[S-CG56] Ocean Floor Geosciences

[SCG56-09] Geochemistry and distribution of REY-rich mud in the eastern off the Takuyo-Daigo Seamount within the Minamitorishima EEZ

*Koichiro Fujinaga^1,2, Kazutaka Yasukawa^3,1, Tatsuo Nozaki^4,2,1,5, Shiki Machida^1,2, Yutaro Takaya^6,2,1, Junichiro Ohta^1,2, Moei Yano³, Ryo Shimomura³, Erika Tanaka³, Kazuhide Mimura³, Koichi Horinouchi³, Kenji Matsumoto³, Yoichi Usui⁴, Hirofumi Yamamoto⁴, Kentaro Nakamura³, Yasuhiro Kato^2,3,1, KM17-14C cruise members (1.Ocean Resources Research Center for Next Generation, Chiba Institute of Technology, 2.Frontier Research Centerfor Energy and Resources, School of Engineering, The University of Tokyo, 3.Department of Systems Innovation, School of Engineering, The University of Tokyo, 4.Japan Agencyfor Marine-Earth Science and Technology, 5.Department of Planetology, Graduate Schoolof Science, Kobe University, 6.Department of Resources and Environmental Engineering School of Creative Science and Engineering, Waseda University)

Keywords:rare earth elements and yttrium (REY), REY-rich mud, deep-sea sediment, Minamitorishima Island, deep-sea mineral resources

In 2013, we discovered deep-sea sediment containing 400 – 8,000 ppm of total rare-earth elements and yttrium (REY), which was termed “REY-rich mud”, within the Japanese exclusive economic zone (EEZ) around the Minamitorishima Island (Kato et al., 2013; Iijima et al., 2016; Fujinaga et al., 2016; Ohta et al., 2016; Nakamura et al., 2016; Takaya et al., 2018; Yasukawa et al., 2018). To clarify the mineralogical/chemical characteristics and distribution of the REY-rich mud in the Minamitorishima EEZ, we conducted nine research cruises over five years. During the KM17-14C cruise by R/V KAIMEI from December 16th, 2017 to January 7th, 2018, we investigated the distribution of the REY-rich mud in the eastern off the Takuyo-Daigo Seamount within the Minamitorishima EEZ, one of the most promising areas for REY-rich mud development. We collected five sediment cores by piston/gravity coring, and implemented bulk chemical analyses by using inductively coupled plasma quadrupole mass spectrometry (ICP-QMS) for trace and rare-earth elements, and X-ray fluorescence (XRF) for major elements. In this presentation, we report the sedimentological and geochemical features of the deep-sea sediments including REY-rich mud, and discuss the distribution of the REY-rich mud in the eastern off the Takuyo-Daigo Seamount.