Japan Geoscience Union Meeting 2015

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Oral

Symbol S (Solid Earth Sciences) » S-CG Complex & General

[S-CG57] Structure, evolution and dynamics of mobile belts

Wed. May 27, 2015 4:15 PM - 6:00 PM A06 (APA HOTEL&RESORT TOKYO BAY MAKUHARI)

Convener:*Toru Takeshita(Department of Natural History Sciences, Graduate School of Science, Hokkaido University), Hiroshi Sato(Earthquake Prediction Research Center, Earthquake Research Institute, The University of Tokyo), Koichiro Obana(Research and Development Center for Earthquake and Tsunami, Japan Agency for Marine-Earth Science and Technology), Takuya NISHIMURA(Disaster Prevention Research Institute, Kyoto University), Yukitoshi Fukahata(Disaster Prevention Research Institute, Kyoto University), Aitaro Kato(Graduate School of Environmental Studies, Nagoya University), Jun Muto(Department of Earth Sciences, Tohoku University), Katsushi Sato(Division of Earth and Planetary Sciences, Graduate School of Science, Kyoto University), Shuichi Kodaira(Institute for Research on Earth Evolution Japan Agency for Marine-Earth Science and Technology), Takeshi Sagiya(Disaster Mitigation Research Center, Nagoya University), Tatsuya Ishiyama(Earthquake Research Institute, University of Tokyo), Makoto MATSUBARA(National Research Institute for Earth Science and Disaster Prevention), Yasutaka Ikeda(Department of Earth and Planetary Science, Graduate School of Science, University of Tokyo), Chair:Bunichiro Shibazaki(International Institute of Seismology and Earthquake Engineering, Building Research Institute)

5:18 PM - 5:21 PM

[SCG57-P18] Dislocation creep induced layer structures ? in mafic rocks, Tanzawa Mountain

3-min talk in an oral session

*Tomoki MIZUNO1, Katsuyoshi MICHIBAYASHI1 (1.Institute of Geosciences, Shizuoka University)

Tanzawa plutonic complex is located in the northen part of Izu-Bonin-Mariana (IBM) arc. The complex has been exposed by the collision of IBM arc and Japan islands. The exposed process is related to uplifting of Tanzawa plutonic complex along the Kannawa fault. Mafic rocks near the Tanzawa plutonic complex show metamorphosed and deformed textures. The purpose of this study is to reveal microstructures of metamorphosed mafic rocks occurred near the Tanzawa plutonic complex. They are highly deformed and show well-developed layer structures. The mafic rocks consist mainly of amphibole and plagioclase. Amphibole grains are elongated. Plagioclase grains are polygonal. The mean grain sizes of amphibole are in a range between 30 and 110 micron, whereas those of plagioclase are in a range between 25 and 115 micron. Within the well layered rocks, aspect ratios become smaller, as increasing grain sizes. Crystal-preferred orientations (CPOs) of amphibole and plagioclase were measured by a scanning electron microscope (SEM) equipped with electron back-scattered diffraction (EBSD). Amphibole CPOs show (100) [001] patterns. Plagioclase CPOs show (001) [100] patterns. It suggests that their deformation mechanisms are dominantly dislocation creep. Some elongated amphibole grains have grain boundaries perpendicular to the foliations, which appear to be also an evidence of dislocation creep. Consequently, the mafic rocks could result from dislocation creep during the development of layer structures associated with uplifting of the Tanzawa plutonic complex.