西藏多龙矿集区铜金流体演化过程探讨——来自硫同位素的证据  

Investigation of fluid evolution in Duolong copper-gold ore district,Tibet:Evidence from sulfur isotope

作　　者：孙嘉[1] 段先哲 李玉彬 SUN Jia;DUAN XianZhe;LI YuBin(MNR Key Laboratory of Metallogeny and Mineral Assessment,Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing 100037,China;School of Nuclear Resource Engineering,University of South China,Hengyang 421001,Hunan,China;Geological Survey of Tibet,Lhassa 850000,Tibet,China)

机构地区：[1]中国地质科学院矿产资源研究所自然资源部成矿作用和资源评价重点实验室,北京100037 [2]南华大学,核资源工程学院,湖南衡阳421001 [3]西藏自治区地质调查院,西藏拉萨850000

出　　处：《矿床地质》2021年第5期1085-1099,共15页Mineral Deposits

基　　金：国家自然科学基金青年科学基金项目(编号:41902098);国家重点研发计划项目(编号:2017YFC0601403);中国地质调查局地质调查工作项目(编号:1212011120994)联合资助。

摘　　要：西藏多龙矿集区发育世界典型的斑岩铜矿系统,文章选取区内多个代表性矿床开展硫同位素研究,并结合前人数据,为探讨该成矿系统成矿物质来源、流体演化过程提供了新证据。研究表明,波龙、拿若、拿厅、拿顿和铁格隆南矿床δ^(34)S平均值相似(接近于0),指示含矿岩浆提供了各矿床所需的硫元素。此外,区内典型矿床流体演化过程可分为2类:①流体演化主要受控于温度变化,表现为δ^(34)S随温度降低而降低(如拿顿矿床);②流体演化受温度和氧化还原状态共同影响,表现为δ^(34)S随温度降低而升高(如:波龙和拿若矿床),或是随温度降低,δ^(34)S波动变化范围较大(如拿厅和铁格隆南矿床)。结合岩相学证据,文章推测热液体系氧化还原状态的变化是由水岩反应所导致,最后,文章提出多龙矿集区内矿化阶段硫化物通常具有较低的δ^(34)S,指示成矿流体为高氧化性流体,并且该特征在类似矿床的找矿勘查工作中也可发挥积极的指示作用。The Duolong ore district in Tibet hosts a world-class porphyry copper system.In this paper,we investigate the sulfur isotope of the representative porphyry and epithermal deposits in this district,which provides new evidence for interpretation of ore-related hydrothermal processes.Our study indicates that the Bolong,Naruo,Nating,Nadun,and Tiegelongnan have similar averageδ^(34)S values and close to 0.Thus,it is suggested that sulfur was sourced from intrusions.Meanwhile,it is inferred that the fluid evolution is mainly controlled by:①decrease of temperature,which is featured by the lowering ofδ^(34)S(the Nadun deposit);②decrease of temperature and oxidation state,which is characterized by increase ofδ^(34)S(Bolong and Naruo deposits),or the large variation ofδ^(34)S(Nating and Tiegelongnan deposits).Based on petrological evidence,it is concluded that the change of oxidation state is mostly caused by water‒rock interaction.In addition,we propose that the sulfides form ore forming stage are featured by relatively lowerδ^(34)S,implying the ore‒forming fluids are oxidized.Thus,such features could be applied in exploration of porphyry deposits.

关 键 词：地球化学 硫同位素 流体演化 氧化还原状态 斑岩铜矿系统 多龙矿集区 

分 类 号：P618.41[天文地球—矿床学]