1998 Fiscal Year Final Research Report Summary
Activity of proto-Pacific superplume from the viewpoint of Paleozoic ophiolites in Southwest Japan.
| Project/Area Number |
08640572
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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 | HIROSHIMA UNIVERSITY |
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Principal Investigator |
HAYASAKA Yasutaka Faculty of Science HIROSHIMA UNIVERSITY Research Associate -> 広島大学, 理学部, 助手 (10198830)
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| Project Period (FY) |
1996 – 1998
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| Keywords | Pacific superplume / Southwest Japan / Paleozoic ophiolite / Oe-yama ophiolite / Yakuno ophiolite / Paleozoic accretionary complex / Jurassic accretionary complex |
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| Research Abstract |
1. Oe-yama ophiolite : Ashidachi complex shows the Sm-Nd isotopic ages of 560 Ma for coarse-grained gabbro, and 350 to 450Ma for the fine-grained gabbro.
2. Yakuno ophiolite : Gneissose metagabbro shows the Sm-Nd isotopic ages from 340 to 38OMa. U-Pb dating for the zircon from two samples of tonarite in the Asago-cho area yield ages of 282 and 285Ma respectively. Gabbro migmatite was discovered from the Lower gabbro member in the Asago-cho area, at where the partial melting process was well documented at the base of immature island arc.
3. Greenstones in the Jurassic accretionary complex : Greenstone of Masuda area shows the Sm-Nd isotopic ages of ca. 340Ma Alkaline basalt such as ankaramite was found from the greenstones in Mochigase-cho area, which shows very high Nb/Zr ratio that it was similar to HIMU basalt.
4. Cphiolite of other areas : Age determinations using Sm-Nd, Rb-Sr isochron methodand the U-Pb for zircon by SHRIMP were carried out about the Schmidt Peninsula ophiolite of the northern Sakhalin, and the ages ca. 125Ma were obtained. Metamorphic facies and geochemical analysis were enforced about the Mariana forearc ophiolite, and a resemblance with the Yakuno ophiolite was found.
5. construction of the geochemical data base : Data base system using "filemaker Pro ver. 3.O" was composed as a relational database for geochemistry.
6. Summary : A coeval activities from 350 to 400Ma among Paleozoic ophiolitic rocks such as fine-grained gabbro and diabase intruded in the Ce-yama ophiolite, the sea mount group of the Akiyoshi terrane, the gneissose metagabbro of the Yakuno ophiolite, greenstones in the Jurassic accretionary complex are prominent in Southwest Japan. The simultaneous activities might be occurred to make superplume lasted from Devonian to early Carboniferous time in the proto-Pacific region.
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Research Products
(14 results)
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[Publications] Sakashima, T., Takeshita, T., Itaya, T., andHayasaka, Y.: "Stratigraphy, geologic structures, and K-Ar ages of the Ryuhozan metamor phic rocks in western Kyushu, Japan." Jour.Geol.Soc.Japan. Vol.105-3. 161-180 (1999)
Description
「研究成果報告書概要(欧文)」より
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[Publications] Herzig, C.T., Kimbrough, D.L., Tainosho, Y., Kagami, S., Iizumi, S.and Hayasaka, Y.: "Late Cretaceous U/Pb zircon ages and Precambrian crustal inheritancein Ryoke belt granitoids, Kinki and Yanai districts, Japan." Geochemical Journal. vol.32. 21-31 (1998)
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「研究成果報告書概要(欧文)」より
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[Publications] Shimamoto, T., Hayasaka, Y., Shiota, T., Oda, M.and Takeshita, T., edrs.: "Tectonics and Metamorphism". Published by SOUBUN Co., Ltd., Tokyo, Japan, 404 (1996)
Description
「研究成果報告書概要(欧文)」より
