地球化学
Online ISSN : 2188-5923
Print ISSN : 0386-4073
ISSN-L : 0386-4073
総説(特集)
レアアース泥の起源:独立成分分析による数理統計的アプローチを中心に
安川 和孝中村 謙太郎藤永 公一郎岩森 光加藤 泰浩
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ジャーナル オープンアクセス

2018 年 52 巻 4 号 p. 171-210

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Since the discovery of rare-earth elements and yttrium (REY)-rich mud in the Pacific Ocean, a variety of research has been conducted to understand its spatial distribution and genesis. In this paper, we review the latest research outcomes on REY-rich mud, including the discovery of “extremely REY-rich mud” containing >5,000 ppm of total REY, a promising deep-sea mineral resource in Japan’s exclusive economic zone surrounding Minamitorishima Island. Then, we introduce a new statistical approach based on independent component analysis (ICA) to clarify the origin of REY-rich mud in the Pacific and Indian oceans, with a theoretical background and a protocol of ICA application on geochemical data. Independent components extracted from a multi-elemental dataset of ~4,000 samples demonstrate distinctive geochemical features, and their spatiotemporal distributions indicate that the sedimentation rate is an underlying key factor for REY-enrichment. We also refer to an important link between the genesis of REY-rich mud and Earth system dynamics. Finally, we focus on some challenges to be overcome. One of the most significant questions concerns the formation mechanism of the extremely REY-rich mud. An important key to this question is the depositional age of the extraordinary sediment layer.

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© 2018 日本地球化学会
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