稀土元素地球化学对湘东大富岭矿床铀成矿的指示意义  

Geochemical Characteristics of REE as Indicators for Uranium Metallogenesis in the Dafuling Deposit in Eastern Hunan Province

作　　者：范鹏飞 廖志权 李满根[1] 陈念楠 欧阳平宁 张鑫 FAN Peng-fei;LIAO Zhi-quan;LI Man-gen;CHEN Nian-nan;OUYANG Ping-ning;ZHANG Xin(School of Earth Sciences,East China University of Technology,Nanchang 330013,China;Changsha Uranium Geology Institute,Changsha 410007,China;Hunan Engineering Technology Research Center for Evaluation and Comprehensive Utilization of Associated Radioactive Mineral Resources,Changsha 410007,China;The Seventh Geological Brigade of Jiangxi Bureau of Geology,Ganzhou 341000,China)

机构地区：[1]东华理工大学地球科学学院,南昌330013 [2]核工业二三○研究所,长沙410007 [3]湖南省伴生放射性矿产资源评价与综合利用工程技术研究中心,长沙410007 [4]江西省地质局第七地质大队,赣州341000

出　　处：《科学技术与工程》2025年第5期1792-1802,共11页Science Technology and Engineering

基　　金：中国核工业地质局基金(2023-24-1,2023-24-3,地LCEQ01)。

摘　　要：大富岭矿床隶属于湘东明月峰矿田,是近年来新发现的花岗岩外带型铀矿床。该矿床的矿石矿物特征和稀土元素特征尚未有报道,为进一步理清矿石矿物特征和稀土元素的特征,探讨稀土元素对铀成矿的指示意义,采用扫描电镜、电子探针、激光剥蚀电感耦合等离子体质谱(laser ablation-inductively coupled plasma-mass spectrometry,LA-ICP-MS)等技术研究了该矿床的主要矿石矿物——沥青铀矿,并首次利用LA-ICP-MS测试了沥青铀矿的稀土元素。实验结果表明,大富岭铀矿床沥青铀矿主要由UO_(2)、CaO和PbO组成,ThO_(2)含量极低,∑REE含量偏低,轻重稀土分异明显,(La/Yb)_(N)远大于1,轻稀土明显富集,Eu负异常,沥青铀矿的主量元素和稀土元素均表明其形成于温度低于350℃的中低温热液环境,指示大富岭矿床为典型的中低温热液脉型铀矿床。稀土元素指示成矿作用过程中成矿热液从高盐度向低盐度转变,热液环境由还原环境逐渐过渡到弱氧化环境,暗示了来源于地壳深部或岩石圈地幔的成矿热液沿着大富岭地区区域性深断裂上升,在经历一系列物理化学条件变化后,最终大富岭矿床适宜位置富集成矿。Dafuling(DFL)deposit is a part of the Mingyuefeng ore field in eastern Hunan Province,China,is a typical perigranitic uranium deposit discovered recently.The characteristics of the ore minerals and the features of rare earth elements in this deposit have not been previously documented.In order to further elucidate the characteristics of ore minerals and rare earth elements(REE),as well as explore their indicative significance for uranium metallogenesis.Herein,uraninite,the primary ore mineral in the deposit,was investigated via scanning electron microscopy and electron probe microanalysis.Additionally,laser ablation-inductively coupled plasma-mass spectrometry(LA-ICP-MS)was used for the first time to determine the in situ the REE characteristics of uraninite.Uraninite exhibits a distinct fractionation between light rare earth elements(LREE)and heavy rare earth elements(HREE),while displaying a negative Eu anomaly.The(La/Yb)_(N)ratio exceeds 1,indicating a significant enrichment of LREE.Both major elements and REE in uraninite suggest its formation within a hydrothermal environment at temperatures ranging from moderate to low,below 350℃.Consequently,DFL deposit can be classified as a typical hydrothermal vein-type uranium deposit.The REE serve as indicators of the transition of ore-bearing hydrothermal fluids from high salinity to low salinity,and the hydrothermal environment gradually shifts from a reducing state to a weakly oxidizing state.These observations suggest that the ore-bearing hydrothermal fluid responsible for metallogenesis originating from the deep crust or lithospheric mantle,ascended along regional deep faults,and subsequently underwent a series of physical and chemical transformations,eventually accumulated mineralization in suitable locations within DFL deposit.

关 键 词：沥青铀矿 LA-ICP-MS 稀土元素 热液脉型铀矿床 大富岭矿床 明月峰矿田 

分 类 号：P595[天文地球—地球化学] P611[天文地球—地质学]