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 IijimaKatsuhiko Suzuki, Yasuhiro Kato*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

39 Citations (Scopus)


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 (ΣREY) 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.

Original languageEnglish
Pages (from-to)575-590
Number of pages16
Issue number6
Publication statusPublished - 2016
Externally publishedYes


  • Deep-sea mineral resources
  • Geochemistry
  • Minamitorishima island
  • REY-rich mud
  • Rare-earth elements

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology


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