西藏柯月锌多金属矿床地质特征及成矿时代初步研究

柯月锌多金属矿床是北喜马拉雅锑金多金属成矿带上新发现的重要矿床。矿体主要呈脉状、透镜状产于近南北向张扭性断裂中,金属矿物主要有方铅矿、闪锌矿、辉锑矿、脆硫锑铅矿、硫锑铅矿、黄铁矿、毒砂、黄铜矿等,非金属矿物主要有石英、铁锰碳酸盐、方解石等。矿石组构以热液充填交代成因为主。流体包裹体初步研究表明,包裹体以液体包裹体为主,还有少量纯气体和纯液体包裹体。成矿流体为中低温、中低盐度、低密度H2O-Na Cl体系。流体中气液成分以H2O为主,液相中局部含有少量的HCO-3、CO2-3和CO2,气相中局部有少量CO2、CH4、N2。根据含矿石英脉中绢云母40Ar-39Ar定年,准确限定柯月矿床成矿热液活动的时限为21.3 Ma。矿床地质特征表明,柯月为中低温热液脉状锌多金属矿床,是后碰撞造山成矿作用的产物。

A preliminary study of geological features and metallogenic epoch in Keyue Zn-polymetallic deposit, Tibet

Keyue is a newly discovered important deposit located along the antimony-gold polymetallic metallogenic belt. Orebodies are manly distributed in the nearly NS tensile fractures in vein and lenticular forms. Metallic minerals include galena, sphalerite, stibnite, jamesonite, boulangerite, pyrite, arsenopyrite, copper etc., whereas non-metallic minerals include quartz, ferrimanganic carbonate, calcite etc. The main ore fabrics are formed by typical filling and metasomatism of hydrothermal solution. The preliminary research on fluid inclusions indicates that the fluid inclusions in Keyue are mainly liquid inclusions, including a small amount of pure vapor inclusions and pure liquid inclusions. The ore-forming fluid is of middle-low temperature, low salinity, low density H₂O-NaCl system. The vapor and liquid components of fluid inclusions are mainly H₂O, the liquids also have a little HCO₃^-, CO₃^2-, CO₂, and the vapors also have some CO₂,CH₄, N₂. According to the analytical results of ⁴⁰Ar-³⁹Ar isotopic data of sericite in the ore-bearing vein, the date of the hydrothermal activity of Keyue deposit can be defined at about 21.3 Ma accurately. According to the geological features, the Keyue deposit is a medium-low temperature hydrothermal vein zinc polymetallic deposit, which is the product of post-collision of India plate and Eurasian plate.