1996 Fiscal Year Final Research Report Summary
Phase transformation and rheology of minerals in the Earth's crust and mantle
| Project/Area Number |
06402019
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Petrology/Mineralogy/Science of ore deposit
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| Research Institution | HOKKAIDO UNIVERSITY |
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Principal Investigator |
FUJINO Kiyoshi Hokkaido Univ., Graduate School of Science, Prof., 大学院・理学研究科, 教授 (40116968)
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| Co-Investigator(Kenkyū-buntansha) |
IRIFUNE Tetsuo Ehime Univ., Faculty of Science, Prof., 理学部, 教授 (80193704)
NIIDA Kiyoaki Hokkaido Univ., Graduate School of Science, Assoc.Prof., 大学院・理学研究科, 助教授 (30111149)
MATSUEDA Hiroharu Hokkaido Univ., Graduate School of Science, Assoc.Prof., 大学院・理学研究科, 助教授 (20108921)
MIURA Hiroyuki Hokkaido Univ., Graduate School of Science, Lecturer, 大学院・理学研究科, 講師 (70157436)
KIKUCHI Takeshi Hokkaido Univ., Graduate School of Science, Assoc.Prof., 大学院・理学研究科, 助教授 (60211190)
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| Project Period (FY) |
1994 – 1996
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| Keywords | majorite / perovskite / enstatite / analytical electron microscopy / laser-heated diamond anvil cell / multi anvil cell / lithium niobate phase / phase transition |
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| Research Abstract |
Three following subjects were intensively studied and the following results were obtained, respectively.
1. Aluminous garnet-perovskite phase transformation
Laser-heated diamond anvil cell experiments using natural garnets as starting materials, and analytical electron microscopy of the recovered samples showed the following results ; 1) although the main post-garnet phase under the lower mantle condition is orthorhombic perovskite, some Al-rich phase (s) and stishovite coexist with orthorhombic perovskite depending on temperature and prssure, 2) the silicate LiNbO_3 phase was found for the first time as a metastable phase transformed from the orthorhombic perovskite, 3) there are positive correlations between Fe, Al and Ca contents in perovskite, and these contents tend to increase with pressure.
2. Cubic-tetragonal transition in (Mg, Fe) SiO_3 majorite
Analytical electron microscopy of the synthetic majorite by multi anvil cell and the natural meteorite majorite showed that the synthetic majorite is tetragonal, while natural majorite is cubic. Microstructures of synthetic majorites indicate the wide stability range of cubic phase at higher temperatures thah-1900ﾟC at 20 GPa. The boundary temperature between cubic and tetragonal phases increases with Fe content.
3. Phase transition of enstatite under high pressure and hihg temperature
High temperature and high pressure in situ X-ray diffraction experiments using synchrotron radiation showed that there exists a wide stability range of monoclinic C2/c phase on the high pressure side of orthorhombic Pbca. The beta anble of this C2/c is signficantly smaller than that of high temperature C2/c, indicating that these two phases are the different structures with each other. There is a possibility that monoclinic P2_1/c has a stability field between orthorhombic Pbca and monoclinic C2/c at lower temperatures.
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