研究業績

地球化学 52, 4, 171-210 (2018)
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

著者

安川和孝・中村謙太郎・藤永公一郎・岩森光・加藤泰浩

カテゴリ

学術論文

Abstract

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.