伊豆・小笠原弧のスミスリフト : 海洋性島弧における背弧リフトの形成の一例(<特集>ユーラシア東縁における白亜紀-中新世テクトニクス-リフティングはいかに準備されたか-)

概要

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The Philippine Sea has been formed through the episodic backarc rifting- and spreading. Newest and active backarc rifting was found along the volcanic front of the Izu-Bonin Arc. We presented newly obtained data concerning the Sumisu Rift, a backarc rift of the Izu-Bonin Arc to understand the Tohoku Arc in the Miocene related to the opening of the Japan Sea. The Sumisu Rift is situated near behind the volcanic front between the Sumisujima and Torishima islands, including the sedimentary basins with about 2000m deep. This rift has been formed by a normal faulting with a N-S trend since about 2 Ma. In the rift, a backarc volcanism dominated by basalt (BABB) with a small amount of dacite and rhyolite has been continued after the rift initiation and formed small bodies of volcanoes. The sedimentation in the rift basin is dominated by hemipelagite and arc-derived ashes, especially thick pumice deposits after 0.2 Ma and the burying of the basin has rapidly proceeded.
地学団体研究会の論文
1991-09-25