| Project/Area Number |
16540379
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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 |
Solid earth and planetary physics
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| Research Institution | The University of Tokyo |
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Principal Investigator |
OGAWA Masaki University of Tokyo, Graduate School of Arts and Sciences, Associate Professor, 大学院総合文化研究科, 助教授 (30194450)
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| Project Period (FY) |
2004 – 2006
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| Project Status |
Completed (Fiscal Year 2006)
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| Budget Amount *help |
¥3,700,000 (Direct Cost: ¥3,700,000)
Fiscal Year 2006: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 2005: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 2004: ¥2,200,000 (Direct Cost: ¥2,200,000)
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| Keywords | mantle convection / plate tectonics / magmatism / superplume / mantle evolution / numerical modeling / マントルの熱・化学的状態 / 数値シミュレーション / 数値モデル |
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| Research Abstract |
A series of realistic numerical models have been developed for the Earth' s mantle magmatism and mantle convection including plate tectonics. The numerical models show under what condition superplumes well develop in the Earth and how the dynamic behavior of superplumes has changed in the evolutionary history of the Earth' s mantle. More specifically, the numerical models show that:
(1) Superplumes naturally develop from the chemical differentiation by ridge volcanism and the mass transport by plate tectonics when the internal heating by the decay of radioactive elements is strong enough. Subducted oceanic crusts sediment on the core mantle boundary to form a pile strongly heated by the decaying radioactive elements ; the superplumes are compositionally dense but thermally buoyant, and are neutrally buoyant as a whole.
(2) The superplumes formed in this way were very hot in the Archean owing to the strong internal heating. Parts of the superplumes were detached and rose up to the surface as narrow plumes. The narrow plumes induced magma at great depth and frequently formed new plate boundaries when the plumes hit the lithosphere. The frequent plate boundary formation kept plate tectonics rather steady.
(3) As the internal heat source has decayed in the Earth's history, however, the activity of superplumes has also decayed. The plume activity has became more intermittent and new plate boundary formation has became rare. The rare formation of new plate boundary made plate tectonics intermittent, too.
The deep magma-generation in (2) is consistent with the observation of komatiiite in the Archean and the intermittent superplume activity is consistent with the Wilson cycle of continental drift. As a whole, the numerial models developed here well capture the overall features of the Earth's mantle evolution.
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