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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]

• Two metalliferous sediments from a newly discovered Tangyin hydrothermal field were studied. • TVG11-2 was derived from a high-temperature black chimney. • ROV11-R2 was directly derived from a low-temperature hydrothermal vent. • Lower sulfur isotopic compositions indicate the contribution of magmatic H 2 S. We present and compare mineralogy and sulfur isotopic composition data of two surface metalliferous sediment samples, TVG11-2 and ROV11-R2, from the newly discovered Tangyin hydrothermal field in the southern Okinawa Trough (S-OT), and one surface metalliferous sediment sample 2-T4 from the Iheya North Knoll hydrothermal field in the middle Okinawa Trough (M–OT). The purpose of this study is to better understand the hydrothermal ore-forming environment and material source in the S-OT. Samples TVG11-2 and ROV11-R2 were derived from different types of chimneys. Sample TVG11-2 was derived from a black chimney which experienced formation process from high temperature to low temperature, with large gradients and fluctuations. ROV11-R2 was directly derived from a low-temperature white chimney or low-temperature diffuse flow. The sulfur isotopic compositions of sulfides and native sulfur in the S-OT are significantly lower than the sulfur isotopic compositions of pyrite and native sulfur in the M–OT, indicating there is another source with a lower sulfur isotopic composition. The low forming temperature and similar basement rocks of rhyolite in Iheya North Knoll, and dacite in Tangyin exclude phase separation and basement rock differences as the main reasons for low sulfur isotopic compositions in TVG11-2 and ROV11-R2. The occurrence of different bacterial communities between S-OT and M–OT may affect the sulfur isotopic compositions, but the influencing mechanism is still unclear. The addition of magmatic H 2 S may be the most possible reason for lower sulfur isotopic compositions in the Tangyin hydrothermal field. [ABSTRACT FROM AUTHOR]