Geochemical characteristics of sedimentary core in the northern Okinawa Trough: Response to hydrothermal activity

Due to its unique geographical location and geological structure, the Okinawa Trough has become an ideal natural laboratory for studying the "source sink" processes, paleoenvironmental evolution, and extreme systems of sedimentation in the western Pacific marginal seas. In this study, we selected the HOBAB1-S10 sedimentary core from the western slope area of the northern Okinawa Trough as the research object and conducted AMS ¹⁴C dating. We analyzed the grain size, major and trace elements, rare earth elements, total organic carbon, total nitrogen, δ¹³C_org, and δ¹⁵N, studied the material sources and their shares during MIS3-LGM, and finally explored the influence of hydrothermal activity in the trough on the geochemical characteristics of sediments. Results indicate that during the period of 45~22.5 ka, the material source in this area was stable. The values of (La/Sm) UCC and (Gd/Yb) UCC indicate that the sediment in Core HOBAB1-S10 comes mainly from the Yellow River. During the period of 31~32 ka, elements of Cu, Zn, Co, U, and As were significantly enriched in sediments, which were 1-2 orders of magnitude higher than the background values, indicating that there may be additional source contributions besides terrestrial materials. The high Mo/Mn ratio of the samples (average 5.71) indicated the possibility of hydrothermal activity and material input in the northern Okinawa Trough. This study provided a theoretical basis for studying the mechanism of hydrothermal activity in the Okinawa Trough and for future exploration of hydrothermal activity in the northern Okinawa Trough.