The geochemistry and mineralogy of sediments provide relevant information for the understanding of the origin and metallogenic mechanism of ferromanganese nodules and crusts. At present, there are still few studies on the sediment origin of the Clarion–Clipperton Zone (CCZ) of the east Pacific, particularly on the systematic origin of sediments with a longer history/length. Here, bulk sediment geochemistry and clay mineral compositions were analyzed on a 5.7 m gravity core (GC04) obtained at the CCZ, an area rich in polymetallic nodules. The results indicate that the average total content of rare earth elements (REE), including yttrium (REY), in sediments is 454.7 ppm and the REEs distribution patterns normalized by the North American Shale Composite of samples are highly consistent, with all showing negative Ce anomalies and more obvious enrichment in heavy REE (HREE) than that of light REE (LREE). Montmorillonite/illite ratio, discriminant functions and smear slide identification indicate multiple origins for the material, and are strongly influenced by contributions from marine biomass, while terrestrial materials, seamount basalts and their alteration products and authigenic source also make certain contributions. The REY characteristics of the sediments in the study area are different from those of marginal oceanic and back-arc basins, and more similar to pelagic deep-sea sediments. Based on LREE/HREE-1/δCe and LREE/HREE-Y/Ho diagrams, we conclude that samples from the study area had pelagic sedimentary properties which suffered from a strong “seawater effect”.

Deep-sea sediments generally refer to the sediments distributed on the seafloor with a depth of more than 2000 m. Many rare earth elements and yttrium (REY)-rich sediments were recently discovered in the sea area of Minamitorishima Island, Northwest Pacific. To understand the material source and REY enrichments of sediments in this area, here, we performed clay minerals and Sr-Nd isotopes analyses on gravity core GC1601 gained in the Southeast Sea area of Minamitorishima Island. The clay mineral composition of the core is very similar to that of terrigenous materials, and its montmorillonite/illite (M/I) ratio ranges from 0.09 to 0.20 with an average of 0.15, indicating that the sediments in the study area should be mainly dominated by terrestrial sources, consistent with the results of Sr-Nd isotope study. Considering that the study area is far away from the mainland and in the downwind direction of the East Asian monsoon, we propose that the terrigenous material of the sediments in the study area is likely East Asian dust. The εNd values of GC1601 show a positive correlation with P₂O₅, Co, Ni, and Cu, and have an increasing trend with increasing depth, approaching that of the seawater, indicating that the sedimentary environment in the area is relatively stable. Although the total REY content (ΣREY) of the core increases with depth, due to the large supply of terrigenous materials for the sediments, it is difficult for the study area to form high-grade REY-rich muds.