北祁连金属成矿省时-空格局、演化及成矿作用

SPACIOUS-TEMPORAL FRAME,EVOLUTION AND MINERALIZATION OF THE NORTHERN QILIAN METALLOGENETIC PROVINCE

北祁连金属成矿省在地质历史演化过程的不同构造环境内形成了四个主要金属成矿幕。中元古代成矿幕为地幔底劈、陆壳裂解构造环境,沿深大断裂形成镁铁-超镁铁侵入岩带和金川超大型铜-镍硫化物矿床;中-晚元古代成矿幕为陆内裂谷构造环境,在火山-沉积地层下部基性火山凝灰岩内形成陈家庙式块状硫化物铜-铁矿床,上部深海沉积富碳泥质岩层形成镜铁山式大型沉积热液喷流型铁-铜矿床;早古生代成矿幕为裂陷海槽成矿环境,中-晚寒武世裂谷岛弧环境形成白银厂式锌-铅-铜型块状硫化物矿床,早-中奥陶世与蛇绿岩套件生形成铜-锌型块状硫化物矿床和岩浆岩型铬铁矿床,晚奥陶世弧后盆地环境形成红沟式铜-铁型块状硫化物矿床;晚古生代-中、新生代成矿幕为陆内造山挤压性构造环境,形成与韧性剪切构造有关的石英碳酸盐脉型和构造蚀变岩型金矿床。

Four metallogenetic epochs occurred in different tectonic environments during the evolution of the Northern Qilian metallogenetic province through geological time . The Middle Proterozoic epoch witnessed the tectonic environment of breakup of the crust caused by mantle dispirism, in which ultramafic-mafic rocks were intruded along a deep fault belt and the Jinchuan superlarge magmatic Cu-Ni sulphide deposit was formed. In the Middle-Late Proterozoic epoch the crust was further broken to form an intracontinental rift in which the volcanogenic massive Cu-Fe sulphide deposits hosted by basaltic tuff were formed in the lower volcano-sedimentary sequence, while the sedex type large Jingtieshan Fe-Cu deposits were formed within the upper abyssal carbon-rich argillaceous sedimentary sequence. The Early Palaeozoic epoch saw the formation of the aulacogen, within which the Baiyinchang-type superlarge massive base and precious metal sulphide deposits hosted by quartz keretophyric tuff were formed in the Middle-Late Cambrian rifted island arc, the massive Cu-Zn sulphide deposits and magmatic chromite deposits associated with the Early-Middle Ordovician ophiolite suite were formed in the ancient oceanic ridge, and the Honggou-type massive Cu-Fe sulphide deposits hosted by spilite were formed in the Late Ordovician back-arc basin environment. In the Late Paleozoic-Mesozoic epoch the metallogenetic province went into an intracontinental orogenic stage characteristic of the compressive tectonic environment , in which quartz-carbonate vein-type and tectonic-altered type gold deposits associated with ductile-shear structures were widely present within the metallogenetic province.