日本地球惑星科学連合2015年大会

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セッション記号 S (固体地球科学) » S-CG 固体地球科学複合領域・一般

[S-CG57] 変動帯の構造・進化とダイナミクス

2015年5月27日(水) 18:15 〜 19:30 コンベンションホール (2F)

コンビーナ:*竹下 徹(北海道大学大学院理学院自然史科学専攻)、佐藤 比呂志(東京大学地震研究所地震予知研究センター)、尾鼻 浩一郎(海洋研究開発機構 地震津波海域観測研究開発センター)、西村 卓也(京都大学防災研究所)、深畑 幸俊(京都大学防災研究所)、加藤 愛太郎(名古屋大学大学院環境学研究科)、武藤 潤(東北大学大学院理学研究科地学専攻)、佐藤 活志(京都大学大学院理学研究科地球惑星科学専攻)、小平 秀一(海洋研究開発機構 地球内部ダイナミクス領域)、鷺谷 威(名古屋大学減災連携研究センター)、石山 達也(東京大学地震研究所)、松原 誠(防災科学技術研究所)、池田 安隆(東京大学大学院理学系研究科地球惑星科学専攻)

18:15 〜 19:30

[SCG57-P18] 丹沢山地マフィック変成岩の層状構造は転位クリープ起源?

*水野 那希1道林 克禎1 (1.静岡大学・理・地球科学)

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.