粤北鹅公塘铀矿床方解石C-O同位素组成与稀土元素地球化学特征  

Characteristics and Geological Implications of Carbon and Oxygen Isotopes and REE of Calcite from Egongtang Deposit in Northern Guangdong Province

作　　者：王慧 钟福军 吴德海 潘家永[1] 舒田田 严杰 李海东[1,3] 张蕊 刘斌 WANG Hui;ZHONG Fu-jun;WU De-hai;PAN Jia-yong;SHU Tian-tian;YAN Jie;LI Hai-dong;ZHANG Rui;LIU Bin(State Key Laboratory of Nuclear Resources and Environment,East China University of Technology,Nanchang 330013,China;School of Resources,Environment and Jewelry,Jiangxi College of Applied Technology,Ganzhou 341000,China;No.290 Institute,CNNC,Shaoguan 512026,China;Natural Resources Bureau of Huichang County,Huichang 342600,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]江西应用技术职业学院资源环境与珠宝学院,江西赣州341000 [3]核工业二九〇研究所,广东韶关512026 [4]会昌县自然资源局,江西赣州342600

出　　处：《稀土》2023年第3期86-97,I0005,共13页Chinese Rare Earths

基　　金：国家自然科学基金项目(41862010;42002095;41772066);核资源与环境国家重点实验室自主基金项目(Z1906;2020Z08);核资源与环境国家重点实验室开放基金项目(2020NRE03)。

摘　　要：鹅公塘铀矿床位于南岭成矿带中段黄沙铀矿区,矿体主要赋存在断裂构造带与辉绿岩脉的交汇部位,方解石是该矿床中主要的脉石矿物,贯通整个铀成矿阶段,为了探讨鹅公塘铀矿床成矿物质和成矿流体的来源,研究了不同成矿期次方解石的碳氧同位素组成与稀土元素地球化学特征。结果表明,从矿前期→成矿期→矿后期方解石,方解石δ13CPDB平均值依次为-6.0‰、-6.3‰、-9.0‰,δ18OSMOW依次为14.5‰、14.8‰、13.8‰;方解石稀土元素配分模式均为轻稀土富集型,∑REE依次为72.51×10^(-6)、116.44×10^(-6)、67.96×10^(-6),LREE/HREE比值依次为7.89、7.19、6.36,(La/Yb)N依次为15.63、14.20、8.20,δEu依次为0.66、0.74、1.10,与印支期花岗岩具有相似的稀土元素配分型式以及Eu负异常。综合区域地质背景以及上述元素地球化学特征认为,成矿流体主要来源于地幔,并伴有部分大气成因的地下水,当富铀流体上升至浅部开放环境,地幔CO_(2)脱气作用导致了混合流体中的碳酸铀酰络合物解体,有利于成矿,印支期花岗岩为成矿提供了丰富的成矿组分。Egongtang deposit is located in Huangsha uranium mining area in the middle part of Nanling metallogenic belt.The uranium ore body mainly occurs at the intersection of fault structure belt and diabase vein.Calcite is the dominant gangue mineral in ores through the whole uranium mineralization stages.In order to study the source of ore⁃forming materials and ore⁃forming fluids in Egongtang uranium deposit,the geochemical characteristics of carbon and oxygen isotopes and REE of calcite in different metallogenic periods were studied.The results show that,the average values ofδ13CPDB of calcite from early to late mineralization are-6.0‰,-6.3‰,-9.0‰,andδ18OSMOW values are 14.5‰,14.8‰,13.8‰,indicating that the carbon in ore⁃forming fluid is mainly derived from mantle degassing.The REE distribution patterns of calcite are LREE enriched,and the∑REE contents of each stage are 72.51×10^(-6),116.44×10^(-6),67.96×10^(-6),LREE/HREE ratios are 7.89,7.19,6.36,(La/Yb)N ratios are 15.63,14.20,8.20,δEu are 0.66,0.74,1.10,respectively.It is similar to Indosinian granite in REE distribution pattern and negative Eu anomaly.Based on the regional geological background and the geochemical character⁃istics of the above elements,it is considered that the ore⁃forming fluid is mainly derived from the mantle,accompanied by some atmospheric groundwater.When the uranium rich fluid rises to the shallow open environment,the CO2 degassing of the mantle leads to the disintegration of the uranyl carbonate complex in the mixed fluid,which is conducive to mineralization.The Indosinian granite provides abundant ore⁃forming components for mineralization.

关 键 词：方解石 碳氧同位素 稀土元素 成矿流体 鹅公塘矿床 

分 类 号：P611[天文地球—矿床学] P595[天文地球—地质学]