[S-GC56_30PM2] 固体地球化学・惑星化学

[SGC56-12] 南鳥島EEZ内におけるレアアース泥の構成鉱物の特徴およびその成因への示唆

*大田 隼一郎¹、高谷 雄太郎²、藤永 公一郎²、安川 和孝¹、中村 謙太郎¹、町田 嗣樹³、原口 悟¹、加藤 泰浩² (1.東京大学工学系研究科システム創成学専攻、2.東京大学工学系研究科エネルギー・資源フロンティアセンター、3.早稲田大学創造理工学部環境資源工学科)

キーワード：レアアース, レアアース泥, 深海底鉱物資源

The KR13-02 cruise was conducted in the southern part of the Minamitorishima to explore rare-earth elements and yttrium-rich mud (REY-rich mud) within Japanese Exclusive Economic Zone (EEZ) on January 2013. During the cruise, seven sediment cores were successfully collected. The results of bulk sediment analyses showed that one of the cores (PC05) has an extremely REY-concentrated layer with 6,596 ppm total REY (Kato et al., 2013; Suzuki et al., 2013) which is three times higher than the maximum concentration in the mud previously reported for the eastern South and central North Pacific Ocean (2,230 ppm; Kato et al., 2011). In addition to REY, P concentration in the layer is also noticeably high (Kato et al., 2013; Suzuki et al., 2013), suggesting that Ca phosphate (apatite) is mainly responsible for the REY-enrichment in the layer, as in the case for the mud presented in other areas (Kashiwabara et al., 2014). However, factors contributing the extreme enrichment of REY, which in turn might provide important insights into the genesis of REY-rich mud, are still uncertain. In the present contribution, we report mineralogical features of Minamitorishima REY-rich mud including the extremely REY-concentrated layer and discuss about its genesis.