[M-IS13] New frontiers in geology

[MIS13-P10] Origin and depositional setting of hematite-quartz schist of Sanbagawa metamorphic rocks in the Nagatoro area, Kanto Mountains, Japan

*Moei Yano^1,2, Kazutaka Yasukawa², Tatsuo Nozaki^3,2,4,1, Koichiro Fujinaga^1,2, Mitsuki Ogasawara², Kentaro Nakamura^2,1, Yasuhiro Kato^2,1 (1.Chiba Institute of Technology, 2.The University of Tokyo, 3.JAMSTEC, 4.Kobe University)

Keywords:umber, hematite-quartz schist, hydrothermal ferromanganese sediment, Sanbagawa metamorphic Belt, bulk geochemistry

A number of strata-bound Fe-Mn and Mn ore deposits are distributed in the Japanese accretionary complexes. Studies on these deposits have been limited to weakly metamorphosed geological units such as the Chichibu and Shimanto Belts. In the Nagatoro area in Kanto Mountains, central Japan, belonging to the Sanbagawa high-P/T metamorphic belt, basic schist, quartz schist, and psammitic/pelitic schist are mainly distributed, and the hematite-quartz schist also occurs with these schists. The hematite-quartz schist constitutes alternate layers of muddy, dark reddish-purple and siliceous, reddish-brown portions. We hypothesized that the schist is a strata-bound Fe-Mn ore (umber) originating from hydrothermal ferromanganese sediment and has undergone the Sanbagawa metamorphism. In this study, we analyzed the major- and trace-element composition of the muddy and siliceous portions of the hematite-quartz schist. In this presentation, we report the results of the analyses and discuss the origin and depositional setting of the Nagatoro hematite-quartz schist.