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Alteration and dehydration of subducting oceanic crust within subduction zones : implications for decollement step-down and plate-boundary seismogenesis

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Please use this identifier to cite or link to this item:http://hdl.handle.net/2115/66991

Title: Alteration and dehydration of subducting oceanic crust within subduction zones : implications for decollement step-down and plate-boundary seismogenesis
Authors: Kameda, Jun Browse this author
Inoue, Sayako Browse this author
Tanikawa, Wataru Browse this author
Yamaguchi, Asuka Browse this author
Hamada, Yohei Browse this author
Hashimoto, Yoshitaka Browse this author
Kimura, Gaku Browse this author
Issue Date: 18-Apr-2017
Publisher: Springer
Journal Title: Earth planets and space
Volume: 69
Start Page: 52
Publisher DOI: 10.1186/s40623-017-0635-1
Abstract: The alteration and dehydration of predominantly basaltic subducting oceanic crustal material are thought to be important controls on the mechanical and hydrological properties of the seismogenic plate interface below accretionary prisms. This study focuses on pillow basalts exposed in an ancient accretionary complex within the Shimanto Belt of southwest Japan and provides new quantitative data that provide insight into clay mineral reactions and the associated dehydration of underthrust basalts. Whole-rock and clay-fraction X-ray diffraction analyses indicate that the progressive conversion of saponite to chlorite proceeds under an almost constant bulk-rock mineral assemblage. These clay mineral reactions may persist to deep crustal levels (similar to 320 degrees C), possibly contributing to the bulk dehydration of the basalt and supplying fluid to plate-boundary fault systems. This dehydration can also cause fluid pressurization at certain horizons within hydrous basalt sequences, eventually leading to fracturing and subsequent underplating of upper basement rock into the overriding accretionary prism. This dehydration-induced breakage of the basalt can explain variations in the thickness of accreted basalt fragments within accretionary prisms as well as the reported geochemical compositions of mineralized veins associated with exposed basalts in onland locations. This fracturing of intact basalt can also nucleate seismic rupturing that would subsequently propagate along seismogenic plate interfaces.
Rights: https://creativecommons.org/licenses/by/4.0/
Type: article
URI: http://hdl.handle.net/2115/66991
Appears in Collections:理学院・理学研究院 (Graduate School of Science / Faculty of Science) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 亀田 純

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