西藏甲玛铜多金属矿床辉钼矿中铼的分布特征及富集机制  

Distribution characteristics and enrichment mechanism of rhenium in the molybdenite of the Jiama copper polymetallic deposit,Tibet

作　　者：田松林 彭勃 唐菊兴[1,2] 冉凤琴 顾枫华 韩警锐 赵媛 张捷 TIAN SongLin;PENG Bo;TANG JuXing;RAN FengQin;GU FengHua;HAN JingRui;ZHAO Yuan;ZHANG Jie(College of Earth and Planetary Sciences,Chengdu University of Technology,Chengdu 610059,China;Institute of Mineral Resources,Chinese Academy of Geological Science,Beijing 100037,China)

机构地区：[1]成都理工大学地球与行星科学学院,成都610059 [2]中国地质科学院矿产资源研究所,北京100037

出　　处：《岩石学报》2025年第5期1685-1703,共19页Acta Petrologica Sinica

基　　金：国家重点研发计划项目(2022YFC2905003);国家自然科学基金项目(42230813、42402078)联合资助详细信息。

摘　　要：全球的铼(Re)资源主要来自斑岩铜矿中的辉钼矿。目前, 关于Re富集机制研究主要集中在俯冲背景下弧环境的斑岩型铜矿床, 相对而言, 碰撞背景下Re富集机制的研究仍十分薄弱。西藏冈底斯成矿带发育大量的富铼斑岩型铜矿床, 均形成于碰撞背景。本文以其中最为典型的甲玛铜多金属矿床中的辉钼矿为研究对象, 采用显微结构观察、电子探针(EPMA)和LA-ICP-MS分析技术, 查明了Re在辉钼矿中的赋存分布状态, 探讨了碰撞背景下Re的富集机制。根据辉钼矿赋存脉体的蚀变特征, 将其划分为三个类型: (1)Mol-A: 产于钾长石-黑云母化的A脉中, Re含量最低(0.1×10^(-6)~262.0×10^(-6), 平均值116.1×10^(-6));(2)Mol-B: 产于石英有关的B脉中, Re含量最高(150.4×10^(-6)~1420×10^(-6), 平均值690.8×10^(-6));(3)Mol-D: 产于石英-绢云母化D脉中, Re含量介于Mol-A与Mol-B之间(10×10^(-6)~1010×10^(-6), 平均值374.9×10^(-6))。结果显示, Cu、Au、Bi、Te等亲铜元素与Re的地球化学行为是解耦的。研究表明, Re在甲玛矿床中主要以类质同象和原子吸附形式分别赋存于辉钼矿晶格内部和表面, 且分布极不均匀, 部分呈现带状、核部富集的分布特征。在早期成矿流体高温、高氧逸度、富CO_(2)条件下Re以高氧化态气相形式进行远距离迁移富集, 随着温度、氧逸度下降, Re转向低氧化态液相迁移富集于硫化物熔体中, 伴随着CO_(2)逃逸、流体沸腾等因素使Re大量分配进入辉钼矿中发生沉淀, 而晚期浅部地层有机沉积物竞争吸附Re则造成辉钼矿中部分Re损失。氧逸度可能是辉钼矿中Re富集的重要机制, 控制着不同演化阶段中Re的存在形式。早期成矿流体氧逸度高, Re主要以稳定的Re^(7+)形式存在, 随着水岩反应的进行导致流体氧逸度降低, 使得流体Re^(7+)转向Re^(4+)形式稳定存在。最终Re^(4+)大量替换辉钼矿中Mo^(4+)形成了甲玛富Re辉钼矿�The global rhenium (Re) resources are mainly derived from molybdenite in porphyry copper deposits. At present, the research on the enrichment mechanism of Re is mainly focused on the porphyry deposits in the arc environment under the subduction background, however, the research on the enrichment mechanism of Re under the collision background is still weak. A large number of Re-rich porphyry copper deposits are developed in the Gangdese metallogenic belt, Tibet. In this paper, molybdenite in the Jiama copper polymetallic deposit under the typical collision background is taken as the research object. Microstructure observation, EPMA and LA-ICP-MS analysis techniques were used to identify the occurrence and distribution of Re in molybdenite, from which the enrichment mechanism of Re under the collision background was discussed. According to the alteration characteristics of molybdenite veins, the ore is divided into three types: (1) Mol-A: developed in A-type veins related to K-feldspar-biotite, with the lowest Re contents of 0.1×10^(-6)~262.0×10^(-6) (averag 116.1×10^(-6));(2) Mol-B: developed in B-type veins related to quartz, with highest Re contents (150.4×10^(-6)~1420×10^(-6), averag 690.8×10^(-6));(3) Mol-D: developed in the D-type veins related to quartz-sericite, with moderate Re contents in between Mol-A and Mol-B (10×10^(-6)~1010×10^(-6), averag 374.9×10^(-6)). The results show that the geochemical behavior of Cu, Au, Bi, Te and Re is decoupled. In summary, the research shows that Re mainly occurs in the interior and surface of molybdenite lattice in the form of isomorphism and atomic adsorption in the Jiama deposit, whose distribution is extremely uneven, partially showing the distribution characteristics of banded and core enrichment. Under the condition of high temperature, high oxygen fugacity and rich CO_(2) in the early stage, Re migrates and enriches in the form of high oxidation state gas phase. With the decrease of temperature and oxygen fugacity, Re turns to low oxidation state liquid ph

关 键 词：甲玛 铼 辉钼矿 富集机制 碰撞背景 

分 类 号：P578.291[天文地球—矿物学] P618.87[天文地球—地质学]