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Geochemical Journal
Geochemical Journal An open access journal for geochemistry
Published for geochemistry community from Geochemical Society of Japan.

Geochemistry of REY-rich mud in the Japanese Exclusive Economic Zone around Minamitorishima Island

Koichiro Fujinaga, Kazutaka Yasukawa, Kentaro Nakamura, Shiki Machida, Yutaro Takaya, Junichiro Ohta, Shuhei Araki, Hanjie Liu, Ryo Usami, Ryota Maki, Satoru Haraguchi, Yoshiro Nishio, Yoichi Usui, Tatsuo Nozaki, Toshitsugu Yamazaki, Yuji Ichiyama, Akira Ijiri, Fumio Inagaki, Hideaki Machiyama, Koichi Iijima, Katsuhiko Suzuki, Yasuhiro Kato, KR13-02, MR13-E02 Leg 2 and KR14-02 Cruise Members
Geochemical Journal, Vol. 50, No. , P. 575-590, 2016

ABSTRACT

We report detailed lithological and chemical characteristics of deep-sea sediments, including rare-earth elements and yttrium-rich mud (REY-rich mud), in the Japanese Exclusive Economic Zone (EEZ) around Minamitorishima Island. Three research cruises obtained fourteen sediment cores collected by piston coring. Based on the visual descriptions and geochemical analysis of the sediment cores, we confirm the presence of REY-rich mud containing more than 400 ppm total REY (∑REY) in the southern and northwestern areas of the Minamitorishima EEZ. The REY-rich mud layers are characterized by abundant grains of phillipsite, biogenic calcium phosphate, and manganese oxides, and are widely distributed in relatively shallow depths beneath the seafloor. In contrast, relatively thick, non-REY-rich mud lies near the seafloor in the northern areas of the EEZ. In the three cores from the southern part of the EEZ, we also confirm the presence of highly/extremely REY-rich mud layers. Further accumulation of geochemical data from the sediments will be required to constrain the extent of the highly/extremely REY-rich mud layers.

KEYWORDS

REY-rich mud, rare-earth elements, geochemistry, deep-sea mineral resources, Minamitorishima Island

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