新疆若羌县柯可•卡尔德钨锡矿床地质特征与流体包裹体研究

地处东、西昆仑与阿尔金构造带结合处的白干湖是近年在我国西北地区勘查发现的一处具超大型远景规模的钨锡矿田,包括柯可卡尔德、白干湖、巴什尔希和阿瓦尔四个矿床。其中,柯可卡尔德钨锡矿勘查程度最高、规模最大,野外调查发现其含矿石英脉体有沿走向扭动、雁列式排列、产状低缓等特征,热液活动则可明显分为成矿前、成矿期和成矿后三期作用。该矿床流体包裹体主要有汽液两相、含子盐汽液三相、单一液相(包括纯水和纯 CO2型)、含 CO2汽液三相、同时含CO2和子盐汽液四相等5种类型,成矿前石英以前两种包裹体为主,亦有少量含 CO2汽液三相型;成矿期可分为早、晚两个阶段,早阶段是钨锡的主成矿阶段,包含五种类型包裹体,晚阶段表现为弱的硫化物矿化,主要为汽液两相型;成矿后石英包裹体主要为汽液两相型。显微测温与激光拉曼探针分析表明成矿流体主要成分为 H2O和 CO2,气相含少量 CH4和 N2;氢、氧同位素研究结果显示三期流体分别主要为变质热液、岩浆热液和大气降水。该矿床系中高温、中低盐度的岩浆热液矿床,流体经历了不混溶作用和混合作用,这可能是促使矿质沉淀的主要因素。

Study on Geological Characteristics and Fluid Inclusion of the Kekekaerde W-Sn Deposit in Ruoqiang County, Xinjiang

The Baiganhu tungsten ore field in southeastern Xinjiang Province is a large deposit discovered in recent decade.It consists of four tungsten-tin deposits:Awar,Bashierxi,Baiganhu and Kekekaerd(KK in short),with the KK being well-explored,large-scale one.Field investigation indicates that the W-Sn quartz veins of the KK deposit veins are characterized by twisting along the trend,echelon array,and flat attitude,and hydrothermal activities can be divided into three stages such as pre-ore,mineralized and post-ore.Fluid inclusions consist of five types:G-L two phases,G-L-D three phases,CO2 or water single phase,CO2-H2O three phases,and CO2-H2O-NaCl four phases.The first two types occur mainly in pre-ore stage,with minor CO2G-L three phase type.Mineralization stage can be divided into early stage and late stage,with the early one being the major mineralization stage containing five inclusion types and the late one being weak sulfate mineralization containing G-L two phase type.Post-ore stage is dominated by G-L two phase type.Microthermometry and Ramman analyses show that the mineralized fluid compositions are dominated by H2O and CO2,with minor CH4and N2.H-O isotopic compositions of fluid inclusions in the three type veins indicate that ore-forming fluid was a mixture of magmatic water,atmospheric water and metamorphic water.The deposit should be a magmatic hydrothermal deposit formed in the condition of high T and low-medium salinity.The fluid underwent fluid immiscibility and mixing,and this may be the leading factor for tungsten precipitation.