Thermal Conductivity and Thermal Diffusivity of Ferrosilite under High Temperature and High Pressure

• Published in: Journal of earth science (Wuhan, China) China), 2022-06, Vol.33 (3), p.770-777
• Main Authors: Feng, Bo, Guo, Xinzhuan
• Format: Article
• Language: English
• Subjects: Asteroids; Biogeosciences; Diffusion coefficients; Diffusivity; Earth and Environmental Science; Earth Sciences; Ferrous silicates; Geochemistry; Geology; Geotechnical Engineering & Applied Earth Sciences; Heat conductivity; Heat transfer; High pressure; High temperature; Iron; Pacific Plate Subduction and the Yanshanian Movement in Eastern China; Porosity; Silica; Silicon dioxide; Specific heat; Temperature; Temperature distribution; Thermal conductivity; Thermal diffusivity; Thermal evolution; Thermal properties; Thermal structure; Thermodynamic properties; Upper mantle
• ISSN: 1674-487X; 1867-111X
• DOI: 10.1007/s12583-021-1574-0

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 + SiO 2 → FeSiO 3 . 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 × 10 3 T −1 − 9.269 × 10 4 T −2 and D = 0.424 + 0.223 × 10 3 T −1 + 1.64 × 10 4 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). 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.