西藏青草山斑岩铜金矿床含矿斑岩锆石U-Pb年代学及岩石成因  

Zircon U-Pb Ages and Petrogenesis of Ore-Bearing Porphyry for Qingcaoshan Porphyry Cu-Au Deposit,Tibet

作　　者：郑海涛[1,2] 郑有业[1] 徐净 吴松[3] 郭建慈 高顺宝[2] 次琼 Zheng Haitao;Zheng Youye;Xu Jing;Wu Song;Guo Jianci;Gao Shunbao;Ci Qiong(State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences,Wuhan 430074,China;Geological Survey Institute,China University of Geosciences,Wuhan 430074,China;School of Earth Science and Resources,China University of Geosciences,Beijing 100083,China;Tibet Autonomous Region Geological and Mineral Exploration and Development Bureau,Lhasa 850000,China)

机构地区：[1]中国地质大学地质过程与矿产资源国家重点实验室,湖北武汉430074 [2]中国地质大学地质调查研究院,湖北武汉430074 [3]中国地质大学地球科学与资源学院,北京100083 [4]西藏自治区地质矿产勘查开发局,西藏拉萨850000

出　　处：《地球科学》2018年第8期2858-2874,共17页Earth Science

基　　金：国家自然科学基金项目(No.41302065);中国地质调查局项目(Nos.12120114081401;12120114000701);中央高校基本科研业务费专项资金(No.CUGL170413)

摘　　要：西藏青草山Cu-Au矿床是班公湖-怒江缝合带北侧新发现的具有大型远景的斑岩型矿床,但该矿床含矿斑岩的年龄、成因及源区一直未得到有效的约束.对青草山花岗闪长岩以及含矿花岗岩闪长斑岩进行了锆石年代学、Hf同位素以及岩石地球化学研究.结果显示,花岗闪长岩与含矿花岗闪长斑岩的侵入时代分别为131.2±0.3Ma与117.9±0.8Ma,代表了班公湖-怒江缝合带早期的成岩作用以及斑岩Cu-Au成矿作用.二者具有相似的地球化学特征,表明二者可能具有相同的岩浆源区,是不同时期同源岩浆活动的产物.结合含矿花岗闪长斑岩锆石Hf同位素组成,认为青草山含矿斑岩形成于班公湖-怒江洋壳向北俯冲过程中,是下地壳部分熔融的产物,受到了少量地幔物质的混合.The Qingcaoshan porphyry Cu-Au deposit,located in the northern Bangong Co-Nujiang belt,is a newly discovered porphyry deposit with huge potential.However,the age,origin and source area of the ore-bearing porphyry have not been effectively constrained.In this paper,we present the zircon geochronology,Hf isotope,and geochemistry of Qingcaoshan granodiorite and granodiorite porphyry.The analysis results show that the ages of granodiorite porphyry and granodiorite are 117.9±0.8 Ma and 131.2±0.3 Ma,respectively,which represent porphyry mineralization of Bangong Co-Nujiang metallogenic belt.They also exhibit relatively uniform in-situ zircon Hf isotopic compositions.In conclusion,Qingcaoshan ore-bearing porphyries were derived from the partial melting of mafic lower crust,which were induced by the subduction of the Bangong Co-Nujiang ocean crust,and they were also mixed by a small amount of enriched lithospheric mantle.

关 键 词：岩石成因 锆石U-Pb年龄 斑岩铜金矿床 青草山 班公湖-怒江成矿带 西藏 地球化学 地质年代学 

分 类 号：P597[天文地球—地球化学]