粤北地区琶江铀矿床沥青铀矿原位微区年代学和元素分析:对铀成矿作用的启示  

In-situ microchronology and elemental analysis of pitchblende in the Pajiang uranium deposit,northern Guangdong:Implications for uranium mineralization

作　　者：李海东[1,2,3] 田世洪 刘斌 胡鹏 吴建勇 陈正乐 LI Haidong;TIAN Shihong;LIU Bin;HU Peng;WU Jianyong;CHEN Zhengle(State Key Laboratory of Nuclear Resources and Environment,East China University of Technology,Nanchang 330013,China;Research Institute NO.290,CNNC,Shaoguan 512029,China;Research Center for Petrogenesis and Mineralization of Granitoid Rocks,China Geological Survey,Wuhan 430205,China;Institute of Geomechanics,Chinese Academy of Geological Sciences,Beijing 100081,China)

机构地区：[1]东华理工大学核资源与环境国家重点实验室,江西南昌330013 [2]核工业二九○研究所,广东韶关512029 [3]中国地质调查局花岗岩成岩成矿地质研究中心,湖北武汉430205 [4]中国地质科学院地质力学研究所,北京100081

出　　处：《地学前缘》2024年第2期270-283,共14页Earth Science Frontiers

基　　金：中国核工业地质局项目(202140,202239);中国地质调查局花岗岩成岩成矿地质研究中心开放基金项目(PMGR202107);中国铀业有限公司东华理工大学核资源与环境国家重点实验室联合创新基金(NRE2021-01,NRE2021-09,2022NRE-LH-05);江西省“双千计划”创新领军人才长期项目(2020101003);东华理工大学高层次人才引进配套经费资助项目(1410000874)。

摘　　要：琶江铀矿床处于桃山—诸广铀成矿带南段,位于佛冈岩体南西部,是佛冈岩体内发现的唯一一个铀矿床。铀矿化严格受断裂构造控制,是典型的花岗岩型铀矿。本文采用岩相学、扫描电镜(SEM)、电子探针(EPMA)及原位激光剥蚀电感耦合技术(LA-ICP-MS)对琶江铀矿床矿石矿物沥青铀矿及黄铁矿进行了矿物学、微区地球化学及年代学研究。结果表明:沥青铀矿LA-ICP-MS U-Pb定年结果为(49.70±0.1)Ma,为晚白垩世,位于华南区域主成矿时代(75~50 Ma)范围内,表明琶江铀矿床与区域成矿时代一致,属于区域性成矿事件。该铀矿床沥青铀矿稀土元素总量为(311.5~368.3)×10^(-6),U/Th比值为17067~26524,显示中低温热液成因,结合稀土元素TE 1,3为0.95~1.01,具类四组分效应特征,指示成矿流体富F。此外,琶江铀矿床黄铁矿Co/Ni比值介于5~26,暗示其为热液成因。根据以上分析,认为该矿床为中低温热液型矿床。The Pajiang uranium deposit is located in the southern Taoshan-Zhuguang uranium metallogenic belt of the southwestern Fogang pluton.It is a typical granite-related U deposit,the only one found in the Fogang pluton,and uranium mineralization is strictly controlled by fault structures.In this paper,the mineralogy,microgeochemistry and chronology of pitchblende and pyrite in the Pajiang uranium deposit are studied by means of petrography,scanning electron microscopy(SEM),electron probe microanalysis(EPMA)and in-situ laser ablation inductively coupled technique(LA-ICP-MS).In-situ LA-ICP-MS U-Pb dating of pitchblende yielded a weighted mean age of 49.70±0.1 Ma,which corresponds to the Late Cretaceous,and is within the main metallogenic epoch(7550 Ma)of South China.This indicates that the formation of the Pajiang uranium deposit is consistent with regional metallogeny and belongs to a regional metallogenic event.The total rare earth element(REE)content in pitchblende was(311.5368.3)×10^(-6)and the U/Th ratio was 1706726524,suggesting that the uranium deposit is of medium-low-temperature hydrothermal origin.The TE 1,3 value of REE was 0.951.01,with quasi tetrad effect characteristics,indicating fluorine enrichment in the ore-forming fluids.In addition,the Co/Ni ratio of pyrite ranged between 526 in the Pajiang uranium deposit,suggesting the uranium deposit is of hydrothermal origin.Based on the above analysis,it is considered that the Pajiang uranium deposit is of medium-low-temperature hydrothermal type.

关 键 词：沥青铀矿 黄铁矿 年代学 地球化学 琶江铀矿床 

分 类 号：P619.14[天文地球—矿床学] P597[天文地球—地质学] P595P611