对北祁连山火山喷溢型贱金属硫化物矿床区域成矿的探讨

北祁连山加里东优地槽褶皱山系由厚层海相火山岩系和沉积建造组成。其内已经发现数十个火山岩型块状硫化物矿床,可划分为三种类型,即Cu(Fe)型(或红沟型)、Cu-Zn型(或蛇绿岩套型)及Cu-Pb-Zn型(或白艰厂型)。不同类型矿床分别形成于不同地质环境且趋向于在特定时-空范围产出:Cu(Fe)型矿床集中分布在南部达坂山成矿带,成矿与晚奥陶世双峰态细碧角斑岩系有关,矿床形成于弧间或弧后盆地环境;Cu-Zn型矿床分布在北部九个泉—错沟、猪嘴哑吧一银硐沟矿带,与早—中奥陶世蛇绿岩套有关,矿床形成于大洋扩张构造环境;Cu-Pb-Zn型矿床集中分布在祁连、白银成矿区,矿床产出与中寒武世中酸性石英角斑凝灰岩有关,形成于优地槽发展早期阶段裂谷岛弧环境。

Types and regional tectonic setting of volcanogenic effusive type base metal sulfide deposits in north Qilian mountain

Located in West China, the North Qilian Mountain Caledonian eugeosynclinal orogenic belt 100-300 km in width extends some 1200 km in NWW direction. It consists mainly of Lower Paleozoic thick marine volcanic rocks and sedimentary formations, within which several tens of volcanogenic massive base metal sulfide deposits have been found. These deposits might be grouped into three types: copper(iron)type (Honggou type), copper-zinc type (ophiolite type) and copper-lead-zinc type(Baiyinehang type). Different types of deposits occur in different geological environments and tend to be cofined within their respective spatial-temporal domains.The copper(iron)type deposits, which were formed in a back arc or interarc basin rift environment, are concentrated in Dabanshan metallogenic zone in the south and related to Late Ordovician bimodal spilite-keratophyre sequence, with orebodies hosted by spilite. The copper-zinc type ore deposits are distributed in Yindonggou-Zhuzuiyaba and Cuogou-Jiugequan metallogenie zones in the north and occur in basalts of the Middle Ordovician ophiolite suite, suggesting that they were formed in an ocean-floor extensional environment. The copper-lead-zinc type ore deposits, which were formed in a rift volcanic arc environment during oceanization at the early evolution stage of the Caledonian eugeosynoline, are concentrated in Baiyinchang and Qilian metallogenic areas and occur in Early Cambrian spilite-keratophyre sequence, with orebodies hosted by quartz keratophyric tuff.