Thermal equation of state of magnesite to 32 GPa and 2073 K

Konstantin D. Litasov, Yingwei Fei, Eiji Ohtani, Takahiro Kuribayashi, Kenichi Funakoshi

Research output: Contribution to journalArticlepeer-review

46 Citations (Scopus)

Abstract

Pressure-volume-temperature relations have been measured to 32 GPa and 2073 K for natural magnesite (Mg0.975Fe0.015Mn0.006Ca 0.004CO3) using synchrotron X-ray diffraction with a multianvil apparatus at the SPring-8 facility. A least-squares fit of the room-temperature compression data to a third-order Birch-Murnaghan equation of state (EOS) yielded K0 = 97.1 ± 0.5 GPa and K′ = 5.44 ± 0.07, with fixed V0 = 279.55 ± 0.02 Å3. Further analysis of the high-temperature compression data yielded the temperature derivative of the bulk modulus (∂KT/∂T)P = -0.013 ± 0.001 GPa/K and zero-pressure thermal expansion α = a0 + a1T with a0 = 4.03 (7) × 10-5 K-1 and a1 = 0.49 (10) × 10-8 K-2. The Anderson-Grüneisen parameter is estimated to be δT = 3.3. The analysis of axial compressibility and thermal expansivity indicates that the c-axis is over three times more compressible (KTc = 47 ± 1 GPa) than the a-axis (KTc = 157 ± 1 GPa), whereas the thermal expansion of the c-axis (a0 = 6.8 (2) × 10-5 K-1 and a1 = 2.2 (4) × 10-8 K-2) is greater than that of the a-axis (a0 = 2.7 (4) × 10-5 K-1 and a1 = -0.2 (2) × 10-8 K-2). The present thermal EOS enables us to accurately calculate the density of magnesite to the deep mantle conditions. Decarbonation of a subducting oceanic crust containing 2 wt.% magnesite would result in a 0.6% density reduction at 30 GPa and 1273 K. Using the new EOS parameters we performed thermodynamic calculations for magnesite decarbonation reactions at pressures to 20 GPa. We also estimated stability of magnesite-bearing assemblages in the lower mantle.

Original languageEnglish
Pages (from-to)191-203
Number of pages13
JournalPhysics of the Earth and Planetary Interiors
Volume168
Issue number3-4
DOIs
Publication statusPublished - 2008 Jul 1

Keywords

  • Equation of state
  • Magnesite
  • Mantle
  • Subduction
  • Synchrotron X-ray diffraction

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Geophysics
  • Physics and Astronomy (miscellaneous)
  • Space and Planetary Science

Fingerprint Dive into the research topics of 'Thermal equation of state of magnesite to 32 GPa and 2073 K'. Together they form a unique fingerprint.

Cite this