| Project/Area Number |
10440128
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| Research Category |
Grant-in-Aid for Scientific Research (B).
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
固体地球物理学
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| Research Institution | Ehime University |
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Principal Investigator |
IRIFUNE Tetsuo Ehime Univ., Faculty of Science Professor, 理学部, 教授 (80193704)
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| Co-Investigator(Kenkyū-buntansha) |
INOUE Toru Ehime Univ., Faculty of Science Instructor, 理学部, 助手 (00291500)
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| Project Period (FY) |
1998 – 2000
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| Project Status |
Completed (Fiscal Year 2000)
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| Budget Amount *help |
¥4,600,000 (Direct Cost: ¥4,600,000)
Fiscal Year 2000: ¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1999: ¥2,400,000 (Direct Cost: ¥2,400,000)
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| Keywords | synchrotron radiation / in situ X-ray observation / spinel / majorite / phase transition / high-pressure high-temperature / 660 km discontinuity / ポストスピネル / Spring-8 / 放射光実験 / パイロライト / マントル / ペロフスカイト / イルメナイト |
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| Research Abstract |
Phase transitions in Mg_2SiO_4, MgSiO_3, Ca_<0.5>Mg_<0.5>SiO_3 and pyrolite were studied by in situ X-ray diffraction using synchrotron radiation. It was found that the transitions to MgSiO_3 perovskite-related phases in all of these compositions were significantly (〜2 GPa) lower than those determined by quench experiments. It is suggested that the postspinel phase transition may not be responsible for the 660 km seismic discontinuity, or currently used pressure scales may be invalid at the P/T conditions of the lower mantle regime. A possible scenario to reconcile these experimental results with the observed seismic profile is proposed based on the calculations of the density and seismic velocity changes in subducting oceanic crust and pyrolitic mantle materials.
The dissociation of Ca_<0.5>Mg_<0.5>SiO_3 into an assemblage of MgSiO_3 and CaSiO_3 perovskites was firstly confirmed on the basis of in situ X-ray observation under simultaneous high pressure and high temperature conditions. The mutual solubilities of Mg- and Ca-components in these perovskite were found to be very limited at the pressures (21〜28 GPa) and temperatures (1000〜1800℃) studied. It is suggested that the diamond inclusions of lower mantle origin reported in Brazil may be formed at relatively low temperatures (<1200℃) related to the subduction of slabs.
Development of technology to produce higher pressures in multianvil apparatus using sintered diamond anvils was pursued in the final year of the present program. As a result, in situ X-ray observations are now possible at pressures to 40 GPa and temperatures to 1500℃. Preliminary experimental studies have been made on the phase transitions and P-V-T relations in MgAl_2O_4 and Ca_<0.5>Mg_<0.5>SiO_3 under these conditions.
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