小秦岭-北秦岭地区铀成矿的构造演化背景

Tectonic Setting of Uranium Mineralization in Xiaoqinling-north Qinling Area

小秦岭-北秦岭地区位于秦岭造山带东部,长期处于华北板块、秦岭微地块和扬子板块边缘构造活动地带,具备良好的古陆块边缘铀成矿条件。分析多期次不同类型铀成矿作用与相应的秦岭造山带构造演化背景的关系,有利于理解区域铀成矿规律和创新铀矿成因理论。文章通过对区内典型铀矿床(点)进行对比分析,总结出铀成矿的成因机制,并以秦岭造山带形成与演化的视角来分析不同类型铀成矿作用发生的构造背景。分析显示在小秦岭-北秦岭构造带的华阳川地区、蓝田牧护关岩体以及“商南-丹凤三角区”等3地,存在伟晶岩型、碳酸岩型和构造岩浆热液叠加改造型等3种铀矿类型,成矿期次历经古元古代、古生代奥陶纪—泥盆纪、早中生代三叠纪、晚中生代侏罗纪以来等4个时期。研究结果表明北秦岭-小秦岭地区的铀矿具有“古老地层+深大断裂+岩浆作用”耦合成矿的成因机制,铀成矿作用均发生在秦岭造山带块体之间相互作用的由碰撞转向伸展的构造体制转换阶段。

Xiaoqinling-north Qinling area is located in the east of the Qinling orogenic belt.It has long been in the tectonic active zone on the edge of North China plate,Qinling micro block and Yangtze plate,and has favorable uranium metallogenic conditions due to the edge of ancient landmass.Studies on the relationship between multi-stage and different types of uranium mineralization and the corresponding tectonic evolution background of Qinling orogenic belt,is conducive to understanding the regional uranium mineralization pattern and innovating the theory of uranium genesis.This paper compared the typical uranium deposits in the Xiaoqinling-north Qinling area,summarized the general model of uranium mineralization,and analyzed the tectonic background of different types of uranium mineralization from the perspective of the formation and evolution of Qinling orogenic belt.The analysis results showed that there are three types of uranium deposits in Huayangchuan area,Lantian Muhuguan granite and"Shangnan Danfeng triangle"of Xiaoqinling-north Qinling structural belt,including pegmatite type,carbonatite type and superimposed reformed uranium deposit.The metallogenic age includes Paleoproterozoic,Paleozoic Ordovician Devonian,Early Mesozoic Triassic and Late Mesozoic Jurassic.The uranium deposits in the Xiaoqinling-north Qinling area have a general metallogenic model of coupling mineralization of"ancient strata,deep faults and magmatism".Uranium mineralization occurs in the transformation stage of tectonic system from collision to extension of the interaction between blocks of Qinling orogenic belt.