The Okinawa Trough is a back-arc, initial marginal sea basin located behind the Ryukyu trench-arc system. Pb-Zn-(Cu) mineralization associated with volcanism has been recognized more than 15 hydrothermal fields in this trough. Fluid inclusions and HeAr isotopic compositions were studied in sulfide-sulfate chimneys at Yonaguni Knoll IV hydrothermal field, South Okinawa Trough. Studies of fluid inclusion in sphalerite, anglesite and barite indicate formation temperatures between 220 °C and 357 °C and varying fluid salinities (1.9 to 8.55 equiv. wt% NaCl) that fall within the range observed at modern active mid-ocean ridge hydrothermal fields. The trapping temperatures heterogeneity and wide variations in salinities of partial fluid inclusions reveal phase separation and fluid mixing beneath the seafloor. The resulting brine favored the release and transportation of additional metal ions besides Pb and Zn and led to a complex mineralization at higher levels. The ³He/⁴He ratio values (1.5 to 6.6Ra) of co-existing minerals also suggest a mixing fluid source, which can be calculated that basaltic magma He and seawater He mixed in varying degrees, with the proportions of basaltic magma He varied from 36% to 80% during the crystallization of sphalerite. Even in barite, the proportion of basaltic magma He can reach ~6%, supporting the contribution of the mantle He to the hydrothermal fluid. Anglesite-hosted fluid inclusions indicate that the existence of multiple hydrothermal fluid reservoirs in the sub-seafloor where the accumulation and migration of the hydrothermal fluid caused the rocks and terrigenous sediments to be altered intensely and promoted the lateral migration and mineralization of hydrothermal fluid under the seafloor.

冲绳海槽是一个弧后的初始边缘海盆，位于琉球海沟弧系统后面。与火山作用有关的 Pb-Zn-(Cu) 矿化已在该槽中 15 个以上的热液区中得到确认。流体包裹体和 He在南冲绳海槽与那国 Knoll IV 热液场的硫化物-硫酸盐烟囱中研究了 Ar 同位素组成。对闪锌矿、角铁矿和重晶石中的流体包裹体的研究表明，地层温度介于 220 °C 和 357 °C 之间，并且流体盐度（1.9 到 8.55 当量重量百分比 NaCl）在现代活跃的洋中脊热液场观察到的范围内. 部分流体包裹体的圈闭温度非均质性和盐度的广泛变化揭示了海底下的相分离和流体混合。由此产生的盐水有利于释放和运输除 Pb 和 Zn 之外的其他金属离子，并导致更高水平的复杂矿化。在³他/ ⁴共存矿物的He比值（1.5～6.6Ra）也表明存在混合流体源，可以计算出玄武质岩浆He与海水He有不同程度的混合，玄武质岩浆He的比例从36%到80不等。 % 闪锌矿结晶过程中。即使在重晶石中，玄武质岩浆 He 的比例也可以达到~6%，支持地幔 He 对热液流体的贡献。Anglesite 赋存的流体包裹体表明海底存在多个热液流体储层，热液的聚集和运移使岩石和陆源沉积物发生强烈蚀变，促进了海底热液的横向运移和成矿作用。海底。