1993 Fiscal Year Final Research Report Summary
Development of crust in the island arcs
| Project/Area Number |
02402018
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| Research Category |
Grant-in-Aid for General Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Research Field |
鉱物学(含岩石・鉱床学)
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| Research Institution | The University of Tokyo |
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Principal Investigator |
KUSHIRO Ikuo The University of Tokyo, Graduate School of Science Professor, 大学院・理学系研究科, 教授 (80011526)
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| Co-Investigator(Kenkyū-buntansha) |
TADA Ryuji The University of Tokyo, Graduate School of Science Associate Professor, 大学院・理学系研究科, 助教授 (30143366)
MATSUMOTO Ryo The University of Tokyo, Graduate School of Science Professor, 大学院・理学系研究科, 教授 (40011762)
TAKAHASHI Hiroko (永原 裕子) The University of Tokyo, Graduate School of Science Associate Professor, 大学院・理学系研究科, 助教授 (80172550)
OZAWA Kasuhito The University of Tokyo, Graduate School of Science Associate Professor, 大学院・理学系研究科, 助教授 (90160853)
TORIUMI Mitsuhiro The University of Tokyo, Graduate School of Science Professor, 大学院・理学系研究科, 教授 (10013757)
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| Project Period (FY) |
1990 – 1993
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| Keywords | Island Arc / crust / mantle / magma / partial melting / xenolith / trace elements / peridotites |
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| Research Abstract |
Ptrological and geochemical studies on the crustal rocks rocks of Japanese Island arcs experimental studies on the upper mantle materials have been carried out during the three-year research period. The lower crustal rocks inferred from the xenolithic inclusions in basaltic rocks are mainly gabbro, amphibolite and granulite with basaltic compositions, which were most probably formed from basaltic magmas generated in the upper mantle. Many experimental studies were made on the origin of basaltic magmas in the upper mantle ; however, reliable compositions of partial melts formed from mantle peridotite have not been obtained. In the present studies, a new method using diamond aggregates was developed and reliable compositions of partial melts could be obtained over a pressure range from 10 to 30 kbar. Also, fractional melting and hydrous melting (with 0.1-1 wt.% H^2O) of peridotites were made and compositional changes of partial melts and the residues were determined. Strong effect of water on the degree of partial melting was demonstraed. The compositions of partial melts formed in mantle wedge obtained in these experiments are significantly more mafic than those of the crusts of the NE Honshu arc. This fact strongly suggests that thick ultramafic cumulates were formed during the formation of the crustal rocks of the NE Honshu arc. It is also suggested that the fertile mantle materials must have been supplied into the mantle wedge to form the crust of the NE Honshu arc.
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