Geochemical characteristics of surface sediments from the central-northern Okinawa Trough and their implications for terrestrial and hydrothermal inputs

By analyzing major, trace, and rare earth elements (REEs) in 127 surface sediment samples, we investigated the sources and controlling factors of sediments in the central-northern Okinawa Trough, and explores the significance of element composition as indicators of terrigenous input and hydrothermal signals. Results indicate that the sediments in the study area are composed mainly of SiO₂, CaO, and Al₂O₃, taking 54.25% to 78.11% of the total mass. R-mode factor analysis revealed that terrigenous clastic input is the primary factor con element composition, followed by volcanic/hydrothermal alteration, biogeochemical processes, and authigenic sedimentation. Based on compositional characteristics, the sediments were classified into three types. Cluster III sediments are dominated by terrigenous detrital and are enriched in elements such as SiO₂, Al₂O₃, K₂O, TiO₂, Li, Be, Sc, Cu, Pb, and Zn; Cluster II sediments are characterized by extremely high CaO and Sr contents, reflecting the dominance of biogenic carbonates; and Cluster I represents a mixture of terrigenous detrital and biogenic components. Discrimination of (La/Sm)_UCC-(Gd/Yb)_UCC confirmed that the Yellow River is the most important sediment source in the central-northern Okinawa Trough, while the Yangtze River, East China Sea shelf clays, and volcanic-hydrothermal activities exert localized influences. Sediments near hydrothermal areas show enrichment of chalcophile elements (e.g., Cu, Pb, Zn) and weak positive Eu anomalies, indicating spatially-restricted hydrothermal contributions. This study provided key geochemical evidence for deeper understanding of sediment composition and provenance in the central-northern Okinawa Trough.