Japan Geoscience Union Meeting 2018

Presentation information

[JJ] Poster

M (Multidisciplinary and Interdisciplinary) » M-ZZ Others

[M-ZZ41] Marine manganese deposits: from basic to applied sciences

Wed. May 23, 2018 1:45 PM - 3:15 PM Poster Hall (International Exhibition Hall7, Makuhari Messe)

convener:Akira Usui(Marine Core Research Center, Kochi University), Yoshio Takahashi(Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo), Katsuhiko Suzuki(国立研究開発法人海洋研究開発機構・海底資源研究開発センター, 共同), Takashi Ito(Faculty of Education, Ibaraki University)

[MZZ41-P05] Geochemical features of ferromanganese nodules in the Minamitorishima EEZ

*Koichi Horinouchi1, Ryo Shimomura1, Kentaro Nakamura1, Shiki Machida2,3, Kazutaka Yasukawa1,2, Koichiro Fujinaga2,1, Tatsuo Nozaki3,4,2, Junji Torimoto3, Yasuhiro Kato1,2,3 (1.School of Engineering, Univ. Tokyo, 2.ORCeNG, Chiba Institute of Technology, 3.JAMSTEC, 4.Kobe Univ.)

Keywords:ferromanganese nodule, Deep-ocean mineral resources, Minamitorishima EEZ, critical metals, bulk chemical anaylsis

Ferromanganese (Fe-Mn) nodules are spherical solid materials mainly composed of Fe-Mn-(oxyhydr)oxides, which are widely distributed on the deep seafloor around the world. Because they are enriched in critical metals such as Co and Ni, they are expected as a potential resource for these elements.

In 2010, a dense field of Fe-Mn nodules was discovered for the first time on a small seamount approximately 300 km east of Minamitorishima Island, in the Japanese Exclusive Economic Zone (EEZ) [1]. Collected Fe-Mn samples are structurally and compositionally similar to Fe-Mn crusts in the Minamitorishima EEZ, suggesting that they originated from hydrogenetic precipitation of Fe-Mn-(oxyhydr)oxides [1].

In 2016, to investigate the distribution and variation in chemical composition of Fe-Mn nodules in the Minamitorishima EEZ, the cruise YK16-01 of R/V Yokosuka was conducted. During this cruise, we discovered several areas where Fe-Mn nodules were densely distributed in the eastern to southeastern part of the Minamitorishima EEZ. We collected Fe-Mn nodule samples by seven dives of the Shinkai 6500 in the eastern to southern parts of the Minamitorishima EEZ.

In this study, major and trace element analyses of collected samples have been performed to understand geochemical features, and the origin of Fe-Mn nodules in the Minamitorishima EEZ. In the presentation, we will discuss the cause of the variation in geochemical features and its implication for the growth process of the Fe-Mn nodules.

[1] Machida, S. et al. (2016) "Geology and geochemistry of ferromanganese nodules in the Japanese Exclusive Economic Zone around Minamitorishima Island." Geochemical Journal 50, 539-555.