新たな深海底鉱物資源“レアアース泥”の探査と 開発に向けた取り組み<b> </b>

Abstract

Deep-sea mineral resources have attracted considerable attention in the last few decades as a new source of base metals and rare metals. Recently, we discovered that mud with high rare-earth elements and yttrium (REY) concentrations (termed“ REY-rich mud”) is widely distributed on the deep-sea floor of the Pacific Ocean. REYrich mud has the following great advantages as a mineral resource: (1) high concentrations of REY, (2) remarkable abundance, (3) high exploration efficiency due to homogeneous stratiform distribution, (4) very low concentrations of radioactive elements (e.g., Th and U), and (5) ease of REY extraction and recovery. During the R/V Kairei cruise KR13-02, we discovered extremely high-grade REY-rich mud (the maximum REY content exceeds 6,500 ppm) in the Japanese Exclusive Economic Zone (EEZ) around Minamitorishima. We also found that the distribution of the REY-rich mud can be explored by a shipboard sub-bottom profiler. The REYrich mud within the Japanese EEZ has enormous significance in terms of securing the strategic mineral resource, because REY are critical in the advancement and development of high-tech manufacturing and green technology. Currently, we are continuing to explore the distribution of REY-rich mud in the Minamitorishima EEZ. In addition, together with private-sector corporations, we are also starting to address the challenges for developing the new deep-sea mineral resource, including various technical issues (e.g., how to lift the mud from the seabed deeper than 5000 m of water depth), environmental impact assessments, and economic evaluations. The collaborative efforts of industry, academia, and the government are the key to success of deep-sea mining of REY-rich mud.