西藏斯弄多铅锌矿床成矿岩体LA-ICP-MS锆石U-Pb年龄及地质意义  

LA-ICP-MS Zircon U-Pb Age of Granite Porphyry in the Sinongduo Lead-Zinc Deposit and Its Geological Significance

作　　者：张遵遵[1,2] 于玉帅[1,2] 杨竹森[3] 刘英超[4] ZHANG Zun-zun;YU Yu-shuai;YANG Zhu-sen;LIU Ying-chao(Wuhan Centre of China Geological Survey,Wuhan 430205,China;Research Center of Granitic Diagenesis and Mineralization,CGS,Wuhan 430205,China;Institute of Mineral Resources,CAGS,Beijing 100037,China;Institute of Geology,GAGS,Beijing 100037,China)

机构地区：[1]中国地质调查局武汉地质调查中心,武汉430205 [2]中国地质调查局花岗岩成岩成矿地质研究中心,武汉430205 [3]中国地质科学院矿产资源研究所,北京100037 [4]中国地质科学院地质研究所,北京100037

出　　处：《矿物岩石地球化学通报》2018年第6期1152-1162,共11页Bulletin of Mineralogy, Petrology and Geochemistry

基　　金：国家自然科学基金项目(41503040);国家重点研发计划课题(2016YFC0600306)

摘　　要：斯弄多铅锌矿床位于南冈底斯-念青唐古拉成矿带北缘铅锌银多金属矿带上,该矿床铅锌矿化与矿区花岗斑岩密切相关,为典型的热液脉型-矽卡岩型铅锌矿床。为厘定其成岩成矿时代,本文对矿区花岗斑岩进行了锆石LA-ICP-MS U-Pb年龄测定。结果得到2组年龄,一组年龄介于(75.1±1.8)^(77.7±1.8)Ma之间,加权平均年龄为(75.7±0.9)Ma(MSWD=0.27,n=11),可能反映岩浆在岩浆房演化过程中结晶的锆石年龄;另一组年龄为(67.5±1.4)^(69.4±1.4)Ma,加权平均年龄为(68.8±1.2)Ma(MSWD=0.31,n=6),代表花岗斑岩真实的结晶年龄,这一花岗斑岩的年龄(68.8±1.2)Ma明显早于冈底斯带内主碰撞期形成的矽卡岩型矿床。结合该成矿带其他矿床的成岩、成矿年龄,本文认为南冈底斯-念青唐古拉成矿带在印-亚大陆碰撞早期或新特提斯洋壳俯冲晚期,也伴有较强的铅锌多金属成矿作用。The Sinongduo lead-zinc deposit is located in the north of South Gangdese-Nyainqentanglha metallogenic belt. The lead and zinc mineralization is closely related to the granite porphyry, and is a typical hydrothermal vein and skarn type lead-zinc mineralization. In order to constrain the age of rock and mineralization, we measured the zircon U-Pb age for the granite porphyry by laser ablation inductively coupled plasma mass spectrometry(LA-ICP-MS) which has been thought to be closely related to lead-zinc mineralization. The zircons U-Pb isotopic compositions can be divided into two groups. The first group(11 analyses) yields 206Pb/238U age from 75.1 Ma to 77.7 Ma, with a weighted mean 206Pb/238U age of(75.7±0.9) Ma(MSWD=0.27). The age may indicate the timing of crystallization of zircon in the magma chamber. The second group has ages ranging from 67.5 Ma to 69.4 Ma, with an average of(68.8±1.2) Ma(MSWD=0.31, n=6), which represents the crystallization age of granite porphyry, earlier than the main-collision epoch of the Indo-Asia continental collision. Based on the ages of ignesous rocks and mineralization of other porphyry/skarn deposit in this belt, we can conclude that intense lead-zinc polymetallic mineralization in the northern of South Gangdese-Nyainqentanglha metallogenic belt is associated with the early collision or late period subduction for new Tethys oceanic crust, also accompanied.

关 键 词：花岗斑岩 锆石U-PB年龄 斯弄多铅-锌矿床 冈底斯-念青唐古拉成矿带 西藏 

分 类 号：P597[天文地球—地球化学]