TERRAPUB Geochemical Journal
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Geochemical Journal, Vol. 50 (No. 6), pp. 557-573, 2016
doi:10.2343/geochemj.2.0431

Discovery of extremely REY-rich mud in the western North Pacific Ocean

Koichi Iijima,1 Kazutaka Yasukawa,2,3 Koichiro Fujinaga,3,4 Kentaro Nakamura,2 Shiki Machida,1 Yutaro Takaya,5 Junichiro Ohta,6 Satoru Haraguchi,6 Yoshiro Nishio,7 Yoichi Usui,1 Tatsuo Nozaki,1,4,8 Toshitsugu Yamazaki,9,10 Yuji Ichiyama,11 Akira Ijiri,12,1 Fumio Inagaki,12,1 Hideaki Machiyama,1 Katsuhiko Suzuki,1 Yasuhiro Kato4,3,2,1* and KR13-02 Cruise Members

1Research and Development Center for Submarine Resources, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka, Kanagawa 237-0061, Japan
2Department of Systems Innovation, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
3Ocean Resources Research Center for Next Generation, Chiba Institute of Technology, 2-17-1 Tsudanuma, Narashino, Chiba 275-0016, Japan
4Frontier Research Center for Energy and Resources, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
5Department of Resources and Environmental Engineering, School of Creative Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjyuku-ku, Tokyo 169-8555, Japan
6Department of Solid Earth Geochemistry, JAMSTEC, 2-15 Natsushima-cho, Yokosuka, Kanagawa 237-0061, Japan
7Department of Marine Resource Sciences, Faculty of Agriculture and Marine Science, Kochi University, 200 Monobe Otsu, Nankoku, Kochi 783-8502, Japan
8Department of Planetology, Graduate School of Science, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe, Hyogo 657-8501, Japan
9Department of Ocean Floor Geoscience, Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8564, Japan
10Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8561, Japan
11Department of Earth Sciences, Faculty of Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
12Kochi Institute for Core Sample Research, JAMSTEC, 200 Monobe Otsu, Nankoku, Kochi 783-8502, Japan

(Received March 31, 2015; Accepted June 25, 2016)

Abstract: We have discovered deep-sea mud that is extremely enriched in rare-earth elements and yttrium (together called REY) in the Japanese Exclusive Economic Zone around Minamitorishima Island, in the western North Pacific Ocean. The maximum total REY concentration reaches approximately 7000 ppm, which is much higher than that reported for conventional REY deposits on land and other known potential REY resources in the ocean. The extremely REY-rich mud is characterized by abundant phillipsite and biogenic calcium phosphate. In addition, the stratigraphic layer with the highest REY concentration occurs just ~3 m beneath the seafloor. The shallow burial of these strata together with the high REY content, especially those of heavy rare-earth elements, suggest that the newly discovered extremely REY-rich mud may be a promising REY resource.
We have discovered deep-sea mud that is extremely enriched in rare-earth elements and yttrium (together called REY) in the Japanese Exclusive Economic Zone around Minamitorishima Island, in the western North Pacific Ocean. The maximum total REY concentration reaches approximately 7000 ppm, which is much higher than that reported for conventional REY deposits on land and other known potential REY resources in the ocean. The extremely REY-rich mud is characterized by abundant phillipsite and biogenic calcium phosphate. In addition, the stratigraphic layer with the highest REY concentration occurs just ~3 m beneath the seafloor. The shallow burial of these strata together with the high REY content, especially those of heavy rare-earth elements, suggest that the newly discovered extremely REY-rich mud may be a promising REY resource.
Key words: extremely REY-rich mud, rare-earth elements, deep-sea mineral resources, Minamitorishima Island, western North Pacific Ocean


*Corresponding author E-mail: ykato@sys.t.u-tokyo.ac.jp


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