藏南拉木由塔锑(金)矿床S、Pb同位素组成及指示意义

Sulfur,Lead Isotope Composition Characteristics and the Relevant Instructive Significance of the Lamuyouta Sb(Au) Deposit,South Tibet

西藏拉木由塔锑(金)矿床位于藏南Sb-Au成矿带东段,矿(化)体主要赋存于中侏罗统遮拉组地层与辉绿(玢)岩脉接触带上。在分析该矿床成矿地质条件的基础上,系统研究了矿石硫、铅同位素组成特征,并通过与区域成矿带中典型矿床硫、铅同位素组成的对比分析,探讨了矿床成矿物质来源。研究表明矿石硫化物的硫同位素组成变化范围较窄,成矿热液δ34SΣS在0值附近,与藏南Sb-Au成矿带中典型矿床的δ34S值相似,反映其来源与岩浆硫密切相关。矿石铅同位素组成变化范围较大,为异常铅,且构成了铅二次等时线,求得放射性成因铅源区年龄为1 638 Ma,反演了矿石铅的两阶段演化过程,推断其来源于上地壳古陆结晶基底,该研究成果能为藏南特提斯喜马拉雅锑金成矿带的研究提供一定的帮助。

Lamuyouta Sb（Au） deposit is located in the eastern section of Sb-Au metallogenic belt,south Tibet.The ore body mainly occurs at the contact between the strata of the Middle Jurassic Zhala Formation and diabase（allgovite） veins.Based on the analysis of geological and ore-forming conditions,this paper systematically focuses on the composition characteristics of S,Pb isotopes in the sulfide ore minerals,as well as a comparison of S,Pb isotope composition among other typical ore deposits developed in the same regional metallogenic belt.In addition,it also discusses the sources of the ore-forming materials.Studies have shown that the composition of S isotope in sulfide ore minerals has a narrow variation range and the δ34SΣS in the ore-forming hydrothermal system is about 0,which is similar to other typical ore deposits developed in regional metallogenic belt,south Tibet.It is estimated that the sulfur origin is closely related to the magmatic sulfur.The isotopic composition of ore lead is varied greatly and belongs to anomalous lead,which constitutes a secondary isochron of lead.And then,it is calculated that the age about the lead with radiogenic source is 1,638 Ma,which inverts two-stage evolution process of ore lead.Therefore,it is speculated that they sourced from ancient crystalline basement of upper continental crust,in order to provide some help for the study of Himalayan-Tethyan antimony-gold metallogenic belt in Tibet.