（エントリー）Discovery of extremely REY-rich mud in the South Pacific Ocean

<p>Rare-earth elements & yttrium (“REY”) play a crucial role in the development of high-tech electronics and energy-efficient appliances. However, the global supply of REY resources faces potential risks, production dominance by China and the environmental concerns due to radioactive contents in REY ores onshore. Under such circumstances, REY-rich mud is attracting attention as a new REY resource[1]. Particular attention has been paid to the 'extremely REY-rich mud' with a total REY concentrations (ΣREY) exceeding 5000 ppm found within Japan's exclusive economic zone (EEZ) around Minamitorishima in the western North Pacific[2, 3]. The extremely REY-rich mud, which is important in terms of resources, has so far been found only in the Minamitorishima EEZ and ODP site 1149 to the north of the EEZ. Recent study have also reported layers with relatively high concentrations of REY (ΣREY = 2000–4000 ppm) from the Penrhyn Basin in the central South Pacific[4]. In this study, therefore, we analyse chemical compositions of ten deep-sea sediment cores recovered during the GH83-3 Cruise. We report the first discovery of extremely REY-rich mud from the Penrhyn Basin and discuss their geochemical characteristics and with previously studied the REY-rich mud. [1] Y. Kato et al., “Deep-sea mud in the Pacific Ocean as a potential resource for rare-earth elements,” Nat Geosci, vol. 4, no. 8, pp. 535–539, Aug. 2011. [2] K. Iijima et al., “Discovery of extremely REY-rich mud in the western North Pacific Ocean,” Geochem J, vol. 50, no. 6, pp. 557–573, 2016. [3] K. Fujinaga et al., “Geochemistry of REY-rich mud in the Japanese Exclusive Economic Zone around Minamitorishima Island,” Geochem J, vol. 50, no. 6, pp. 575–590, 2016. [4] J. Ohta, K. Yasukawa, K. Nakamura, K. Fujinaga, K. Iijima, and Y. Kato, “Geological features and resource potential of deep-sea mud highly enriched in rare-earth elements in the Central Pacific Basin and the Penrhyn Basin,” Ore Geol Rev, vol. 139, p. 104440, Dec. 2021.</p>