1998 Fiscal Year Final Research Report Summary
Geodynamics of generation of oceanic crust-an example of the Oman ophiolite
| Project/Area Number |
09041101
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| Research Category |
Grant-in-Aid for international Scientific Research
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| Allocation Type | Single-year Grants |
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| Section | Field Research |
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| Research Field |
Geology
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| Research Institution | Niigata University |
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Principal Investigator |
MIYASHITA Sumio Niigata Univ., Faculty of Science, Professor, 理学部, 教授 (60200169)
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| Co-Investigator(Kenkyū-buntansha) |
TAKAZAWA Eiichi Niigata Univ., Faculty of Science, Lecturer, 理学部, 講師 (80222082)
ISHIKAWA Tsuyoshi Shizuoka Univ., Faculty of Science, Lecturer, 理学部, 講師 (30270979)
UMINO Susumu Shizuoka Univ., Faculty of Science, Associate Professor, 理学部, 助教授 (30192511)
川幡 穂高 地質調査所, 海洋地質部, 主任研究官
ARAI Shoji Kanazawa Univ., Faculty of Science, Professor, 理学部, 教授 (20107684)
MASUDA Toshiaki Shizuoka Univ., Faculty of Science, Professor (20107684)
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| Project Period (FY) |
1997 – 1998
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| Keywords | ophiolite / oceanic crust / Oman / mantle / layered gabbro |
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| Research Abstract |
The results obtained from this research project are summarized for each group.
Mantle group clarified an interaction between melt and mantle in the mantle-crust transition zone. Also they round the interaction was quite hetrogenous palce to place. Analyses of spinel using river sand show that the mantle peridotites of the Oman ophiolite are highly depleted compared to oceanic mantle, suggesting that signiricant modification or the mantle peridotite occured during later island arc stage.
Gabbro group round two series of gabbros previously regarded as successive complex, which were formed at advancing and dying magma chambers beneath ocean ridges, respectively. This is explained by overlapping ocean ridges where propagation and retreating or ridges appeared. The central part of ridge segment where thick Moho transition zone occurs was determined through regional detailed geological mapping in the northern Oman ophiolite. From the central part to the tip or ridge segmenl, mineral compositions or layered gabbro varies systematically from less evolved to more evolved compositions.
Upper crust group measured direction and thickness of dikes from extensive area in the northern Oman ophiolite. They found that the direction of dikes varies for each several km length, indicating the smallest order of segmentation of ocean ridges. The thickness of dikes increases from the central part to tip of the ridge segment in more large scale which is presumed from the petrological features of gabbro and mantle peridotite.
Structural group found two different mineral lineations on foliation plane in the metamorphic sole beneath the Oman ophiolite. Also they clarified that the degree of preferred orientation is quite various even in one outcrop.
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