1994 Fiscal Year Final Research Report Summary
In Situ X-ray Diffraction Study on Silicate Perovskite and the Chemical Composition of the Lower Mantle
| Project/Area Number |
05452071
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
固体地球物理学
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| Research Institution | University of Tokyo |
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Principal Investigator |
YAGI Takehiko Institute for Solid State Physics Associate Professor, 物性研究所, 助教授 (20126189)
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| Co-Investigator(Kenkyū-buntansha) |
KONDO Tadashi Institute for Solid State Physics Research Associate, 物性研究所, 助手 (20252223)
UTSUMI Wataru Institute for Solid State Physics Research Associate, 物性研究所, 助手 (60193918)
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| Project Period (FY) |
1993 – 1994
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| Keywords | Lower mantle / Silicate perovskite / Equation of state / High pressure |
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| Research Abstract |
The purpose of the present study was to discuss the chemical composition of the lower mantle through the precise determination of equation of state of silicate perovskite, which is believed to be the most abundant mineral of the Earth's lower mantle. For this purpose, we first developed several different types of high pressure and high temperature apparatuses for in situ X-ray diffraction study, using sintered diamond as an anvil material.
Among them, the Drickamer-type apparatus covers the widest range of pressure. Because of the large deviatoric stresses, however, this apparatus was not suitable for precise equation of state study. We used both cubic-anvil type and 6-8 type double stage apparatus for the present study. We have made many improvements in using these apparatuses and we have succeeded in measuring the equation of state of MgSiO_3 perovskite up to 29 GPa and 2000K.Analyzing these data, we have obtained accurate equation of state on MgSiO_3 perovskite under the uppermost condition of the lower mantle. Compared to the previous studies, the accuracy of the present measurement was improved dramatically. Considering the possibilities of many systematic errors in the measurement, however, the absolute reliability of the present equation of state is still not high enough to give any strong constraints on the chemical composition of the lower mantle. If we make discussions using the mean value obtained by the present analysis, the chemical composition of the lower mantle seems to be slightly rich in Si compared to the upper mantle. In order to strengthen this conclusion, we are planning to extend our measurement further into higher pressure regions.
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