Distribution of REY-Rich Mud in Deep-Sea Sediments from the Magellan Seamount Trail Zone in the Northwestern Pacific

Abstract

Deep-sea sediments enriched in rare earth elements and yttrium (REY) are gaining interest as new sources of REY. The northwestern Pacific is considered as one of the most promising regions with high REY resource potential; however, information on this region outside of the Japanese exclusive economic zone around Minamitorishima is limited. This study aimed to perform bulk chemical analyses on ten sediment cores obtained from the Ogasawara Fracture Zone, and Eastern Mariana and Pigafetta basins in northwestern Pacific. A noticeable peak of total REY content (Sigma REY) > 1600 ppm was found in a core, indicating the possible distribution of highly REY-enriched mud in the area; moreover, the low sedimentation rate in this region, resulting from a water depth of 6000 m, is also favorable for the development of REY-rich mud. Correlations between elemental concentrations and shale-normalized REY patterns strongly suggest that REY enrichment is primarily associated with biogenic calcium phosphates. The downcore profiles of Sigma REY content were not consistent in the depths and the number of REY-enriched layers among the studied cores, presumably affected by core penetration depth, supply of detrital materials from nearby topographic highs and physical erosion by bottom currents. Our results provide a better understanding of the REY-rich mud properties and its distribution in the deep-sea sediments of these regions of the northwestern Pacific.