As such, salt melts forming in open, differentially degassing systems could represent an end-member to the formation of IOA deposits. Another end-member involves autometasomatic decarbonation reactions involving ferroan carbonatites with co-genetic melts or host rocks generating CO2 capable of oxidizing carbonatites to enhance magnetite-apatite saturation. The syntectic decarbonation end-member presented here examines the reactions of carbonate melts of mantle origin or from syntectic reactions with limestone, with cogenetic silicate magmas. Although carbonate and silicate melts can coexist at magmatic pressure (P) and T, their compositions must be peralkalic. However, as P decreases, immiscibility or reactivity between these melts is such that CO2 is exsolved (decarbonation) to the point that at near surface conditions, decarbonation is complete. The addition of CO2 to silicate melt will drive the conversion of FeO to Fe2O3 in order to make carbon monoxide (CO), thus shifting the redox equilibria. For most silicate magmas, the amount of dissolved carbonate and CO2 is quite limited, and differential CO2 degassing results. These carbonate: silicate melt reactions then may result in oxidation of the silicate magma, to enhance immiscibility of IOA (liquation) and elemental partitioning associated with liquid-liquid immiscibility. This could be an oxidative mechanism for Fe-Ti tholeiites (ferrobasalts) and diorites to reach a two-liquid field and form IOA melts via liquation. Carbonates would typically be consumed in these reactions, although CO2 is an important degassing product that would substantially increase ?V of the reaction, which has implications during high-level emplacement.
DS201909-2104
2019
Steele-MacInnis, M.Walter, B.F., Steele-MacInnis, M., Giebel, R.J., Marks, M.A.W., Markl, G.Fluids exsolved from the Kaiserstuhl carbonatite, SW Germany: brine generation by boiling.Goldschmidt2019, 1p. AbstractEurope, Germanydeposit - Kaiserstuhl

Abstract: Studies on fluid inclusions in carbonatitic rocks are essential to understand the physicochemical processes involved in carbonatite-related hydrothermal ore mineralization. Although little is known about the composition of carbonatite-derived fluids. We investigated fluid inclusions in the Kaiserstuhl carbonatites, SW Germany [1,2] and identified four different types typically known from carbonatitic systems worldwide [3]: (I): Vapor-poor H2O-NaCl fluids with <50 wt.% salinity. (II): Vapor-rich H2O-NaCl-CO2 fluids with <5 wt.% salinity. (III): Multi-component fluids with high salinity and CO2. (IV): Multi-component fluids with high salinity, no CO2. Homogenization temperatures (156 to 530°C) of all fluid types generally show a wide range [this study, 2]. Primary type I fluid inclusions occur in early magmatic olivine/monticellite, as well as paragenetically later apatites and calcites [2]. This indicates a ubiquitous existence of a saline brine, which does not reach saturation with respect to halite, during early to late crystallization stages. Liquidus surface modelling based quantifications for fluid type III suggest that carbonatite melts predomonantly exsolve Na-K-sulfate-carbonate/bicarbonate-chloride brines (type III or IV, respectively). Such fluid inclusions, with type III (CO2-free) on one side and type IV (and II, both CO2-rich) on the other side, may represent immiscible fluids that were trapped after segregation by boiling from a parental highly saline brine (type I). Fluid boiling, in turn, is probably triggered by a rapid pressure release during “pneumatic hammer-like,” discontinuous melt ascent.
DS202006-0955
2020
Steele-MacInnis, M.Walter, B.F., Steele-MacInnis, M., Giebel, R.J., Marks, M.A.W., Markl, G.Complex carbonatite-sulfate brines in fluid inclusions from carbonatites: estimating compositions in the system H2O-Na-K-CO3-SO4-Cl. KaiserstuhlGeochimica et Cosmochimica Acta, Vol. 277, pp. 224-242. pdfEurope, Germanycarbonatite

Abstract: Studies of fluid inclusions in carbonatitic rocks are essential for understanding physicochemical processes involved in carbonatite-related hydrothermal ore mineralization and fenitization. However, the composition of many carbonatite-derived fluids is challenging to quantify, which hampers their detailed interpretation. Here, we present a systematic study of microthermometry of fluid inclusions found in carbonatites from the Kaiserstuhl (SW Germany), and a simple numerical model to estimate the compositions of such fluids, which are typical of numerous carbonatites worldwide. Four types of fluid inclusions have been identified in the Kaiserstuhl carbonatites: (I) vapor-poor H2O-NaCl fluids with <50?wt.% salinity; (II) vapor-rich H2O-NaCl-CO2 fluids with <5?wt.% salinity; (III) multi-component fluids with high salinity and high CO2 contents; and (IV) multi-component fluids with high salinity but little to no CO2. At present, it is only possible to quantify fluid compositions for types I and II. For the complex types III and IV, we conducted predictive modeling of the liquidus surface based on the Margules equations. The results suggest that carbonatite melts predominantly exsolve Na-K-sulfate-carbonate/bicarbonate-chloride brines (types III or IV). Such fluid inclusions may represent immiscible fluids that were trapped after segregation by boiling from a parental highly saline brine (type I). Fluid boiling, in turn, was probably triggered by a rapid pressure release during melt ascent. The present model enables quantification of fluid compositions associated with carbonatitic magmatism.
DS202007-1184
2020
Steele-MacInnis, M.Walter, B.F., Steele-MacInnis, M., Gielbel, R.J., Marks, M.A.W., Markl, G.Complex carbonatite-sulfate brines in fluid inclusions from carbonatites: estimating compositions in the system H2O-Na-K-CO3-SO4-ClGeochimica et Cosmochimica Acta, Vol. 277, pp. 224-242. pdfEurope, Germanydeposit - Kaiserstuhl

Abstract: Studies of fluid inclusions in carbonatitic rocks are essential for understanding physicochemical processes involved in carbonatite-related hydrothermal ore mineralization and fenitization. However, the composition of many carbonatite-derived fluids is challenging to quantify, which hampers their detailed interpretation. Here, we present a systematic study of microthermometry of fluid inclusions found in carbonatites from the Kaiserstuhl (SW Germany), and a simple numerical model to estimate the compositions of such fluids, which are typical of numerous carbonatites worldwide. Four types of fluid inclusions have been identified in the Kaiserstuhl carbonatites: (I) vapor-poor H2O-NaCl fluids with <50?wt.% salinity; (II) vapor-rich H2O-NaCl-CO2 fluids with <5?wt.% salinity; (III) multi-component fluids with high salinity and high CO2 contents; and (IV) multi-component fluids with high salinity but little to no CO2. At present, it is only possible to quantify fluid compositions for types I and II. For the complex types III and IV, we conducted predictive modeling of the liquidus surface based on the Margules equations. The results suggest that carbonatite melts predominantly exsolve Na-K-sulfate-carbonate/bicarbonate-chloride brines (types III or IV). Such fluid inclusions may represent immiscible fluids that were trapped after segregation by boiling from a parental highly saline brine (type I). Fluid boiling, in turn, was probably triggered by a rapid pressure release during melt ascent. The present model enables quantification of fluid compositions associated with carbonatitic magmatism.
DS202104-0610
2021
Steele-MacInnis, M.Steele-MacInnis, M., Manning, C.E.Hydrothermal properties of geologic fluids.Elements, Vol. 16, pp. 375-380.Mantlewater

Abstract: Aqueous fluids are critical agents in the geochemical evolution of Earth’s interior. Fluid circulation and fluid-rock reactions in the Earth take place at temperatures ranging from ambient to magmatic, at pressures from ambient to extreme, and involve fluids that range from nearly pure H2O through to complex, multicomponent solutions. Consequently, the physical and chemical properties of hydrothermal fluids vary widely as functions of geologic setting; this variation strongly impacts fluid-driven processes. This issue will focus on the nature of geologic fluids at hydrothermal conditions and how such fluids affect geologic processes in some major settings.
DS202109-1494
2021
Steele-MacInnis, M.Walter, B.F., Giebel, R.J., Steele-MacInnis, M., Marks, M.A., Kolb, J., Markl, G.Fluids associated with carbonatitic magmatism: a critical review and implications for carbonatite magma ascent.Earth Science Reviews , Vol. 215, 103509, 27p. PdfMantlemagmatism

Abstract: Carbonatites are formed from volatile-rich melts, commonly associated with a characteristic hydrothermal footprint. However, studies of their fluid inclusions are relatively scarce and heterogeneous in terms of detail and completeness of the data presented. Here, we review and discuss comprehensively the results of previous studies and derive a general model for the formation and properties of fluids associated with carbonatitic magmatism. Worldwide, four types of fluid inclusion occur in carbonatites: (type I/HS) vapour-poor H2O-NaCl fluids with up to 50 wt% salinity; (type II/HC) vapour-rich H2O-NaCl-CO2 fluids with <5 wt% salinity; (type III/DS) multi-component fluids with high salinity and without CO2; and (type IV/CDS) multi-component fluids with high salinity and high CO2. This global dataset suggests continuous fluid release from deep to shallow-level intrusions. Modelling of the liquidus surface indicates that carbonatite magmas generally exsolve a saline brine (type I/HS). This brine separates/evolves into a Na-K-sulfate-carbonate/bicarbonate-chloride brine with or without CO2 (types III/DS and IV/CDS), trapped together with low salinity CO2-rich fluids produced by immiscibility. Fluid immiscibility is related to rapid pressure release during fast, forceful and discontinuous magma ascent, which we envisage as a "pneumatic jackhammer" model for carbonatite ascent and emplacement. In this model, cyclic and progressive fluid flux via pressure build-up and subsequent catastrophic pressure release results in a self-sustaining crustal ascent of the buoyant, low-viscosity magma. This process allows for rapid and efficient magma ascent, in particular above the brittle-ductile transition zone, where pressures that prevailed during apatite crystallization have been estimated in numerous complexes. Moreover, this model provides an explanation for the apparent absence of shallow carbonatite magma chambers (in a classical sense) and identifies fenitization as a phenomenon induced by both fluids released during magma ascent and residual fluids.
DS201112-0998
2011
Steelguru.comSteelguru.comRio Tinto diamond project in India wins social awareness award. Bundersteelguru.com, July 12, 1p.IndiaNews item - Rio Tinto
DS1993-1525
1993
Steels, L.Steels, L., McDermott, J.The knowledge level in expert systemsAcademic Press, 288p. approx. $ 50.00GlobalBook -ad, Expert systems
DS1989-1449
1989
Steenfelt, A.Steenfelt, A.High technology metals in alkaline and carbonatitic rocks in Greenland:recognition and explorationXiii International Geochemical Exploration Symposium, Rio 89 Brazilian, p. 66. AbstractGreenlandCarbonatite, alkaline rocks, Rare earths
DS1992-0571
1992
Steenfelt, A.Gilotti, J.A., Friderichsen, J.D., Higgins, A.K., Steenfelt, A.A new eclogite province in the Arctic Caledonides, southeast Greenland 77to 78 degGeological Society of America (GSA) Abstract Volume, Vol. 24, No. 3, March p. 23. abstractGreenlandEclogite, Xenoliths
DS1999-0711
1999
Steenfelt, A.Steenfelt, A., Jensen, S.M., Larsen, L.M., Stendal, H.Diamond exploration in southern West GreenlandAssocation of Exploration Geologists (AEG) 19th. Diamond Exploration Methods Case Histories, pp. 76-84.GreenlandKimberlite - petrology, Sisimuit, Sarfartoq, Maniitsoq
DS2001-1126
2001
Steenfelt, A.Steenfelt, A.Geochemical atlas of Greenland - west and south GreenlandDanmarks og Gronlands Geologiske Undersogelse Rapport, 2001/46, 33p. 1 CD ROMGreenlandGeochemistry
DS2001-1127
2001
Steenfelt, A.Steenfelt, A.Calibration of stream sediment dat a from Geochemical atlas of Greenland - west and south Greenland.Danmarks og Gronlands Geologiske Undersogelse Rapport, 2001/47, 43p. 1 CD ROMGreenlandGeochemistry
DS2002-0780
2002
Steenfelt, A.Jensen, S.M., Hanson, H., Secher, K., Steenfelt, A., Schjoth, F., Rasmussen, T.M.Kimberlites and other ultramafic alkaline rocks in the Sismiut-Kangerfussuaq region, southwest Greenland.Geology of Greenland Survey Bulletin, No. 191, pp. 57-66.GreenlandDistribution and magnetic signatures of dykes
DS200712-1036
2007
Steenfelt, A.Steenfelt, A., Neilsen, T.D.F., Sand, K.K., Secher, K.,Tappe, S.Kimberlites, ultramafic lamprophyres and carbonatites in west Greenland - an update on occurrences, ages and diamonds.Geological Association of Canada, Gac-Mac Yellowknife 2007, May 23-25, Volume 32, 1 pg. abstract p.79.Europe, GreenlandGeochronology
DS200812-0999
2007
Steenfelt, A.Sand, K.K., Nielsen, T.F.D., Secher, K., Steenfelt, A.Kimberlite and carbonatite exploration in southern West Greenland: summary of previous activities and recent work by the kimberlite research group at the Geological Survey of Denmark and Greenland.Vladykin Volume 2007, pp. 127-140.Europe, Denmark, GreenlandExploration activity
DS200812-1154
2008
Steenfelt, A.Tappe, S., Steenfelt, A., Heaman, L.M., Romer, R.J., Simonetti, A., Muehlenbachs, K.The alleged carbonatitic kimberlitic melt continuum: contrary evidence from West Greenland.Goldschmidt Conference 2008, Abstract p.A934.Europe, GreenlandDeposit - Safartoq
DS200912-0733
2009
Steenfelt, A.Steenfelt, A., Jensen, S.M., Nielsen, T.F.D., Sand, K.K., Secher, K.Diamonds and lithospheric mantle properties in the neo-proterzoic igneous province of southern West Greenland. ( Garnet Lake area).Geological Survey of Denmark and Greenland, Bulletin 17, pp. 65-68.Europe, GreenlandDiamond exploration - brief overview
DS200912-0745
2009
Steenfelt, A.Tappe, S., Heaman, L.M., Romer, R.L., Steenfelt, A., Simonetti, A., Muehlenbach, K., Stracke, A.Quest for primary carbonatite melts beneath cratons: a West Greenland perspective.Goldschmidt Conference 2009, p. A1314 Abstract.Europe, GreenlandCarbonatite
DS201012-0755
2009
Steenfelt, A.Steenfelt, A., Jensen, S.M., Nielsen, T.F.D., Sand, K.K.Provinces of ultramafic lamprophyre dykes, kimberlite dykes and carbonatite in West Greenland characterised by minerals and chemical components in surface media.Lithos, Vol. 112 S pp. 116-123.Europe, GreenlandGeochemistry
DS201112-1029
2011
Steenfelt, A.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
DS201212-0720
2012
Steenfelt, A.Tappe, S., Smart, K.A., Stracke, A., Romer, R.L., Steenfelt, A., Muehlenbachs, K.Carbon fluxes beneath cratons: insights from West Greenland kimberlites and carbonatites.Goldschmidt Conference 2012, abstract 1p.Europe, GreenlandMelting
DS201212-0721
2012
Steenfelt, A.Tappe, S., Steenfelt, A., Nielsen, T.Astheospheric source of Neoproterozoic and Mesozoic kimberlites from the North Atlantic craton, West Greenland: new high precision U-Pb and Sr-Nd isotope dat a on perovskite.Chemical Geology, Vol. 320-321, pp. 113-127.Europe, GreenlandGeochronology
DS201604-0632
2016
Steenfelt, A.Steenfelt, A., Kolb, J., Thrane, K.Metallogeny of South Greenland: a review of geological evolution, mineral occurrences and geochemical exploration data. Jurassic K dykes section 4.7( 1p.)Ore Geology Reviews, Vol. 77, pp. 194-245.Europe, GreenlandKimberlite dykes
DS201705-0882
2017
Steenfelt, A.Tappe, S., Romer, R.L., Stracke, A., Steenfelt, A., Smart, K.A., Muehlenbachs, K., Torsvik, T.H.Sources and mobility of carbonate melts beneath cratons, with implications for deep carbon cycling, metasomatism and rift initiation.Earth and Planetary science Letters, Vol. 466, pp. 152-167.MantleMetasomatism, magma, carbonatite

Abstract: Kimberlite and carbonatite magmas that intrude cratonic lithosphere are among the deepest probes of the terrestrial carbon cycle. Their co-existence on thick continental shields is commonly attributed to continuous partial melting sequences of carbonated peridotite at >150 km depths, possibly as deep as the mantle transition zone. At Tikiusaaq on the North Atlantic craton in West Greenland, approximately 160 Ma old ultrafresh kimberlite dykes and carbonatite sheets provide a rare opportunity to study the origin and evolution of carbonate-rich melts beneath cratons. Although their Sr-Nd-Hf-Pb-Li isotopic compositions suggest a common convecting upper mantle source that includes depleted and recycled oceanic crust components (e.g., negative ?eHf?eHf coupled with View the MathML source>+5‰d7Li), incompatible trace element modelling identifies only the kimberlites as near-primary low-degree partial melts (0.05-3%) of carbonated peridotite. In contrast, the trace element systematics of the carbonatites are difficult to reproduce by partial melting of carbonated peridotite, and the heavy carbon isotopic signatures (-3.6 to View the MathML source-2.4‰d13C for carbonatites versus -5.7 to View the MathML source-3.6‰d13C for kimberlites) require open-system fractionation at magmatic temperatures. Given that the oxidation state of Earth's mantle at >150 km depth is too reduced to enable larger volumes of ‘pure’ carbonate melt to migrate, it is reasonable to speculate that percolating near-solidus melts of carbonated peridotite must be silicate-dominated with only dilute carbonate contents, similar to the Tikiusaaq kimberlite compositions (e.g., 16-33 wt.% SiO2). This concept is supported by our findings from the North Atlantic craton where kimberlite and other deeply derived carbonated silicate melts, such as aillikites, exsolve their carbonate components within the shallow lithosphere en route to the Earth's surface, thereby producing carbonatite magmas. The relative abundances of trace elements of such highly differentiated ‘cratonic carbonatites’ have only little in common with those of metasomatic agents that act on the deeper lithosphere. Consequently, carbonatite trace element systematics should only be used with caution when constraining carbon mobility and metasomatism at mantle depths. Regardless of the exact nature of carbonate-bearing melts within the mantle lithosphere, they play an important role in enrichment processes, thereby decreasing the stability of buoyant cratons and promoting rift initiation - as exemplified by the Mesozoic-Cenozoic breakup of the North Atlantic craton.
DS202102-0237
2021
Steenfelt, A.Yakmchuck, C., Kirkland, C.L., Cavosie, A.J., Szilas, K., Hollis, J., Gardinerm N.J., Waterton, P., Steenfelt, A., Martin, L.Stirred not shaken; critical evaluation of a proposed Archean meteorite impact in West Greenland.Earth and Planetary Science Letters, Vol. 557, doi.org/10.1016/ j.epsl.2020.116730 9p. PdfEurope, Greenlandmeteorite

Abstract: Large meteorite impacts have a profound effect on the Earth's geosphere, atmosphere, hydrosphere and biosphere. It is widely accepted that the early Earth was subject to intense bombardment from 4.5 to 3.8 Ga, yet evidence for subsequent bolide impacts during the Archean Eon (4.0 to 2.5 Ga) is sparse. However, understanding the timing and magnitude of these early events is important, as they may have triggered significant change points to global geochemical cycles. The Maniitsoq region of southern West Greenland has been proposed to record a ~3.0 Ga meteorite impact, which, if confirmed, would be the oldest and only known impact structure to have survived from the Archean. Such an ancient structure would provide the first insight into the style, setting, and possible environmental effects of impact bombardment continuing into the late Archean. Here, using field mapping, geochronology, isotope geochemistry, and electron backscatter diffraction mapping of 5,587 zircon grains from the Maniitsoq region (rock and fluvial sediment samples), we test the hypothesis that the Maniitsoq structure represents Earth's earliest known impact structure. Our comprehensive survey shows that previously proposed impact-related geological features, ranging from microscopic structures at the mineral scale to macroscopic structures at the terrane scale, as well as the age and geochemistry of the rocks in the Maniitsoq region, can be explained through endogenic (non-impact) processes. Despite the higher impact flux, intact craters from the Archean Eon remain elusive on Earth.
DS202109-1473
2021
Steenfelt, A.Hollis, J.C., Kirk;amd, C.., Hartnady, M., Barham, M., Steenfelt, A.Earth's continents share an ancient crustal ancestor.Eos, https://doi.org/10.1029/2021EO162087.Europe, Greenlandgeochronology - zircon

Abstract: The jigsaw fit of Earth’s continents, which long intrigued map readers and inspired many theories, was explained about 60 years ago when the foundational processes of plate tectonics came to light. Topographic and magnetic maps of the ocean floor revealed that the crust—the thin, rigid top layer of the solid Earth—is split into plates. These plates were found to shift gradually around the surface atop a ductile upper mantle layer called the asthenosphere. Where dense oceanic crust abuts thicker, buoyant continents, the denser crust plunges back into the mantle beneath. Above these subduction zones, upwelling mantle melt generates volcanoes, spewing lava and creating new continental crust.
DS201412-0501
2014
Steenkamp, B.Le Roux, T., Steenkamp, B.Airborne geophysical characteristics of a few Angolan kimberlites.GSSA Kimberley Diamond Symposium and Trade Show provisional programme, Sept. 12, title onlyAfrica, AngolaGeophysics
DS201212-0099
2012
Steenkamp, H.M.Butler, J.P., Jamieson, R.A., Steenkamp, H.M., Robinson, P.Discovery of coesite eclogite from the Nordyane UHP domain, Western Gneiss region, Norway: field relations, metamorphic history and tectonic significance.Journal of Metamorphic Geology, in press availableEurope, NorwayCoesite
DS202006-0954
2020
Steenkamp, J.D.Van Zyl, H.J., Bam, W.G., Steenkamp, J.D.Identifying barriers to growth in mineral value chains. ( not specific to diamonds)Journal of the Southern African Institute of Mining and Metallurgy, 8p. PdfAfrica, South Africalegal

Abstract: Despite the importance that barrier identification has for policy-making and industry stakeholders alike; little guidance exists on consistent processes to systematically identify barriers that are hindering the different sectors of a value chain’s expansion and growth. This article describes the development of a framework that supports the identification of barriers to growth in mineral value chains. The resultant process was applied to the case of the manganese value chain in South Africa, and revealed 31 barriers within this industry. The results were validated by a panel of experts and the feedback was used to rework and improve the framework.
DS201112-0304
2011
Steenkamp, N.C.Eriksson, P.G., Rigby, M.J., Bandopadhyay, P.C., Steenkamp, N.C.The Kaapvaal Craton, South Africa: no evidence for a supercontinental affinity prior to 2.0 Ga?International Geology Review, Vol. 53, 11-12, pp. 1312-1330.Africa, southern AfricaGondwana
DS201112-0305
2011
Steenkamp, N.C.Eriksson, P.G., Rigby, M.J., Bandopadhyay, P.C., Steenkamp, N.C.The Kaapvaal Craton, South Africa: no evidence for a supercontinental affinity prior to 2.0 Ga?International Geology Review, Vol. 53, no. 11-12, pp. 1312-1330.Africa, South AfricaTectonics
DS1986-0530
1986
Steenkamp, N.S.L.Martin, D.C., Steenkamp, N.S.L., Lill, . J.W.Application of a statistical analysis technique for design of high rock slopes at Palabora mine, South AfricaInstitute of Mining and Metallurgy (IMM) Special Publishing Mining Latin America, pp. 241-255South AfricaCarbonatite, Palabora
DS1960-1033
1968
Steenland, N.C.Steenland, N.C.Structural Significance and Analysis of Mid-continent Gravity High Discussion of Paper by R.l. Coons Et.al. 1967.American Association of Petroleum Geologists Bulletin., Vol. 52, No. 11, PP. 2263-2264.GlobalMid-continent
DS1991-1656
1991
Steenland, N.C.Steenland, N.C.Discussion on variable depth magnetization mapping: applications to the Athabasca basin, northern Alberta and Saskatchewan by M. PilkingtonGeophysics, Vol. 56, No. 2, February p. 308Alberta, SaskatchewanGeophysics -magnetics, Athabasca Basin
DS2003-0699
2003
Steensma, G.Kellett, R.L., Zahynacz, R., Steensma, G.The role of borehole geophysics in improving the geophysical imaging of kimberlites in a8 Ikc Www.venuewest.com/8ikc/program.htm, Session 8, POSTER abstractAlbertaStratigraphy
DS200412-0970
2003
Steensma, G.Kellett, R.L., Zahynacz, R., Steensma, G.The role of borehole geophysics in improving the geophysical imaging of kimberlites in a sedimentary setting: Alberta, Canada.8 IKC Program, Session 8, POSTER abstractCanada, AlbertaDiamond exploration Stratigraphy
DS1989-0108
1989
SteeplesBerendsen, P., Newell, K.D., Watney, W.L., Dovsteon, J., SteeplesPreliminary report on the Texaco deep Precambrian drill hole in The midcontinent rift systemUnited States Geological Survey (USGS) Open file, United States Geological Survey (USGS)-Missouri G.S. Symp: Mineral resource potential of, p. 2. (abstract.)GlobalTectonics
DS1996-0723
1996
Steeples, D.Keiswetter, D., Black, R., Steeples, D.Seismic reflection analysis of the Manson Impact Structure, IowaJournal of Geophysical Research, Vol. 101, No. 3, March 10, pp. 5823-5834.IowaStructure, Impact structure
DS1975-0421
1976
Steeples, D.W.Steeples, D.W., Yarger, H.L., Robinson, R.Integrated Geophysical Exploration for Kimberlites in KansasEos, Vol. 57, No. 10, P. 762, (ABTR.).GlobalKimberlite, Central States, Geophysics
DS1989-1029
1989
Steeples, D.W.Miller, R.D., Steeples, D.W., Brannan, M.Mapping a bedrock surface under dry alluvium with shallow seismicreflectionsGeophysics, Vol. 54, No. 12, December pp. 1528-1534GlobalGeophysics -seismics, Alluvium -general applica
DS1989-1431
1989
Steeples, D.W.Somanas, C., Knapp, R.W., Yarger, H.L., Steeples, D.W.Geophysical model of the Midcontinent geophysical anomaly in northeasternKansasKansas Geological Survey, Bulletin. 226, pp. 215-228KansasGeophysics, Midcontinent
DS1989-1450
1989
Steeples, D.W.Steeples, D.W.Geophysics in KansasKansas Geological Survey, Bulletin. 226, 312pKansasGeophysics, Regional
DS1993-1526
1993
Steeples, D.W.Steeples, D.W., Miller, R.D.Basic principles and concepts of practical shallow seismic reflectionprofiling.Mining Engineering, Vol. 45, No. 10, Oxtober pp. 1297-1302.GlobalGeophysics -seismics, General application
DS1996-1568
1996
Steeples, D.W.Xia, J., Sprowl, D.R., Steeples, D.W.A model of Precambrian geology of Kansas derived from gravity and magneticdata.Computers and Geosciences, Vol. 22, No. 8, pp. 883-895.KansasGeophysics - magnetics, Precambrian
DS1998-0343
1998
SteerDiaconescu, C.C., Knapp, J., Brown, L., Steer, StillerPrecambrian Moho offset and tectonic stability of the East European Platform from URSEIS deep profile....Geology, Vol. 26, No. 3, March pp. 211-214.GlobalGeophysics - seismics, Makorovo fault zone
DS1995-0091
1995
Steer, D.N.Baird, D.J., Knapp, J.H., Steer, D.N., et al.Upper mantle reflectivity beneath the Williston basin phase change Moho, and origin of intracratonic basinsGeology, Vol. 23, No. 5, May pp. 431-434SaskatchewanTrans Hudson Orogeny, Craton
DS1995-0092
1995
Steer, D.N.Baird, D.J., Knapp, J.H., Steer, D.N., Brown, L.D., NelsonUpper mantle reflectivity beneath the Williston Basin, phase change @and origin of intracratonic basinsGeology, Vol. 23, No. 5, May pp. 431-434.SaskatchewanTrans Hudson Orogeny, Crust
DS1996-1366
1996
Steer, D.N.Steer, D.N., Brown, L.D., Knapp, J.H., Baird, D.J.Comparison of explosive and vibroseis source energy penetration during COCORP deep seismic Williston BasinGeophysics, Vol. 61, No. 1, Jan-Feb. pp. 211-221.Alberta, SaskatchewanGeophysics -seismics, Williston Basin
DS1998-1405
1998
Steer, D.N.Steer, D.N., Knapp, J.H., Brown, L.D.Super deep reflection profiling: exploring the continental mantle lidTectonophysics, Vol. 286, No. 1-4, Mar. 10, pp. 111-22.MantleGeophysics - seismic
DS1998-1406
1998
Steer, D.N.Steer, D.N., Knapp, J.H., Brown, L.D., et al.Deep structure of the continental lithosphere in an unextended orogen: an explosive source seismic ..UralsTectonics, Vol. 17, No. 2, Apr. pp. 143-157.GlobalGeophysics - seismic
DS201412-0150
2013
Steer, P.Cowie, P.A., Scholz, C.H., Roberts, G.P., Faure Walker, J.P., Steer, P.Viscous roots of active seismogenic faults revealed by geologic slip rate variations.Nature Geoscience, Vol. 6, 12, pp. 1036-1040.Europe, ItalyDuctile crust
DS200512-1045
2004
Stefan, I.A.Stefan, I.A., Francis, D.Proterozoic mantle xenoliths in ultramafic dykes near Wawa, Ontario: implications for the lithospheic mantle underneath the central North American craton.Geological Society of America Annual Meeting ABSTRACTS, Nov. 7-10, Paper 17-7, Vol. 36, 5, p. 47.Canada, Ontario, WawaPicrite, ailikites
DS200712-1037
2006
Stefan, W.Stefan, W., Garnero, E., Renaut, R.A.Signal restoration through deconvolution applied to deep mantle seismic probes.Geophysical Journal International, Vol. 167, 3, Dec. 1, pp. 1353-1362.MantleGeophysics - seismics
DS1990-0787
1990
Stefanik, M.Jurdy, D.M., Stefanik, M.Models for the hotspot distributionGeophysical Research Letters, Vol. 17, No. 11, October pp. 1965-1968GlobalHotspots, Subduction zones
DS1991-0814
1991
Stefanik, M.Jurdy, D.M., Stefanik, M.The forces driving the plates: constraints from kinematics and stressobservationsPhil. Transactions Royal Society of London, Vol. 337, No. 1645, October 15, pp. 127-140GlobalMantle, Plate tectonics
DS1992-0811
1992
Stefanik, M.Jurdy, D.M., Stefanik, M.The forces driving the plates: constraints from kinematics and hotspotsEos Transactions, Vol. 73, No. 14, April 7, supplement abstracts p. 272MantleHotspots, Tectonics
DS1995-0901
1995
Stefanik, M.Jurdy, D.M., Stefanik, M., Scotese, C.R.Paleozoic plate tectonicsJournal of Geophysical Research, Vol. 100, No. 9, Sept. 10, pp. 7965-76GlobalTectonics -Plate, Paleozoic
DS1995-1823
1995
Stefanov, Yu.M.Stefanov, Yu.M., et al.Placer diamonds from Olkhovaya River, Kamchatka, Russia: is there asource?Eos, Vol. 76, No. 46, Nov. 7. p.F538. Abstract.Russia, KamchatkaPlacers, alluvials, Deposit -Olkhovaya River
DS201901-0058
2018
Stefansson, A.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.
DS202005-0744
2020
Stefansson, A.Labidi, J., Barry, P.H., Bekaert, D.V., Broadley, M.W., Marty, B., Giunta, T., Warr, O., Sherwood Lollar, B., Fischer, T.P., Avice, G., Caracusi, A., Ballentine, C.J., Halldorsson, S.A., Stefansson, A., Kurz, M.D., Kohl, I.E., Young, E.D.Hydrothermal 15N15N abundances constrain the origins of mantle nitrogen.Nature, Vol. 580, 7803 pp. 367-371. Mantlenitrogen

Abstract: Nitrogen is the main constituent of the Earth’s atmosphere, but its provenance in the Earth’s mantle remains uncertain. The relative contribution of primordial nitrogen inherited during the Earth’s accretion versus that subducted from the Earth’s surface is unclear1,2,3,4,5,6. Here we show that the mantle may have retained remnants of such primordial nitrogen. We use the rare 15N15N isotopologue of N2 as a new tracer of air contamination in volcanic gas effusions. By constraining air contamination in gases from Iceland, Eifel (Germany) and Yellowstone (USA), we derive estimates of mantle d15N (the fractional difference in 15N/14N from air), N2/36Ar and N2/3He. Our results show that negative d15N values observed in gases, previously regarded as indicating a mantle origin for nitrogen7,8,9,10, in fact represent dominantly air-derived N2 that experienced 15N/14N fractionation in hydrothermal systems. Using two-component mixing models to correct for this effect, the 15N15N data allow extrapolations that characterize mantle endmember d15N, N2/36Ar and N2/3He values. We show that the Eifel region has slightly increased d15N and N2/36Ar values relative to estimates for the convective mantle provided by mid-ocean-ridge basalts11, consistent with subducted nitrogen being added to the mantle source. In contrast, we find that whereas the Yellowstone plume has d15N values substantially greater than that of the convective mantle, resembling surface components12,13,14,15, its N2/36Ar and N2/3He ratios are indistinguishable from those of the convective mantle. This observation raises the possibility that the plume hosts a primordial component. We provide a test of the subduction hypothesis with a two-box model, describing the evolution of mantle and surface nitrogen through geological time. We show that the effect of subduction on the deep nitrogen cycle may be less important than has been suggested by previous investigations. We propose instead that high mid-ocean-ridge basalt and plume d15N values may both be dominantly primordial features.
DS2002-1297
2002
Stefansson, R.Ragnarsson, S., Stefansson, R.Plume driven plumbing and crustal formation in IcelandJournal of Geophysical Research, August 10: 1029/2001JB000584IcelandTectonics, Hot spots
DS200812-0347
2008
Stefenhofer, J.Field, M., Stefenhofer, J., Robey, J., Kurzlaukis, S.Kimberlite hosted diamond deposits of southern Africa: A review.Ore Geology Reviews, Vol. 34, pp. 33-75.Africa, South Africa, BotswanaReview
DS200612-1368
2005
Steffen, H.Steffen, H., Kaufmann, G.Glacial isostatic adjustment of Scandinavia and northwestern Europe and the radial viscosity structure of the Earth's mantle.Geophysical Journal International, Vol. 163, 2, pp. 801-812.Europe, ScandinaviaGeophysics - istostasy
DS200612-1369
2006
Steffen, H.Steffen, H., Kaufmann, G., Wu, P.Three dimensional finite element modeling of the glacial isostatic adjustment in Fennoscandia.Earth and Planetary Science Letters, In press - availableEurope, Greenland, FennoscandiaSeismic tomography, mantle viscosity
DS200712-1038
2007
Steffen, H.Steffen, H., Wu, P., Kaufmann, G.Sensitivity of crustal velocities in Fennoscandia to radial and lateral viscosity variations in the mantle.Earth and Planetary Science Letters, Vol. 257, 3-4, May 30, pp. 474-485.Europe, ScandinaviaGeophysics - seismics
DS1975-0819
1978
Steffen, O.K.H.Moss, A.S.E., Steffen, O.K.H.Geotechnology and Probability in Open Pit Mine PlanningCommonwealth Min. Met. Congress 11th., PAPER No. 20, 8P.South AfricaDiamond Mining Recovery, Kimberlite Pipes
DS1997-1099
1997
Steffen, O.K.H.Steffen, O.K.H.Planning of open pit Mines on a risk basisJournal of African Institute of Mining and Metallurgy, March/April pp. 47-56South AfricaMining, Open pit, economics
DS202007-1131
2020
Steffen, R.Chisenga, C., Van der Meijde, M., Yan, J., Fadel. I., Atekwana, E.A., Steffen, R., Ramotoroko, C.Gravity derived crustal thickness model of Botswana: its implication for the Mw 6.5 April 3, 2017, Botswana earthquake. Tectonophysics, Vol. 787, 228479 12p. PdfAfrica, Botswanageophysics - gravity

Abstract: Botswana experienced a Mw 6.5 earthquake on 3rd April 2017, the second largest earthquake event in Botswana's recorded history. This earthquake occurred within the Limpopo-Shashe Belt, ~350 km southeast of the seismically active Okavango Rift Zone. The region has no historical record of large magnitude earthquakes or active faults. The occurrence of this earthquake was unexpected and underscores our limited understanding of the crustal configuration of Botswana and highlight that neotectonic activity is not only confined to the Okavango Rift Zone. To address this knowledge gap, we applied a regularized inversion algorithm to the Bouguer gravity data to construct a high-resolution crustal thickness map of Botswana. The produced crustal thickness map shows a thinner crust (35-40 km) underlying the Okavango Rift Zone and sedimentary basins, whereas thicker crust (41-46 km) underlies the cratonic regions and orogenic belts. Our results also show localized zone of relatively thinner crust (~40 km), one of which is located along the edge of the Kaapvaal Craton within the MW 6.5 Botswana earthquake region. Based on our result, we propose a mechanism of the Botswana Earthquake that integrates crustal thickness information with elevated heat flow as the result of the thermal fluid from East African Rift System, and extensional forces predicted by the local stress regime. The epicentral region is therefore suggested to be a possible area of tectonic reactivation, which is caused by multiple factors that could lead to future intraplate earthquakes in this region.
DS2000-0279
2000
Steffen, W.Falkowski, P., Scholes, R.J., Steffen, W.Climate change: the Global Carbon cycle: a test of our knowledge of Earth as a systemScience, Vol. 290, No. 5490, Oct. 13, pp.291-306.GlobalCarbon cycle
DS201112-0561
2011
Steffensen, J.P.Kurbatov, A.V., Mayewski, P.A., Steffensen, J.P., West, A., Kennett, Bunch, Handley, Introne, Shane, Mercer etcDiscovery of a nanodiamond rich layer in the Greenland ice sheet.Journal of Glaciology, Vol. 56, no. 199, pp. 747-757.Europe, GreenlandGeomorphology
DS1990-1411
1990
Stegena, L.G.Stegena, L.G., Meissner, R.O.Heat production and seismic velocity of crustal rocksTerra Nova, Vol. 2, No. 1, pp. 87-90OntarioTectonics, Kapuskasing Uplift, Craton
DS201612-2323
2016
Steger, S.Nasdala, L., Steger, S., Reissner, C.Raman study of diamond based abrasives, and possible artefacts in detecting UHP microdiamond.Lithos, Vol. 265, pp. 317-327.TechnologyUHP - microdiamond

Abstract: Raman spectral characteristics of a range of diamond-based abrasives (powders and sprays) and drilling and cutting tools, originating from preparation laboratories worldwide, are presented. Some abrasives show strong broadening of the main diamond band [FWHM (full width at half band-maximum) > 5 cm- 1] accompanied by strong band-downshift (View the MathML source?˜ = 1316-1330 cm- 1). Others are characterised by moderate band broadening (FWHM = 1.8-5 cm- 1) at rather regular band position (View the MathML source?˜ = 1331-1333 cm- 1). In addition we found that a "fresh" abrasive and its used analogue may in some cases show vast differences in their Raman spectra. The Raman parameters of diamond-based abrasives overlap widely with Raman parameters of UHP (ultra-high pressure) microdiamond. It is hence impossible to assign diamond detected in a geological specimen to either an introduced artefact or a genuine UHP relict, from the Raman spectrum alone. Raman is an excellent technique for the detection of minute amounts of diamond; however it does not provide conclusive evidence for the identification of UHP microdiamond. The latter requires thorough verification, for instance by optical microscopy or, if doubts cannot be dispelled, transmission electron microscopy.
DS200912-0115
2008
Stegman, D.Clark, S.R., Stegman, D., Muller, R.D.Episodicity in back arc tectonic regimes.Physics of the Earth and Planetary Interiors, Vol. 171, 1-4, pp. 265-279.MantleTectonics
DS2002-1547
2002
Stegman, D.R.Stegman, D.R., Richards, M.A., Baumgardner, J.R.Effects of depth dependent viscosity and plate motions on maintaining a relatively uniform mid-ocean ridge basalt reservoir in whole mantle flow.Journal of Geophysical Research, Vol. 107, No. 6, ETG 5 DOI 10.1029/2001JB000192MantleGeophysics - seismics, mantle flow
DS200612-0483
2006
Stegman, D.R.Gottschaldt, K.D., Walzer, U., Hendel, R.F., Stegman, D.R., Baumgartner, J.R., Muhlhaus, H.B.Stirring in 3 d spherical models of convection in the Earth's mantle.Philosophical Magazine, Vol. 86, no. 21-22, pp. 3175-3204.MantleConvection
DS200612-1233
2006
Stegman, D.R.Schellart, W.P., Freeman, J., Stegman, D.R.Subduction induced mantle convection on Earth: poloidal versus toroidal flow.Geochimica et Cosmochimica Acta, Vol. 70, 18, p. 10, abstract only.MantleSubduction
DS200612-1370
2006
Stegman, D.R.Stegman, D.R., Freeman, J., Schellart, W.P., Moresi, L.N., May, D.Evolution and dynamics of subduction zones from 4-D geodynamic models.Geochimica et Cosmochimica Acta, Vol. 70, 18, p. 58. abstract only.MantleSubduction
DS200812-1014
2008
Stegman, D.R.Schellart, W.P., Stegman, D.R., Freeman, J.Global trench migration velocities and slab migration induced upper mantle volume fluxes: constraints to find an Earth reference frame based on minimizing viscous dissipation.Earth Science Reviews, Vol. 88, 1-2, May pp. 118-144.MantlePlate tectonics - subduction, convection, hotspot
DS200912-0560
2008
Stegman, D.R.OzBench, M., Regenauerlieb, K., Stegman, D.R., Morra, G., Farrington, R., Hale, A., May, D.A., Freeman, J.A model comparison study of large scale mantle lithosphere dynamics driven by subduction.Physics of the Earth and Planetary Interiors, Vol. 171, 1-4, pp. 224-234.MantleTectonics
DS201112-0921
2011
Stegman, D.R.Schellart, W.P., Stegman, D.R., Farrington, R.J., Moresi, L.Influence of lateral slab edge distance on plate velocity, trench velocity, and subduction partitioning.Journal of Geophysical Research, Vol. 116, B10, B10408.MantleSubduction
DS201412-0168
2014
Stegman, D.R.Davies, C.J., Stegman, D.R., Dumberry, M.The strength of gravitational core mantle coupling.Geophysical Research Letters, Vol. 41, 11, pp. 3786-3792.MantleGeophysics - gravity
DS201412-0169
2014
Stegman, D.R.Davies, C.J., Stegman, D.R., Dumberry, M.The strength of gravitational core-mantle coupling.Geophysical Research Letters, Vol. 41, 11, pp. 3786-3792.MantleGeophysics - gravity
DS201810-2393
2018
Stegman, D.R.Zhou, Q., Hu, J., Liu, L., Chaparro, T., Stegman, D.R., Faccenda, M.Western U.S. seismic anisotropy revealing complex mantle dynamics.Earth and Planetary Science Letters, Vol. 500, pp. 156-167.United Statesgeodynamics

Abstract: The origin of the complex pattern of SKS splitting over the western United States (U.S.) remains a long-lasting debate, where a model that simultaneously matches the various SKS features is still lacking. Here we present a series of quantitative geodynamic models with data assimilation that systematically evaluate the influence of different lithospheric and mantle structures on mantle flow and seismic anisotropy. These tests reveal a configuration of mantle deformation more complex than ever envisioned before. In particular, we find that both lithospheric thickness variations and toroidal flows around the Juan de Fuca slab modulate flow locally, but their co-existence enhances large-scale mantle deformation below the western U.S. The ancient Farallon slab below the east coast pulls the western U.S. upper mantle eastward, spanning the regionally extensive circular pattern of SKS splitting. The prominent E-W oriented anisotropy pattern within the Pacific Northwest reflects the existence of sustaining eastward intrusion of the hot Pacific oceanic mantle to beneath the continental interior, from within slab tears below Oregon to under the Snake River Plain and the Yellowstone caldera. This work provides an independent support to the formation of intra-plate volcanism due to intruding shallow hot mantle instead of a rising mantle plume.
DS201212-0369
2012
Stegnitskii, Yu.B.Konstantinov, K.M., Stegnitskii, Yu.B.The late Silurian-Early Devonian natural remanent magnetization of kimberlites and traps in the Yakutian Diamondiferous province.Doklady Earth Sciences, Vol. 442, 1, pp. 152-158.Russia, YakutiaGeophysics
DS201809-2106
2018
Stegnitskiy, Y.B.Ustinov, V.N., Mosigi, B., Kukui, I.M., Nikolaeva, E., Campbell, J.A.H., Stegnitskiy, Y.B., Antashchuk, M.G.Eolian indicator mineral dispersion haloes from the Orapa kimberlite cluster, Botswana.Mineralogy and Petrology, doi.org/10.1007/s00710-018-0627-2 9p.Africa, Botswanadeposit - Orapa

Abstract: This paper presents the results of an investigation into the structure of eolian kimberlite indicator minerals (KIMs) haloes present within Quaternary Kalahari Group sediments (up to 20 m thick) overlying the Late Cretaceous kimberlites in the Orapa field in North-East Botswana. A database of more than 8000 samples shows that kimberlites create a general mineralogical blanket of KIMs of various distances of transportation from primary sources in the Orapa area. Models of the reflection and dispersion patterns of KIMs derived from kimberlite pipes including AK10/ AK22/AK23 have been revealed based on 200 selected heavy mineral samples collected during diamond prospecting activities in Botswana from 2014 to 2017. Short distance eolian haloes situated close to kimberlite bodies cover gentle slopes within plains up to 500 × 1000 m in size. They have regularly have oval or conical shapes and are characterized by the presence mainly of unabraded or only slightly abraded KIMs. A sharp reduction of their concentration from hundreds and thousands of grains / 20 l immediately above kimberlites toto 10 grains/20 l at a distance of only 100-200 m from the pipes is a standard feature of these haloes. The variation of concentration, morphology and abrasion of specific KIMs with increasing distance from the primary sources has been investigated and presented herein. Sample volumes recommended for pipes present within a similar setting as those studied, with different depth of sedimentary cover are as follows: up to 10-20 m cover at 20-50 l, 20-30 m cover at 50-100 l and 30-80 m cover at 250 l. It is important to appreciate that the discovery of even single grains of unabraded or slightly abraded KIMs in eolian haloes are of high prospecting significance in this area. The results of the research can be applied to in diamond prospecting programs in various regions with similar environments.
DS201810-2386
2018
Stegnitskiy, Y.B.Ustinov, V.N., Bartolomeu, A.M.F., Zagainy, A.K., Felix, J.T., Mikoev, I.I., Stegnitskiy, Y.B., Lobkova, L.P., Kukui, I.M., Nikolaeva, E.V., Antonov. S.A.Kimberlites distribution in Angola and prospective areas for new discoveries.Mineralogy and Petrology, doi.org/10.1007/ s00710-018-0628-1 14p.Africa, Angolakimberlites

Abstract: Based on a comprehensive analysis of kimberlite pipes of Angola, including the near surface structural setting, deep lithospheric structure, pipe morphology and emplacement, mineralogical and petrographic features, diamond characteristics and locations of secondary deposits four geographical regions have been outlined within Angola representing four types of diamond bearing potential. These areas include high diamond bearing potential pipes, possible potential, no potential, and unclear potential areas. It was found that the depth of magmatism and diamond potential of kimberlites increases from the Atlantic coast in southwestern Angola into the continent in the north-easterly direction. Areas prospective for the discovery of new primary diamond deposits have been identified.
DS201412-0765
2014
Stegnitskiy, Yu.B.Sablukov, S.M., Sablukova, L.I., Stegnitskiy, Yu.B., Karpenko, M.A.Origin of the mantle xenoliths with green garnets from kimberlites ( dike Newlands, southern Africa and Nyurbinskaya pipe, Yakutia.Deep Seated Magmatism, its sources and plumes, Ed. Vladykin, N.V., pp. 178-202.RussiaDeposit - Newlands, Nyurbinskaya
DS201510-1801
2014
Stegnitskiy, Yu.B.Sablukov, S.M., Sablukova, L.I., Stegnitskiy, Yu.B., Karpenko, M.A.Origin of the mantle xenoliths with green garnets from kimberlites ( Dike Newlands, southern Africa and Nyurbinskaya pipe, Yakutia).Deep-seated magmatism, its sources and plumes, Proceedings of XIII International Workshop held 2014., Vol. 2014, pp. 178-202.Africa, South Africa, Russia, YakutiaDeposit - Dike Newlands, Nyurbinskaya

Abstract: Green garnets occur in concentrates of diamondiferous kimberlite bodies in Yakutia (Udachnaya, Mir, etc.), South Africa (Newlands, Bellsbank), Venezuela (Guaniamo sills), and Canada (Mud Lake field). Mantle xenoliths of rocks containing such garnets are very rare. We found peridotite xenoliths with green garnet in situ in kimberlites of the Newlands dike. Xenoliths are irregular in form, 4.5*1.9 cm, 1.5*0.8 cm, and 1.0*0.5 cm in size, and have similar modal compositions: gar(70)+ol(28)+sp(2), gar(9)+ol(90)+sp(1) and gar(50)+ol(30)+sp(20). Rock texture is medium-crystalline, while structure is massive. We also identified a garnet macrocryst of 0.5*0.4 cm in size with a pale green kelyphytic rim. Garnet composition in the studied samples is quite constant and is characterized by the high Cr2O3 content (10.94-11.99%) and CaO content (19.52-24.94%) at the reduced contents of TiO2 (0.24-0.52%). The chrome spinel is high Cr2O3 (55%) content and the low TiO2 (0.5-0.6%) content. Olivine is high-Mg (Fo95), but elevated CaO content (0.09%). Isotopic composition of oxygen in garnet (d18O = 4.05-4.25 pm) and olivine (d18O = 4.91 pm) differs drastically from the mantle values. Rb-Sr and Sm-Nd isotopic composition show the relatively "young" model age of the sample relative to the