| Project/Area Number |
10304042
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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 | Chiba University |
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Principal Investigator |
HIROI Yoshikuni Chiba University, Dept.of Sci., Professor, 理学部, 教授 (40019427)
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| Co-Investigator(Kenkyū-buntansha) |
FURUKAWA Noboru Chiba University, Dept.of Sci., Assistant, 理学部, 助手 (40251194)
KANAGAWA Kyuichi Chiba University, Dept.of Sci., Associ.Professor, 理学部, 助教授 (40185898)
TSUKUI Masashi Chiba University, Dept.of Sci., Associ.Professor, 理学部, 助教授 (50192191)
TAGIRI Michio Ibaraki University, Dept.of Sci., Professor, 理学部, 教授 (50007829)
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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 |
¥37,800,000 (Direct Cost: ¥37,800,000)
Fiscal Year 2000: ¥3,200,000 (Direct Cost: ¥3,200,000)
Fiscal Year 1999: ¥6,900,000 (Direct Cost: ¥6,900,000)
Fiscal Year 1998: ¥27,700,000 (Direct Cost: ¥27,700,000)
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| Keywords | Fluid phase / High-grade metamorphics / High-P and high-T / Partial melting / Uplift processes / Hydration reactions / Carbonation reactions / Borosilicate minerals / 高度変性岩類 / マグマ |
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| Research Abstract |
Sample collection, field observation, petrography, and chemical analysis of rocks as well as high-pressure and high-temperature experiments of mineral synthesis and partial melting of rocks have been performed. Sample collection was carried out in the Hidaka, Abukuma and Ryoke metamorphic belts and also in the Omine Mountains. Overseas study samples are from Sri Lanka, South Africa and China. It has been revealed that the rocks have experienced variable local retrograde reactions with fluids of different compositions. Khondalite from Sri Lanka, in particular, shows evidence indicative of the presence of fluid rich in a component other than H2O and CO2. It is also unraveled that some high-grade metamorphic rocks suffered partial melting at the peak of metamorphism. Some structural and textural features of the Chinese ultra high-pressure metamorphic rocks suggest that partial melting was a significant process for the high-density rocks to uplift after the subduction down to c. 100 km in depth. The study of Omine granitic rocks was successful in observing the euhedral internal growth structures in anhedral quartz grains as the SEM CL images, which may be useful in getting new insights into the crystallization processes of granitic magmas. A paper reporting the origin of new borosilicate mineral "ominelite" and the new geochemical behaviors of boron is being in preparation. High-pressure and high-temperature experimental studies of high-grade metamorphic rocks with additional water have shown that partial melting occurs locally at the grain boundaries between some specified minerals as a kind of eutectic reactions at relatively low temperatures. With increasing temperatures compositions of partial melts become highly variable as the results of partial melting taking place more extensively at many places in the rocks.
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