1997 Fiscal Year Final Research Report Summary
GRANITIC MAGMA GENESIS IN OCEANIC ARC SETTING AND CONTINENTAL CRUST FORMING PROCESSES
| Project/Area Number |
08454154
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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 |
Petrology/Mineralogy/Science of ore deposit
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| Research Institution | YOKOHAMA NATIONAL UNIVERSITY |
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Principal Investigator |
ARIMA Makoto YOKOHAMA NATIONAL UNIVERSITY FACULTY OF EDUCATION AND HUMAN SCIENCES PROFESSOR, 教育人間科学部, 教授 (10184293)
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| Project Period (FY) |
1996 – 1997
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| Keywords | OCEANIC ARC / TONALITE / HIGH PRESSURE EXPERIMENT / PARTIAL MELTING / LOW CRUST / TANZAWA / IZU-BONIN-MARIANA (IBM) ARC |
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| Research Abstract |
In order to evaluate granitic magma generation and crustal growth in the oceanic island arc system, a series of hydrous partial melting experiments on low-K basalt compositions were done together with petrological and geochemical studies on the Miocene Tanzawa plutonic complex. Melt compositions in the high pressure melting experiments show low-K calc-alkalic trends, and are classified as metaluminous or peraluminous tonalite. These features are similar to the felsic rocks in the Izu-Bonin-Mariana (IBM) arc, e.g., Tanzawa plutonic rocks. The anatectic origin of Tanzawa tonalites is consistent with geochemical modeling, which demonstrate that the REE characteristics of Tanzawa plutonic rocks (which represents the middle crust of the IBM arc) can be generated by partial melting of amphibolite in the lower crust (-50% melting at 1050ﾟC and below 1.2GPa). The Tanzawa plutonic complex is interpreted to be exposed middle crust of the IBM arc, which was uplifted during the collision. Partial melting of hydrated mafic lower crust might play an important role in felsic middle crust formation in the IBM arc.
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[Publications] Arima, M.and Kato, H.: "The origin of garnet phenocrysts in Miocene volcanic rocks from the Nijosan volcanic district, southwest Japan" In Synthetic and Natural Rock Systems, Felicitation Volume in honor of Kenzo Yagi (Gupta, A.K., and Onuma, K., and Arima, M., eds.). National Academy of Sciences, India, Allied Press.211-232 (1997)
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[Publications] Hirata, D., Yamashita, H., Taniguchi, H., Nishikawa, T., Aoike, K., Suzui, M., Saito, N., and Arima, M.: "Evolution of a volcanic edifice in the Izu-Ogasawara (Bonin) arc : Lithological cheracteristics of a 1500 meter core sample in Hachijojima" Bull.Kanagawa Prefect.Mus. (Nat.Sci.). No.26. 57-88 (1997)
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