2005 Fiscal Year Final Research Report Summary
Geochronological research about the relation of Proterozoic rocks, western of Kolkata, with 1700Ma rocks in Nepal.
| Project/Area Number |
15540441
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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 | Kanto Gakuen University |
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Principal Investigator |
TAKIGAMI Yutaka Kanto Gakuen Univ., Department of Law, Professor, 法学部, 教授 (40206909)
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| Co-Investigator(Kenkyū-buntansha) |
SAKAI Harutaka Kyushu Univ., Graduate School of Social and Cultural Studies, Professor, 大学院・比較社会文化研究院, 教授 (90183045)
ORIHASHI Yuji Tokyo Univ., Earthquke Inst., Assistant, 地震研究所, 助手 (70313046)
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| Project Period (FY) |
2003 – 2005
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| Keywords | 40Ar-39Ar age / Rare Earth Element / Spidergram / 1700Ma / Proterizoic / Nepal / International reserch / India |
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| Research Abstract |
In peninsular India, there are Proterozoic Lavas extending large area. The ages of these rocks are reported 1500-1600 Ma by K-Ar and Rb-Sr dating methods and we have reported the relation of these rocks to the Dwar Khola dolerite (1600-1800Ma 40Ar-39Ar ages) from Siwalik of Sub-Himalaya, situated about 400km north, before. We have collected these samples in 2003 and report 40Ar-39Ar age results in this paper.
These volcanic rocks are situated in the Proterozoic metamorphic and granitic rocks and divided 4 parts ((Dalma, Dhanjori and Jagarnathpur, Ongabila). Plateau ages about 1700-1800 Ma as those of Nepal dolerites cannot be obtained.
All age spectrum show disturbed pattern by metamorphism or excess Ar pattern.
From these results, we conclude 5 ages for these volcanic rocks.
1)1800-2000Ma ; original age same as those of Nepal Dolerites.
2)1550-1670Ma ; original age or metamorphic age
3)1400Ma ; metamorphic age
4)950-1050Ma ; metamorphic age which is recognized in intruded rocks in Napier Complex, Antarctica.
5)450-550Ma ; metamorphic age corresponding to the Pan African Metamorphism.
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