| Project/Area Number |
13304042
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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 | Chiba University |
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Principal Investigator |
KANAGAWA Kyuichi Chiba University, Department of Earth Sciences, Associate Professor, 理学部, 助教授 (40185898)
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| Co-Investigator(Kenkyū-buntansha) |
TAKESHITA Toru Hiroshima University, Department of Earth and Planetary Systems Science, Professor, 大学院・理学研究科, 教授 (30216882)
HIROI Yoshikuni Chiba University, Department of Earth Sciences, Professor, 理学部, 教授 (40019427)
ITO Tanio Chiba University, Department of Earth Sciences, Professor, 理学部, 教授 (50111448)
ANDO Jun-ichi Hiroshima University, Department of Earth and Planetary Systems Science, Research Associate, 大学院・理学研究科, 助手 (50291480)
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| Project Period (FY) |
2001 – 2003
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| Project Status |
Completed (Fiscal Year 2003)
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| Budget Amount *help |
¥51,740,000 (Direct Cost: ¥39,800,000、Indirect Cost: ¥11,940,000)
Fiscal Year 2003: ¥4,420,000 (Direct Cost: ¥3,400,000、Indirect Cost: ¥1,020,000)
Fiscal Year 2002: ¥9,750,000 (Direct Cost: ¥7,500,000、Indirect Cost: ¥2,250,000)
Fiscal Year 2001: ¥37,570,000 (Direct Cost: ¥28,900,000、Indirect Cost: ¥8,670,000)
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| Keywords | superplastic flow / deformation microstructure / EBSD / crystallographic preferred orientation / mylonite / granite / gabbro / peridotite / ハンレイ岩マイロナイト / CPO / 斜長石 / 斜方輝石 / 巣斜輝石 / 単斜輝石 |
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| Research Abstract |
We have made detail microstructural observations and crystallographic orientation analyses of constituent minerals using an electron backscatter diffraction (EBSD) technique on granite mylonites along the Hatagawa Shear Zone in the Abukuma Mountains, and gabbro mylonites and a peridotite mylonite both from the Hidaka metamorphic belt. These mylonites were formed in the middle crust, the lower crust and the uppermost mantle, respectively.
Although strain is localized in these mylonites into fine-grained (【less than or equal】50 μm) polymineralic aggregate mainly composed of reaction products, its main constituent mineral grains show neither shape nor crystallographic preferred orientations. This indicates that the fine-grained polymineralic aggregate in these mylonites is deformed by grain boundary sliding, verifying superplastic flow in the crust and mantle.
The fine-grained polymineralic aggregate is forming a stress-supporting network in the granite ultramylonite and in the peridotite mylonite, implying superplastic flow of these mylonites. In contrast, it is plagioclase aggregate which is forming a stress-supporting network in the gabbro ultrarmylonite. Because plagioclase grains develop both shape and crystallographic preferred orientations, the plagioclase aggregate is deformed by dislocation creep. Hence the rheology of the gabbro ultramylonite is approximated by crystal plastic flow of plagioclase, but not by superplastic flow.
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