TY - JOUR

T1 - Thermal equation of state of NaMg0.5Si2.5O6 and new data on the compressibility of clinopyroxenes

AU - Dymshits, A. M.

AU - Sharygin, I. S.

AU - Podborodnikov, I. V.

AU - Litasov, K. D.

AU - Shatskiy, A. F.

AU - Otani, E.

AU - Pushcharovskii, D. Yu

PY - 2015/3/1

Y1 - 2015/3/1

N2 - 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: V0 = 407.2 (5) Å3, the space group P2/n, KT0 = 103 (2) GPa, KT0 = 6.2 (7), ∂KT/∂T = −0.018 (7), α = 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 (KT). 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.

AB - 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: V0 = 407.2 (5) Å3, the space group P2/n, KT0 = 103 (2) GPa, KT0 = 6.2 (7), ∂KT/∂T = −0.018 (7), α = 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 (KT). 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.

UR - http://www.scopus.com/inward/record.url?scp=84928315940&partnerID=8YFLogxK

U2 - 10.1134/S1028334X15030113

DO - 10.1134/S1028334X15030113

M3 - Article

AN - SCOPUS:84928315940

VL - 461

SP - 273

EP - 276

JO - Doklady Earth Sciences

JF - Doklady Earth Sciences

SN - 1028-334X

IS - 1

ER -