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Russian Geology and Geophysics

2015 year, number 1-2

1.
PROBLEMS RELATED TO CRYSTALLOGENESIS AND THE DEEP CARBON CYCLE

N.V. Sobolev1,2, N.L. Dobretsov3,4, E. Ohtani5,6, L.A. Taylor7, H.P. Schertl8, Yu.N. Palyanov1,2, K.D. Litasov1,2
1pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia, ul. Pirogova 2, Novosibirsk, 630090, Russia
2Novosibirsk State University
3A.A. Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
4Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia
5V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
6Department of Earth Science, Tohoku University, 980-8578 Sendai, Japan
7Planetary Geosciences Institute, University of Tennessee, Knoxville, USA
8Institute of Geology, Mineralogy and Geophysics, Ruhr University, 44780 Bochum, Germany
Keywords: Mantle, core, subduction, magmatism, high pressures and temperatures, experiment, peridotide, eclogite, diamond, carbon

Abstract >>
We present an analytical review of the key results and research trends in the Deep Carbon Cycle program. The first section addresses the issues related to subduction zones with emphasis on geological and geophysical data on Kamchatka and the Kokchetav paleosubduction zone. Experimental studies over a wide pressure range are discussed in the section Crystallogenesis and experimental mineralogy. The papers addressing the diamond issues on the example of the Yakutian diamondiferous province are grouped in the sections Diamond crystallogeny and Diamond and kimberlite magmatism.

DOI: http://dx.doi.org/10.1016/j.rgg.2015.01.001



2.
AN INTEGRATE MODEL OF SUBDUCTION: CONTRIBUTIONS FROM GEOLOGY, EXPERIMENTAL PETROLOGY, AND SEISMIC TOMOGRAPHY

N.L. Dobretsov1,2, I.Yu. Koulakov1,2, K.D. Litasov3,2, E.V. Kukarina1,2
1A.A. Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
2Novosibirsk State University, ul. Pirogova 2,Novosibirsk, 630090, Russia
3V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
Keywords: Subduction, volcano, lava composition, migration of melts and fluids, phase change, dehydration, seismicity, Kamchatka, Kokchetav

Abstract >>
We summarize the available knowledge of subduction gained from geology, petrology, and seismology and consider the advantages and drawbacks of each method. Regional and local seismic tomography reveals complex systems of fluid and melt migration at different depths above subducting slabs. The physicochemical evolution of the magma storage system maintaining active volcanism is modeled with reference to a wealth of geological and geophysical data. Subduction-related processes are discussed by the examples of active (Kamchatka and Japan arcs) and ancient (Kokchetav metamorphic complex) subduction zones. Comprehensive geological and geophysical studies in Kamchatka and Japan prove the leading role of andesite magma in subduction of oceanic crust and, on the other hand, show that modeling independent migration paths of melts and fluids is problematic. The case study of Kamchatka provides more insights into melting in intermediate magma reservoirs at depths of about 5080 and 30 km and highlights the significance of shallow magma sources at the pre-eruption stage. The Kokchetav metamorphics, which are exhumed suprasubduction rocks, offer an exceptional opportunity to estimate directly the compositions and ages of subduction-related melts.

DOI: http://dx.doi.org/10.1016/j.rgg.2015.01.002



3.
GEOLOGICAL, HYDROGEOCHEMICAL, AND MICROBIOLOGICAL CHARACTERISTICS OF THE OIL SITE OF THE UZON CALDERA (Kamchatka)

N.L. Dobretsov1,2, E.V. Lazareva3, S.M. Zhmodik3,2, A.V. Bryanskaya4, V.V. Morozova5, N.V. Tikunova5, S.E. Peltek4, G.A. Karpov6, O.P. Taran7, O.L. Ogorodnikova7, I.S. Kirichenko3, A.S. Rozanov4, I.V. Babkin5, O.V. Shuvaeva8, E.P. Chebykin9
1A.A. Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
2Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia
3V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
4Institute of Cytology and Genetics, Siberian Branch, Russian Academy of Sciences, pr. Akademika Lavrentyeva 10, Novosibirsk, 630090, Russia
5Institute of Chemical Biology and Fundamental Medicine, Siberian Branch, Russian Academy of Sciences, pr. Akademika Lavrentyeva 8, Novosibirsk, 630090, Russia
6Institute of Volcanology and Seismology, Far East Branch, Russian Academy of Sciences, Piip blvd. 9, Petropavlovsk-Kamchatskii, 683000, Russia
7Boreskov Institute of Catalysis, Siberian Branch, Russian Academy of Sciences, pr. Akademika Lavrentyeva 5, Novosibirsk, 630090, Russia
8Nikolaev Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences, pr. Akademika Lavrentyeva 3, Novosibirsk, 630090, Russia
9Limnological Institute, Siberian Branch, Russian Academy of Sciences, ul. Ulan-Batorskaya 3, Irkutsk, 664033, Russia
Keywords: Hydrothermal oil, Uzon caldera, hydrogeochemistry, Archaea, Kamchatka

Abstract >>
This study used geological, geochemical, and microbiological data to examine the Uzon oils and conditions within the Uzon caldera. The trace-element compositions of crude oils and solutions from boreholes and hydrothermal springs were determined by ICP MS. The majority of hydrothermal manifestations within the Uzon caldera are controlled by three trends of faults. The major fault zone, trending nearly E-W is located between Kikhpinych and Taunshits volcanoes. It acts as a magma conduit and hosts numerous oval-shaped hydrothermal vents. The oil site is situated on the periphery of the hottest area of highest hydrothermal activity within the Eastern thermal field. On the Eh-pH diagram, most solutions of the Uzon caldera define distinct fields and trends which correlate with the stability fields for sulfur and iron. The oil site is characterized by very wide variations in temperature and Eh-pH parameters of pore solutions. The geochemical signatures of the solutions at this site are broadly similar to those from other areas of the Uzon caldera but differ in their sulfide ion and sulfate ion concentrations. These differences can be explained by mixing of deep chloride-sodium hydrothermal solutions and solutions produced during surface oxidation of sulfide-containing material. With respect to the average continental crust, the Uzon oil is enriched in S, As, and Hg. The crude oil and solutions have broadly similar concentrations of B, S, Cl, As, Se, Br, Cd, I, Hg, and Pb and highly variable concentrations of Ti, V, Cr, Co, Ni, Cu, Cd, Nb, and Sn. The community structure of archaeal assemblages in springs and test pits at the Eastern thermal field was analyzed by 16S rRNA library and pyrosequencing methods. It was found that the proportion of archaea in the microbial communities of the Uzon caldera ranges from 2 to over 70% of the total sequences identified. Crenarchaeota were found in large proportions in all samples except one. The majority of the sequences in four samples were affiliated with Euryarchaeota, which comprise methanogenic archaea, extreme halophiles, and some extreme thermophiles. The results of geological, mineralogical-geochemical, microbiological and physicochemical studies of oil seeps in the Uzon caldera reveal distinctive geochemical characteristics of crude oil and the complexity of oil formation.

DOI: http://dx.doi.org/10.1016/j.rgg.2015.01.003



4.
STRUCTURAL LOCATION, COMPOSITION, AND GEODYNAMIC NATURE OF DIAMONDBEARING METAMORPHIC ROCKS OF THE KOKCHETAV SUBDUCTIONCOLLISION ZONE OF THE CENTRAL ASIAN FOLD BELT (northern Kazakhstan)

M.M. Buslov1,2, N.L. Dobretsov3,2, G.M. Vovna4, V.I. Kiselev4
1V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
2Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia
3A.A. Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
4Far Eastern Geological Institute, Far Eastern Branch of the Russian Academy of Sciences, pr. 100 Let Vladivostoku 159, Vladivostok, 690022, Russia
Keywords: Subduction, collision, diamond-bearing calc-silicate rocks, eclogites, protoliths, olistostrome, exhumation, thrusts, tectonic rocks, geochronology, geochemistry, Kokchetav microcontinent

Abstract >>
We present data on different aspects of geology, mineralogy, petrology, geochemistry, and geochronology of diamond-bearing metamorphic rocks of the Kumdy-Kol terrane, which show the similarity of their protolith to the sedimentary rocks of the Kokchetav microcontinent. The structural location of the studied objects in the accretion-collision zone evidences that the subduction of the Kokchetav microcontinent beneath the Vendian-Cambrian Ishim-Selety island arc is the main mechanism of transport of graphite-bearing terrigenous carbonate rocks to zones of their transformation into diamond-bearing metamorphic rocks. The sedimentary rocks of the Kokchetav microcontinent, which are enriched in graphite and iron sulfides and carbonates, contain all components necessary for diamond crystallization in deep-seated subduction zone. This is in agreement with the experimental data and the compositions of fluid-melt inclusions in the minerals of diamond-bearing rocks.

DOI: http://dx.doi.org/10.1016/j.rgg.2015.01.004



5.
CARBONATE, SILICATE, AND SULFIDE MELTS: HETEROGENEITY OF THE UHP MINERAL-FORMING MEDIA IN CALC-SILICATE ROCKS FROM THE KOKCHETAV MASSIF

A.O. Mikhno1,2, A.V. Korsakov1,2
1V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
2Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia
Keywords: Partial melting, ultrahigh-pressure metamorphism, carbonatite melt, silicate melt, sulfide melt, Kokchetav Massif

Abstract >>
We present data on carbonatite, silicate, and sulfide melts and their immiscibility at different stages of ultrahigh-pressure metamorphism of rocks of the Kokchetav Massif (northern Kazakhstan). The identified silicate, silicate-carbonate, and sulfide inclusions are regarded as crystallization products of high-pressure melts. The detected reactionary garnet-K-feldspar-allanite-calcite simplectite structures as inclusions in garnet and as identical structures around it evidence that they resulted from carbonatite melt crystallization. Carbonate melting was probably triggered by the present free fluid phase (mostly H<sub>2</sub>O) and/or a high content of alkalies in the system. The coexistence of carbonate and silicate inclusions testifies to the immiscibility of carbonatite and silicate melts. The presence of K-cymrite in the polyphase inclusions indicates that the minimum pressure of silicate melt intake is ~4.5 GPa. The maximum pressure of this intake is 67 GPa at 10001100 ºC and corresponds to the peak of metamorphism of the Kokchetav Massif rocks. Most likely, the field of immiscibility of carbonatite and silicate melts lies within 4.57 GPa and 9501100 ºC. The carbonatite melt can dissolve up to 18 wt.% SiO<sub>2</sub>, and the silicate melt, up to 4.5 vol.% CaCO<sub>3</sub>.

DOI: http://dx.doi.org/10.1016/j.rgg.2015.01.005



6.
CATHODOLUMINESCENCE MICROSCOPY OF THE KOKCHETAV ULTRAHIGHPRESSURE CALC-SILICATE ROCKS: What can we learn from silicates, carbon-hosting minerals, and diamond?

H.-P. Schertl1, R.D. Neuser1, A.M. Logvinova2,3, R. Wirth4, N.V. Sobolev2,3
1Ruhr-University Bochum, Institute of Geology, Mineralogy and Geophysics, 44780 Bochum, Germany
2V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
3Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia
4Geoforschungs zentrum Potsdam, Germany
Keywords: Diamond, garnet, pyroxene, K-amphibole, sapphirine, corundum, ultrahigh-pressure metamorphism, cathodoluminescence, Kokchetav massif

Abstract >>
A comprehensive study of a key calc-silicate rock of complex composition, an ultrahigh-pressure metamorphic rock of the Kokchetav massif, has been studied. New thin sections were examined by cathodoluminescence microscopy, probe microanalysis, and transmission/analytical electron microscopy. The obtained results confirmed the presence of microdiamonds and indicative signs of ultrahigh pressures (K in clinopyroxene) for seven of the eight previously recognized interlayers of the sample. Only one interlayer (3) containing paragenesis forsterite + Ti-clinohumite + dolomite + luminescent garnet (Mg # = 86 to 95) + clinopyroxene free of potassium and perovskite impurities lacks diamonds. Symplectitic rims replacing garnet in this interlayer are formed by spinel growing into augite clinopyroxene with a scarce impurity of sapphirine and corundum and lack hydrous minerals. Garnets (Mg# = 81 to 82) of the diamond-containing interlayers (1 and 2a) and (4-8) having Mg#=38-53 do not exhibit luminescence. They are present, together with K-clinopyroxenes, in the Mg-calcite matrix. A distinctive feature of the symplectitic rims is abundant segregations of corundum, often needle-like, and sapphirine in the augite clinopyroxene matrix with a minor spinel impurity. The symplectitic rims contain high-Mg phlogopite and K-amphibole; the latter was found in the metamorphic rocks for the first time. The different roles of hydrous minerals at the early stages of retrograde metamorphism for different interlayers reflect different fluid mobilities even within a sample.

DOI: http://dx.doi.org/10.1016/j.rgg.2015.01.006



7.
PHASE RELATIONS IN CARBONATE SYSTEMS AT PRESSURES AND TEMPERATURES OF LITHOSPHERIC MANTLE: REVIEW OF EXPERIMENTAL DATA

A.F. Shatskiy1,2, K.D. Litasov1,2, Yu.N. Palyanov1,2
1V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, ul. Pirogova 2, Novosibirsk, 630090, Russia
2Novosibirsk State University
Keywords: Carbonate, carbonatite, partial melting, carbonated mantle, high-pressure high-temperature experiments

Abstract >>
The paper presents a synopsis of experimentally constrained phase relations in carbonate systems. Three sections of the paper consider, respectively, PT diagrams of simple carbonates (MgCO 3, CaCO 3, FeCO 3, BaCO 3, SrCO 3, K 2CO 3, and Na 2CO 3); isobaric T-X diagrams of binary and ternary systems (CaCO 3-MgCO 3, CaCO3-FeCO 3, CaCO 3-FeCO 3-MgCO 3, BaCO 3-CaCO 3, SrCO 3-CaCO 3, BaCO 3-SrCO 3, CaCO 3-MgCO 3-BaCO 3, CaCO 3-MgCO 3-SrCO 3, BaCO 3-CaCO 3-SrCO 3, BaCO 3-MgCO 3-SrCO 3, Na 2CO 3-CaCO 3, and K 2CO 3-CaCO 3), and T-X diagrams of the systems MgCO 3-FeCO 3, MgCO 3-CaCO 3, CaCO 3-FeCO 3, MgCO 3-FeCO 3-CaCO 3, K 2CO 3-MgCO 3, Na 2CO 3-MgCO 3, K 2CO 3-FeCO 3, Na 2CO 3-FeCO 3, K 2CO 3-CaCO 3, Na 2CO 3-CaCO 3, K 2CO 3-FeCO 3-MgCO 3, Na 2CO 3-FeCO 3-MgCO 3, K 2CO 3-CaCO 3-MgCO 3, and Na 2CO 3-CaCO 3-MgCO 3 at 6 GPa. The last section deals with temperatures of carbonate magma generation in the upper mantle and with melt compositions. In conclusion, prospects are outlined for further research of phase relations in carbonate system at high pressures and temperatures.

DOI: http://dx.doi.org/10.1016/j.rgg.2015.01.007



8.
THE ROLE OF ROCKS SATURATED WITH METALLIC IRON IN THE FORMATION OF FERRIC CARBONATESILICATE MELTS: EXPERIMENTAL MODELING UNDER LITHOSPHERIC MANTLE PTCONDITIONS

Yu.V. Bataleva1, Yu.N. Palyanov1,2, A.G. Sokol1,2, Yu.M. Borzdov1, O.A. Bayukov3
1V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
2Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia
3Kirensky Institute of Physics, Siberian Branch of the Russian Academy of Sciences, Akademgorodok 50, bld. 38, Krasnoyarsk, 660036, Russia
Keywords: Carbonate-silicate melt, graphite, CO2 fluid, iron carbide, garnet, redox gradient, high-pressure experiment

Abstract >>
Experimental modeling of the processes of formation of ferric carbonate-silicate melts through the carbonate-oxide-metal interaction is performed in the system (Mg,Ca)CO3-SiO2-Al2O3-Fe0 at 6.3 and 7.5 GPa and within 1150-1650 ºC, using a multianvil high-pressure apparatus of «split-sphere type (BARS). Two parallel reactions run in the subsolidus region (1150-1450 ºC): decarbonation, producing pyrope-almandine (Fe# = 0.40-0.75) and CO2 fluid, and redox interaction between carbonate and Fe0, resulting in the crystallization of iron carbide in assemblage with magnesiowüstite (Fe# = 0.75-0.85). It is shown that the reduction of carbonate or CO2 fluid by iron carbide and parallel redox interaction of magnesiowüstite tite with CO2 produce graphite in assemblage with Fe3+-containing magnesiowüstite. In the temperature range 1450-1650 ºC, generation of carbonate-silicate melts coexisting with pyrope-almandine, magnesiowüstite, magnetite, ferrospinel, and graphite takes place. The composition of the produced melts is as follows: SiO2 ≈ 10-15 wt.%, ∑Fe(FeO + Fe 2O 3) = = 36-43 wt.%, and Fe3+/∑Fe ≈ 0.18-0.23. These Fe3+-enriched carbonate-silicate melts/fluids are saturated with carbon and are the medium of graphite crystallization. Oxide and silicate phases (almandine, ferrospinel, and magnetite) coexisting with graphite are also characterized by high Fe3+/∑Fe values. It has been established that Fe3+-enriched carbonate-silicate melts can result from the interaction of Fe0-containing rocks with carbonated rocks. In the reduced mantle (with the presence of iron carbides or oxides), melts of this composition can be the source of carbon and the medium of graphite crystallization at once. After separation and ascent, these ferric carbonate-silicate melts can favor oxidizing metasomatism in the lithospheric mantle.

DOI: http://dx.doi.org/10.1016/j.rgg.2015.01.008



9.
THE CRYSTAL STRUCTURE OF GIRVASITE, NaCa2Mg3(PO4)3(CO3)(H2O)6, A COMPLEX PHOSPHATE CARBONATE HYDRATE BASED ON ELECTRONEUTRAL HETEROPOLYHEDRAL LAYERS

S.V. Krivovichev1,2, A.P. Chernyatieva1, S.N. Britvin1,2, V.N. Yakovenchuk2
1St. Petersburg State University, Department of Crystallography, Universitetskaya Nab. 7/9, St. Petersburg, 199034, Russia
2Nanomaterials Research Centre, Kola Science Centre, Russian Academy of Sciences, ul. Fersmana 14, Apatity, Murmansk Region, 184200, Russia
Keywords: Girvasite, crystal structure, phosphate-carbonate, complexation, structural complexity, Kola Peninsula

DOI: http://dx.doi.org/10.1016/j.rgg.2015.01.009



10.
FIRSTPRINCIPLES CALCULATIONS OF THE STATE EQUATIONS AND RELATIVE STABILITY OF IRON CARBIDES AT THE EARTHS CORE PRESSURES

K.D. Litasov1,2, Z.I. Popov3, P.N. Gavryushkin1,2, S.G. Ovchinnikov4,5,6, A.S. Fedorov4,5,6
1V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
2Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia
3L.V. Kirensky Institute of Physics, Siberian Branch of the Russian Academy of Sciences, Akademgorodok, 50, Building 38, Krasnoyarsk, 660036, Russia Novosibirsk
4L.V. Kirensky Institute of Physics, Siberian Branch of the Russian Academy of Sciences, pr. Svobodnyi 79, Krasnoyarsk, 660041, Russia
5Siberian Federal University, pr. Svobodnyi 79, Krasnoyarsk, 660041, Russia
6Siberian Federal University
Keywords: Iron carbide, Earths core, first-principles (or quantum-chemical) calculations, density, bulk modulus, magnetic moment

Abstract >>
Recent experimental studies have demonstrated that Fe 3C is more stable than Fe 7C 3 under PT -conditions of the Earths core. Theoretical calculations at 0 K, in turn, show the possible stability of Fe 2C at the core pressures. Therefore, a theoretical modeling of iron carbides at ≤500 GPa is carried out. Energetically stable phases and the pressures of magnetic transitions at 0 K are determined. The parameters of magnetic transitions for Fe 7C 3 and Fe 3C are consistent with those determined in the previous papers. The phase transition from Pnnm to Pnma in Fe 2C at 28 GPa is estimated. At >100 GPa, Fe 2C loses its magnetic moment. Assuming carbon to be the only light element in the system, the first-principles calculations yield 2.7-2.9 and 2.0-2.2 wt.% C at the boundary of the inner core at 5000 and 7000 K, respectively.

DOI: http://dx.doi.org/10.1016/j.rgg.2015.01.010



11.
THE EQUATIONS OF STATE OF FORSTERITE, WADSLEYITE, RINGWOODITE, AKIMOTOITE, MgSiO3PEROVSKITE, AND POSTPEROVSKITE AND PHASE DIAGRAM FOR THE Mg2SiO4 SYSTEM AT PRESSURES OF UP TO 130 GPa

P.I. Dorogokupets1, A.M. Dymshits2,3, T.S. Sokolova1, B.S. Danilov1, K.D. Litasov2,3
1Institute of the Earths Crust, Siberian Branch of the Russian Academy of Sciences, ul. Lermontova 128, Irkutsk, 664033, Russia
2V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
3Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia
Keywords: Equation of state, Gibbs energy, forsterite, wadsleyite, ringwoodite, MgSiO -perovskite, akimotoite, MgSiO -postperovskite, periclase, Helmholtz free energy

Abstract >>
The equations of state of forsterite, wadsleyite, ringwoodite, MgSiO 3-perovskite, akimotoite, and postperovskite are set up by joint analysis of experimentally measured isobaric heat capacity, bulk moduli, thermal expansion depending on temperature at ambient pressure, and volume at room and higher temperatures. Modified equations of state based on the Helmholtz free energy are used to construct a thermodynamic model. The derived equations of state permit calculation of all thermodynamic functions for the minerals depending on temperature and volume or temperature and pressure. A phase diagram of the system MgSiO 3-MgO is constructed based on the differences in the Gibbs energy calibrated using the referred experimental points. The seismic boundaries at depths of 410 and 520 km and in the zone D ″ are interpreted on the basis of the phase transitions. The global upper/lower mantle discontinuity at a depth of 660 km remains debatable; it is in poor agreement with experimental and computational data on the dissociation of ringwoodite to perovskite and periclase.

DOI: http://dx.doi.org/10.1016/j.rgg.2015.01.011



12.
SOUND VELOCITY MEASUREMENT BY INELASTIC X-RAY SCATTERING AT HIGH PRESSURE AND TEMPERATURE BY RESISTIVE HEATING DIAMOND ANVIL CELL

E. Ohtani1,2, K. Mibe3, T. Sakamaki1, S. Kamada1, S. Takahashi1, H. Fukui4, S. Tsutsui5, A.Q.R. Baron6
1Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
2V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, ul. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
3Earthquake Research Institute, University of Tokyo, Tokyo 113-0032, Japan
4Graduate School of Material Science, University of Hyogo, Hyogo 678-1297, Japan
5Research and Utilization Division, SPring-8, JASRI, Sayo, Hyogo, 679-5198, Japan
6Materials Dynamics Laboratory, RIKEN SPring-8 Center, RIKEN, Sayo, Hyogo 679-5148, Japan
Keywords: Sound velocity, hcp-iron, high pressure and temperature, inner core, inelastic X-ray scattering, diamond anvil cell, resistive heating

Abstract >>
We determined the compressional velocity of hcp-Fe in a wide pressure and temperature range using high-resolution inelastic X-ray scattering (IXS) combined with in situ X-ray powder diffraction (XRD) on samples in resistively heated diamond anvil cells: Our measurements extend up to 174 GPa at room temperature, to 88 GPa at 700 K, and to 62.5 GPa at 1000 K. Our data obtained at room temperature and high temperature are well described by a linear relation to density, extending the range of verification of Birchs law beyond previous work and suggesting only a small temperature dependence up to 1000K. When we compare the present results with the preliminary reference Earth model (PREM), we can conclude that there is either a strong temperature effect on Birchs law at temperatures above 1000 K or the composition of the core is rather different from that commonly expected, i.e., containing heavy elements.

DOI: http://dx.doi.org/10.1016/j.rgg.2015.01.012



13.
CONDITIONS OF DIAMOND CRYSTALLIZATION IN KIMBERLITE MELT: EXPERIMENTAL DATA

Yu.N. Palyanov1,2, A.G. Sokol1,2, A.F. Khokhryakov1,2, A.N. Kruk1,2
1V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
2Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia
Keywords: Diamond formation, kimberlite melt, HP-HT experiment

Abstract >>
Experiments on diamond crystallization in kimberlite melt were performed for 40 h at 6.3 GPa in the temperature range of 1300-1570 ºC and at 7.5 GPa in the temperature range of 1450-1570 ºC, using a multianvil high-pressure in the temperature range of apparatus of split-sphere type. Group I kimberlite from the Udachnaya-East pipe and a synthetic multicomponent mixture modeling the average composition of group II kimberlites were used as starting materials. The experiments have shown that diamond growth on seed crystals in the kimberlite melt in equilibrium with olivine, pyroxene, and garnet starts from 1400 ºC at 7.5 GPa and from 1520 ºC at 6.3 GPa. Diamond nucleation requires higher temperature and pressure, 1570 ºC and 7.5 GPa. The alkali-enriched and silicate-depleted derivates of kimberlite melts ensure the growth and nucleation of diamond at lower P and T values: 1400 ºC at 7.5 GPa and 1520 ºC at 6.3 GPa. The results obtained evidence that temperature, pressure, and the composition of crystallization medium are the main factors controlling diamond formation processes in the kimberlite melts and their derivates.

DOI: http://dx.doi.org/10.1016/j.rgg.2015.01.013



14.
DIAMOND THERMOELASTIC PROPERTIES AND IMPLICATIONS FOR DETERMINING THE PRESSURE OF FORMATION OF DIAMONDINCLUSION SYSTEMS

R.J. Angel1, M. Alvaro1, F. Nestola1, M.L. Mazzucchelli2
1Department of Geosciences, University of Padua, Via G. Gradenigo, 6, Padua, 35131, Italy
2Department of Earth and Environmental Sciences, University of Pavia, Via A. Ferrata, 1, Pavia, 27100, Italy
Keywords: Diamond, equation of state, compressibility, thermal expansion, high pressure, high temperature

Abstract >>
The formation conditions of diamond can be determined from the residual pressure of inclusions trapped within the diamond, as measured in ambient conditions, and the equations of state (EoS) of the mineral inclusion and the host diamond. The EoS parameters of the diamond and the inclusion phase are therefore critical for determining the precision and accuracy of the calculation of formation conditions of diamonds. The questions we address are: (1) How precise are these calculations? and, in particular, (2) Do we know the EoS parameters of diamond to a precision and accuracy which do not contribute significantly to the geological conclusions drawn from these calculations? We present a review of the recentmost compressional data, simulations, and direct elastic measurements of diamond and show them to be consistent with a room temperature bulk modulus of K 0 T = = 444(2) GPa and a pressure derivative K′ = 4.0. In combination with a thermal-pressure model with parameters a V 300,0 = 2.672(3)10 -6 K -1 and a single Einstein temperature θ E = 1500K, the volume variation of diamond from room conditions to pressures and temperatures exceeding those in the Earths transition zone is described to within the levels of uncertainty inherent in both experimental and computational determinations. For olivine inclusions in diamond, these uncertainties in the diamond EoS parameters lead to uncertainties in the entrapment pressures of no more than 0.001 GPa at low temperatures and 0.008 GPa at higher temperatures.

DOI: http://dx.doi.org/10.1016/j.rgg.2015.01.014



15.
INTERFACE PARTITION COEFFICIENTS OF TRACE ELEMENTS IN CARBONATESILICATE PARENTAL MEDIA FOR DIAMONDS AND PARAGENETIC INCLUSIONS (experiments at 7.08.5 GPa)

A.V. Kuzyura1, Yu.A. Litvin1, T. Jeffries2
1Institute of Experimental Mineralogy, Russian Academy of Sciences, ul. Akademika Osipyana 4, Chernogolovka, 142432, Moscow Region, Russia
2Science Facilities Department, Natural History Museum, Cromwell Road, London, SW7 5BD, Great Britain
Keywords: race elements, carbonate-silicate system, diamond genesis, diamond formation chamber, experiment

Abstract >>
Interface partition coefficients K D TE of a representative set of trace elements (TE) in the partly molten diamond-forming peridotite-eclogite-carbonatite system are experimentally determined at 7.0-8.5 GPa. The experimental data evidence that trace-element partition does not depend on the melt composition, with heavy rare-earth elements (HREE) concentrating mainly in garnet. Model TE partition coefficients for the natural diamond-forming carbonatite melts of mantle chambers are calculated based on TE concentrations in minerals of peridotite and eclogite parageneses of diamond inclusions, on the one hand, and on the experimental K D TE coefficients, on the other. The results show that the TE of the parental media are mostly the mantle peridotite components, with the parental media being depleted in medium (Ba, La, Ce, Pr, Nd, Sm, Eu, Gd) and heavy (Tb, Dy, Ho, Er, Yb, Lu, Hf) rare-earth elements relative to the primitive peridotite. The elevated contents of Sr, Nb, and Ce in the completely miscible carbonate-silicate melts might be due to the participation of metasomatic agents in the formation of chambers of diamond-generating carbonatite magmas.

DOI: http://dx.doi.org/10.1016/j.rgg.2015.01.015



16.
TYPOMORPHIC FEATURES OF GRAPHITE INCLUSIONS IN DIAMOND: EXPERIMENTAL DATA

A.F. Khokhryakov1,2, D.V. Nechaev1
1V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
2Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia
Keywords: Diamond, graphite inclusions, typomorphic features, experiment

Abstract >>
Diamond crystals with graphite inclusions synthesized during the experimental modeling of natural diamond formation in chloride and carbonate systems under mantle PT-conditions were studied to elucidate the specifics of the protogenetic graphite inclusions. It has been established that the inclusions of graphite, both primary ones and those resulted from sodium oxalate decomposition, form compact clusters of grains and plates of different shapes in diamond. Diamonds rich in graphite inclusions are black and opaque. Their distinctive feature is significant low-frequency shift (to 1328 cm-1) and broadening (to 6.5 cm-1) of the Raman line, testifying to high residual deformation. Based on the data of previous experiments and the results obtained in this study, we consider peculiarities of protogenetic, syngenetic, and epigenetic graphite inclusions in diamond and their possible use as typomorphic features in the investigation of natural diamonds and reconstruction of their genesis.

DOI: http://dx.doi.org/10.1016/j.rgg.2015.01.016



17.
ISOTOPE FRACTIONATION OF CARBON DURING DIAMOND CRYSTALLIZATION IN MODEL SYSTEMS

V.N. Reutsky1, Yu.N. Palyanov1,2, Yu.M. Borzdov1, A.G. Sokol1
1V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
2Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia
Keywords: Diamond, carbon isotopes, fractionation, experiment, high pressures, oxygen fugacity

Abstract >>
A systematic experimental study of fractionation of carbon isotopes during diamond crystallization in model systems near the IW and CCO buffers helped to estimate the effective partition coefficients of carbon isotopes between diamond and crystallization medium. In the systems Fe(Ni,Co)-C, near the IW buffer, diamond is heavier than the solution of carbon in metal melt by 4.5 at 5.5 GPa and 1400-1500 C. In the system (Na 2CO 3CO 2)-C, near the CCO buffer, diamond is lighter than the carbonate fluid by 2.6 at 7.5 GPa and 1400-1700 C. The values of fractionation are close but not equal to calculated equilibrium values and decrease as the rate of diamond crystallization increases. With regard to the low effectiveness of carbon isotope diffusion in diamond, the effective partition coefficients of carbon isotopes obtained during real diamond crystallization are the most informative for interpretation of data for natural diamonds. Based on the experimental results, we propose a scheme of the primary isotope specialization of diamond. Isotopically heavy diamonds (δ 13C PDB of 0 to -5) crystallize in zones of metal melts (in the case of isotope depletion, δ 13C VPDB decreases to -10 or lower). Isotopically light diamonds (δ 13C VPDB of -10 to -7) crystallize in more oxidized mantle zones. The interaction of different types of mantle matter with contrasting redox characteristics causes wide variations in the carbon isotope composition of diamond and in the composition of diamond-hosted inclusions.

DOI: http://dx.doi.org/10.1016/j.rgg.2015.01.017



18.
CONDITIONS OF KIMBERLITE MAGMA GENERATION: EXPERIMENTAL CONSTRAINTS

A.G. Sokol1, A.N. Kruk2
1Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia
2V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
Keywords: Experiment, mantle, kimberlite, metasomatism, magma, alkali-rich carbonatite, nominally anhydrous minerals

Abstract >>
Melting and multiple saturation experiments with systems simulating primary kimberlite magma compositions at 5.5-6.5 GPa provide constraints on magma generation conditions. The liquidus of model kimberlitic systems exceeds the hottest temperatures of lithospheric mantle (1400 ºC) but is 150-200 ºC lower in systems with lower CO 2/(CO2 + H2O) ratios. The high melting points require additional heat sources for the generation of kimberlite magmas. Multiple saturation of experimental melts and the stability of individual near-liquidus phases depend on both major-element contents and X CO2 (as the CO2/(CO2 + H2O) molar ratio) in the starting composition. Generally, olivine-bearing assemblages are stable at X CO2 < 0.5, while an increase in MgO/CaO from 1.8 to > 4.0 leads to progressive changes in the equilibrium assemblages: Ol + Grt + Cpx → Ol + Grt + + Opx + Cpx → Ol + Grt + Opx. The results of geochemical reconstructions and multiple saturation experiments indicate partial or complete wehrlitization of the kimberlitic source regions. Most of primary magmas with X CO2 < 0.5 may have been derived from carbonated garnet lherzolite. Some highly calcic (MgO/CaO < 2) magmas with X CO2 < 0.5 likely originated from carbonated garnet wehrlite. A probable scenario is that melts and/or fluids repeatedly metasomatized and oxidized the protolith (caused its carbonation and phlogopitization) and thus provided conditions for buffering CO2 and H2O fugacities in the forming kimberlitic magma, at least early in the melting history. During later magma generation, water was, likely, extracted from nominally anhydrous minerals having hydrated (OH) defects in the structure.

DOI: http://dx.doi.org/10.1016/j.rgg.2015.01.018



19.
PARAGENESIS AND COMPLEX ZONING OF OLIVINE MACROCRYSTS FROM UNALTERED KIMBERLITE OF THE UDACHNAYA-EAST PIPE (Yakutia): RELATIONSHIP WITH THE KIMBERLITE FORMATION CONDITIONS AND EVOLUTION

N.V. Sobolev1,2, A.V. Sobolev3,4, A.A. Tomilenko1, S.V. Kovyazin1, V.G. Batanova3,4, D.V. Kuzmin1,2
1V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
2Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia
3V.I. Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, ul. Kosygina 19, Moscow, 119991, Russia
4Uni Grenoble Alpes, ISTerre, F-38041 Grenoble, France
Keywords: Kimberlite, olivine, clinopyroxene, pyrope, trace elements, paragenesis, diamond

Abstract >>
Unaltered Mg-olivine (Fo 85-94) is a predominant mineral of the kimberlite block (serpentine-free) of the Udachnaya-East pipe, and it prevails in peridotite xenoliths and as inclusions in diamonds. The kimberlite of this pipe, like a series of hypabyssal kimberlites in other regions, contains two main types of olivine macrocrysts according to their size and morphology: those rounded or irregularly shaped (olivine I) and euhedral phenocrysts (olivine II), which are usually no larger than 0.5 mm and very seldom reach 1 mm in size. This study was focused on several thousand olivine samples assigned both to olivines I and to olivines II, with a gradual transition between them. Particular attention was paid to the search for mineral inclusions in olivine and for phenocrysts with a clear zoning. In the phenocryst cores of homogeneous composition, we have revealed orthopyroxene inclusions as well as clinopyroxene (chrome-diopside and chrome-omphacite) inclusions with wide variations in the Na2O and Cr2O3 contents, significantly higher than the previously established ones: up to 6.00 wt.% Na2O and 4.23 wt.% Cr2O3. Convincing evidence for the high-pressure origin of the olivine macrocryst cores is the presence of pyrope inclusions with 1.41-9.14 wt.% Cr2O3, 4.64-6.61 wt.% CaO, and Mg# = 75.6-83.7 in six samples, which testifies to the high-pressure lherzolite paragenesis of the phenocrysts cores. The cores of the studied olivine phenocrysts are identical in the contents of Ni, Co, Ca, Cr, and Mn to olivines from diamonds and peridotite xenoliths. However, they differ significantly in the steady elevated Ti content, equal to 100-300 ppm for the majority of the phenocrysts, including those containing pyroxene and pyrope inclusions.

DOI: http://dx.doi.org/10.1016/j.rgg.2015.01.019



20.
CARBONATITE METASOMATISM OF PERIDOTITE LITHOSPHERIC MANTLE: IMPLICATIONS FOR DIAMOND FORMATION AND CARBONATITEKIMBERLITE MAGMATISM

N.P. Pokhilenko1, A.M. Agashev2, K.D. Litasov1, L.N. Pokhilenko2
1Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia
2V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
Keywords: Mantle, melting, diamond, peridotite, kimberlite, carbonatite, experiment

Abstract >>
Mineral inclusions in diamond record its origin at different depths, down to the lower mantle. However, most diamonds entrained with erupting kimberlite magma originate in lithospheric mantle. Lithospheric U-type diamonds crystallize during early metasomatism of reduced ( f O2 at the IW oxygen buffer) depleted peridotite in the roots of Precambrian cratons. Evidence of the metasomatic events comes from compositions of garnets in peridotitic xenoliths and inclusions in diamonds. On further interaction with carbonatitic melt, peridotite changes its composition, while diamond no longer forms in a more oxidized environment ( f O2 near the CCO buffer). Silicate metasomatism of depleted peridotite (by basanite-like melts) does not induce diamond formation but may participate in generation of group I kimberlite. Low-degree (below 1%) partial melting of metasomatized peridotite produces a kimberlite-carbonatite magmatic assemblage, as in the case of the Snap Lake kimberlite dike. Occasionally, mantle metasomatism may occur as reduction reactions with carbonates and H2O giving rise to hydrocarbon compounds, though the origin of hydrocarbons in the deep mantle remains open to discussion. Melting experiments in carbonate systems show hydrous carbonated melts with low H2O to be the most plausible agents of mantle material transport. An experiment-based model implies melting of carbonates in subducting slabs within the mantle transition zone, leading to formation of carbonatitic diapirs, which can rise through the mantle by buoyancy according to the dissolution-precipitation mechanism. These processes, in turn, can form oxidized channels in the mantle and maintain diamond growth at the back of diapirs by reducing carbon from carbonated melts. When reaching the lithospheric base, such diapirs form a source of kimberlite and related magmas. The primary composition of kimberlite often approaches carbonatite with no more than 10-15% SiO2.

DOI: http://dx.doi.org/10.1016/j.rgg.2015.01.020



21.
EVIDENCE FOR PHASE TRANSITIONS IN MINERAL INCLUSIONS IN SUPERDEEP DIAMONDS OF THE SAO LUIZ DEPOSIT (Brazil)

D.A. Zedgenizov1,2, V.S. Shatsky1,3,2, A.V. Panin4, O.V. Evtushenko4, A.L. Ragozin1, H. Kagi5
1V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
2Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia
3A.P. Vinogradov Institute of Geochemistry, Siberian Branch of the Russian Academy of Sciences, ul. Favorskogo 1A, Irkutsk, 664033, Russia
4Institute of Strength Physics and Materials Science, Siberian Branch of the Russian Academy of Sciences, pr. Akademicheskii 2/4, Tomsk, 634021, Russia
5University of Tokyo, Tokyo 113-0032, Japan
Keywords: Diamond, inclusions, deformation, superdeep minerals, upper mantle, transition zone, lower mantle

Abstract >>
Evidence for phase transitions in mineral inclusions in superdeep diamonds of alluvial placers in the São Luiz River deposits (Brazil) is obtained by the electron backscatter diffraction technique. It has been shown that the crystal structure of superdeep diamonds is significantly deformed around inclusions of MgSi-, CaSi-, and CaTiSi-perovskites, SiO2 (stishovite?), and Mg2SiO4 (ringwoodite?). On the contrary, significant deformations around inclusions of olivine, ferropericlase, and majoritic garnet are not detected. The absence of deformation near these minerals reveals the lack of phase transitions with dramatic volume changes. The present study suggests that the formation of superdeep diamonds proceeds at different levels of the sublithospheric mantle, transition zone, and lower mantle.

DOI: http://dx.doi.org/10.1016/j.rgg.2015.01.021



22.
A UNIQUE DIAMONDIFEROUS PERIDOTITE XENOLITH FROM THE UDACHNAYA KIMBERLITE PIPE (Yakutia): ROLE OF SUBDUCTION IN DIAMOND FORMATION

A.M. Logvinova1,2, L.A. Taylor3, E.N. Fedorova1, A.P. Yelisseyev1, G. Howarth4, V.N. Reutskii1, R. Wirth4, N.V. Sobolev1,2
1V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
2Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia
3Department of Earth & Planetary Sciences, University of Tennessee, Knoxville, TN USA
4Helmholtz Centre Potsdam, GFZ German Research Centre for Geoscience, Potsdam, Germany
Keywords: Mantle, xenolith, peridotite, diamond, subduction, spectroscopy, photoluminescence, isotopy

Abstract >>
A unique xenolith of diamond-bearing pyrope peridotite has been studied, which consists of enstatite (Al2O3 = 0.39-0.43 wt.%; Cr2O3 = 0.20-0.23 wt.%; FeO = 4.81-5.1 wt.%; average Mg# = 92.7) and pyrope (Cr2O3 = 4.43-5.11 wt.%; CaO = 4.15-4.8 wt.%; Mg# = 83.6-84.1). The xenolith is small (10.5 g) but contains more than 30,000 diamond microcrystals (10-700 μm). High-resolution 2D and 3D X-ray tomographic images show the volume ratios of rock-forming minerals and an uneven distribution of diamonds in the xenolith (enstatite - 38 vol.%; pyrope - 35 vol.%; diamond - 9.5 vol.%; sulfides - 4 vol.%; and the remainder is mainly alteration products), with diamonds and sulfides being localized in the same zone. The sulfides are pentlandite and djerfisherite. Isotope and FTIR spectroscopic studies showed an extremely light carbon isotope composition (δ 13 av = -22.9) of the diamonds and minor nitrogen impurities (<15 ppm) in them. Nitrogen is present mainly in aggregated form. The phase composition of nanoinclusions in the diamonds was investigated by transmission electron microscopy (TEM), including electron diffraction and analytical electron microscopy (AEM). It has been shown that all nanoinclusions are polyphase structures consisting of Mg-Al-silicate-enriched phases, Ca-carbonate, graphite, and fluid. The fluid phase has high concentrations of K, Cl, and O. The mineral inclusions in the diamonds are identified as high-Mg olivine. The data obtained indicate that the formation of diamonds in the studied xenolith was a one-act process and that the fluid/melt metasomatizing ultramafic substrate was of crustal origin. This testifies to the crucial role of deep metasomatic processes in the formation of the Udachnaya kimberlite pipe.

DOI: http://dx.doi.org/10.1016/j.rgg.2015.01.022



23.
AN EBSD STUDY OF OLIVINE INCLUSIONS IN SIBERIAN DIAMONDS: EVIDENCE FOR SYNGENETIC GROWTH?

R.D. Neuser1, H.-P. Schertl1, A.M. Logvinova2,3, N.V. Sobolev2,3
1Ruhr-University Bochum, Institute of Geology, Mineralogy and Geophysics, 44780 Bochum, Germany
2V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Science, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
3Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia
Keywords: Diamond, olivine, crystallographic relations, back-scattered electron diffraction

Abstract >>
Crystallographic relations between four diamonds from the Yubileinaya pipe (Yakutia) and inclusions of eight olivine crystals in them are first studied by the EBSD method. Crystallographic coincidence between the olivine and diamond has been revealed in 15 samples, though we failed to make an unambiguous conclusion about the sequence of the mineral crystallization. It is confirmed that the new approach is promising for elucidation of the regularities of the mutual orientation of diamond and inclusion. However, more samples are required to establish whether the olivines formed earlier than the diamonds (protogenetic inclusions) or synchronously with them (syngenetic inclusions).

DOI: http://dx.doi.org/10.1016/j.rgg.2015.01.023



24.
MULTIPLE GROWTH EVENTS IN DIAMONDS WITH CLOUDY MICROINCLUSIONS FROM THE MIR KIMBERLITE PIPE: EVIDENCE FROM THE SYSTEMATICS OF OPTICALLY ACTIVE DEFECTS

S.Yu. Skuzovatov1, D.A. Zedgenizov2,3, A.L. Rakevich4, V.S. Shatsky1,2,3, E.F. Martynovich4
1A.P. Vinogradov Institute of Geochemistry, Siberian Branch of the Russian Academy of Sciences, ul. Favorskogo 1a, Irkutsk, 664033, Russia
2V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
3Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia
4Institute of Laser Physics, Siberian Branch of the Russian Academy of Sciences, Irkutsk Branch, ul. Lermontova 130a, Irkutsk, 664033, Russia
Keywords: Diamond, nitrogen, hydrogen, FTIR spectroscopy, photoluminescence

Abstract >>
We present new data on the main and additional optically active defects in diamonds with cloudy microinclusions from the Mir kimberlite pipe. It has been found that reshaping might have occurred either in a closed system with nitrogen and hydrogen depletion or owing to new portions of a diamond-forming fluid/melt. The internal structure and the distribution of optically active defects suggest both continuous growth of such diamonds and a multistage scenario with a series of postcrystallizational transformations, including resorption, high-temperature annealing, and degradation of nickel-nitrogen complexes.

DOI: http://dx.doi.org/10.1016/j.rgg.2015.01.024



25.
FTIR MAPPING OF DIAMOND PLATES OF ECLOGITIC AND PERIDOTITIC XENOLITHS FROM THE NYURBINSKAYA PIPE (Yakutia): GENETIC IMPLICATIONS

Z.V. Spetsius, I.N. Bogush, O.E. Kovalchuk
Geological Scientific and Research Enterprise (NIGP), ALROSA OJSC, Chernyshevskoe shosse 16, Mirnyi, Republic of Sakha (Yakutia), 678174, Russia
Keywords: Diamond, mantle xenoliths, eclogites, peridotites, nitrogen and hydrogen impurities

Abstract >>
Results of studies of IR absorption and photo- and cathodoluminescence of diamonds from peridotitic and eclogitic xenoliths from the Nyurbinskaya pipe. The internal structure of diamonds of different genesis and the changes in their impurity composition throughout the crystals are analyzed. A comparison is made for the spectral parameters of crystals from xenoliths of different genesis and from kimberlites of this pipe. The internal structure of 38 eclogitic and 4 peridotitic diamond (class -4 to +2 mm) crystals is examined on their 0.4-0.8 mm thick plane-parallel plates. We present results of a detailed study of diamonds with different characteristics from four eclogitic and two peridotitic xenoliths from the Nyurbinskaya pipe. Areal mapping of diamond plates from xenoliths showed varying contents of total nitrogen, its aggregates, and hydrogen and their zonal distribution in the investigated crystals. Peridotitic diamonds are characterized by low and medium nitrogen contents, a high degree of nitrogen aggregation, and low contents of hydrogen and seldom show signs of growth interruption. Eclogitic diamonds have high contents of nitrogen and hydrogen; there are many zoned diamonds with signs of multistage growth among them, which indicates that they are of several growth generations. The composition of inclusions, the distribution of nitrogen impurity, and the degree of nitrogen aggregation in diamonds testify to a predominance of eclogite paragenesis crystals in the Nyurbinskaya pipe. The internal structure of eclogitic paragenesis crystals, the arrangement of diamonds in eclogitic xenoliths, and other facts argue for their later, compared with peridotitic xenolith diamonds, formation from fluid or fluid-melt during metasomatism. This determined the typomorphism of diamonds and high productivity of this pipe.

DOI: http://dx.doi.org/10.1016/j.rgg.2015.01.025



26.
DEFECTS IN CUBIC DIAMONDS FROM THE PLACERS IN THE NORTHEASTERN SIBERIAN PLATFORM: RESULTS OF IR MICROSPECTROMETRY

S.V. Titkov1,2, A.A. Shiryaev1,3, N.N. Zudina2, N.G. Zudin4, Yu.P. Solodova2
1Institute of Geology of Ore Deposits, Petrography, Mineralogy, and Geochemistry, Russian Academy of Sciences, Staromonetnyi per. 35, Moscow, 119017, Russia
2Russian State Geological Prospecting University, ul. Miklukho-Maklaya 23, Moscow, 117937, Russia
3A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Leninskii pr. 31, korp. 4, Moscow, 119071, Russia
4Rony Kerob Ltd, Leningradskii pr. 69, bld.1, Moscow, 125315, Russia
Keywords: Natural diamonds, cubic habit, nitrogen impurity, IR microspectroscopy, crystal zoning, plastic deformation, placers

Abstract >>
Defects in yellowish-green, yellow, and orange diamonds of cubic habit from placers of the northeastern Siberian Platform were studied by IR spectroscopy. In addition to the main A, C, and, probably, B defects, the diamonds contain X and Y centers and amber defects of different types and show absorption bands at 1240, 1270, and 1290-1295 cm-1, peaks in the region 1350-1380 cm-1, and bands within 3100-3300 cm-1. Diamonds of different colors contain different associations of structural defects, though they belong to the same variety II according to the Orlov classification. According to the integral spectra of the diamond crystals, the content of structural nitrogen impurity is low, 60-265 ppm. However, spatially resolved spectroscopic examination of diamond plates has revealed highly nonuniform distribution of defects in all diamond crystals. The general regularity for the studied diamonds is a decrease in the total nitrogen content and in the relative fraction of the major A defect from core to periphery of a crystal. The content of structural nitrogen impurity in the core reaches 900 ppm, which is higher than the average N content in widespread octahedral diamond crystals. The presence of C, Y, and X defects in the majority of the samples indicates short postgrowth annealing of these diamonds. The genetic significance of the obtained data on structural defects is discussed.

DOI: http://dx.doi.org/10.1016/j.rgg.2015.01.026