Japan Geoscience Union Meeting 2018

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[JJ] Poster

B (Biogeosciences) » B-BG Biogeosciences & Geosphere-Biosphere Interactions

[B-BG02] Interrelation between Life, Water, Mineral, and Atmosphere

Mon. May 21, 2018 1:45 PM - 3:15 PM Poster Hall (International Exhibition Hall7, Makuhari Messe)

convener:Ken Takai(Extremobiosphere Research Center, Japan Agency for Marine-Earth Science & Technology), Kentaro Nakamura(Department of Systems Innovation, School of Engineering, University of Tokyo), Yuichiro Ueno(東京工業大学大学院地球惑星科学専攻, 共同), Yohey Suzuki(Graduate School of Science, The University of Tokyo)

[BBG02-P06] Fe-kaolinite formed in granite saprolite beneath sedimentary kaolin deposits

*Tetsuichi Takagi1, Mayumi Jige2, Yoshio Takahashi3, Minako Kurisu3, Yuki Tsunazawa1, Kazuya Morimoto1, Mihoko Hoshino1, Katsuhiro Tsukimura1 (1.Geological Survey of Japan, AIST, 2.Osaka-Ohtani University, 3.University of Tokyo)

Keywords:kaolin, granite saprolite, XAFS

Fe-kaolinite was found from granite saprolite underneath sedimentary kaolin deposits in the Seto district. The clay fractions of granite saprolite consist mostly of kaolinite with subordinate micaceous clay, quartz and feldspars. The kaolinite in clay fractions contained an average 3.30-3.72 wt. % of Fe2O3, indicative of Fe-kaolinite. Fe+Si was inversely proportional to Al in Fe-kaolinite, indicating coupled substitution between Fe+Si and Al. XANES spectroscopy showed that about 60 to 70 % of Fe in the clay fractions is ferric iron, and EXAFS spectroscopy indicated that Fe is situated in octahedral sites replacing Al. The features of Fe-kaolinite suggest that Fe oxidation occurred with mineral decomposition and elemental leaching during the kaolinization of sedimentary kaolin deposits.