1996 Fiscal Year Final Research Report Summary
Modeling for the development of the crust
| Project/Area Number |
06302031
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 総合 |
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| Research Field |
Petrology/Mineralogy/Science of ore deposit
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
HIRAJIMA Takao Graduate School of Earth Science, Associate Professor., 大学院理学研究科, 助教授 (90181156)
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| Co-Investigator(Kenkyū-buntansha) |
OBATA Masaaki Kumamoto Univ., Professor., 理学部, 教授 (20126486)
TAGIRI Michio Ibaragi Univ., Professor., 理学部, 教授 (50007829)
KITAMURA Masao Kyoto Univ., Professor., 大学院理学研究科, 教授 (70004489)
MITUHIRO Toriumi Tokyo Univ., Professor., 大学院理学研究科, 教授 (10013757)
HIROI Yoshikuni Chiba Univ., Professor., 理学部, 教授 (40019427)
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| Project Period (FY) |
1994 – 1996
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| Keywords | Memamorphism / Modeling / P-T path / Rock texture / Migmatite / Ultrahigh-pressure rock |
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| Research Abstract |
This research was organized to construct a quantitative nemerical model for repressenting the rock forming mechanism and kinematic process in the lower crust using the high quality natural data on petrology, mineralogy, geochemistry and continuum dynamics. The study group is composed of a "data collection" group and "modeling" group.
1) In Sanbagawa belt, the difference of subduction path between neighboring regions is deciphered. It became clear that the direction of the uplift of the belt is parallel to the trend of the subduction direction.
2) In Abukuma and Ryoke belts, partial melting took place in a wider area of the higher grade parts than hitherto recognized. New dating techniques such as SHRIMP and CHIME make clear the protolith and metamophic timings of these belts. Many sector zoned garnets were found from the higher grade parts of these belts. The growth of such garnet and the abrupt texture change from schistose to gneissose in the higher grade parts were ascribed to the par
… More
tial melting of crustal material in the higher grade part. An hypothesis on the thermal source of the Ryoke belt ascribed to the subduction of the oceanic ridge was denied by this study.
3) In the Su-Lu region, the transition of igneous rocks to ultrahigh pressure (UHP) rocks, and the overprinting of medium pressure (MP) assemblage on the UHP rocks are clarified, which demonstrated that some MP orthogneiss of the Su-Lu region were once located in the depth of 100km depth and that the decomposition process of UHP rocks are fairly rapid without significant cooling.
4) 2-dimensional X-ray mappings reveal that the irreversible crystallization in over-saturated system, realized by overstepping of univarinat line, is common even in the higher grade metamorphic rocks, and that the element exchange took place even in the core of the garnet in the lower grade rock. These fact suggest that the careful treatment is need to determine the P-T-t path of metamorphic rock by inversion analyzes.
5) These data give quantitative constraints on the modeling. The guide line for producing the quantitative numerical model for explaining various physical phenomenons in the lower crust is proposed. Less
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