粤北书楼丘矿床脉石矿物地球化学特征及其意义  

Geochemical Characteristics and Significance of Gangue Minerals in Shulouqiu Deposit,Northern Guangdong

作　　者：叶永钦[1,2,3] 祁家明 刘文泉[1,2,3] YE Yongqin;QI Jiaming;LIU Wenquan(Research Institute No.290,CNNC,Shaoguan,Guangdong 512029;Guangdong Provincial Key Laboratory of Environmental Protection and Nuclear Radiation Tracking Research,Shaoguan,Guangdong 512029,China;Guangdong Provincial Engineering Technology Research Center of Radioactive Eco-environmental Protection,Shaoguan,Guangdong 512029,China)

机构地区：[1]核工业二九〇研究所,广东韶关512029 [2]广东省环境保护核辐射追踪研究重点实验室,广东韶关512029 [3]广东省放射性生态环境保护工程技术研究中心,广东韶关512029

出　　处：《铀矿地质》2022年第6期1098-1110,共13页Uranium Geology

基　　金：科技部国家重点研发计划“深地资源勘查开发”重点专项“华南热液型铀矿基地深部探测技术示范”(编号:2017YFC0602600);中国核工业地质局铀矿地质项目(编号:202035-4、202035-6);中国铀业有限公司-东华理工大学联合创新基金资助项目(编号:NRE2021-05)联合资助。

摘　　要：书楼丘矿床是粤北长江铀矿集区内典型铀矿床之一。为揭示书楼丘矿床铀成矿流体和成矿物质的来源,文章系统研究了成矿期脉石矿物(方解石、萤石和黄铁矿)微量元素、稀土元素和同位素地球化学特征。成矿期黄铁矿微量元素比值(Nb/Ta值和Zr/Hf值)特征及其相关性分析表明成矿流体来源于深部,且在成矿过程中受到外源流体的混入;成矿期紫黑色萤石稀土元素特征表明书楼丘矿床成矿流体部分继承了富铀花岗岩体;方解石和萤石的La/Ho-Y/Ho图解表明,形成书楼丘矿床的成矿流体源于同一流体体系;成矿期方解石具有比较稳定的碳同位素组成和较高的δ^(18)O_(PDB)值,其δ^(13)C_(PDB)值平均为-7.4‰,δ^(18)O_(PDB)值平均为-17.68‰,明显表现出地幔来源的特点,但在成矿过程中可能发生了较强的水岩交换作用或有大气降水的混入;成矿期黄铁矿Pb同位素比值和HolmesHoutermans图解反映出成矿流体中的铅来源于富铀的地质体,富铀岩体为铀成矿提供矿质。结合前人研究结果认为,幔源富铀成矿流体从深部向上运移过程中,由于物理化学条件的改变,导致沥青铀矿从流体中沉淀析出,形成铀矿化。Shulouqiu deposit is one of the typical uranium deposits in the Changjiang uranium metallogenic cluster area,northern Guangdong.In order to reveal the source of uranium ore-forming fluids and minerals in Shulouqiu deposit,the trace elements,REE(Rare Earth Elements)and isotopic geochemical characteristics of ore-forming phase gangue minerals(i.e.Calcite,fluorite and pyrite)were studied systematically.The characteristics and correlation analysis of trace element ratios(i.e.Nb/Ta value and Zr/Hf value)of pyrites during the metallogenic phase indicated that the oreforming fluid originated from the deep earth,and was mixed by external fluids during the mineralization process.The REE characteristics of purple-black fluorite in the metallogenic phase indicated that the ore-forming fluid of the Shulouqiu deposit partly inherited the uranium-rich granite body.The La/Ho~Y/Ho diagrams of calcite and fluorite showed that the ore-forming fluids that formed the Shulouqiu deposit originated from the same fluid system.Calcite in the ore-forming period has a relatively stable carbon isotope composition and a higherδ^(18)O_(PDB)value.The average value of δ^(13)C_(PDB)andδ^(18)O_(PDB)was-7.4‰and-17.68‰,respectively,obviously showing the characteristics of mantle origin which might resulted from the strong water-rock exchange or the atmospheric precipitation during the mineralization process.The Pb isotope ratio and the Holmes-Houtermans diagram of pyrite during the ore-forming period reflected that the lead in the ore-forming fluid originated from uranium-rich geological bodies,and the uraniumrich pluton provided minerals for uranium mineralization.Combined with the above results,it was believed that the uranium mineralization was formed form precipitation of the fluid during the upward migration of mantle-derived uranium-rich ore-forming fluids from the deep,due to the change of physical and chemical conditions.

关 键 词：脉石矿物 地球化学 成矿流体 矿床成因 书楼丘矿床 粤北 

分 类 号：P595[天文地球—地球化学]