西藏尤卡朗铅银矿床流体包裹体研究

Fluid inclusions of Youqialang lead-silver deposit in Tibet

西藏尤卡朗铅银矿床位于班公湖—怒江结合带以南、雅鲁藏布江结合带以北的冈底斯—念青唐古拉山中生代岩浆弧。矿区的含矿地层为上侏罗统拉贡塘组顶部的石英岩层,矿体受到裂隙构造控制。含矿脉体的石英中发现两类流体包裹体,即Ⅰ型水溶液包裹体和Ⅱ型H_2O-CO_2包裹体,均一温度为160℃～250℃,推测成矿温度为中温。流体盐度范围为1.65%～12.29%,峰值在3%～5%之间,部分数据具有较高的盐度值,表明高盐度的岩浆热液流体来源,受后期地下水热液的混合。热地下水的不断涌入改变了热液的成分,是成矿作用的重要因素,成矿流体中还含有CO_2,对于铅锌硫化物的沉淀起到促进的作用。

The Youqialang lead-silver deposit in Tibet is located in Gandise-Nyainqentanglha range Mesozoic magmatic arc, in the south of Bangonghu-Nujiang junction belt and north of Yaluzangbu River junction belt. Its ore-bearing strata are quartzite on the top of Lagongtang Formation of Upper Jurassic. The orebodies are controlled by structural fractures. Quartz in ore- bearing veins contains two types of fluid inclusions,they are aqueous inclusions（Type I ） and H2O-CO2 inclusions （Type 11 ）. According to the range of their homogenization temperatures （ 160 ℃-250℃ ）, we inferred that the ore-forming temperature of the deposit was mesotherm. The salinity ranges from 1.65% - 12.29% ,and its peak value ranges from 3% -5%. Part of the data with higher salinity reflects that the source of high-salinity magmatic hydrothermal fluids is mixed by heated groundwater in the later period. The composition of the hydrotherm changed due to the inburst of thermal groundwater, which is an important factor of mineralization. Ore-forming fluids also contain CO2 ,which promoted the deposition of lead and zinc sulfide.