1997 Fiscal Year Final Research Report Summary
The early stage of the development of the Sambagawa metamorphic belt estimated from the metamorphic clasts within the Kuma Group
| Project/Area Number |
08640570
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Geology
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| Research Institution | SHIMANE UNIVERSITY |
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Principal Investigator |
TAKASU Akira Shimane University, Interdisciplinary Faculty of Science and Engineering, Professor, 総合理工学部, 教授 (00183848)
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| Co-Investigator(Kenkyū-buntansha) |
OHIRA Hiroto Shimane University, Interdisciplinary Faculty of Science and Engineering, Assist, 総合理工学部, 助手 (60273918)
IIZUMI Shigeru Shimane University, Interdisciplinary Faculty of Science and Engineering, Profes, 総合理工学部, 教授 (80032639)
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| Project Period (FY) |
1996 – 1997
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| Keywords | Sambagawa / Kuma Group / clasts / accretionary prism / high-P metamorphism / geochronology / garnet / eclogite |
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| Research Abstract |
Geological survery and sampling of the metamorphic rocks from the Kanto Mountains, Kii Peninsula and Shikoku in the Sambagawa metamorphic belt and Wakasa in the Sangun metamorphic belt have been done. We petrographically compared the high-grade metamorphic clasts with the high-P type metamorphic rocks presently exposed in southwest Japan together with the other metamorphic rocks such as those from the Hida, Himalayan and Kyrghstan metamorphic belts. We chemically analyzed the constituent minerals including garnet, amphibole, epidote and white micas by using an electron probe micro-analyzer, and also examined these minerals in respect to the chemical zoning, backscattered electron image and elemental color mapping. These studies revealed that the high-grade metamorphic clasts from the Kuma Group are very much similar to the epidote amphibolite facies metamorphic rocks within the tectonic blocks such as the Iratsu and Tonaru amphibolite masses.
The 40Ar/39Ar dating results suggest that the peak metamorphic age of the Kuma metamorphic clasts is 145-189 Ma and obviously older than that of the Besshi nappe complex (90-100 Ma). The fission track age of the Kuma metamorphic clasts (65-70 Ma) is also older than that of the Besshi nappe complex (45-58 Ma). These studies suggest that the Kuma nappe complex is earlier stage metamorphic rocks compared with the Besshi nappe complex and it was exhumed earlier than the metamorphic rocks within the Besshi nappe complex.
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