东昆仑东段什多龙铅锌矿成矿物质来源分析:来自矿石原位S同位素证据

Source analysis of metallogenic material of Shiduolong Pb-Zn deposit in the eastern part of East Kunlun:In-situ S isotope evidence from the ore

什多龙铅锌矿床位于东昆仑造山带东段都兰地区,矿体主要赋存在印支期花岗岩与碳酸盐岩的接触带中,其次也赋存在印支期花岗岩体中的构造节理裂隙蚀变带内。该矿区的稳定同位素研究成果较少,在一定程度上影响了矿区的成矿物质来源及矿床成因的深入研究。在详细矿区地质调查基础上,本文选取了9件矿石中的金属硫化物样品开展激光原位S同位素示踪研究。结果显示:黄铁矿的δ34SV-CDT值在4.80‰~6.80‰之间,均值为6.20‰;方铅矿的δ34SV-CDT值在4.00‰~5.50‰之间,均值为4.93‰,表明硫化物的S同位素组成既具岩浆硫的特征,又有围岩硫的加入。通过对矿石原位S同位素特征分析,并结合矿区成矿地质条件、地质演化背景等特征,本文认为什多龙铅锌矿形成于俯冲构造背景,为与印支期中深成壳幔混合型花岗质岩浆、碳酸盐岩围岩、构造裂隙及流体混合作用有关的岩浆热液矿床,根据赋矿岩石的差异又可分为矽卡岩型及岩浆热液脉型两种矿床类型,并共同构成了一套接触交代—岩浆热液充填的成矿系统。

The Shiduolong Pb-Zn deposit is located in the Dulan area of the eastern extension of East Kunlun orogenic belt.The ore bodies mainly occur in the contact zones between the Indo-Sinian granites and carbonate rocks,and secondly in the tectonic joint fissure alteration zones of the Indo-sinian granites.The research results of stable isotopes in this deposit are few,which to some extent affect the in-depth study on the source of metallogenic material and the genesis of this deposit.Based on the detailed geological survey of this deposit,9 metal sulfide samples in ores were selected to carry out laser in-situ S isotope tracing research.The δ34SV-CDT values of pyrite are 4.80‰~6.80‰,with an average value of 6.20‰,and the δ34SV-CDT values of galena are 4.00‰~5.50‰,with an average value of 4.93‰.It is shown that the S isotopic compositions of sulfides have both the magmatic sulfur and the surrounding rock sulfur.Through analyzing the in-situ S isotope characteristic of ores,and combining with metallogenic geological conditions,the geological evolution background of mining area,it is considered that Shiduolong Pb-Zn deposit forms in the subduction tectonic background,belongs to the magmatic hydrothermal deposit,which is related to the mid-deep crust-mantle mixed granitic magmatism in the Indochina period,carbonate surrounding rocks,tectonic fractures and fluid mixing.According to the difference of ore-hosting rocks,it can be divided into skarn type and magmatic hydrothermal vein type deposits,and together they constitute a set of metallogenic system of contact metasomatism-magmatic hydrothermal filling.