新疆白干湖钨锡矿流体包裹体特征及成因

白干湖钨锡矿床位于新疆祁漫塔格加里东褶皱带的转折部位,是东昆仑西段1个较好的钨锡(金)矿区,对白干湖矿区主成矿阶段形成的含黑钨矿石英脉中发育的包裹体进行岩相学及测温研究.研究结果表明:矿区主要发育3类包裹体:气液两相水溶液包裹体(I)、水溶液-CO2三相包裹体(Ⅱ)以及纯CO2两相包裹体(Ⅲ)；Ⅰ型包裹体液相组分主要为NaCl水溶液,含少量KCl,其均一温度变化范围为160-310℃,盐度为1.82％～16.43％;Ⅱ型水溶液-CO2三相包裹体气相组分含有CO2及CH4等组分,均一温度为247～320℃,w(NaCl)为2.8％～9.4％；Ⅲ型CO2两相包裹体含量较少,均一温度为19.8～27.7℃；白干湖钨锡矿床成矿流体为中低盐度、中高温的NaCl-H2O-CO2体系.在成矿过程中,由于温度及压力降低,流体发生相分离成为较高盐度的水溶液流体和较低盐度的富CO2流体,钨锡成矿物质趋向于富集在中高盐度水溶液相中,并导致白干湖钨锡矿的成矿作用.

Characteristics of fluid inclusions and ore genesis of Baiganhu tungsten-tin deposit,Xinjiang

The geotectonic setting of Baiganhu tungsten-tin deposit is located in the transition area of Qimantag Caledonian fold belt,a relatively good W,Sn(and Au) mineralization region in the west of Eastern Kunlun orogenic belt.Based on the review of predecessors’ works as well as the studied regarding petrography,microthermometry of fluid inclusions from wolframite-containing quartz-vein formed in the major mineralizing stage,fluid inclusions are in three types,i.e.,2-phased aqueous solution inclusion(type I),3-phased CO2-aqueous fluid inclusion(type II) and 2-phased pure CO2 fluid inclusion(type III).The liquid phase of type I inclusions is mainly NaCl aqueous,containing a little KCl,whose homogenization temperatures vary from 160 ℃ to 310 ℃,with salinities from 1.82% to 16.43% NaCl.Type II inclusions,with the gas phase containing CO2 and CH4,are homogenized between 247?320 ℃,and their salinities vary from 2.8% to 9.4% NaCl.The locally found 2-phased CO2 fluid inclusions(type III) are homogenized from 19.8 ℃ to 27.7 ℃.The ore-forming fluid of Baiganhu W-Sn deposit belongs to the NaCl-H2O-CO2 hydrothermal system with medium-low salinity and medium-high temperature.During the minerogenesis,due to phase segregation with the decrease of temperature and pressure,the ore-forming fluid separates into relatively high salinity aqueous fluid and slightly lower salinity CO2-rich fluid,Metallogenic elements such as W and Sn tend to be concentrated in the medium-low salinity aqueous fluid,which might play an important role in the metallogenic process of Baiganhu W-Sn deposit.