Doklady Earth Sciences

, Volume 461, Issue 1, pp 273–276 | Cite as

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

  • A. M. DymshitsEmail author
  • I. S. Sharygin
  • I. V. Podborodnikov
  • K. D. Litasov
  • A. F. Shatskiy
  • E. Otani
  • D. Yu. Pushcharovskii


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 0 = 407.2 (5) Å3, the space group P2/n, K T0 = 103 (2) GPa, K T0 = 6.2 (7), ∂K T /∂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 (K 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.


Bulk Modulus DOKLADY Earth Science Enstatite Spodumene Spatial Group 
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Copyright information

© Pleiades Publishing, Ltd. 2015

Authors and Affiliations

  • A. M. Dymshits
    • 1
    • 2
    Email author
  • I. S. Sharygin
    • 1
    • 2
  • I. V. Podborodnikov
    • 1
    • 2
  • K. D. Litasov
    • 1
    • 2
  • A. F. Shatskiy
    • 1
    • 2
  • E. Otani
    • 3
  • D. Yu. Pushcharovskii
    • 4
  1. 1.Sobolev Institute of Geology and Mineralogy, Siberian BranchRussian Academy of SciencesNovosibirskRussia
  2. 2.Novosibirsk State UniversityNovosibirskRussia
  3. 3.Tohoku UniversitySendaiJapan
  4. 4.Moscow State UniversityMoscowRussia

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