TY - JOUR
T1 - P-V-T equation of state of MgSiO3 perovskite and MgO periclase
T2 - Implication for lower mantle composition
AU - Aizawa, Yoshitaka
AU - Yoneda, Akira
N1 - Funding Information:
The authors would like to thank Prof. I. Jackson for his constructive comments and valuable suggestions. This work was financially supported by Research Fellowships (to Y.A.) from the Japan Society for Promotion of Science for young scientists. Appendix A A.1
PY - 2006/4/14
Y1 - 2006/4/14
N2 - The P-V-T equation of state (EOS) for magnesium silicate perovskite (MgSiO3) and periclase (MgO) was obtained by fitting measured P, V, T data. The EOS of MgSiO3 perovskite was determined by applying the Mie-Grüneisen-Debye approach, based on three alternative bulk modulus values (KT0 = 240, 250 and 261 GPa), yielding substantially different values for high-order thermoelastic parameters such as the Grüneisen parameter (γ) and the temperature derivative of bulk modulus ((∂KT/∂T)P). Combined with the EOS of magnesiowüstite, we calculated the density (ρ), bulk modulus (KS) and seismic parameter (φ) for simplified pyrolitic lower mantle along a plausible adiabat (temperature at 670 km, Ta = 1900 K), and compared these values to those of a seismological model (PREM). The results based on KT0 of 261 GPa, which has been commonly used, showed good agreement with PREM, within 0.5% for ρ, and 2-3% for KS and φ, throughout the lower mantle. The EOS obtained using the recent KT0 data (240-250 GPa), substantially overestimated KS and φ by 5-10%, requiring a progressive enrichment in (Mg,Fe)O with increasing depth. In addition, a more realistic vibrational density of states (VDOS) model (Kieffer-type model) was applied to calculate the EOS. The effect of VDOS on thermoelastic parameters was not large enough to modify those conclusions.
AB - The P-V-T equation of state (EOS) for magnesium silicate perovskite (MgSiO3) and periclase (MgO) was obtained by fitting measured P, V, T data. The EOS of MgSiO3 perovskite was determined by applying the Mie-Grüneisen-Debye approach, based on three alternative bulk modulus values (KT0 = 240, 250 and 261 GPa), yielding substantially different values for high-order thermoelastic parameters such as the Grüneisen parameter (γ) and the temperature derivative of bulk modulus ((∂KT/∂T)P). Combined with the EOS of magnesiowüstite, we calculated the density (ρ), bulk modulus (KS) and seismic parameter (φ) for simplified pyrolitic lower mantle along a plausible adiabat (temperature at 670 km, Ta = 1900 K), and compared these values to those of a seismological model (PREM). The results based on KT0 of 261 GPa, which has been commonly used, showed good agreement with PREM, within 0.5% for ρ, and 2-3% for KS and φ, throughout the lower mantle. The EOS obtained using the recent KT0 data (240-250 GPa), substantially overestimated KS and φ by 5-10%, requiring a progressive enrichment in (Mg,Fe)O with increasing depth. In addition, a more realistic vibrational density of states (VDOS) model (Kieffer-type model) was applied to calculate the EOS. The effect of VDOS on thermoelastic parameters was not large enough to modify those conclusions.
KW - Equation of state
KW - Lower mantle
KW - Perovskite
KW - Thermoelastic parameters
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U2 - 10.1016/j.pepi.2005.10.002
DO - 10.1016/j.pepi.2005.10.002
M3 - Article
AN - SCOPUS:33644910909
SN - 0031-9201
VL - 155
SP - 87
EP - 95
JO - Physics of the Earth and Planetary Interiors
JF - Physics of the Earth and Planetary Interiors
IS - 1-2
ER -