2000 Fiscal Year Final Research Report Summary
Comparison of gabbroic inclusions derived from lower crust beneath the northeast Japan Arc, their ragiogenic ages and petrological significances.
| Project/Area Number |
09640540
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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 | NIIGATA UNIVERSITY |
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Principal Investigator |
FUJIBAYASHI Norie Faculty of Education and Human Science, NIIGATA UNIVERSITY, TITLE OF POSITION : Associate Professor, 教育人間科学部, 助教授 (20238603)
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| Project Period (FY) |
1997 – 2000
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| Keywords | ultramafic inclusions / mafic inclusions / Northeast Japan Arc / Izu-Ogasawara Arc / Fossa Magna / Island-arc tholeiite / oceanic tholeiite / alkali basalt |
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| Research Abstract |
Ultramafic and mafic inclusions from the Northeast Japan Arc, Izu-Ogasawara Arc and Fossa Magna Region were studied. Based on their mineral chemistries, most of them are interpreted to be cumulates from arc tholeiite, formed in magma chambers at the depth near the crust-mantle boundary. Some amphibole-poor ultramafic and mafic xenoliths from the lchinomegata maar ejecta and the Miocene Ogi basalt, however, are the cumulates formed by crystallization of oceanic tholeiite. Clinopyroxenites from the lchinomegata maar and olivine gabbro from the Miocene Atsumi dolerite are crystallized from alkali basalt magmas. Gabbronorites from the Fuji volcano and the Yatsugatake volcano are cumulates from dacitic magmas mixed with basaltic magmas. Sr isotope ratios of the inclusions from the Pliocene volcanics in Sanogawa area are low (0.7031-33), and able to be characterized as the products of back-arc magmatism in the Ancient Izu-Shichitou Arc. Some gabbroic inclusions from the Yatsugatake volcano have low Sr isotopic ratios (<0.7040) significant of the Izu=ogasawara arc volcanoes, and the others show high ivalues (>0.7040) significant of frontal volcanos in the Northeast Japan Arc. Sr isotope ratios of the most gabbroic inclusions from the Atsumi dolerite show low values (0.7032-33), but some olivine gabbros show high values (0.7038-39). Useful isochron ages are only determined for inclusions from the Atsumi area by Sm-Nd method. The ages are from 28 to 32 Ma for the olivine gabbros and 54 to 66 Ma for gabbros.
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Research Products
(8 results)
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[Publications] Nagao, T., Kakubuchi, S, Fujibayashi, N., Hase, Y.and Nagamine, S.: "Characteristics of trace elements, rare-earth elements, and Sr and Nd isotopic ratios of Amakusa-Shimoshima basalts, southern Kyushu."Ann.Rep.Center Instrumental Anal.Yamaguchi Univ.. 8. 38-43 (2000)
Description
「研究成果報告書概要(欧文)」より
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[Publications] Fujibayashi, N., Ymamoto, G., Nomura, T., Kagami, H.and Nagao, T.: "Basalt-andesite, and andesite-rhyolite magma mixing recorded in essential pyroclastics and gabbroic inclusions in the Houei Ejecta, Fuji Volcano."Mem.Geol.Soc.Japan. 53. 135-155 (1999)
Description
「研究成果報告書概要(欧文)」より
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