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Papers by Anna Dymshits

Primary Composition of Kimberlite Melt

Minerals, Oct 31, 2023

Equation of state for Mg3Al2Si3O12 pyrope: Implications for post-garnet transitions and mantle dynamics

Physics of the Earth and Planetary Interiors

CCDC 1581824: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

CCDC 1581798: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

CCDC 1579564: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

CCDC 1579553: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Spreadsheets to calculate P–V–T relations, thermodynamic and thermoelastic properties of silicates in the MgSiO₃–MgO system

Modified equations of state (EoS) of forsterite, wadsleyite, ringwoodite, akimotoite, bridgmanite... more Modified equations of state (EoS) of forsterite, wadsleyite, ringwoodite, akimotoite, bridgmanite and post-perovskite based on the Helmholtz free energy are described using Microsoft Excel spreadsheets. The equations of state were set up by joint analysis of reference experimental data and can be used to calculate thermodynamic and thermoelastic parameters and <i>P–V–T</i> properties of the Mg-silicates. We used Visual Basic for Applications module in Microsoft Excel and presented a simultaneous calculation of full set of thermodynamic and thermoelastic functions using only <i>T–P</i> and <i>T–V</i> data as input parameters. Phase transitions in the MgSiO₃–MgO system play an important role in the interpretation of the seismic boundaries of the upper Earth's mantle and in the D″ layer. Therefore, proposed EoSes of silicates in the MgSiO₃–MgO system have clear geophysical implications. The developed ...

Diamondiferous lamproites of Ingashi field, Siberian craton

Geological Society, London, Special Publications, 2021

Ingashi lamproite dykes are the only known primary sources of diamond in the Irkutsk district (Ru... more Ingashi lamproite dykes are the only known primary sources of diamond in the Irkutsk district (Russia) and the only non-kimberlitic one in the Siberian craton. The Ingashi lamproite field is situated in the Urik-Iya graben within the Prisayan uplift of the Siberian craton. The phlogopite-olivine lamproites contain olivine, talc, phlogopite, serpentine, chlorite, olivine, garnet, chromite, orthopyroxene, clinopyroxene as well as Sr-F-apatite, monazite, zircon, armolcolite, priderite, potassium Mg-arfvedsonite, Mn-ilmenite, Nb-rutile and diamond. The only ultramafic lamprophyre dyke is composed mainly of serpentinized olivine and phlogopite in the talc-carbonate groundmass and is similar to Ingashi lamproites accessory assemblage with the same major element compositions. Trace element and Sr-Nd isotopic relationships of the Ingashi lamproites are similar to classic lamproites. Different dating methods have provided the ages of lamproites: 1481 Ma (Ar-Ar phlogopite), 1268 Ma (Rb-Sr who...

Minerals, 2020

To gain better insight into the thermal state and composition of the lithospheric mantle beneath ... more To gain better insight into the thermal state and composition of the lithospheric mantle beneath the Upper Muna kimberlite field (Siberian craton), a suite of 323 clinopyroxene xenocrysts and 10 mantle xenoliths from the Komsomolskaya-Magnitnaya (KM) pipe have been studied. We selected 188 clinopyroxene grains suitable for precise pressure (P)-temperature (T) estimation using single-clinopyroxene thermobarometry. The majority of P-T points lie along a narrow, elongated field in P-T space with a cluster of high-T and high-P points above 1300 °C, which deviates from the main P-T trend. The latter points may record a thermal event associated with kimberlite magmatism (a “stepped” or “kinked” geotherm). In order to eliminate these factors, the steady-state mantle paleogeotherm for the KM pipe at the time of initiation of kimberlite magmatism (Late Devonian–Early Carboniferous) was constrained by numerical fitting of P-T points below T = 1200 °C. The obtained mantle paleogeotherm is simi...

High Pressure Research, 2018

Modified equations of state (EoS) of forsterite, wadsleyite, ringwoodite, akimotoite, bridgmanite... more Modified equations of state (EoS) of forsterite, wadsleyite, ringwoodite, akimotoite, bridgmanite and post-perovskite based on the Helmholtz free energy are described using Microsoft Excel spreadsheets. The equations of state were set up by joint analysis of reference experimental data and can be used to calculate thermodynamic and thermoelastic parameters and P-V-T properties of the Mg-silicates. We used Visual Basic for Applications module in Microsoft Excel and presented a simultaneous calculation of full set of thermodynamic and thermoelastic functions using only T-P and T-V data as input parameters. Phase transitions in the MgSiO 3 -MgO system play an important role in the interpretation of the seismic boundaries of the upper Earth's mantle and in the D ′′ layer. Therefore, proposed EoSes of silicates in the MgSiO 3 -MgO system have clear geophysical implications. The developed software will be interesting to specialists who are engaged to study the mantle mineralogy and Earth's interior.

Crystal Growth & Design, 2018

The high-temperature structural properties of solid benzene were studied at 1.5-8.2 GPa up to 20 ... more The high-temperature structural properties of solid benzene were studied at 1.5-8.2 GPa up to 20 melting or decomposition using multianvil apparatus and in situ neutron and X-ray diffraction. The crystal structure of deuterated benzene phase II (P21/c unit cell) was refined at 3.6-8.2 GPa 22 and 473-873 K. Our data show a minor temperature effect on the change in the unit cell parameters 23 of deuterated benzene at 7.8-8.2 GPa. At 3.6-4.0 GPa we observed the deviation of deuterium 24 atoms from the benzene ring plane and minor «zigzag» deformation of the benzene ring, enhancing 25 with the temperature increase caused by the displacement of benzene molecules and decrease of 26 van der Waals bond length between the π-conjuncted carbon skeleton and the deuterium atom of 27 adjacent molecule. Deformation of benzene molecule at 723-773 K and 3.9-4.0 GPa could be 28 related to the benzene oligomerization at the same conditions. In the pressure range of 1.5-8.2 GPa 29 benzene decomposition was defined between 773-923 K. Melting was identified at 2.2 GPa and 30 573 K. Quenched products analyzed by Raman spectroscopy consist of carbonaceous material.

Computers & Geosciences, 2016

We present Microsoft Excel spreadsheets for calculation of thermodynamic functions and P-V-T prop... more We present Microsoft Excel spreadsheets for calculation of thermodynamic functions and P-V-T properties of MgO, diamond and 9 metals, Al, Cu, Ag, Au, Pt, Nb, Ta, Mo, and W, depending on temperature and volume or temperature and pressure. The spreadsheets include the most common pressure markers used in in situ experiments with diamond anvil cell and multianvil techniques. The calculations are based on the equation of state formalism via the Helmholtz free energy. The program was developed using Visual Basic for Applications in Microsoft Excel and is a timeefficient tool to evaluate volume, pressure and other thermodynamic functions using T-P and T-V data only as input parameters. This application is aimed to solve practical issues of high pressure experiments in geosciences and mineral physics.

Thermoelastic properties of chromium oxide Cr2O3 (eskolaite) at high pressures and temperatures

Physics and Chemistry of Minerals, 2016

A new synchrotron X-ray diffraction study of chromium oxide Cr2O3 (eskolaite) with the corundum-t... more A new synchrotron X-ray diffraction study of chromium oxide Cr2O3 (eskolaite) with the corundum-type structure has been carried out in a Kawai-type multi-anvil apparatus to pressure of 15 GPa and temperatures of 1873 K. Fitting the Birch–Murnaghan equation of state (EoS) with the present data up to 15 GPa yielded: bulk modulus (K0,T0), 206 ± 4 GPa; its pressure derivative K′0,T, 4.4 ± 0.8; (∂K0,T/∂T) = ‒0.037 ± 0.006 GPa K‒1; a = 2.98 ± 0.14 × 10−5 K−1 and b = 0.47 ± 0.28 × 10‒8 K‒2, where α0,T = a + bT is the volumetric thermal expansion coefficient. The thermal expansion of Cr2O3 was additionally measured at the high-temperature powder diffraction experiment at ambient pressure and α0,T0 was determined to be 2.95 × 10−5 K−1. The results indicate that coefficient of the thermal expansion calculated from the EoS appeared to be high-precision because it is consistent with the data obtained at 1 atm. However, our results contradict α0 value suggested by Rigby et al. (Brit Ceram Trans J 45:137–148, 1946) widely used in many physical and geological databases. Fitting the Mie–Grüneisen–Debye EoS with the present ambient and high-pressure data yielded the following parameters: K0,T0 = 205 ± 3 GPa, K′0,T = 4.0, Grüneisen parameter (γ0) = 1.42 ± 0.80, q = 1.82 ± 0.56. The thermoelastic parameters indicate that Cr2O3 undergoes near isotropic compression at room and high temperatures up to 15 GPa. Cr2O3 is shown to be stable in this pressure range and adopts the corundum-type structure. Using obtained thermoelastic parameters, we calculated the reaction boundary of knorringite formation from enstatite and eskolaite. The Clapeyron slope (with {\text{d}}P/{\text{d}}T = - 0.014$$dP/dT=-0.014 GPa/K) was found to be consistent with experimental data.

Experimental study of the pyroxene-garnet phase transition in the Na2MgSi5O12 system at pressures of 13–20 GPa: First synthesis of sodium majorite

Doklady Earth Sciences, 2010

Contributions to Mineralogy and Petrology, 2009

Oxygen fugacity (fO 2 ) conditions were determined for 29 peridotite xenoliths from the A154-Nort... more Oxygen fugacity (fO 2 ) conditions were determined for 29 peridotite xenoliths from the A154-North and A154-South kimberlites of the Diavik diamond mine using the newly developed flank method modified specifically for measuring Fe 3? in mantle-derived pyropic garnets. The results indicate that the garnet-bearing lithospheric mantle beneath the central Slave craton is vertically layered with respect to oxidation state. The shallow (\140 km), ''ultradepleted'' layer is the most oxidized section of garnetbearing subcratonic mantle thus far measured, up to one log unit more oxidizing relative to the FMQ buffer [Dlog fO 2 (FMQ) ? 1]. The lower, more fertile layer has fO 2 conditions that extend down to Dlog fO 2 (FMQ) -3.8, consistent with xenolith suites from other localities worldwide. Based on trace element concentrations in garnets, two distinct metasomatic events affected the mantle lithosphere at Diavik. An oxidized fluid imparted sinusoidal chondrite-normalized REE patterns on garnets throughout the entire depth range sampled. In contrast, a reducing melt metasomatic event affected only the lower portion of the lithospheric mantle. The fO 2 state of the Diavik mantle sample suggests that diamond formation occurred by reduction of carbonate by fluids arising from beneath the lithosphere. Communicated by J. Hoefs.

Composition of the kimberlite melt of the Komsomolskaya-Magnitnaya pipe (Upper Muna field, Siberian craton)

Phase boundary between cubic B1 and rhombohedral structures in (Mg,Fe)O magnesiowüstite determined by in situ X-ray diffraction measurements

Physics and Chemistry of Minerals, 2017

The phase relations and equation of state of (Mg0.08Fe0.92)O magnesiowüstite (Mw92) have been stu... more The phase relations and equation of state of (Mg0.08Fe0.92)O magnesiowüstite (Mw92) have been studied using the Kawai-type high-pressure apparatus coupled with synchrotron radiation. To determine the phase boundary between the NaCl-type cubic (B1) and rhombohedral (rB1) structures in Mw92, in situ X-ray observations were carried out at pressures of 0–35 GPa and temperatures of 300–1473 K. Au and MgO were used as the internal pressure markers and metallic Fe as oxygen fugacity buffer. The phase boundary between B1 and rB1 structures was described by a linear equation P (GPa) = 1.6 + 0.033 × T (K). The Clapeyron slope (dP/dT) determined in this study is close to that obtained at pressures above 70 GPa but steeper than that obtained for FeO. An addition of MgO to FeO structure expands the stability field of the rB1 phase to lower pressures and higher temperatures. Thus, the rB1 phase may be stabilized with respect to the B1 phase at a lower pressures. The pressure–volume–temperature equation of state of B1-Mw92 was determined up to 30 GPa and 1473 K. Fitting the hydrostatic compression data up to 30 GPa with the Birch–Murnaghan equation of state (EoS) yielded: unit cell volume (V0,T0), 79.23 ± 4 Å3; bulk modulus (K0,T0), 183 ± 4 GPa; its pressure derivative (K′T), 4.1 ± 0.4; (∂K0,T/∂T) = −0.029 ± 0.005 GPa K‒1; a = 3.70 ± 0.27 × 10−5 K−1 and b = 0.47 ± 0.49 × 10−8 K−2, where α0,T = a + bT is the volumetric thermal expansion coefficient. The obtained bulk modulus of Mw92 is very close to the value expected for stoichiometric iron-rich (Mg,Fe)O. This result confirms the idea that the bulk modulus of (Mg,Fe)O is greatly affected by the actual defect structure, caused by either Mg2+ or vacancies.

Confocal Raman spectroscopic study of melt inclusions in olivine of mantle xenoliths from the Bultfontein kimberlite pipe (Kimberley cluster, South Africa): Evidence for alkali‐rich carbonate melt in the mantle beneath Kaapvaal Craton

Journal of Raman Spectroscopy, 2021

Synthesis of Na-bearing majorte in the system Mg3Al2Si3O12 -Na2MgSi5O12 at 11-20 GPa: solid solutions and structural features

Vestnik Otdelenia nauk o Zemle RAN, 2011

Geochemistry International, 2014

The CaO-MgO-Al 2 O 3 -SiO 2 -Na 2 O multicomponent system was experimentally studied at 7.0 and 8... more The CaO-MgO-Al 2 O 3 -SiO 2 -Na 2 O multicomponent system was experimentally studied at 7.0 and 8.5 GPa using an anvil with hole toroidal high pressure apparatus to examine two binary joins: pyropegrossular and grossular-Na majorite. These and literature data were employed to simulate the liquidus sur face of the pyrope-grossular-Na majorite system. The liquidus surface of garnet of predominantly pyrope composition is dominant in the diagram, and the garnet contains much of the Na 2 MgSi 5 O 12 end member. Melting was observed in this region at temperatures above 1900°C, and the solidus of the system occurs at temperatures below 1550°C. The pyrope-grossular system shows a miscibility gap at 50-65 mol % of the pyrope component and two series of garnet solid solutions. The dominant phase at grossular and Na majorite mixing is pyroxene, and garnet crystallizes within a fairly narrow field in the grossular rich region. All garnets synthesized in the systems have elevated Si and Na concentrations and belong to the majorite series, for which a uniform mechanism of isomorphism (Mg, Ca) + Al = Si + Na was proved.

Primary Composition of Kimberlite Melt

Minerals, Oct 31, 2023

Equation of state for Mg3Al2Si3O12 pyrope: Implications for post-garnet transitions and mantle dynamics

Physics of the Earth and Planetary Interiors

CCDC 1581824: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

CCDC 1581798: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

CCDC 1579564: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

CCDC 1579553: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Spreadsheets to calculate P–V–T relations, thermodynamic and thermoelastic properties of silicates in the MgSiO₃–MgO system

Modified equations of state (EoS) of forsterite, wadsleyite, ringwoodite, akimotoite, bridgmanite... more Modified equations of state (EoS) of forsterite, wadsleyite, ringwoodite, akimotoite, bridgmanite and post-perovskite based on the Helmholtz free energy are described using Microsoft Excel spreadsheets. The equations of state were set up by joint analysis of reference experimental data and can be used to calculate thermodynamic and thermoelastic parameters and <i>P–V–T</i> properties of the Mg-silicates. We used Visual Basic for Applications module in Microsoft Excel and presented a simultaneous calculation of full set of thermodynamic and thermoelastic functions using only <i>T–P</i> and <i>T–V</i> data as input parameters. Phase transitions in the MgSiO₃–MgO system play an important role in the interpretation of the seismic boundaries of the upper Earth's mantle and in the D″ layer. Therefore, proposed EoSes of silicates in the MgSiO₃–MgO system have clear geophysical implications. The developed ...

Diamondiferous lamproites of Ingashi field, Siberian craton

Geological Society, London, Special Publications, 2021

Ingashi lamproite dykes are the only known primary sources of diamond in the Irkutsk district (Ru... more Ingashi lamproite dykes are the only known primary sources of diamond in the Irkutsk district (Russia) and the only non-kimberlitic one in the Siberian craton. The Ingashi lamproite field is situated in the Urik-Iya graben within the Prisayan uplift of the Siberian craton. The phlogopite-olivine lamproites contain olivine, talc, phlogopite, serpentine, chlorite, olivine, garnet, chromite, orthopyroxene, clinopyroxene as well as Sr-F-apatite, monazite, zircon, armolcolite, priderite, potassium Mg-arfvedsonite, Mn-ilmenite, Nb-rutile and diamond. The only ultramafic lamprophyre dyke is composed mainly of serpentinized olivine and phlogopite in the talc-carbonate groundmass and is similar to Ingashi lamproites accessory assemblage with the same major element compositions. Trace element and Sr-Nd isotopic relationships of the Ingashi lamproites are similar to classic lamproites. Different dating methods have provided the ages of lamproites: 1481 Ma (Ar-Ar phlogopite), 1268 Ma (Rb-Sr who...

Minerals, 2020

To gain better insight into the thermal state and composition of the lithospheric mantle beneath ... more To gain better insight into the thermal state and composition of the lithospheric mantle beneath the Upper Muna kimberlite field (Siberian craton), a suite of 323 clinopyroxene xenocrysts and 10 mantle xenoliths from the Komsomolskaya-Magnitnaya (KM) pipe have been studied. We selected 188 clinopyroxene grains suitable for precise pressure (P)-temperature (T) estimation using single-clinopyroxene thermobarometry. The majority of P-T points lie along a narrow, elongated field in P-T space with a cluster of high-T and high-P points above 1300 °C, which deviates from the main P-T trend. The latter points may record a thermal event associated with kimberlite magmatism (a “stepped” or “kinked” geotherm). In order to eliminate these factors, the steady-state mantle paleogeotherm for the KM pipe at the time of initiation of kimberlite magmatism (Late Devonian–Early Carboniferous) was constrained by numerical fitting of P-T points below T = 1200 °C. The obtained mantle paleogeotherm is simi...

High Pressure Research, 2018

Modified equations of state (EoS) of forsterite, wadsleyite, ringwoodite, akimotoite, bridgmanite... more Modified equations of state (EoS) of forsterite, wadsleyite, ringwoodite, akimotoite, bridgmanite and post-perovskite based on the Helmholtz free energy are described using Microsoft Excel spreadsheets. The equations of state were set up by joint analysis of reference experimental data and can be used to calculate thermodynamic and thermoelastic parameters and P-V-T properties of the Mg-silicates. We used Visual Basic for Applications module in Microsoft Excel and presented a simultaneous calculation of full set of thermodynamic and thermoelastic functions using only T-P and T-V data as input parameters. Phase transitions in the MgSiO 3 -MgO system play an important role in the interpretation of the seismic boundaries of the upper Earth's mantle and in the D ′′ layer. Therefore, proposed EoSes of silicates in the MgSiO 3 -MgO system have clear geophysical implications. The developed software will be interesting to specialists who are engaged to study the mantle mineralogy and Earth's interior.

Crystal Growth & Design, 2018

The high-temperature structural properties of solid benzene were studied at 1.5-8.2 GPa up to 20 ... more The high-temperature structural properties of solid benzene were studied at 1.5-8.2 GPa up to 20 melting or decomposition using multianvil apparatus and in situ neutron and X-ray diffraction. The crystal structure of deuterated benzene phase II (P21/c unit cell) was refined at 3.6-8.2 GPa 22 and 473-873 K. Our data show a minor temperature effect on the change in the unit cell parameters 23 of deuterated benzene at 7.8-8.2 GPa. At 3.6-4.0 GPa we observed the deviation of deuterium 24 atoms from the benzene ring plane and minor «zigzag» deformation of the benzene ring, enhancing 25 with the temperature increase caused by the displacement of benzene molecules and decrease of 26 van der Waals bond length between the π-conjuncted carbon skeleton and the deuterium atom of 27 adjacent molecule. Deformation of benzene molecule at 723-773 K and 3.9-4.0 GPa could be 28 related to the benzene oligomerization at the same conditions. In the pressure range of 1.5-8.2 GPa 29 benzene decomposition was defined between 773-923 K. Melting was identified at 2.2 GPa and 30 573 K. Quenched products analyzed by Raman spectroscopy consist of carbonaceous material.

Computers & Geosciences, 2016

We present Microsoft Excel spreadsheets for calculation of thermodynamic functions and P-V-T prop... more We present Microsoft Excel spreadsheets for calculation of thermodynamic functions and P-V-T properties of MgO, diamond and 9 metals, Al, Cu, Ag, Au, Pt, Nb, Ta, Mo, and W, depending on temperature and volume or temperature and pressure. The spreadsheets include the most common pressure markers used in in situ experiments with diamond anvil cell and multianvil techniques. The calculations are based on the equation of state formalism via the Helmholtz free energy. The program was developed using Visual Basic for Applications in Microsoft Excel and is a timeefficient tool to evaluate volume, pressure and other thermodynamic functions using T-P and T-V data only as input parameters. This application is aimed to solve practical issues of high pressure experiments in geosciences and mineral physics.

Thermoelastic properties of chromium oxide Cr2O3 (eskolaite) at high pressures and temperatures

Physics and Chemistry of Minerals, 2016

A new synchrotron X-ray diffraction study of chromium oxide Cr2O3 (eskolaite) with the corundum-t... more A new synchrotron X-ray diffraction study of chromium oxide Cr2O3 (eskolaite) with the corundum-type structure has been carried out in a Kawai-type multi-anvil apparatus to pressure of 15 GPa and temperatures of 1873 K. Fitting the Birch–Murnaghan equation of state (EoS) with the present data up to 15 GPa yielded: bulk modulus (K0,T0), 206 ± 4 GPa; its pressure derivative K′0,T, 4.4 ± 0.8; (∂K0,T/∂T) = ‒0.037 ± 0.006 GPa K‒1; a = 2.98 ± 0.14 × 10−5 K−1 and b = 0.47 ± 0.28 × 10‒8 K‒2, where α0,T = a + bT is the volumetric thermal expansion coefficient. The thermal expansion of Cr2O3 was additionally measured at the high-temperature powder diffraction experiment at ambient pressure and α0,T0 was determined to be 2.95 × 10−5 K−1. The results indicate that coefficient of the thermal expansion calculated from the EoS appeared to be high-precision because it is consistent with the data obtained at 1 atm. However, our results contradict α0 value suggested by Rigby et al. (Brit Ceram Trans J 45:137–148, 1946) widely used in many physical and geological databases. Fitting the Mie–Grüneisen–Debye EoS with the present ambient and high-pressure data yielded the following parameters: K0,T0 = 205 ± 3 GPa, K′0,T = 4.0, Grüneisen parameter (γ0) = 1.42 ± 0.80, q = 1.82 ± 0.56. The thermoelastic parameters indicate that Cr2O3 undergoes near isotropic compression at room and high temperatures up to 15 GPa. Cr2O3 is shown to be stable in this pressure range and adopts the corundum-type structure. Using obtained thermoelastic parameters, we calculated the reaction boundary of knorringite formation from enstatite and eskolaite. The Clapeyron slope (with {\text{d}}P/{\text{d}}T = - 0.014$$dP/dT=-0.014 GPa/K) was found to be consistent with experimental data.

Experimental study of the pyroxene-garnet phase transition in the Na2MgSi5O12 system at pressures of 13–20 GPa: First synthesis of sodium majorite

Doklady Earth Sciences, 2010

Contributions to Mineralogy and Petrology, 2009

Oxygen fugacity (fO 2 ) conditions were determined for 29 peridotite xenoliths from the A154-Nort... more Oxygen fugacity (fO 2 ) conditions were determined for 29 peridotite xenoliths from the A154-North and A154-South kimberlites of the Diavik diamond mine using the newly developed flank method modified specifically for measuring Fe 3? in mantle-derived pyropic garnets. The results indicate that the garnet-bearing lithospheric mantle beneath the central Slave craton is vertically layered with respect to oxidation state. The shallow (\140 km), ''ultradepleted'' layer is the most oxidized section of garnetbearing subcratonic mantle thus far measured, up to one log unit more oxidizing relative to the FMQ buffer [Dlog fO 2 (FMQ) ? 1]. The lower, more fertile layer has fO 2 conditions that extend down to Dlog fO 2 (FMQ) -3.8, consistent with xenolith suites from other localities worldwide. Based on trace element concentrations in garnets, two distinct metasomatic events affected the mantle lithosphere at Diavik. An oxidized fluid imparted sinusoidal chondrite-normalized REE patterns on garnets throughout the entire depth range sampled. In contrast, a reducing melt metasomatic event affected only the lower portion of the lithospheric mantle. The fO 2 state of the Diavik mantle sample suggests that diamond formation occurred by reduction of carbonate by fluids arising from beneath the lithosphere. Communicated by J. Hoefs.

Composition of the kimberlite melt of the Komsomolskaya-Magnitnaya pipe (Upper Muna field, Siberian craton)

Phase boundary between cubic B1 and rhombohedral structures in (Mg,Fe)O magnesiowüstite determined by in situ X-ray diffraction measurements

Physics and Chemistry of Minerals, 2017

The phase relations and equation of state of (Mg0.08Fe0.92)O magnesiowüstite (Mw92) have been stu... more The phase relations and equation of state of (Mg0.08Fe0.92)O magnesiowüstite (Mw92) have been studied using the Kawai-type high-pressure apparatus coupled with synchrotron radiation. To determine the phase boundary between the NaCl-type cubic (B1) and rhombohedral (rB1) structures in Mw92, in situ X-ray observations were carried out at pressures of 0–35 GPa and temperatures of 300–1473 K. Au and MgO were used as the internal pressure markers and metallic Fe as oxygen fugacity buffer. The phase boundary between B1 and rB1 structures was described by a linear equation P (GPa) = 1.6 + 0.033 × T (K). The Clapeyron slope (dP/dT) determined in this study is close to that obtained at pressures above 70 GPa but steeper than that obtained for FeO. An addition of MgO to FeO structure expands the stability field of the rB1 phase to lower pressures and higher temperatures. Thus, the rB1 phase may be stabilized with respect to the B1 phase at a lower pressures. The pressure–volume–temperature equation of state of B1-Mw92 was determined up to 30 GPa and 1473 K. Fitting the hydrostatic compression data up to 30 GPa with the Birch–Murnaghan equation of state (EoS) yielded: unit cell volume (V0,T0), 79.23 ± 4 Å3; bulk modulus (K0,T0), 183 ± 4 GPa; its pressure derivative (K′T), 4.1 ± 0.4; (∂K0,T/∂T) = −0.029 ± 0.005 GPa K‒1; a = 3.70 ± 0.27 × 10−5 K−1 and b = 0.47 ± 0.49 × 10−8 K−2, where α0,T = a + bT is the volumetric thermal expansion coefficient. The obtained bulk modulus of Mw92 is very close to the value expected for stoichiometric iron-rich (Mg,Fe)O. This result confirms the idea that the bulk modulus of (Mg,Fe)O is greatly affected by the actual defect structure, caused by either Mg2+ or vacancies.

Confocal Raman spectroscopic study of melt inclusions in olivine of mantle xenoliths from the Bultfontein kimberlite pipe (Kimberley cluster, South Africa): Evidence for alkali‐rich carbonate melt in the mantle beneath Kaapvaal Craton

Journal of Raman Spectroscopy, 2021

Synthesis of Na-bearing majorte in the system Mg3Al2Si3O12 -Na2MgSi5O12 at 11-20 GPa: solid solutions and structural features

Vestnik Otdelenia nauk o Zemle RAN, 2011

Geochemistry International, 2014

The CaO-MgO-Al 2 O 3 -SiO 2 -Na 2 O multicomponent system was experimentally studied at 7.0 and 8... more The CaO-MgO-Al 2 O 3 -SiO 2 -Na 2 O multicomponent system was experimentally studied at 7.0 and 8.5 GPa using an anvil with hole toroidal high pressure apparatus to examine two binary joins: pyropegrossular and grossular-Na majorite. These and literature data were employed to simulate the liquidus sur face of the pyrope-grossular-Na majorite system. The liquidus surface of garnet of predominantly pyrope composition is dominant in the diagram, and the garnet contains much of the Na 2 MgSi 5 O 12 end member. Melting was observed in this region at temperatures above 1900°C, and the solidus of the system occurs at temperatures below 1550°C. The pyrope-grossular system shows a miscibility gap at 50-65 mol % of the pyrope component and two series of garnet solid solutions. The dominant phase at grossular and Na majorite mixing is pyroxene, and garnet crystallizes within a fairly narrow field in the grossular rich region. All garnets synthesized in the systems have elevated Si and Na concentrations and belong to the majorite series, for which a uniform mechanism of isomorphism (Mg, Ca) + Al = Si + Na was proved.