新疆萨Ⅰ金矿床石英菱镁岩与金成矿作用研究

Study on gold mineralization in listvenite of No. Ⅰ Sartohay gold deposit,Xinjiang

新疆西准噶尔萨Ⅰ金矿床由含金糜棱岩化石英菱镁岩和含金石英脉组成,矿体围岩为石英菱镁岩、碳酸盐-滑石片岩和蛇纹岩。根据岩相学研究,将萨Ⅰ金矿床的形成过程划分为5个阶段:黄铁矿-石英-碳酸盐阶段(Ⅰ)、自然金-辉砷镍矿-铬云母阶段(Ⅱ)、黄铁矿-碳酸盐-石英阶段(Ⅲ)、自然金-硫化物-石英阶段(Ⅳ)和碳酸盐阶段(Ⅴ)。阶段Ⅰ和阶段Ⅱ对应于石英菱镁岩经历的韧-脆性变形时期,其他3个阶段形成于脆性变形期间,反映出构造性质由挤压向拉伸环境转换的过程。阶段Ⅱ和阶段Ⅳ分别对应于Au-As和Au-Cu成矿作用。金矿化与石英菱镁岩经历的剪切变形过程相关。含金糜棱岩化石英菱镁岩的微量元素含量明显高于未变形的石英菱镁岩,说明剪切带流体输送了相关微量元素和成矿元素。在韧性变形向脆性变形转换过程中,流体压力骤降,含金络合物分解形成金矿。萨Ⅰ金矿床是产在糜棱岩化石英菱镁岩中的严格受剪切带控制的热液脉型金矿床。

The No.Ⅰ Sartohay gold deposit is hosted by listvenite, carbonate-talc schist and serpentinite. The ores are composed of auriferous mylonitized listvenite and auriferous quartz vein. The ore-forming process can be divided into five stages： pyrite-quartz-carbonate stage （stage Ⅰ）, gold-gersdorffite-mariposite stage （Ⅱ, Au-As mineralization）, pyrite-carbonate-quartz stage （Ⅲ）, gold-chalcopyrite-quartz stage （Ⅳ, Au-Cu mineralization） and carbonate stage （Ⅴ）. Stage Ⅰ and Ⅱ occurred in the transition period from ductile to brittle deformation, and stage Ⅲ to Ⅴoccurred in the brittle deformation period. Gold mineralization is controlled by mylonitization. The content of trace elements in auriferous mylonitized listvenite is apparently higher than that in undeformed listvenite, which demonstrates that the fluid in the shear zone transported trace elements and metallogenetic elements. The decrease of pressure from ductile to brittle deformation induced gold deposition.