Thermal Conductivity and Thermal Diffusivity of Ferrosilite under High Temperature and High Pressure
Bo Feng, Xinzhuan Guo
Journal of Earth Science ›› 2022, Vol. 33 ›› Issue (3) : 770-777.
Thermal Conductivity and Thermal Diffusivity of Ferrosilite under High Temperature and High Pressure
Orthopyroxene is an important constitutive mineral in the crust and the upper mantle. Its thermal properties play a key role in constructing the thermal structure of the crust and the upper mantle. In this study, we developed a new method to synthesize polycrystalline ferrosilite, one end-member of orthopyroxene, via the reaction of FeO + SiO2 → FeSiO3. We found that the P-T condition of 3 GPa and 1 273 K is suitable to synthesize dense ferrosilite samples with low porosity. We employed the transient plane-source method to investigate the thermal conductivity κ and thermal diffusivity D of synthetic ferrosilite at 1 GPa and 293–873 K, of which, κ = 1.786 + 1.048 × 103 T −1 − 9.269 × 104 T −2 and D = 0.424 + 0.223 × 103 T −1 + 1.64 × 104 T −2. Our results suggest phonon conduction should be the dominant mechanism at P-T conditions of interest since the thermal conductivity and the thermal diffusivity of ferrosilite both decrease with increasing temperature. The calculated heat capacity of ferrosilite at 1 GPa increases with temperature, which increases with increasing temperature with about 10% per 100 K (<500 K) and 4% per 100 K (>500 K). Iron content of an asteroid significantly influences its thermal evolution history and temperature distribution inside. It is expected that the mantle temperature of the Fe-rich asteroid will be higher and the Fe-rich asteroid’s cooling history will be longer.
ferrosilite / high pressure / thermal conductivity / thermal diffusivity / synthesis
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