2018 Fiscal Year Final Research Report
Investigation on upper mantle heterogeneity through sea-floor spreading system
| Project/Area Number |
15H03717
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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 |
Solid earth and planetary physics
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| Research Institution | Kobe University |
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Principal Investigator |
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| Co-Investigator(Kenkyū-buntansha) |
三ヶ田 均 京都大学, 工学研究科, 教授 (10239197)
松野 哲男 神戸大学, 海洋底探査センター, 特命講師 (80512508)
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| Research Collaborator |
Nakakuki Tomoeki
Nakahigashi Kazuo
Nogi Yoshifumi
Morishita Tomoaki
Sato Hiroshi
Harigane Yumiko
Ogawa Kazunori
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| Project Period (FY) |
2015-04-01 – 2019-03-31
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| Keywords | 海洋底地球科学 / 上部マントル比抵抗構造 / マントル不均質 / 海底拡大系 / 背弧海盆 |
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| Outline of Final Research Achievements |
Our main results of 2-D electrical resistivity structure and of numerical simulation lead us to propose a hypothesis that the low viscosity region in the mantle wedge due to hydration driven by water release from the subducting slab results in highly asymmetric seafloor spreading, which is commonly recognized in many back-arc basins. The resistivity structure was imaged through marine magnetotelluric experiment across a spreading segment in the Southern Mariana Trough back-arc basin. This result shows that a low resistivity region exists beneath the spreading axis and is asymmetrically extended to the subducting slab; the low resistivity region is interpreted as asymmetric melting in the mantle wedge due to hydration driven by water release from the subducting slab. Further, numerical simulation results indicate that the spreading axis is kept locating above the low viscosity mantle zone that capture the mantle upwelling zone due to water release from the subducting slab.
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| Free Research Field |
海底物理学
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| Academic Significance and Societal Importance of the Research Achievements |
背弧海盆の形成では、その初期には非対称な海洋底拡大を伴っていることが多い。上部マントルの拡大軸に対しての非対称な比抵抗構造と、背弧拡大の変遷を示す数値モデリングの結果から、非対称な海洋底拡大の要因を説明するモデルを提案し、背弧海盆形成の新しい知見が得られた。すなわち、スラブから脱水した水により上部マントルに不均質な構造が生じ、水による粘性低下などにより、非対称な海洋底拡大が起こることが分かった。
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