新疆准噶尔—东天山地区产于韧性剪切带中的金矿床成矿流体与碳、硫、铅同位素

Ore-forming Fluids and Carbon, Sulphur and Lead Isotope Studied on Ductile-Shear-Zone-type Gold Deposits in Junggar—East Tianshan Mts. Area, Xinjiang

韧性剪切带型金矿床是新疆准噶尔—东天山地区重要金矿类型。本文以科克萨依、康古尔、红石金矿为典型矿床,研究它们的流体包裹体均一温度、爆裂温度、包裹体成分、包裹体水的来源等,并进行了硫、铅同位素及近矿围岩碳同位素、矿体石英包裹体中CO2、CH4气体的碳同位素分析。结果表明,硫、铅为深源,暗示了本区金成矿物质的地幔来源。部分碳为有机碳,反映了本区年轻碳质沉积地层中有机碳参与了金的迁移与成矿作用。综合研究表明,在本区特定的后碰撞地质背景下,在构造挤压与伸展作用中形成的韧性剪切带中的金矿床金成矿物质源于深源,成矿流体主要是变质水。岩浆作用、变质作用、碳质围岩地层有机碳参与成矿,变质流体与岩浆热液及天水等流体的不同程度的混合与叠加,形成本区特征的韧性剪切带型金矿床。

The ductile-shear-zone-type gold deposit is one of important types of gold deposits in Junggar-East Tianshan Mrs. area, Xinjiang Autonomous Region. In this paper, we report detailed homogenization temperature, decrepitated temperature and compositional analyses on fluid inclusion, sulphur and lead isotope analyses as well as carbon isotope analyses of CO2 in quartz from both ore and wallrocks of three typical gold deposits （i. e. , Kekesayi, Kanggur and Hongshi）. The results indicate that sulphur, lead and a part of carbon are deeply derived, implying a mantle source for gold. A part of carbon isotope of CO2 in quartz from ore and wallrocks have organic feature, reflecting involvement of organic carbon from young carbonic sedimentary strata in gold mineralization. The preliminary studies indicate that gold in ductile-shear-zone-type deposits in Junggar area is deeply derived during structural compression and extension under post-collision geological setting. Gold mineralization is mainly related to metamorphism. The ductile-shear-zone-type gold deposits in the area are characterized by involvement of organic carbon from carbonic sedimentary strata in the gold mineralization and varying degrees of mixing between magmatic and meteoric waters.