Geochronologic constraints on magmatic intrusions and mineralization of the Zhunuo porphyry copper deposit in Gangdese,Tibet  

作　　者：ZHENG YouYe ZHANG GangYang XU RongKe GAO ShunBao PANG YingChun CAO Liang DU AnDao SHI YuRuo 

机构地区：[1]Facuty of Earth Resources, China University of Geosciences, Wuhan 430074, China [2]State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China [3]No. 2 Geological Team, Tibet Bureau of Geology and Exploration, Lhasa 850003, China [4]National Geological Analytical and Testing Center, Chinese Academy of Geological Sciences, Beijing 100037, China [5]Beijing Ion Microprobe Center of the Chinese Academy of Geological Sciences, Beijing 100037, China

出　　处：《Chinese Science Bulletin》2007年第22期3139-3147,共9页

基　　金：Supported by the National Key Project for Basic Research of China (Grant No. 2002CB412610);National Key Project for New-round National Resource Investiga-tions (Grant No. 200210200001);pre-National 973 Project (Grant No. 2005CCA05600)

摘　　要：In situ zircon U-Pb ages for the recently discovered Zhunuo porphyry copper deposit in the western part of the Gangdese metallogenic belt in Tibet were determined by sensitive high-resolution ion mi-croprobe(SHRIMP) . The ages can be divided into two separate groups,reflecting more than four major tectono-magmatic events in the area. The 62.5±2.5 Ma age of inherited zircons may be related to the volcanic eruption of the Linzizong Group formed shortly after the India-Asia continental collision. The 50.1±3.6 Ma age most likely corresponds to the time of underplating of mantle-derived mafic magma in Gangdese. The 15.6±0.6 Ma age obtained from magmatic zircons is interpreted as the age of crystalli-zation of the Zhunuo ore-forming porphyry. Finally,a molybdenite Re-Os isochron age of 13.72±0.62 Ma is consistent with another zircon U-Pb age of 13.3 ±0.2 Ma,representing the time of copper mineraliza-tion. These ages,in combination with available literature data,indicate that magmatic crystallization and copper mineralization in the Gangdese metallogenic belt became gradually younger westward,and further suggest that the Zhunuo porphyry copper deposit was formed in the same tectonic stage as other porphyry copper deposits in the eastern and central Gangdese belt. This conclusion provides critical information for future exploration of porphyry copper deposits in western Gangdese.In situ zircon U-Pb ages for the recently discovered Zhunuo porphyry copper deposit in the western part of the Gangdese metallogenic belt in Tibet were determined by sensitive high-resolution ion microprobe （SHRIMP）. The ages can be divided into two separate groups, reflecting more than four major tectono-magmatic events in the area. The 62.5±2.5 Ma age of inherited zircons may be related to the volcanic eruption of the Linzizong Group formed shortly after the India-Asia continental collision. The 50.1±3.6 Ma age most likely corresponds to the time of underplating of mantle-derived mafic magma in Gangdese. The 15.6±0.6 Ma age obtained from magmatic zircons is interpreted as the age of crystallization of the Zhunuo ore-forming porphyry. Finally, a molybdenite Re-Os isochron age of 13.72±0.62 Ma is consistent with another zircon U-Pb age of 13.3±0.2 Ma, representing the time of copper mineralization. These ages, in combination with available literature data, indicate that magmatic crystallization and copper mineralization in the Gangdese metallogenic belt became gradually younger westward, and further suggest that the Zhunuo porphyry copper deposit was formed in the same tectonic stage as other porphyry copper deposits in the eastern and central Gangdese belt. This conclusion provides critical information for future exploration of porphyry copper deposits in western Gangdese.

关 键 词：斑岩 铜 堆积物 西藏 锝 

分 类 号：P57[天文地球—矿物学]