西藏多龙矿集区拿顿铜金矿床成矿时代的厘定及其找矿指示意义  

Timing of Cu-Au mineralization in Nadun Cu-Au deposit of Duolong district,Tibet,and its implication for mineral exploration

作　　者：孙嘉[1] 毛景文[1] 王佳新[1] 姚佛军[1] 李玉彬 SUN Jia;MAO JingWen;WANG JiaXin;YAO FuJun;LI YuBin(MNR Key Laboratory of Metallogeny and Mineral Assessment,Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing 100037,China;Geological Survey of Tibet,Lhasa 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]西藏自治区地质调查院,拉萨西藏85000

出　　处：《矿床地质》2020年第6期1091-1102,共12页Mineral Deposits

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

摘　　要：西藏多龙矿集区是中国新发现的具有世界级规模的铜金矿集区。目前,该矿集区的中部和北部已发现多个斑岩型和斑岩-浅成低温热液型矿床,而区内西南部也发现了多个铜金矿床,指示了良好的找矿潜力。拿顿是矿集区内西南部具有代表性的铜金矿床,矿化类型为浅成低温热液型。野外地质调查表明,该矿床成矿作用可分为2个阶段,早阶段矿化主要赋存于角砾岩筒中,并与角砾岩筒同时形成,而晚阶段矿化主要以脉体形式产出,切穿角砾岩筒及早阶段矿化。年代学研究结果显示,角砾岩筒中以角砾形式产出的花岗闪长斑岩锆石U-Pb年龄为(117.5±0.7)Ma,被后期花岗闪长斑岩(116.1±1.3Ma)侵入,由此指示角砾岩筒及早阶段矿化形成于116~117 Ma。此外,明矾石40Ar-39Ar年代学研究进一步表明,晚阶段石英-明矾石-硫化物脉形成于(111.3±2.5)Ma,这也证实该矿区成矿作用具有多阶段性特征。文章结果指示,拿顿铜金矿可能存在多期与浅成低温热液型矿化有关的成矿岩体,并且多龙矿集区内也可能存在更多形成于111 Ma而未被发现的矿床。The Duolong Cu-Au district,located in central Tibet,is a newly discovered world-class metallogenic district in China.At present,a number of porphyry and porphyry-epithermal deposits have been discovered in the central and northern parts of the district;meanwhile,several Cu-Au deposits have also been discovered in the southwestern part,implying a promising exploration potential in this region.Nadun is a representative epithermal Cu-Au deposit that located in the southwestern part.Based on field investigation,the Cu-Au mineralization could be divided into two stages,the early-stage mineralization,hosted by the breccia pipe,coincided with the formation of breccia pipe,and the late-stage veins cut the breccia pipe and the early-stage mineralization。Zircon U-Pb geo1092 chorology suggested the granodiorite clast from the breccia pipe formed at(117.5±0.7)Ma,whereas previous studies indicated the breccia pipe was intruded by a granodiorite porphyry dated at(116.1±1.3)Ma,implying the breccia pipe and associated Cu-Au mineralization formed at 116~117 Ma.In addition,alunite 40Ar-39Ar geochorology revealed that quartz-alunite-sulfide veins that truncated the breccia pipe formed at(111.3±2.5)Ma,indicating the Nadun deposit was featured by episodic ore-forming events.Our study highlights the possibility of locating multiple causative porphyry intrusions in the Nadun deposit and the Duolong district as well.

关 键 词：地球化学 锆石U-Pb年龄 明矾石40Ar-39Ar年龄 浅成低温热液型矿化 多龙矿集区 拿顿铜金矿 

分 类 号：P618.41[天文地球—矿床学] P618.51[天文地球—地质学]