1998 Fiscal Year Final Research Report Summary
Experimental Study on the genesis of flood basalt magma
| Project/Area Number |
08404032
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Petrology/Mineralogy/Science of ore deposit
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| Research Institution | University of Tokyo |
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Principal Investigator |
FUJII Toshitsugu Earthquake Res.Inst., University of Tokyo, Professor, 地震研究所, 教授 (00092320)
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| Co-Investigator(Kenkyū-buntansha) |
YASUDA atsushi Ibid., University of Tokyo, Res. Associate, 地震研究所, 助手 (70222354)
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| Project Period (FY) |
1996 – 1998
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| Keywords | flood basalt / Oceanic crust / magma / composite plume / high pressure experiments / partial melting |
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| Research Abstract |
The purpose of the present study is to evaluate the composite-plume model as a source material for continental flood basalt based on the melting experiments at high pressure. Melting experiments have been performed on the composition of MORB which is believed to represent averaged composition of oceanic crust, containing about 9 wt % of MgO. High pressure experiments were done by piston cylinder apparatus at pressure below 2 Gpa, and by multi-anvil apparatus, which was designed and built through this grant, above 2 Gpa. Based on the melting experiments at one atmosphere, composition of pristine magma of Deccan flood basalts was estimated eliminating the effects of low pressure fractional crystallization differentiation. It was concluded that the pristine magma could not be derived from any partial melt of mantle peridotite based on the elemental partitioning data determined through this study. It was shown that the expected major and trace element composition of partial melts of the composite plume, which is composed of the ancient oceanic crust and mantle peridotite, is consistent with the continental flood basalts. Combining the computer simulation on the ascent of the composite plume, it was concluded that the composite plume containing 10 % of oceanic crust can produce Deccan flood basalts magma by partial melting at pressure of 3 Gpa. It is also suggested that similar arguments are applicable for the continental flood basalts in other provinces and for some ocean island basalts.
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