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In this study, analysis of mineralogy and geochemistry of fifteen surface sediment samples from four hydrothermal fields in the middle and southern Okinawa Trough is presented. Sediment samples can be divided into two types: (1) Metalliferous group (MS group) containing large amounts of sulfides and sulfate are enriched in Pb, Zn, Cu, Fe, Au, Ag, Ba, As, Hg, Se, Sb, Mo, slightly enriched in U, V, and have rare earth elements (REE) patterns similar to those of hydrothermal vent fluids and sulfides, indicating formation by a complex combination of wasting and erosion primary massive sulfide deposits and plume fallout of sulfides and sulfate. The occurrence of sphalerite with high contents of Fe and of co-existing pyrrhotite as major Fe-sulfide indicate that these minerals are formed at high temperature with low-sulfur fugacity in the Clam and Jade hydrothermal sites. The enrichment of Pb, Zn, Cu, Au, Ag, Ba, As, Hg, Se, Sb, and Mo is related to the presence of galena, sphalerite, Cu-sulfides, stibnite, and realgar in the sediments. (2) Non-metalliferous group (non-MS group) containing small amounts of pyrite are slightly enriched in Pb, Zn, Cu, Au, Ag, As, Hg, Se, Sb, and Mo relative to the East China Sea (ECS) continental shelf sediments, with REE exhibiting a "shale-like flat" patterns and close to Taiwan sediments in a REE discrimination plot, indicating formation by a large amount of terrigenous materials originated from Taiwan Island and a small amount of particles of sulfides in the hydrothermal nonbuoyant plume. The slight enrichment of Pb, Zn, Cu, Au, Ag, As, Hg, Se, Sb, and Mo maybe caused by co-precipitation with the fine-grained sulfides settling from the nonbuoyant plume. The positive relationships between the HREE fractionation index (Gd/Yb) N, heavy mineral proportion, and δEu suggest that (Gd/Yb) N can be used as a sensitive indicator for reflecting the effect of hydrothermal activity on the sediments. • Hydrothermal surface sediments from the middle and southern Okinawa Trough were researched. • Metalliferous sediments were mainly formed by wasting and erosion of primary massive sulfide deposits. • Non-metalliferous sediments were mainly formed by terrigenous materials with a small amount of fine-grained sulfides from plume. • The presence of sulfides and sulfate cause the enrichment of Pb, Zn, Cu, Au, Ag, Ba, As, Hg, Se, Sb, and Mo. • (Gd/Yb) N can be used to reflect the effect of hydrothermal activity on the sediments. [ABSTRACT FROM AUTHOR]

Sediment provenance and transport, together with the forcing mechanism behind provenance changes in the middle Okinawa Trough over the past 16 kyr, were reconstructed using records of elemental and Sr–Nd isotopic compositions within the chronological framework of accelerator mass spectrometry radiocarbon dating. Results clearly revealed four notable phases of change in the sediment provenance those are closely related to sea-level fluctuations, the development of the Kuroshio Current (KC), magnitude of tidal bottom stress, and climatic variability of the East Asian monsoon. The sediments of Unit 1 (16–13.8 kyr BP) originated primarily from Changjiang, with a small degree originating from paleo-Huanghe as a result of low-stand sea-level deposition. The sediments of Unit 2 (13.8–11.6 kyr BP) originated from Taiwan the strengthening of because of the KC and the gradual landward retreat of the river mouth; the contribution of Changjiang sediments was reduced. The dominant provenance of Unit 3 (11.6–8.3 kyr BP) changed to seafloor erosion or resuspension and Taiwan sediments with an admixture of Changjiang-derived sediments. After that period, currents, especially the intense KC-dominated deposition, led to dominant sediment supplies from Taiwan during the enhanced KC interval of 8.3–5.4 kyr BP. A prominent decrease in Taiwan-derived particle supply at 5.4–2.8 kyr BP resulted from the suppression of the KC related to the Pulleniatina minimum event. This study suggests that Sr–Nd isotope compositions are useful proxies for understanding the linkage between river sediment source-to-sink processes and paleoenvironmental changes in East Asian marginal regions. • Kuroshio Current reentered at 13.8 kyr BP and suppressed after 5.4 kyr BP. • Sediment provenance changes in the middle Okinawa Trough over the last 16 kyr were characterized by four-phase pattern. • Sediment provenance changes reflect the competing effects of sea-level, the Kuroshio Current, and East Asian monsoon climate. • Paleo-Huanghe was an important source of sediment in middle Okinawa Trough during early-middle Holocene. [ABSTRACT FROM AUTHOR]