Thermoelasticity of silicate perovskites and magnesiowüstite and its implications for the Earth’s lower mantle
-
Juichiro Hama
,
Kaichi Suito
Abstract
By assuming an ideal two-component mixture of (Mg,Fe)SiO3 perovskite (MgPv) and (Mg,Fe)O magnesiowüstite (Mw), and by using a thermoelastic model for mantle minerals developed previously, we can reproduce the PREM values of density and velocities vP and vS of compressional and shear waves of the lower mantle within ±0.12%, ±0.28%, and ±0.56% except for the transition layers at the both boundaries. The molar fractions and atomic fractions of iron for MgPv and Mw were adjusted to reproduce the PREM values of r, vP, and vS above the point of z = 871 km (which is slightly inside the lower mantle) under constant-entropy condition. This depth avoids the boundary effect. The adiabatic bulk and shear moduli of the mixture are calculated by the Hashin-Shtrikman method for MgPv and Mw and then arithmetically averaged. The temperature profile was calculated assuming that the lower mantle is adiabatic and T(670 km) = 1873 K. The temperature at the top of D'' becomes 2444 K. Being added the temperature increment of 840 K over D'' (z = 2741-2891 km) estimated by Stacey and Loper (1983) to our value, the temperature at the core-mantle boundary (CMB) becomes 3284 K in agreement with T(CMB) of 3300 ± 500 °C by Brown and McQueen. The molar ratios of Fe/(Mg + Fe) and (Mg + Fe)/Si become 0.12 and 2.10. The calculated thermal expansivity, a, of the mixture under lower mantle conditions is in agreement with a of the lower mantle calculated directly from PEM data by Brown and Shankland, and Anderson. For the addition of 5 mol% of CaSiO3 perovskite to our model, the essential feature of the result is unchanged and the wt% of SiO2, MgO, FeO, and CaO become 40.7, 44.6, 11.0, and 3.7
© 2015 by Walter de Gruyter Berlin/Boston
Articles in the same Issue
- Thermal expansivity of mantle relevant magnesium silicates derived from vibrational spectroscopy at high pressure
- Differential laser-interferometer for thermal expansion measurements
- New diamond anvil cells for gigahertz ultrasonic interferometry and X-ray diffraction
- Elasticity measurement of silica glass under gas pressure
- Sound velocities of wadsleyite b-(Mg0.88Fe0.12)2SiO4 to 10 GPa
- Sound velocities and elastic properties of g-Mg2SiO4 to 873 K by Brillouin spectroscopy
- Harmonic and anharmonic properties of spinel MgAl2O4
- The MD simulation of the equation of state of MgO: Application as a pressure calibration standard at high temperature and high pressure
- Ab initio structure of MgSiO3 ilmenite at high pressure
- Thermoelasticity of silicate perovskites and magnesiowüstite and its implications for the Earth’s lower mantle
- Thermodynamic functions at zero pressure and their relation to equations of state of minerals
- Accuracy of equation-of-state formulations
- Extrapolation of lower mantle properties to zero pressure: Constraints on composition and temperature
- Constraints on the P-V-T equation of state of MgSiO3 perovskite
- Structure analysis and stability field of β-iron at high P and T
- Iron phases at high pressures and temperatures: Phase transition and melting
- Calculated melting curves for phases of iron
- Grüneisen parameter of e-iron up to 300 GPa from in-situ X-ray study
- Grüneisen parameters and isothermal equations of state
Articles in the same Issue
- Thermal expansivity of mantle relevant magnesium silicates derived from vibrational spectroscopy at high pressure
- Differential laser-interferometer for thermal expansion measurements
- New diamond anvil cells for gigahertz ultrasonic interferometry and X-ray diffraction
- Elasticity measurement of silica glass under gas pressure
- Sound velocities of wadsleyite b-(Mg0.88Fe0.12)2SiO4 to 10 GPa
- Sound velocities and elastic properties of g-Mg2SiO4 to 873 K by Brillouin spectroscopy
- Harmonic and anharmonic properties of spinel MgAl2O4
- The MD simulation of the equation of state of MgO: Application as a pressure calibration standard at high temperature and high pressure
- Ab initio structure of MgSiO3 ilmenite at high pressure
- Thermoelasticity of silicate perovskites and magnesiowüstite and its implications for the Earth’s lower mantle
- Thermodynamic functions at zero pressure and their relation to equations of state of minerals
- Accuracy of equation-of-state formulations
- Extrapolation of lower mantle properties to zero pressure: Constraints on composition and temperature
- Constraints on the P-V-T equation of state of MgSiO3 perovskite
- Structure analysis and stability field of β-iron at high P and T
- Iron phases at high pressures and temperatures: Phase transition and melting
- Calculated melting curves for phases of iron
- Grüneisen parameter of e-iron up to 300 GPa from in-situ X-ray study
- Grüneisen parameters and isothermal equations of state
