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 deve...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 1273 K is suitable to synthesize dense ferrosilite samples with low porosity.We employed the transient plane-source method to investigate the thermal conductivityκand 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)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.展开更多
We report here high-pressure investigations on Piplia Kalan eucrite-a member of HED （Howardite -Eucrite-Diogenite） family from asteroid 4-Vesta based on synchrotron X-ray diffraction （up to 16 GPa） and ^57Fe Mossb...We report here high-pressure investigations on Piplia Kalan eucrite-a member of HED （Howardite -Eucrite-Diogenite） family from asteroid 4-Vesta based on synchrotron X-ray diffraction （up to 16 GPa） and ^57Fe Mossbauer spectroscopy （up to 8 GPa）. Dominant with anorthite-rich plagioclase, pigeonite-rich pyroxene and clino-ferrosilite, the sample displayed various phase transitions attaining amorphous character at 16 GPa. These phase transitions of individual components could be explained simultaneously through variations in high-pressure XRD patterns and the Mossbauer parameters. Most prominent P21/c to C2/c transition of pigeonite and ferrosilite was exhibited both as sudden variation in Mossbauer parameters and population inversion of Fe^2＋ in M1 and M2 sites between 2.9 and 3.8 GPa and variation in intensity profile in XRD patterns at 3.56 GPa. Anorthite seemed to respond more to such impact than other components in the sample. Complete amorphization in anorthite which occurred at lower pressure of - 12 GPa implied residual stress experienced due to shock impact. The presence of high pressure （monoclinic） phase of pigeonite and ferrosilite at ambient condition in this eucrite sample confirmed earlier suggestions of an early shock event. This report is an attempt to emphasize the role of anorthite in the determination of the residual stress due to impact process in the parent body thus to understand the behavioral differences amongst HED members.展开更多
基金supported by the CAS“Light of West China”Program(No.Y9CR026)the National Natural Science Foundation of China(No.442072051)。
文摘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 1273 K is suitable to synthesize dense ferrosilite samples with low porosity.We employed the transient plane-source method to investigate the thermal conductivityκand 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)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.
基金Council of Scientific and Industrial Research(CSIR),PLANEX program of India Space Research Organization,Department of Space(Government of India),CSR-SHORE-PSC-02005 and ISRO projects(GP)for funding, CSIR for providing Emeritus Scientist Fellowship(UC)
文摘We report here high-pressure investigations on Piplia Kalan eucrite-a member of HED （Howardite -Eucrite-Diogenite） family from asteroid 4-Vesta based on synchrotron X-ray diffraction （up to 16 GPa） and ^57Fe Mossbauer spectroscopy （up to 8 GPa）. Dominant with anorthite-rich plagioclase, pigeonite-rich pyroxene and clino-ferrosilite, the sample displayed various phase transitions attaining amorphous character at 16 GPa. These phase transitions of individual components could be explained simultaneously through variations in high-pressure XRD patterns and the Mossbauer parameters. Most prominent P21/c to C2/c transition of pigeonite and ferrosilite was exhibited both as sudden variation in Mossbauer parameters and population inversion of Fe^2＋ in M1 and M2 sites between 2.9 and 3.8 GPa and variation in intensity profile in XRD patterns at 3.56 GPa. Anorthite seemed to respond more to such impact than other components in the sample. Complete amorphization in anorthite which occurred at lower pressure of - 12 GPa implied residual stress experienced due to shock impact. The presence of high pressure （monoclinic） phase of pigeonite and ferrosilite at ambient condition in this eucrite sample confirmed earlier suggestions of an early shock event. This report is an attempt to emphasize the role of anorthite in the determination of the residual stress due to impact process in the parent body thus to understand the behavioral differences amongst HED members.
