龙首山成矿带青井地区辉绿岩特征及其与钍铀成矿关系  

Characteristics of Diabase and Its Relation to Th-U Deposit in Qingjing Area of Longshoushan Metallogenic Belt

作　　者：王贵 王伟 马骊 刘涛 戴鹏飞 WANG Gui;WANG Wei;MA Li;LIU Tao;DAI Pengfei(Research Institute NO.203,CNNC,Xianyang,Shaanxi 712000,China)

机构地区：[1]核工业二〇三研究所,陕西咸阳712000

出　　处：《铀矿地质》2021年第5期823-833,共11页Uranium Geology

基　　金：中国核工业地质局项目“甘肃省龙首山成矿带三岔-金边寺地区铀矿资源调查评价与勘查”(编号:202002)资助。

摘　　要：青井地区位于龙首山成矿带西段,近年在该区上侏罗统砾岩中新发现钍铀混合型矿化,矿化在空间上与辉绿岩脉关系密切,沿不同辉绿岩脉发育有不同的蚀变组合和矿化。文章通过对辉绿岩脉的系统研究,认为辉绿岩脉形成于早白垩世,是产于板内构造环境下的具有碱性玄武岩特征的基性岩脉,上侵过程中与围岩发生了混染,同化部分围岩成分,具有较高的U、Th含量。其侵入时代与钍铀矿成矿年龄相差较远,二者在成因上并无关联,但在空间上钍铀矿化明显受到辉绿岩脉的控制,Ⅰ号和Ⅱ号辉绿岩脉夹持区为含矿热液的运移通道,其间所有砾岩均呈紫红色,发育强烈的碱交代热液蚀变组合,Th、U明显富集;在Ⅱ号和Ⅲ号辉绿岩脉之间为灰白色砾岩,发育强碳酸盐化蚀变,Th、U含量明显低于原岩,砾岩中的Th、U被活化迁移;Ⅲ号辉绿岩脉以北则为肉红色砾岩,几乎不发育蚀变。Qingjing area is located in the west part of Longshoushan metallogenic belt.In recent years,thorium-uranium mixed mineralization has been discovered in the upper Jurassic conglomerate,and the mineralization is closely related to diabase dike in space.Different alteration and mineralization can be examined along different diabase dikes.Based on the systematic study of diabase dikes,it was considered that diabase dikes were formed in the Early Cretaceous,which are basic dikes with alkaline basalt characteristics in the intraplate tectonic environment.During the process of upwelling,diabase dikes contaminated the wall rocks and assimilated some wall rock components,and hence bear high U and Th contents.The age of diabase invasion is far from that of thorium-uranium mineralization,but thorium and uranium mineralization is obviously controlled by diabase dyke in space,area clamped by diabasic dikeⅠ and Ⅱ may provide migration channel for ore-bearing hydrothermal,and all the conglomerate in the area is purplish red and developed strong alkali metasomatism hydrothermal alteration combination and enriched in Th and U.Gray conglomerate occurred between diabasic dike Ⅱ and Ⅲ,developed strong carbonate alteration,but with lower Th and U contents than the original rocks.Flesh red conglomerate distributed to the north of diabasic dike Ⅲ,but almost without alteration.

关 键 词：辉绿岩脉 钍铀混合型矿化 青井 龙首山 

分 类 号：P588.124[天文地球—岩石学]