相山铀矿田鹏姑山地区热液蚀变地球化学特征及其对找矿的启示

Geochemical characteristics of hydrothermal alteration in Penggushan district of Xiangshan uranium orefield and its implications for ore prospecting

江西相山铀矿田是我国最大的火山岩型铀矿田之一。鹏姑山地区位于相山铀矿田西部,毗邻邹家山、居隆庵等大型铀矿床,成矿地质条件较好。近些年,鹏姑山地区铀矿勘查取得重要突破,区内热液蚀变具有典型的高温蚀变特征,晚期叠加蚀变较少,是研究高温热液蚀变与铀矿化关系的理想场所。鉴于此,本文在野外地质调查的基础上,通过岩相学和全岩地球化学分析,研究了鹏姑山地区高温热液蚀变的地球化学特征,探讨了高温热液蚀变特征及其与铀矿化的关系。研究结果表明,鹏姑山地区高温热液蚀变主要以钠长石化、去硅化、绿泥石化和伊利石化为主,局部叠加有磷灰石化、黄铁矿化、碳酸盐化和硅化。铀矿化与钠长石化、磷灰石化、碳酸盐化和去硅化蚀变关系较为密切。研究区铀矿化属碱交代型铀矿化,形成于中高温的还原性环境,磷灰石化促使了高品位铀矿化的形成。在碱交代蚀变之上叠加的磷灰石化和碳酸盐化在矿体部位发育最强烈,可视为鹏姑山地区找矿勘查中最重要的找矿标志。

The Xiangshan uranium orefield in Jiangxi Province is one of the largest volcanic⁃related uranium orefields in China.The Penggushan district is located in the western part of the Xiangshan uranium orefield,close to the Julongan and Zoujiashan large uranium deposits,and has favorable minerogenetic conditions.In recent years,a significant breakthrough in the exploration of uranium deposits has been made in the Penggushan area,where the hydrothermal alterations are high⁃temperature alteration with less later superimposed alteration,so it is an ideal place to study the relationship between high⁃temperature hydrothermal alteration and uranium mineralization.In view of this,on the basis of a field geological survey,this paper analyzes the geochemical characteristics of hydrothermal alteration in Penggushan area through petrographic and whole rock geochemical analysis and discusses the characteristics of high⁃temperature hydrothermal alteration and its relationship with uranium mineralization.The results show that the high⁃temperature hydrothermal alterations are commonly dominated by albitization,desilica⁃tion,chloritization,and illytization,and locally overprinted by apatitization,pyritization,carbonation,and silicifi⁃cation.The uranium mineralization shows a close spatial relationship with the albitization,apatitization,carbona⁃tion,and desilication.In the Penggushan district,uranium mineralization is alkali⁃metasomatized and formed in a medium⁃high temperature reductive environment.The occurrence of apatite in fluid is possibly an important factor for the formation of high⁃grade mineralization in the study area.Apatitization and carbonation superimposed on alkali metasomatic alteration are most strongly developed in the ore body,which are regarded as the most important pros⁃pecting indicators in future uranium resource exploration of Penggushan area.