上寨离子吸附型稀土矿床褐帘石结构和成分特征及其对成矿的指示  

Textural and Compositional Characteristics of Allanite from the Shangzhai Ion-adsorption Rare Earth Element Deposit:Implications for Mineralization

作　　者：冯雨周 陈华勇[1,3,4] 郑惠 肖兵 初高彬[1] 张俊岭 FENG Yuzhou;CHEN Huayong;ZHENG Hui;XIAO Bing;CHU Gaobin;ZHANG Junling(CAS Key Laboratory of Mineralogy and Metallogeny,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,Guangdong,China;MOE Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring,Central South University,Changsha 410083,Hunan,China;University of Chinese Academy of Sciences,Beijing 100049,China;Guangdong Provincial Key Laboratory of Mineral Physics and Materials,Guangzhou 510640,Guangdong,China)

机构地区：[1]中国科学院广州地球化学研究所矿物学与成矿学重点实验室,广东广州510640 [2]中南大学有色金属成矿预测与地质环境监测教育部重点实验室,湖南长沙410083 [3]中国科学院大学,北京100049 [4]广东省矿物物理与材料研究开发重点实验室,广东广州510640

出　　处：《大地构造与成矿学》2024年第2期248-258,共11页Geotectonica et Metallogenia

基　　金：广东省基础与应用基础研究重大项目(2019B030302013);有色金属成矿预测与地质环境监测教育部重点实验室(中南大学)开放基金项目(2021YSJS12);国家自然科学基金项目(41725009、42103058);广东省重点实验室运行项目(2020B1212060055);广州市科技计划项目(202102080318)联合资助。

摘　　要：上寨矿床为华南地区新发现的一个同时富含轻重稀土的离子吸附型稀土矿床,矿体位于粗粒黑云母花岗岩风化壳中。褐帘石是粗粒黑云母花岗岩中一种重要的副矿物(占比约为0.11%)。化学成分分析结果显示原生褐帘石具有富轻稀土元素的特征,其轻稀土(LREE)和重稀土元素(HREE)含量以及(La/Yb)N值分别为177940~188928μg/g、3732~5499μg/g和92.6~153。这些原生褐帘石轻稀土元素含量约占全岩轻稀土元素总量的86%,为上寨矿床轻稀土元素的主要来源。通过显微观察结合背散射图像可以发现,上寨矿床成矿母岩中的原生褐帘石被热液流体交代后蚀变形成了氟碳钙铈矿,在这个过程中褐帘石中的轻稀土和Ca元素被淋滤出来后主要进入了氟碳钙铈矿中,指示褐帘石被交代形成氟碳钙铈矿的过程中轻稀土元素发生了活化、迁移和富集。另外,被交代的褐帘石其Fe_(2)O_(3)T、MnO和MgO含量降低,而Sr、Y、Nb、W、Th、U、Zr以及HREE含量增加,这些增加的HREE可能来源于热液流体或其他富HREE的原生矿物。本研究表明,原生褐帘石被热液流体交代有利于轻稀土元素的富集成矿,但对重稀土矿化的贡献较小。The Shangzhai deposit in South China is a newly discovered ion-adsorption rare earth element(REE)deposit with both LREE and HREE mineralization.The ore body occurs in the weathered coarse-grained biotite granite(CGBG).Allanite is an important accessory mineral in the CGBG with a volume proportion of about 0.11%.Geochemical results show that magmatic allanite is characterized by enrichment of LREE with LREE,HREE,and(La/Yb)N ranging from 177940μg/g to 188928μg/g,3732μg/g to 5499μg/g,and 92.6 to 153,respectively.The LREE of magmatic allanite accounts for about 86%of the total LREE of the CGBG and is the most important source of LREE at Shangzhai.Photomicrographs and BSE images show that the magmatic allanite grains in the CGBG have been replaced by hydrothermal synchysite-(Ce).During the magmatic hydrothermal alteration,LREE and Ca released from the allanite were mostly scavenged by synchysite-(Ce),indicating remobilization and enrichment of LREE.Meanwhile,the Fe_(2)O_(3)T,MnO,and MgO contents of the magmatic allanite also decreased during the replacement process,whilst the Sr,Y,Nb,W,Th,U,Zr,and HREE contents increased,of which the increased HREE contents were sourced from the magmatic-hydrothermal fluid or other HREE-rich minerals.

关 键 词：褐帘石 稀土活化 离子吸附型稀土矿床 华南地区 

分 类 号：P57[天文地球—矿物学] P616[天文地球—地质学]