Thermal equation of state of NaMg^sub 0.5^Si^sub 2.5^O^sub 6^ and new data on the compressibility of clinopyroxenes

The results of studies of the P-V-T equations of state (EOS) of Na-pyroxene using the multi-anvil technique and synchrotron radiation at pressures up to 15.3 GPa and temperatures up to 1673 K are presented. By fitting the Birch-Murnaghan EOS, the following parameters were determined: V ^sub 0^ = 407...

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Bibliographic Details
Published in:Doklady earth sciences 2015-03, Vol.461 (1), p.273
Main Authors: Dymshits, A M, Sharygin, I S, Podborodnikov, I V, Litasov, K D, Shatskiy, A F, Otani, E, Pushcharovskii, D Yu
Format: Article
Language:English
Subjects:
Mineral resources
Radiation
Tetrahedra
Thermal energy
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Summary:The results of studies of the P-V-T equations of state (EOS) of Na-pyroxene using the multi-anvil technique and synchrotron radiation at pressures up to 15.3 GPa and temperatures up to 1673 K are presented. By fitting the Birch-Murnaghan EOS, the following parameters were determined: V ^sub 0^ = 407.2 (5) Å^sup 3^, the space group P2/n, K ^sub T0^ = 103 (2) GPa, K ^sub T0^ = 6.2 (7), [partial differential]K ^sub T^/[partial differential]T = -0.018 (7), [alpha] = 3.38(13) + 0.65(62)T. Thus, despite the small volume of the cell, Na-pyroxene has a sufficiently high bulk modulus. This can be caused by the appearance of antipathetic bonds in Na-polyhedron, Si-tetrahedra rotation, and the ordering of Mg and Si cations in the M1 position. Thus, it is substantiated that the phase transformations in the minerals accompanied by the presence of Si in octahedral coordination are characterized by a significant change in the physical characteristics, such as density (ρ) and bulk modulus (K ^sub T^). Such transformations occurring in the minerals and deep Earth can lead to significant jumps in the seismic wave velocities. Therefore, the presence of phases with silicon in sixfold coordination, such as Na-Ca majoritic garnet is of fundamental importance for understanding the Earth's upper mantle.
ISSN:1028-334X
1531-8354
DOI:10.1134/S1028334X15030113