甘肃龙首山成矿带地质构造演化及其对铀成矿的控制作用

Geotectonic Evolution of Longshoushan Metallogenic Belt in Gansu and Its Control Function on Uranium Mineralization

龙首山成矿带大地构造演化主要经历了元古代龙首山边缘沉降带形成和发展、古生代边缘沉降带活化隆起和陆缘带局部坳陷、中新生代断块活动等3个构造时期。龙首山成矿带位于华北古陆西南缘,古陆块及其边缘是重要的铀成矿区域。区内铀成矿受区域大地构造演化控制,铀矿化相应地分为3个成矿期,即元古代成矿期、古生代成矿期和中新生代成矿期。与3个成矿期相对应,龙首山成矿带形成了分别与下元古界变质岩、祁连期重熔型花岗岩和中新生代断块升降有关的3个铀矿化成矿系列。龙首山成矿带成矿模式可概括为:下元古界地层预富集→(吕梁期)伟晶状白岗岩体预富集(或祁连期花岗岩类岩石预富集)→(天山期)断裂构造、热液蚀变预富集→(印支期、四川期和喜马拉雅期)脉体叠加工业富集。

The geotectonic evolution of Longshoushan metallogenic belt experiences three tectonic periods,including the initial stage and development of Proterozoic Longshoushan margin subsiding belt,and the active uplift of Paleozoic subsiding belt and partial collapse of continental margin belt,and the activity of Meso-Cenozoic fault block.Longshoushan metallogenic belt locates at the southwest margin of North China paleoland,and the paleoland and its margin are the most important uranium metallogenic zones. Uranium mineralization is controlled by geotectonic evolution;accordingly uranium-mineralized process is divided into three metallogenic periods,including Proterozoic,Paleozoic and Meso-Cenozoic.Corresponding with the three metallogenic periods,Longshoushan metallogenic belt form three metallogenic series of uranium mineralization,which are separately related to Lower Proterozoic metamorphic rocks,the crustal remelting granites in Qilian stage and the fault block uplift and sag in Meso-Cenozoic.Themetallogenic model of Longshoushan metallogenic belt can be summarized as the pre-enrichment of Lower Proterozoic stratum,the pre-enrichment of（Luliang stage）pegmatoid alaskite（or the pre-enrichment of granitoids in Qilian stage）,the pre-enrichment of（Tianshan stage）fault structure and hydrothermal alteration,and the industrial enrichment of（Indosinian,Sichuan stage and Himalayan）vein material superimposed.