四川巴塘县夏塞银多金属矿床特征

Geological features of the Xiasai silver-polymetallic deposit in West Sichuan,China

夏塞银矿位于川西义敦岛弧造山带燕山晚期绒依措花岗岩体外接触带浅变质岩中,是一个超大型的中低温热液脉型银多金属矿床。通过对该矿床的地质、矿石矿物、流体包裹体与同位素地球化学等进行系统的研究表明,矿体产出严格受断层破碎带控制,矿体主要为脉状、透镜状和浸染状;容矿岩石为上三叠统图姆沟组的浅变质砂岩、粉砂岩和板岩;金属矿物主要有方铅矿、闪锌矿、黄铜矿、黄铁矿、银矿物和硫盐矿物等,脉石矿物为石英、方解石、绢云母、绿泥石等;成矿作用可划分为三期四个阶段;成矿物质来源于围岩和花岗岩,矿床为燕山晚期-喜马拉雅期岩浆期后成矿流体浅成中低温热液充填交代矿床。

The Xiasai silver-polymetallic deposit lies in the exometamorphic zone of the late Yanshanian granite body in the Yidun island arc orogenic belt in West Sichuan. It is a super-large hydrothermal vein type silver-polymetallic deposit. A research on the geologic characteristics, ore mineralogy, fluid inclusions and stable isotope geochemistry indicates that the deposit occurs in the sandstone, siltstone and slate of the Upper Triassic Quegasi Formation and suffered epimetamorphism. The orebodies are mainly veinlike, lenticular and disseminated and controlled strictly by fractured zones. The ore minerals are mainly pyrite, galena, sphalerite, chalcopyrite, Ag sulfosalts and sulfosalts etc. The vein minerals are mainly quartz, calcite, sericitolite and chlorite etc. The ore-forming process can be divided into three phases consisting of four stages. The integrated geological, microelement and isotopic geochemical studies show that silver and other metal elements mainly come from the country rock and granite. The origin of the deposit is genetically an epithermal hydrothermal filling and metasomatic deposit formed by the late magmatic hydrothermal ore-forming fluids. Based on the geological features, the ore-forming regularities and prospecting target for the deposit in this region are discussed. The discovery of the Xiasai silver-polymetallic deposit provides a new idea and an important foundation for prospecting for the similar type of deposits in West Sichuan and the Qinghai- Xizang （Tibet） plateau.