青海省格尔木市西山铜多金属矿成矿岩体锆石U-Pb定年及地球化学特征  

Origin of Magmatic Rocks from Xishan Copper Polymetallic Deposit,Geermu City,Qinghai Province:Insights from Zircon U-Pb Dating and Geochemical Characteristics

作　　者：张雨莲[1] 栗亚芝[1] 贾群子[1] 孔会磊[1] 武明德 南卡俄吾 Zhang Yulian;Li Yazhi;Jia Qunzi;Kong Huilei;Wu Mingde;Nanka Ewu(Xi'an Center of Geological Survey,China Geological Survey,Xi'an 710054,China;Environmental Geological Exploration Bureau of Qinghai Province,Xining 810007,China;Shaanxi Provincial Land Engineering Construction Group,Xi'an 710075,China)

机构地区：[1]中国地质调查局西安地质调查中心,陕西西安710054 [2]青海省环境地质勘查局,青海西宁810007 [3]陕西省土地工程建设集团,陕西西安710075

出　　处：《地球科学》2018年第12期4364-4374,共11页Earth Science

基　　金：中国地质调查局项目(Nos.DD20160367,DD20160013)

摘　　要：格尔木西山铜多金属矿的成矿岩体为似斑状二长花岗岩,位于昆中断裂与昆北断裂之间的秦祁昆晚加里东造山系内,其理论研究工作十分薄弱.以岩石地球化学、同位素年代学为手段进行研究,表明岩体属于高钾钙碱性系列过铝质花岗岩类.稀土、微量元素特征为轻稀土富集型,右倾式,具强负铕异常,富集大离子亲石元素(Th、U、K),明显亏损高场强元素(如P、Ti),相对于Rb和Th明显亏损Ba.岩浆为地壳来源,具弱分离结晶花岗岩特征.在似斑状二长花岗岩中获得岩浆锆石LA-ICP-MSU-Pb加权平均年龄(267.5±3.4Ma)与谐和年龄(267.0±2.9Ma)的数据,表明岩体形成于中二叠世的同时,也约束了成矿作用的下限.矿床类型应为与花岗质岩浆活动有关的构造热液型多金属矿.The magmatic rock of porphyroid monzonitic granite of Xishan copper polymetallic deposit, Geermu City, is located in the Late Caledonian Qinling-Qilian-Kulun orogen between the Central and North Kunlun fault,and the research work is still very poor. Based on the rock geochemistry and isotope chronology, this paper shows that the magmatic rocks belong to high potassium calc-alkaline series and peraluminous granites. The chondrite-normalized rare earth element (REE) distribution patterns of the magmatic rocks are enriched in the light REE (LREE) and display strong negative Eu anomalies. The magmatic rocks are enriched in large ion lithophile elements (Th, U, K), while depleted in high field strength elements (e.g., P, Ti) and in Ba relative to Rb and Th. The magma is the source of the crust and has the characteristics of weakly separated crystalline granite. The U-Pb weighted age (average 267.5±3.4 Ma) and concordant age (267.0±2.9 Ma) acquired in zircon from porphyritic monzonitic granite show that the rock mass formed in middle Permian, which thus constrainted the lower limit of mineralization. The origin of the deposit should be polymetallic tectonic hydrothermal type, which was related to granitic magmatism.

关 键 词：地球化学 锆石U-PB定年 似斑状二长花岗岩 格尔木西山 东昆仑 

分 类 号：P597[天文地球—地球化学]