| Project/Area Number |
25400510
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Multi-year Fund |
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| Section | 一般 |
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| Research Field |
Petrology/Mineralogy/Economic geology
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| Research Institution | Niigata University |
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Principal Investigator |
Shuto Kenji 新潟大学, 自然科学系, 名誉教授 (50143748)
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| Co-Investigator(Kenkyū-buntansha) |
OSANAI Yasuhito 九州大学, 比較社会文化研究科(研究院), 教授 (80183771)
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| Project Period (FY) |
2013-04-01 – 2016-03-31
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| Project Status |
Completed (Fiscal Year 2015)
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| Budget Amount *help |
¥4,810,000 (Direct Cost: ¥3,700,000、Indirect Cost: ¥1,110,000)
Fiscal Year 2015: ¥1,040,000 (Direct Cost: ¥800,000、Indirect Cost: ¥240,000)
Fiscal Year 2014: ¥1,560,000 (Direct Cost: ¥1,200,000、Indirect Cost: ¥360,000)
Fiscal Year 2013: ¥2,210,000 (Direct Cost: ¥1,700,000、Indirect Cost: ¥510,000)
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| Keywords | 東北日本弧 / 島弧横断変化 / 島弧玄武岩 / HFSE / 沈み込み成分 / depleted MORB mantle / アセノスフェア / Sr,Nd同位体比 / DMM / Sr-Nd同位体組成 / 奥尻島 / 高MgOアダカイト質安山岩 / 高TiO2玄武岩 / スラブメルティング / 冷たい沈み込み帯 / 青苗川層 / アダカイト質安山岩 / カルクアルカリ質安山岩 / 大陸地殻 / マグマ混合 / 結晶分化作用 |
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| Outline of Final Research Achievements |
To investigate the nature and origin of across-arc geochemical variations over time in mantle wedge-derived magmas, we have carried out a geochemical examination of arc basalts spanning an age range of 35 Ma to the present in the NE Japan arc. Back-arc basalts erupted at 24-18 Ma, 10-8 Ma, 6-3 Ma and 2.5-0 Ma have higher contents of both HFSE and REE, and incompatible trace element ratios compared to frontal-arc basalts at any given time. Geochemical modeling using Nb/Yb- Nb shows that the frontal-arc and back-arc compositional differences independent of subduction modification can be explained by different degrees of melting (higher degrees of melting for frontal-arc magmas and lower degrees of melting for back-arc magmas) of a nearly homogeneous DMM-like source. We proposed a depleted asthenospheric mantle upwelling model with interaction between asthenospheric mantle-derived magma and overlying lithospheric mantle to explain geochemical characteristics for 35-0 Ma NEJ basalts.
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