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Hydrogeological responses to incoming materials at the erosional subduction margin, offshore Osa Peninsula, Costa Rica

Kameda_et_al-2015-Geochemistry,_Geophysics,_Geosystems.pdf5.74 MBPDF見る/開く

タイトル: Hydrogeological responses to incoming materials at the erosional subduction margin, offshore Osa Peninsula, Costa Rica
著者: Kameda, Jun 著作を一覧する
Harris, Robert N. 著作を一覧する
Shimizu, Mayuko 著作を一覧する
Ujiie, Kohtaro 著作を一覧する
Tsutsumi, Akito 著作を一覧する
Ikehara, Minoru 著作を一覧する
Uno, Masaoki 著作を一覧する
Yamaguchi, Asuka 著作を一覧する
Hamada, Yohei 著作を一覧する
Namiki, Yuka 著作を一覧する
Kimura, Gaku 著作を一覧する
発行日: 2015年 9月
出版者: American Geophysical Union
誌名: Geochemistry geophysics geosystems
巻: 16
号: 8
開始ページ: 2725
終了ページ: 2742
出版社 DOI: 10.1002/2015GC005837
抄録: Bulk mineral assemblages of sediments and igneous basement rocks on the incoming Cocos Plate at the Costa Rica subduction zone are examined by X-ray diffraction analyses on core samples. These samples are from Integrated Ocean Drilling Program Expedition 334 reference Site U1381, similar to 5 km seaward of the trench. Drilling recovered approximately 100 m of sediment and 70 m of igneous oceanic basement. The sediment includes two lithologic units: hemipelagic clayey mud and siliceous to calcareous pelagic ooze. The hemipelagic unit is composed of clay minerals (similar to 50 wt.%), quartz (similar to 5 wt.%), plagioclase (similar to 5 wt.%), calcite (similar to 15 wt.%) and similar to 30 wt.% of amorphous materials, while the pelagic unit is mostly made up of biogenic amorphous silica (similar to 50 wt.%) and calcite (similar to 50 wt.%). The igneous basement rock consists of plagioclase (similar to 50-60 wt.%), clinopyroxene (similar to>25 wt.%), and saponite (similar to 15-40 wt.%). Saponite is more abundant in pillow basalt than in the massive section, reflecting the variable intensity of alteration. We estimate the total water influx of the sedimentary package is 6.9 m(3)/yr per m of trench length. Fluid expulsion models indicate that sediment compaction during shallow subduction causes the release of pore water while peak mineral dehydration occurs at temperatures of approximately similar to 100 degrees C, 40-30 km landward of the trench. This region is landward of the observed updip extent of seismicity. We posit that in this region the presence of subducting bathymetric relief capped by velocity weakening nannofossil chalk is more important in influencing the updip extent of seismicity than the thermal regime.
資料タイプ: article
出現コレクション:雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

提供者: 亀田 純


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