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-P06] Identification of oxide layer structures of ferromanganese nodules in the Minamitorishima EEZ using X-ray CT

*Ryo Shimomura1, Kentaro Nakamura1, Shiki Machida2,3, Kazutaka Yasukawa1,2, Koichiro Fujinaga2,1, Yasuhiro Kato1,2,3 (1.Department of Systems Innovation, School of Engeneering, The University of Tokyo, 2.ORCeNG, Chiba Institute of Technology, 3.JAMSTEC)

Keywords:ferromanganese nodules, X-ray CT analysis, Minamitorishima EEZ

In recent years, it has been discovered that ferromanganese nodules are densely distributed from the south to the east of the Japanese Exclusive Economic Zone (EEZ) around Minamitorishima [1]. Ferromanganese nodules in the Minamitorishima EEZ contain Co at the maximum of 0.65% and Ni at the maximum of 0.8% [2] and thus, expected as a future resource for the critical metals. To focus on the promising areas for the future development of the nodules, it is necessary to elucidate their origin. The internal structure of ferromanganese nodules is one of the most important keys to understanding the origin and growth history of the nodules.
In this study, we conducted X-ray CT analysis of the nodules from the Minamitorishima EEZ to nondestructively identify the internal structures of the nodules. As a result of the analysis, it was defined that the oxide layers of the nodules can be classified into 5 layers on the basis of the difference in X-ray absorption rate. We also found that the X-ray absorption rate corresponds to both the growth texture and chemical composition of the oxide layers. Moreover, several peaks were observed in the histograms of the total oxide layer thickness, and these peaks corresponded to number of oxide layers. This suggests that formations of ferromanganese nodules occur intensively during certain periods when each oxide layer starts growing.

[1] JAMSTEC (2016) press release, August 26, 2016.
[2] Machida et al. (2016) Geochemical Journal, 50, 539–555.