青海青龙沟金矿成矿流体演化特征及矿床成因研究

青龙沟金矿位于柴达木盆地北缘—南祁连造山带中,主矿体赋存于青龙沟背斜褶皱北东翼部NW走向的层间滑脱断裂,矿石类型为蚀变岩型。依据矿石矿物组合和矿物穿切关系将成矿过程划分为3个阶段:Ⅰ.无矿石英脉阶段;Ⅱ.石英-黄铁矿多金属硫化物阶段;Ⅲ.石英碳酸盐阶段。对不同阶段石英中流体包裹体进行岩相学和显微测温研究,结果表明,不同阶段石英中流体包裹体均以气液两相为主,在石英碳酸盐阶段出现纯液相包裹体;均一温度集中在200℃~240℃,170℃~210℃和130℃~160℃。不同阶段压力平均值分别为24.39 MPa,17.30 MPa和11.84 MPa,对应成矿深度分别为2.4 km,1.7 km和1.2 km。结合矿床地质特征以及流体特征显示青龙沟金矿应属于浅成造山型金矿。

Evolution characteristics of fluid and genesis of Qinglonggou gold deposit in Qinghai

Qinglonggou gold deposit is located in the northern margin of Qaidam Basin and sourthern Qilian o- rogenic belt． The deposit is controlled by northwest trending layer slip fault of Qinglonggou anticline fold and be- longs to altered rock type of ore． According to mineral combination and interspersed relationship，the mineraliza- tion process could be divided into three stages: non- ore quartz veins stage (stage Ⅰ)，quartz -pyrite sulphides stage (stage Ⅱ) and quartz carbonate stage (stageⅢ)． Petrographic and microthermometric study of fluid inclu- sions indicate that the fluid inclusions of different stages in quartz are mainly gas- liquid two- phase inclusions，and appear pure liquid in the quartz carbonate stage． The homogenization temperatures are successively concentrated in 200℃ ～240℃， 170℃ ～210℃ and 130℃ ～160℃，correspondingly ore- forming pressure are 24. 39 MPa，17. 30 MPa and 11. 84 MPa while ore- forming depth are 2. 4 km， 1. 7 km and 1. 2 km during the mineralization stages Ⅰ， Ⅱ，Ⅲ． On the basis of fluid features and the geological characteristics，the Qinglonggou gold deposit is defined as an epizonal orogenic in genetic type．