冲绳海槽中部Jade热液活动区中海底热液沉积物的硫同位素组成及其地质意义

Sulfur isotopic composition of seafloor hydrothermal sediment from the Jade hydrothermal field in the central Okinawa Trough and its geological significance

测定了冲绳海槽中部Jade热液活动区中18个热液沉积物样品的硫同位素组式，其中10个硫化物样品的δ34S值为5．2×10－3～7．2×10－3，7个硫酸盐样品的34S值为16．3×10-3～22．3×10-3，1个自然硫样品的δ34S值为8．2×10-3热液沉积物的硫主要来自中、酸性火山岩和海水，并且在流体与沉积物相互作用过程中海底沉积物也可能为热液沉积物的形成提供部分的硫．导致本区热液沉积物中硫化物与其他热液活动区的硫同位素组成不同的原因，主要是各热液活动区的硫源以及有关岩浆活动和构造演变的不同.海底热液体系中硫的演化是一个复杂的过程，涉及被加热海水的上升、流体与火山岩的相互作用、海水硫酸盐和中、酸性火山岩中流的混合作用以及流体与沉积物相互作周等一系列海底热液活动，其中海水和中、酸性火山岩的相互作用是本区硫演化的一个重要机制．

Eighteen samples of hydrothermal sediments from the Jade hydrothermal field in the central Okinawa Trough have been analyzed. Sulfur isotopic values for 10 sulfide samples vary from 5. 2 ×10 - 3 to 7. 2 × 10 - 3, δ34S values for 7 sulfate samples vray from 16. 3 × 10 -3 to 22 - 3 × 10-3, and δ34S value for 1 native sulphur sample is 8. 2 ×10 -3. The major sources of sulfur for hydrothermal sediment are intermediate to acid volcanic rocks and seawater sulfate, and it is peible that the partial sulfur of hydrothermal sediment is from the pelagic sediment by the interaction between hydrothermal fluid and sediment. The reasons of causing the distinct differences in sulfur isotope values for sulfide samples from hydrohermal sediment (compared with other hycdrothermal fields), are the differences in the sources of sulfur, the magmatic activity and the tectonic evoution in different hydrothermal fieds. The sulfur evoution is a long and complex process in the seanoor hydrohermal system, invoving the ascending of heating seawater, the interaction between fluid and vocanic meks, the miking of seawater sulfate and sulfur bo intermediate to acid vodric meks, and the fluid/pelagic - sediment interation. And the interactbo between seawater and intermediate to acid vocanic rocks is a wit mechanism for the sulfur evolution in the Jade hydrothermal field.