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

• Kameda, Jun

• Inoue, Sayako

• Tanikawa, Wataru

• Yamaguchi, Asuka

• Hamada, Yohei

• Hashimoto, Yoshitaka

• Kimura, Gaku

書誌事項

タイトル別名

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

抄録

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.

収録刊行物

• Earth planets and space

  Earth planets and space 69 52-, 2017-04-18

  Springer

キーワード

• Space and Planetary Science
• Geology

詳細情報

• CRID: 1050282814000774528
• NII論文ID: 120006333808
• DOI: 10.1186/s40623-017-0635-1
• HANDLE: 2115/66991
• ISSN: 18805981
• Web Site: http://link.springer.com/content/pdf/10.1186/s40623-017-0635-1.pdf
• Web Site: http://link.springer.com/article/10.1186/s40623-017-0635-1/fulltext.html
• 本文言語コード: en
• 資料種別: journal article
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