斑岩系统中低熔点亲铜元素与稀贵金属赋存状态和富集机制研究:以藏东南普朗超大型斑岩Cu-Au矿床为例  

A case study of the Pulang porphyry Cu-Au deposit,Southeast Tibet

作　　者：王大钊 梁丰 王艳军 李凯旋 刘家军[3,4] 冷成彪 WANG DaZhao;LIANG Feng;WANG YanJun;LI KaiXuan;LIU JiaJun;LENG ChengBiao(National Key Laboratory of Uranium Resources Exploration-Mining and Nuclear Remote Sensing,East China University of Technology,Nanchang 330013,China;State Key Laboratory of Nuclear Resources and Environment,East China University of Technology,Nanchang 330013,China;State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences,Beijing 100083,China;School of Earth Sciences,China University of Geosciences(Beijing),Beijing 100083,China)

机构地区：[1]东华理工大学铀资源探采与核遥感全国重点实验室,南昌330013 [2]东华理工大学核资源与环境国家重点实验室,南昌330013 [3]中国地质大学地质过程与矿产资源国家重点实验室,北京100083 [4]中国地质大学(北京)地球科学与资源学院,北京100083

出　　处：《岩石学报》2025年第2期621-641,共21页Acta Petrologica Sinica

基　　金：第二次青藏高原综合科学考察研究(2021QZKK0301);深地国家科技重大专项(2024ZD1001602);国家自然科学基金重大研究计划重点项目(92462306、92062219、92062101);国家自然科学基金面上项目(42373072);江西省国家级高层次人才创新创业项目(K20230004)联合资助.

摘　　要：斑岩铜矿床常伴生大量低熔点亲铜元素(LMCE,包括Te、Se、Bi、Sb、As等)和稀贵金属(NM,包括Au、Ag、PGE),但这些元素的相互作用关系、富集分异机制及其控制因素尚不清楚。普朗斑岩Cu-Au矿床是位于特提斯-喜马拉雅成矿带中的超大型矿床,矿床中富集伴生元素,具有重要的经济价值,成为探讨这些问题的理想研究对象。本文利用扫描电镜、电子探针及硫化物LA-ICP-MS等原位分析技术对普朗矿床中伴生元素的分布规律、赋存状态及形成过程开展研究。结果表明,LMCE和NM主要以微粒包体形式赋存于硫化物中,并形成富硒方铅矿、辉碲铋矿、辉铋矿、辉硒铋矿、硫银铋矿、银金矿/金银矿、硒银矿、碲银矿、碲钯矿、碲铂矿、砷碲钯矿和富钯辉钴矿等矿物。普朗矿床中的铂族元素矿物(PGM)至少存在早期高温、晚期低温两个阶段的结晶,其中自形粒状的碲钯矿和碲铂矿结晶温度高、结晶空间开阔,可能是高温下直接由LMCE-Pt-Pd熔体固结形成,PGM形成后继续在流体中迁移并被后期结晶的硫化物捕获;而碲银矿±砷锑钯矿±辉碲铋矿±辉铋矿矿物组合具有固溶体分解和二面角等典型的熔体固结结构,推测为低温下NM-LMCE熔体充填在已结晶的硫化物裂隙和孔洞中形成。斑岩铜矿床从岩浆形成到热液出溶再到矿质沉淀的全过程均伴随着LMCE和NM的分异和富集,其中LMCE熔体对NM的高效富集具有重要意义。Porphyry Cu deposits are commonly containing large amounts of low-melting point copper-philic element(LMCE)and noble metals(NM),but the interactions,enrichment and fractionation mechanisms,and control factors of these elements are still unclear.The Pulang porphyry Cu-Au deposit is a giant deposit in the Tethys Himalaya metallogenic belt,which is enriched in associated elements and has important economic value,providing an ideal deposit to discuss these issues.This paper using scanning electron microscopy(SEM),electron probe microanalysis(EPMA),and sulfide LA-ICP-MS in-situ trace element analysis to study the distribution,occurrence states,and enrichment processes of the associated elements in Pulang.This study found that the LMCE and NM in Pulang exist in sulfides in the form of micro-inclusions and form mineral such as Se-bearing galena,tetradymite,bismuthinite,nevskite,matildite,electrum/küstelite,naumannite,hessite,merenskyite,moncheite,mertieite-II and Pd-bearing cobaltite.Platinum group element minerals(PGM)at Pulang experienced at least two crystallization stages:early high-temperature and late low-temperature.The euhedral merenskyite and moncheite grains crystallized at high temperature and open crystal space,which may be formed by direct consolidation of LMCE-Pt-Pd melt at high temperature.After the formation of PGM,they continued to migrate with fluid and were captured by later-crystallized sulfides.The mineral assemblages of hessite±mertieite-II±tetradymite±bismuthinite have typical melt solidification textures,i.e.,exsolution and dihedral angle textures,which was crystallized from NM-LMCE melt that filled in cracks and holes of crystallized sulfides at low temperature.The fractionation and enrichment of LMCE and NM are accompanied by the whole processes from magma generation to hydrothermal exsolution to mineral precipitation in porphyry Cu deposits,among which LMCE melt plays an important role in the efficient enrichment of NM.

关 键 词：斑岩铜矿 低熔点亲铜元素 铂族元素 富集分异机制 普朗 

分 类 号：P575[天文地球—矿物学] P612[天文地球—地质学] P618.41