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The Sheahan Diamond Literature Reference Compilation - Scientific and Media Articles based on Major Keyword - Petrology
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 announcements called 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 Keyword Index
Sheahan Diamond Literature Reference Compilation - Scientific Articles by Author for all years
Each article reference in the SDLRC is tagged with one or more key words assigned by Pat Sheahan to highlight the main topics of the article. In an effort to make it easier for users to track down articles related to a specific topic, KRO has extracted these key words and developed a list of major key words presented in this Key Word Index to which individual key words used in the article reference have been assigned. In most of the individual Key Word Reports the references are in crhonological order, though in some such as Deposits the order is first by key word and then chronological. Only articles classified as "technical" (mainly scientific journal articles) and "media" (independent media articles) are included in the Key Word Index. References that were added in the most recent monthly update are highlighted in yellow.
Petrology is the study of the origin, composition, distribution and structure of rocks, whereas petrography is the detailed description of the composition and texture of the minerals within a rock. Articles tagged with the keyword petrology can thus be about nearly any topic, whereas petrography articles will tend to be either about classifying the physical aspects of an emplaced kimberlite, or applying a petrographic classification system to a specific kimberlite.
Petrography of the Premier Kimberlite. I. a Microscopic And chemical Study of the Rock- Varieties of Blue Ground in The mine and Some Interesting Analytical Results.
Mining Engineering Journal of South Africa, Vol. 9, PT. 1, JULY 15TH. No. 436, PP. 819-820.
Petrography of the Premier Kimberlite. Ii. the Nodular Inclusions in the Blue Ground- an Interesting Graphite Bearing Specimen and the Problem of the Genetic Relationship.
Mining Engineering Journal of South Africa, Vol. 9, PT. 1, JULY 22ND. No. 437, PP. 857-858.
Some Aspects of the Petrography, Mineral Chemistry and Equilibration Temperatures of Some Zircon Bearing Assemblages And Their Constraints on the Paragenesis of Kimberlitic Zircons.
General Petrological Aspects of Paleozoic Alkali Magmatism In the Kola Peninsula and the Rare Earth Distribution in Alkali Ultrabasic Lamprophyre Dikes.
Geochemistry International (Geokhimiya), Vol. 15, No. 3, PP. 124-135.
Magnetite Serpentine Calcite Dykes at Premier Mine and Aspects of Their Relationship to Kimberlite and to Carbonatite Of Alkalic Carbonatite Complexes.
Physics and Chemistry of the Earth., Vol. 9, PP. 61-70.
Mineralogie des Megacristaux des Xenolithes Eclogitiques Etgranulitiques et des Inclusions Cristallines dans Les Diamants Provenant de la Kimberlite du Kasai
Ph.d. Thesis, University Cath. Louvain, Louvain-la-neuve, Belgiqu,
Geochemical and petrographic investigation of the genesis of the cancrinite-syenite niobium bearing carbonatite complex of Lueske Kivu Northeastern Zaire.*G
Ph.D. Thesis University of Berlin (in German), 330p
Petrologic Redox equilibration temperatures in the Benfontein Kimberlite Sills and in the Allende Meteorite, and the T-fo2 Stability Of kimberlitic Ilmenite from the Monastery Diatreme.
Fluorine and Chlorine Contents of Phlogopites in High Pressure Melting experiments on Ultrapotassic Rocks: Implications for Fluorine and Chlorine rservoirs in Mantle Source Regions.
Geological Association of Canada, Vol. 10, P. A 16, (abstract.).
Isotopic and Geochemical Systematics in Tertiary Recent Basalts from Southeastern Australia and Implications for the Evolution of the Subcontinental Lithosphere.
Geochimica et Cosmochimica ACTA., Vol. 49, No. 10, PP. 2051-2067.
Kovalenko, V.I., Solovova, I.P., Ryabchikov, I.D., et al.
Fluidized CO2 sulphide silicate media as agents of mantle metasomatism and megacrysts formation: evidence from a large druse in a spinel lherzolitexenolith
Physics of the Earth and Planetary Interiors, Vol. 45, No.3 April pp. 280-293
Upper mantle amphiboles and micas and TiO2, K2O and P2O5 abundances and 100 Mg (Mg+Fe2) ratios of common basalts and andesites: implications for modal mantle metalso
Barium rich phlogopite in a mantle derived xenolith of the Upper Canada mine kimberlite, Ontario, Canada;implications for BA- reservoir in the uppermantle
Journal of Japanese Association of Mineralogists, Petrologists and Economic, Vol. 83, No. 6, pp. 217-231
Petrology and pyroxene chemistry of Montregian dykes-the origin of concentric zoning and green cores in clinopyroxenes from alkali basalts andlamprophyres
Canadian Journal of Earth Sciences, Vol. 25, No. 12, December pp. 2041-2058
Compositional relations between natrolite, gonnardite, and thomsonite-products of nepheline alteration in alkaline rocks of the Magnet Cove igneouscomplex
Geological Society of America (GSA) Annual Meeting Abstracts, Vol. 21, No. 6, p. A326. Abstract
Petrogenesis of mantle derived large-ion lithophile elements (LILE) enriched Archean monzodiorites and Trachy andesites (sanukitoids) in southwestern Superior Province
Canadian Journal of Earth Sciences, Vol. 26, No. 9, September pp. 1688-1712
Hydrothermal oxygen diffusion in diopside at 1 KB, 900-1200C, a comparison with O diffusion in forsterite, and constraints on OI disequil. in peridotitenodules
Terra, Abstracts of Experimental mineralogy, petrology and, Vol. 2, December abstracts p. 72
Experimental constraints on the relative stability of phlogopite and amphibole in subducted lithosphere
Geological Association of Canada (GAC)/Mineralogical Association of Canada (MAC) Vancouver 90 Program with Abstracts, Held May 16-18, Vol. 15, p. A132. Abstract
Distribution of fluorine between minerals and glass in lamproites, lamprophyres and kamafugites: implications for the role of F in deep mantle derived magmas
Proceedings of Fifth International Kimberlite Conference held Araxa June 1991, Servico Geologico do Brasil (CPRM) Special, pp. 79-81
A semi-quantitative model for fractionation of rhyolite from rhyodacite in a compositionally altered Archean volcanic complex, Superior Province, Canada
Precambrian Research, Vol. 50, No. 1-2. April pp. 49-67
Aluminum solubility in orthopyroxene in equilibrium with garnet; are interpretation of existing experimental dat a &petrogenetic implications garnet peridotite xenolith
Proceedings of Fifth International Kimberlite Conference held Araxa June, pp. 514-515
Mineral chem. of silicate and oxide phases from fertile peridotite equilibrated with a C-O-H fluid phase- a low fO2 dat a set- evaluation of mineralbarometers, therM.
Proceedings of Fifth International Kimberlite Conference held Araxa June 1991, Servico Geologico do Brasil (CPRM) Special, pp. 417-419
Potassium-rich rock Inter relationships determined experimentally
Geological Association of Canada (GAC)/Mineralogical Association of Canada (MAC)/SEG Annual Meeting May 27-29. Toronto, Ontario, Abstract, Vol. 16, p. A136. Abstract
Phlogophite in the generation of olivine melilitites from Namaqualand, South Africa and implications for element fractionation processes in the uppermantle.
Nickel partitioning between olivine and garnet: experimental determination and implications for geothermometry
Geological Association of Canada (GAC), Geological Association of Canada (GAC)/Mineralogical Association of Canada (MAC) Annual Meeting, Abstract, Abstract Vol. p. A16
Age and petrogenesis of two late Archean magmatic suites, northwestern Superior Province, Canada: zircon uranium-lead (U-Pb) (U-Pb) and Lu-Hf isotopic relations
Journal of Petrology, Vol. 34, No. 4, August pp. 817-
Additional mantle reservoirs for Potassium, Barium and other elements characteristics of ultrapotassic and related magmas, implications from high pressure and temperature experi
Geological Association of Canada (GAC), Geological Association of Canada, Abstract Vol. p. A26
Carbon stability in eclogites in the earth's mantle
Geological Association of Canada (GAC), Geological Association of Canada (GAC)/Mineralogical Association of Canada (MAC) Annual Meeting, Abstract, Abstract Vol. p. A61.
Determining the mantle oxidation state through Mossbauer analysis of high pressure phases in the system iron-FeO-MgO-SiO2.
Geological Association of Canada (GAC), Geological Association of Canada (GAC)/Mineralogical Association of Canada (MAC) Annual Meeting, Abstract, Abstract Vol. p. A68.
Experiments at high pressures and applications to the earth's mantle
Mineralogical Association of Canada (MAC) short course SCHEDULED MAY 15-16th. 1993 Edmonton Alberta., Fax for details Luth c/o University of Alberta 403 492-2030
Geological Association of Canada (GAC), Geological Association of Canada (GAC)/Mineralogical Association of Canada (MAC) Annual Meeting, Abstract, Abstract Vol. p. A71.
Kimberlites and kimberlites or apples and orange(ite)s?
Mid-continent diamonds Geological Association of Canada (GAC)-Mineralogical Association of Canada (MAC) Symposium ABSTRACT volume, held Edmonton May, pp. 59-62.
Partial melting experiments on a phlogopite harzburgite at 3.0 GPa in relation to lamproite mantle source regions.
Geological Association of Canada (GAC), Geological Association of Canada (GAC)/Mineralogical Association of Canada (MAC) Annual Meeting, Abstract, Abstract Vol. p. A95.
A petrological and geochemical appraisal of the Mesoproterozoic Diamondiferous Majhgawan pipe of central India: evidence for transitional kimberlite - orangeite ( group II kimberlite) - lamproite rock type.
Gregoire, M., Tinguely, C., Bell, D.R., Le Roex, A.P.
Spinel lherzolite xenoliths from the Premier kimberlite ( Kaapvaal craton) South Africa: nature and evolution of the shallow upper mantle beneath Bushveld Complex.
Continuous gradations among primary carbonatitic, kimberlitic, melilititic, basaltic, picritic and komatiitic melts in equilibrium with garnet lherzolite at 3-8 GPa.
Solubility of niobium in the system CaCO 3-CaF 2-NaNbo 3 at 0.1 GPa pressure: implications for the crystallization of pyrochlore from carbonatite magma.
Contributions to Mineralogy and Petrology, Vol. 148, 3, pp. 281-287.
Safonov, O.G., Perchuk, L.L., Litrvin, Y.A., Bindi, L.
Phase relations in the Ca Mg Si2O6 K Al Si308 join at 6 and s.5 GPa as a model for formation of some potassium bearing deep seated mineral assemblages.
Contributions to Mineralogy and Petrology, Vol. 149, 3, pp. 316-337.
Internal architecture of the Venetia K1 kimberlite: a new geological model and implications for kimberlite emplacement processes, Venetia mine, Limpopo RSA.
Chakhmouradian, A.R., Demeny, A., Reguir, E.P., Hegner, E., Halden, N.M., Yang, P.
'Kimberlite' from Wekusko Lake, Manitoba: re-assessment and implications for further exploration. Beforsite ( primary dolomite carbonatite)... 'notion' could be
Thermodynamic analysis of magnetite + titanite + clinopyroxene equilibration temperatures in apatite bearing intrusion of the Khibin a alkaline complex.
De Assis Janasi, V., Andrade, S., Svisero, D.P.,Vieira de Almeida, V.
Inferencias sobre a evolucao petrologica do manto no sudeste brasileiro a partir de microanalises de elementos traco em piroxenios e olivin a de xenolitos de espinelio peridotitos.
5th Brasilian Symposium on Diamond Geology, Nov. 6-12, abstract p. 85.
An improved and extended internally consistent thermodynamic data set for phases of petrological interest, involving a new equation of state for solids.
Average composition of basic magmas and mantle sources of island arcs and active continental margins estimated from the dat a on melt inclusions and quenched glasses
Vladykin, N.V., Deep Seated Magmatism: its sources and plumes, pp. 22-53.
The high PT stability of apatite and Cl partioning between apatite and hydrous potassic phases in peridotite: an experimental study to 19 Gpa with implcations for the transport of P, Cl, and K in the upper mantle.
Contributions to Mineralogy and Petrology, Vol. 163, 2, pp. 277-296.
Contributions to Mineralogy and Petrology, Vol. 170, 25p.
Technology
Experimental petrology
Abstract: Melting of carbonated sediment in the presence of graphite or diamond was experimentally investigated at 7.5–12 GPa and 800–1600 °C in a multianvil apparatus. Two starting materials similar to GLOSS of Plank and Langmuir (Chem Geol 145:325–394, 1998) were prepared from oxides, carbonates, hydroxides and graphite. One mixture (Na-gloss) was identical in major element composition to GLOSS, and the other was poorer in Na and richer in K (K-gloss). Both starting mixtures contained ~6 wt% CO2 and 7 wt% H2O and were doped at a ~100 ppm level with a number of trace elements, including REE, LILE and HFSE. The near-solidus mineral assemblage contained a silica polymorph (coesite or stishovite), garnet, kyanite, clinopyroxene, carbonates (aragonite and magnesite-siderite solid solution), zircon, rutile, bearthite and hydrous phases (phengite and lawsonite at <9 GPa and the hydrous aluminosilicates topaz-OH and phase egg at >10 GPa). Hydrous phases disappear at ~900 °C, and carbonates persist up to 1000-1100 °C. At temperatures >1200 °C, the mineral assemblage consists of coesite or stishovite, kyanite and garnet. Clinopyroxene stability depends strongly on the Na content in the starting mixture; it remains in the Na-gloss composition up to 1600 °C at 12 GPa, but was not observed in K-gloss experiments above 1200 °C. The composition of melt or fluid changes gradually with increasing temperature from hydrous carbonate-rich (<10 wt% SiO2) at 800-1000 °C to volatile-rich silicate liquids (up to 40 wt% SiO2) at high temperatures. Trace elements were analyzed in melts and crystalline phases by LA ICP MS. The garnet-melt and clinopyroxene-melt partition coefficients are in general consistent with results from the literature for volatile-free systems and silicocarbonate melts derived by melting carbonated peridotites. Most trace elements are strongly incompatible in kyanite and silica polymorphs (D < 0.01), except for V, Cr and Ni, which are slightly compatible in kyanite (D > 1). Aragonite and Fe-Mg carbonate have very different REE partition coefficients (D Mst-Sd/L ~ 0.01 and D Arg/L ~ 1). Nb, Ta, Zr and Hf are strongly incompatible in both carbonates. The bearthite/melt partition coefficients are very high for LREE (>10) and decrease to ~1 for HREE. All HFSE are strongly incompatible in bearthite. In contrast, Ta, Nb, Zr and Hf are moderately to strongly compatible in ZrSiO4 and TiO2 phases. Based on the obtained partition coefficients, the composition of a mobile phase derived by sediment melting in deep subduction zones was calculated. This phase is strongly enriched in incompatible elements and displays a pronounced negative Ta-Nb anomaly but no Zr-Hf anomaly. Although all experiments were conducted in the diamond stability field, only graphite was observed in low-temperature experiments. Spontaneous diamond nucleation and the complete transformation of graphite to diamond were observed at temperatures above 1200-1300 °C. We speculate that the observed character of graphite-diamond transformation is controlled by relationships between the kinetics of metastable graphite dissolution and diamond nucleation in a hydrous silicocarbonate melt that is oversaturated in C.
International Geology Review, Vol. 57, 15, pp. 1940-1974.
Technology
Peridotite, experimental petrology
Abstract: Experimental synthesis of spinel peridotite phase assemblages for a range of compositions that mimic natural samples is used to derive a set of empirical geothermometers and geothermobarometers represented by multiple linear regression best-fit surfaces that link the variables of temperature, pressure, and composition. The calibrated geothermometers use reactions that govern the solubility of Al and Cr in both pyroxenes and the Mg–Fe exchange between silicates and spinel. Geothermobarometers map the Mg–Fe exchange between coexisting olivine and clinopyroxene and pyroxenes and Ca–Mg exchange between coexisting pyroxenes. Application of the geothermometers and geothermobarometers to suites of naturally occurring samples indicates that while reactions governing the Cr and Al solubility and solvus of orthopyroxene give useful estimates of ‘original’ mantle temperatures and pressures, respectively, comparable reactions for clinopyroxene yield estimates that are variably dependent on the transport phase of the sample suites. Temperature and pressure estimates from reactions governing Mg and Fe exchange between silicates and spinel and coexisting silicates are all sensitive to the later transport stage of the samples.
Abstract: We performed laser-heated diamond anvil cell experiments on bulk compositions in the systems MgO-SiO2-H2O (MSH) and MgO-Al2O3-SiO2-H2O (MASH) that constrain the stability of hydrous phases in Earth’s lower mantle. Phase identification by synchrotron powder diffraction reveals a consistent set of stability relations for the high-pressure, dense hydrous silicate phases D and H. In the MSH system phase D is stable to ~ 50 GPa, independent of temperature from ~ 1300 to 1700 K. Phase H becomes stable between 35 and 40 GPa, and the phase H out reaction occurs at ~ 55 GPa at 1600 K with a negative dT/dP slope of ~ -75 K/GPa. Between ~ 30 and 50 GPa dehydration melting occurs at ~ 1800K with a flat dT/dP slope. A cusp along the solidus at ~ 50 GPa corresponds with the intersection of the subsolidus phase H out reaction, and the dT/dP melting slope steepens to ~ 15 K/GPa up to ~ 85 GPa.
Physics of the Earth and Planetary Interiors, Vol. 247, pp. 11-16.
Mantle
Experimental Petrology
Abstract: Lattice thermal conductivity of ferropericlase and radiative thermal conductivity of iron bearing magnesium silicate perovskite (bridgmanite) - the major mineral of Earth’s lower mantle- have been measured at room temperature up to 30 and 46 GPa, respectively, using time-domain thermoreflectance and optical spectroscopy techniques in diamond anvil cells. The results provide new constraints for the pressure dependencies of the thermal conductivities of Fe bearing minerals. The lattice thermal conductivity of ferropericlase Mg0.9Fe0.1O is 5.7(6) W/(m * K) at ambient conditions, which is almost 10 times smaller than that of pure MgO; however, it increases with pressure much faster (6.1(7)%/GPa vs 3.6(1)%/GPa). The radiative conductivity of a Mg0.94Fe0.06SiO3 bridgmanite single crystal agrees with previously determined values for powder samples at ambient pressure; it is almost pressure-independent in the investigated pressure range. Our results confirm the reduced radiative conductivity scenario for the Earth’s lower mantle, while the assessment of the heat flow through the core-mantle boundary still requires in situ measurements at the relevant pressure-temperature conditions.
Earth and Planetary Science Letters, Vol. 434, pp. 129-140.
Technology
Petrology - experimental
Abstract: Transitional melts, intermediate in composition between silicate and carbonate melts, form by low degree partial melting of mantle peridotite and might be the most abundant type of melt in the asthenosphere. Their role in the transport of volatile elements and in metasomatic processes at the planetary scale might be significant yet they have remained largely unstudied. Their molecular structure has remained elusive in part because these melts are difficult to quench to glass. Here we use FTIR, Raman, 13C and 29Si NMR spectroscopy together with First Principle Molecular Dynamic (FPMD) simulations to investigate the molecular structure of transitional melts and in particular to assess the effect of CO2 on their structure. We found that carbon in these glasses forms free ionic carbonate groups attracting cations away from their usual ‘depolymerising’ role in breaking up the covalent silicate network. Solution of CO2 in these melts strongly modifies their structure resulting in a significant polymerisation of the aluminosilicate network with a decrease in NBO/Si of about 0.2 for every 5 mol% CO2 dissolved. This polymerisation effect is expected to influence the physical and transport properties of transitional melts. An increase in viscosity is expected with increasing CO2 content, potentially leading to melt ponding at certain levels in the mantle such as at the lithosphere-asthenosphere boundary. Conversely an ascending and degassing transitional melt such as a kimberlite would become increasingly fluid during ascent hence potentially accelerate. Carbon-rich transitional melts are effectively composed of two sub-networks: a carbonate and a silicate one leading to peculiar physical and transport properties.
Abstract: Carbon dioxide is the most abundant volatile in kimberlite melts and its solubility exerts a prime influence on the melt structure, buoyancy, transport rate and hence eruption dynamics. The actual primary composition of kimberlite magma is the matter of some debate but the solubility of CO2 in kimberlitic melts is also poorly constrained due to difficulties in quenching these compositions to a glass that retains the equilibrium CO2 content. In this study we used a range of synthetic, melt compositions with broadly kimberlitic to carbonatitic characteristics which can, under certain conditions, be quenched fast enough to produce a glass. These materials are used to determine the CO2 solubility as a function of chemical composition and pressure (0.05-1.5 GPa). Our results suggest that the solubility of CO2 decreases steadily with increasing amount of network forming cations from ~ 30 wt.% CO2 at 12 wt.% SiO2 down to ~ 3 wt.% CO2 at 40 wt.% SiO2. For low silica melts, CO2 solubility correlates non-linearly with pressure showing a sudden increase from 0.1 to 100 MPa and a smooth increase for pressure > 100 MPa. This peculiar pressure-solubility relationship in low silica melts implies that CO2 degassing must mostly occur within the last 3 km of ascent to the surface having potential links with the highly explosive nature of kimberlite magmas and some of the geo-morphological features of their root zone. We present an empirical CO2 solubility model covering a large range of melt composition from 11 to 55 wt.% SiO2 spanning the transition from carbonatitic to kimberlitic at pressures from 1500 to 50 MPa.
Contributions to Mineralogy and Petrology, in press available 9p.
Technology
Petrology
Abstract: Kimberlites are rare diamond-bearing volcanic rocks that originate as melts in the Earth’s mantle. The original composition of kimberlitic melt is poorly constrained because of mantle and crustal contamination, exsolution of volatiles during ascent, and pervasive alteration during and after emplacement. One recent model (Russell et al. in Nature 481(7381):352-356, 2012. doi:10.1038/nature10740) proposes that kimberlite melts are initially carbonatitic and evolve to kimberlite during ascent through continuous assimilation of orthopyroxene and exsolution of CO2. In high-temperature, high-pressure experiments designed to test this model, assimilation of orthopyroxene commences between 2.5 and 3.5 GPa by a reaction in which orthopyroxene reacts with the melt to form olivine, clinopyroxene, and CO2. No assimilation occurs at 3.5 GPa and above. We propose that the clinopyroxene produced in this reaction can react with the melt at lower pressure in a second reaction that produces olivine, calcite, and CO2, which would explain the absence of clinopyroxene phenocrysts in kimberlites. These experiments do not confirm that assimilation of orthopyroxene for the entirety of kimberlite ascent takes place, but rather two reactions at lower pressures (<3.5 GPa) cause assimilation of orthopyroxene and then clinopyroxene, evolving carbonatitic melts to kimberlite and causing CO2 exsolution that drives rapid ascent.
Progress in Earth and Planetary Science, Vol. 3, 25, Aug. 22
Mantle
Experimental petrology
Abstract: The Accessible Silicate Earth (ASE) has a higher 142Nd/144Nd ratio than most chondrites. Thus, if the Earth is assumed to have formed from these chondrites, a complement low-142Nd/144Nd reservoir is needed. Such a low-142Nd/144Nd reservoir is believed to have been derived from a melt in the early Earth and is called the Early Enriched Reservoir (EER). Although the major element composition of the EER is crucial for estimating its chemical and physical properties (e.g., density) and is also essential for understanding the origin and fate of the EER, which are both major factors that determine the present composition of the Earth, it has not yet been robustly established. In order to determine the major element composition of the EER, we estimated the age and pressure-temperature conditions to form the EER that would best explain its Nd isotopic characteristics, based on Sm-Nd partitioning and its dependence on pressure, temperature, and melting phase relations. Our estimate indicates that the EER formed within 33.5 Myr of Solar System formation and at near-solidus temperatures and shallow upper-mantle pressures. We then performed high-pressure melting experiments on primitive peridotite to determine the major element composition of the EER at estimated temperature at 7 GPa and calculated the density of the EER. The result of our experiments indicates that the near-solidus melt is iron-rich komatiite. The estimated density of the near-solidus melt is lower than that of the primitive peridotite, suggesting that the EER melt would have ascended in the mantle to form an early crust. Given that high mantle potential temperatures are assumed to have existed in the Hadean, it follows that the EER melt was generated at high pressure and, therefore, its composition would have been picritic to komatiitic. As the formation age of the EER estimated in our study precedes the last giant, lunar-forming impact, the picritic to komatiitic crust (EER) would most likely have been ejected from the Earth by the last giant impact or preceding impacts. Thus, the EER has been lost, leaving the Earth more depleted than its original composition.
Doklady Earth Sciences, Vol. 471, 1, pp. 1144-1148.
Technology
Petrology - experimental
Abstract: Experimental research in the Fe3C-(Fe,Ni)S system was carried out. The objective of the investigation was to model the reactions of carbide-sulfide interaction related to graphite (diamond) formation in reduced lithosphere mantle domains. T ? 1200°C is the formation temperature of the Ni-cohenite + graphite assemblage coexisting with two immiscible melts such as sulfide (Fe60-Ni3-S37)L and metal-sulfide (Fe71-Ni7-S21-C1)L containing dissolved carbon. T ? 1300°C is the generation temperature of a unified melt such as (Fe80-Ni6-S10-C4)L characterized by graphite crystallization and diamond growth. The extraction of carbide carbon during the interaction with the sulfide melt can be considered as one of the potential mechanisms of graphite and diamond formation in the reduced mantle.
Abstract: Carbonates are common rock-forming minerals in the Earth’s crust and act as sinks of atmospheric carbon dioxide. Subduction of hydrothermally altered oceanic lithosphere returns carbon to the interior, where more than three quarters of Earth’s carbon is stored. The contribution of subducted carbonates to the Earth's long-term deep carbon cycle is uncertain and has recently emerged as a topic of intense debate [1]. Moreover, mantle-slab interaction has been proposed as a mechanism to produce super-deep diamonds, thus questioning the use of certain mineral inclusions to infer lower-mantle origin [2]. Here we report new data on the chemical stability and reaction kinetics of carbonates in the mantle from multianvil and diamond-anvil-cell experiments. Our results suggest that carbon can be sequestered into deep Earth through reaction freezing and that the index minerals for super-deep diamonds are not reliable indicators for their formation depths.
Abstract: Experimental studies of phase relations in the oxide–silicate system MgO–FeO–SiO2 at 24 GPa show that the peritectic reaction of bridgmanite controls the formation of stishovite as a primary in situ mineral of the lower mantle and as an effect of the stishovite paradox. The stishovite paradox is registered in the diamond-forming system MgO–FeO–SiO2–(Mg–Fe–Ca–Na carbonate)–carbon in experiments at 26 GPa as well. The physicochemical mechanisms of the ultrabasic–basic evolution of deep magmas and diamondforming media, as well as their role in the origin of the lower mantle minerals and genesis of ultradeep diamonds, are studied.
Doklady earth Sciences, Vol. 483, 1, pp. 1427-1430.
Mantle
petrology
Abstract: Experimental studies were performed in the Fe3C-SiO2-(Mg,Ca)CO3 system (6.3 GP?, 1100-1500°C, 20-40 h). It is established that the carbide-oxide-carbonate interaction leads to the formation of ferrosilite, fayalite, graphite, and cohenite (1100 and 1200°?), as well as a Fe-C melt (1300°?). It is determined that the main processes in the system are decarbonation, redox-reactions of cohenite and a CO2-fluid, extraction of carbon from carbide, and crystallization of metastable graphite (± diamond growth), as well as the formation of ferriferous silicates. The interaction studied can be considered as a simplified model of the processes that occur during the subduction of oxidized crustal material to reduced mantle rocks.
Abstract: When carbonate-rich and silicate rocks are juxtaposed at high subsolidus temperature, their contrasting elemental chemical potentials trigger metasomatism. Kimberlites in contact with felsic-to-mafic rocks should theoretically develop skarn alteration, replacing both the wall rocks and magmatic rocks. Although some kimberlites are well exposed from mining, metasomatic effects in them are difficult to isolate because of the common presence of marginal country rock breccias and assimilated country rock xenoliths. The volatilerich nature of kimberlite melts and faulting prior to the emplacement results in country rock brecciation and incorporation of as much as 70% xenoliths in kimberlite. We discuss several examples of mineralogical, textural and chemical zonation at contacts between felsic-to-mafic xenoliths, in-situ country rocks and kimberlites (Renard, Gahcho Kue, Snap Lake and Orapa). The subsolidus skarn reactions are preceded by magmatic assimilation. It partially melts feldspars and forms diopside and phlogopite coronas on xenoliths. To distinguish between incorporation and assimilation of xenoliths and contact metasomatism, we employed an improved isocon analysis that enables estimation of metasomatic contributions to geochemical diversity. Skarn reactions replace the original kimberlite minerals with serpentine, phlogopite, hydrogarnet, while xenoliths are replaced by serpentine, clinopyroxene, carbonate, chlorite, and pectolite. If the mode of felsic-to-mafic xenoliths exceeds 30%, the textures and the mineralogy of the kimberlite altered by assimilation and skarn reactions may resemble those of the Kimberly-type pyroclastic kimberlite (KPK). The distinct mineralogy of the KPK interclast matrix, the correlation between xenolith modes and the kimberlite texture, the spatial distribution of KPK in Renard and Gahcho Kue kimberlites indicate the principal role of crustal xenoliths in the KPK formation. Our data suggest that metasomatic recrystallization of kimberlites is more widespread than previously recognized, but is complex and accompanied by xenolith assimilation.
Abstract: The evaluation of primary kimberlite compositions is hindered by significant melt modifications during ascent through the lithosphere by entrainment of xenolithic material, volatile degassing, and near surface alteration. Consequently, hypabyssal kimberlite emplaced in the upper crust may not provide a true reflection of the primary kimberlite magma. This contribution places new constraints on kimberlite melt composition by providing an assessment of quenched glass-rich polymineralic melt inclusions hosted in olivine megacrysts from the Monastery kimberlite, South Africa. Melt inclusions predominantly contain variable proportions of euhedral or skeletal grains of calcite, phlogopite, spinel, perovskite, serpentine, and fresh to devitrified glass. Estimates of the bulk compositions of melt inclusions, and the compositions of crystalline phases present therein, are compatible to those of hypabyssal kimberlites worldwide and show a volatile-rich (CO2?+?H2O ~10-17?wt%) carbonated silicate (SiO2 ~27-41?wt%) composition. The glass component has a Si-Mg-Fe-rich and largely CaO-, K2O- and TiO2-free major element composition and is REE-depleted. It also contains approximately 10?wt% H2O but is CO2?free. The glass represents a residual melt that existed after crystallization of the observed mineral assemblage. From some, but not all melt inclusions, apophyses radiate outwards. These fractures typically contain partially devitrified glass that is compositionally identical to the fresh residual glass within the melt inclusions, indicating fracture formation during decompression of the hosting megacryst and at a stage after the melt had evolved. These features are consistent with a trapping of the melt inclusions at high pressure, prior to kimberlite ascent to the surface, in the SCLM at a depth corresponding to 4.5-6?GPa. Textures and compositions of phases within the melt inclusions represent stages of the kimberlite melt and magma evolution. They provide evidence in support of high-pressure experimental studies suggesting a carbonated silicate primary melt rather than a carbonatite. Furthermore, the composition of fresh glass in the melt inclusions, which is compositionally similar to serpentine, suggests that much groundmass serpentine in hypabyssal kimberlites may have formed from similar silicate melt or devitrified glass.
www.minsoccam.org/ MSA/Centennial/ MSA_Centennial _Symposium.html The next 100 years of mineral science, June 20-21, p. 19. Abstract
Europe, Alps
petrology
Abstract: Estimates of the bulk chemical composition of Earth continental crust are highly variable and range from 55-65 wt% SiO2 (Rudnick & Gao 2003). In particular, no consensus exists about the composition of the lower crust. While it is appropriate in some places to distinguish an upper, middle and lower crust, more recent studies advocate that in some places middle and lower crust cannot readily be distinguished based on seismic wave speeds, geochemical compositions and heat flow constraints (Hacker et al. 2015). Analysis of global or regional datasets, however, cannot readily disentangle the relevant processes that control the composition of the crust and, in particular, the lower crust. Crucial for this issue are changes in composition over time. Thus, studying one of best known crustal sections – the Ivrea zone in the Alps – provides new insights as it is unique by exposing an almost complete section of crustal rocks of about 30-35 km, approaching close to the crust-mantle transition. The Ivrea zone represents a Paleozoic continental crust section that is affected by Permian transcrustal magmatism on all crustal levels, allowing for evaluation of the temporal evolution of continental crust. An evaluation of major element chemical trajectories of pre-Permian Ivrea crust and the Permian magmatic addition indicates that the metasedimentary crust is dominated by crustal reworking (mechanical mixing trends), while the magmatic addition closely follows phase equilibria controlled by major element geochemical trends and can be considered as net crustal growth. Recent equilibrium and fractional crystallization experiments designed to understand fractionation processes in the lower crust simulated the liquid (LLD) and cumulate lines of descent (CLD) of primary mantle derived magmas (Müntener & Ulmer 2018). An evaluation of the major element composition indicates that the CLD of hydrous systems is fundamentally different from dry systems. Cumulates derived from hydrous experiments display elevated Al2O3 and CaO contents at low SiO2, producing voluminous andesitic to rhyolitic liquids, which closely overlap with compositions of natural systems, while dry systems follow different fractionation paths. Melting experiments on amphibolite or remelting of basaltic to andesitic cumulates equally produce granitic – rhyolitic liquids of similar composition yet their restites do not present the same variability of the CLD of fractional crystallization experiments. Despite widespread evidence for partial melting and assimilation processes during Permian transcrustal magmatic activity, CLDs from experimental studies on lower crustal differentiation in H2O-bearing systems are comparable to the magmatic evolution in the Ivrea zone and other crustal sections. Dry crystallization and moderate amounts of assimilation may provide similar results. This indicates that global datasets from metamorphic terrains at moderate to high pressure can be evaluated for their igneous versus metasedimentary contribution to the bulk continental lower crust.
Geochimica et Cosmochimica Acta, in press, 61p. Pdf
Mantle
petrology
Abstract: Transport of sulfur via mantle-derived partial melts from deep Earth to the surface reservoirs is a critical step in the deep global sulfur cycle. Given that sulfur is stored mostly in sulfide phases in mantle lithologies, the critical parameter is sulfur concentration at sulfide saturation (SCSS) of mantle-derived magmas. CO2?±?H2O-induced melting beneath oceanic and continental mantle produces incipient CO2-rich melts. Although, SCSS of silicate melts of a variety of compositions is extensively studied, the SCSS of carbonatitic and carbonated silicate melts have not received much attention. Here we present experiments in graphite capsules at pressures (P) of 2.5-6.0 GPa and temperatures (T) of 1350-1650?°C investigating the SCSS of carbonatitic and carbonated silicate melts. All experiments produced quenched Fe?±?Ni-sulfide melt blobs?+?carbonated melt matrix?±?ol?±?cpx?±?opx?±?gt, with melt composition on a CO2-free basis varying from 7 to 40 wt.% SiO2, 0.5 to 7 wt.% Al2O3, and 9 to 17 wt.% FeO* (total FeO). SCSS measured using EPMA increases with SiO2 and T but is not affected by P; the effect of composition being more pronounced than P-T. The composition of sulfide melt phase also affects SCSS. With increasing Ni in the molten sulfide phase, the SCSS changes from 2000 to 4000?ppm (Ni-free) to is 800-3000?ppm (33 wt.% Ni). Comparison of our measured SCSS with the existing SCSS models for nominally CO2-free silicate melts and with one study for carbonated melts show that these parameterizations fail to capture the sulfide saturation values in CO2-rich melts from our study. Using our new SCSS data and previous SCSS data for melt compositions that span the range from carbonatite to basalts via carbonated silicate melts, we develop a new empirical SCSS parameterization. Unlike a previous model, which suggested SCSS of carbonated melt is only affected by melt FeO* (other than P-T) and did not constrain how SCSS evolves from low-silica carbonatitic melt to low-CO2 basaltic melt, our new parameterization captured complex effects of many melt compositional parameters, including silica on SCSS. Using our new SCSS model, we constrained the efficiency of S extraction from the mantle beneath mid-oceanic ridges and continents via low-degree carbonated melts. Deep carbonated melts beneath ridges are expected to mobilize 5-15% of the initial sulfur before nominally-volatile-free peridotite melting begins. In continental mantle, deep kimberlitic melt can act as an agent to mildly enrich the shallow mantle in sulfide as it evolves to a carbonatitic melt upon reactive cooling. Application of our data to subduction zones suggests that low degree carbonatitic melt is not an efficient agent to extract residual sulfide from the subducting oceanic crust.
Abstract: Recent advances in core scanning technologies allow for fast and non-destructive chemical and mineral profiling of rock samples for mineral services and oil and gas exploration. The aim of these automatic core scan methods is to obtain valuable information for profiling drill core cuttings with minimum sample preparation at relatively high speed. In the last decade, a core logging system using an automated infrared-based hyperspectral line-profiling system, Hylogger, has progressed to become an effective standard for the Australian mineral exploration industry. Its results are used to rapidly obtain mineralogical information allowing the characterisation of different geological formations in near real-time. The interpretation of Hylogger data can be challenging for certain complex mineral mixtures. Here we solve this issue by augmenting the Hylogger interpretation with elemental analysis using the Itrax core scanner equipped with an X-ray fluorescence (XRF) spectrometer. The Itrax core scanner produces high-resolution elemental data of major, minor and trace elements in one dimension. We analyse and compare the Hylogger and Itrax data, with each dataset independently cross-checked using X-ray diffraction (XRD) and thin-section petrology and propose a workflow harvesting the mutual strengths of each method. The recommended workflow consists of rapid screening using Hylogger and XRF analysis, providing new insights into the mineralogy based on comparative multiscale element-mineral analysis. The workflow is tested on four different types of volcanic rock samples, where infrared spectra of individual minerals overlap. We tested tuffaceous ash, basaltic, dolerite, and basaltic-andesitic rocks. Our study shows that embedding Itrax core scanner data into the workflow provides a solution to the challenges of interpreting Hylogger data in complex mineral samples. The proposed workflow provides a total system for multiscale, high-resolution petrophysical analyses and rock property modelling.