西准噶尔包古图成矿斑岩年代学与地球化学：岩石成因与构造、铜金成矿意义  

Geochronology and Geochemistry of the Ore-Bearing Porphyries in the Baogutu Area (Western Junggar):Petrogenesis and Their Implications for Tectonics and Cu-Au Mineralization

作　　者：唐功建[1,2] 王强[1] 赵振华[1] Derek A.Wyman 陈海红[4] 贾小辉[1,2] 姜子琦[1,2] 

机构地区：[1]中国科学院广州地球化学研究所同位素年代学与地球化学重点实验室,广东广州510640 [2]中国科学院研究生院,北京100049 [3]悉尼大学地球科学学院地质与地球物理系,澳大利亚新南威尔士 [4]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

出　　处：《地球科学（中国地质大学学报）》2009年第1期56-74,共19页Earth Science-Journal of China University of Geosciences

基　　金：国家重点基础研究发展规划项目(2007CB411308);国家自然科学基金项目(Nos.40721063,40673037,40572042);中国科学院知识创新项目(KZCX2-YW-128)

摘　　要：西准噶尔包古图地区的一些小型斑岩体或脉岩与铜金矿化的关系非常密切,引起了人们的广泛关注.报道了一些斑岩的LA-ICP-MS锆石U-Pb定年结果和岩石地球化学成分资料.Ⅱ、Ⅴ岩体的石英闪长斑岩中岩浆结晶锆石的定年结果分别为314.9±1.7Ma和309.9±1.9Ma,Ⅲ岩体的闪长玢岩中岩浆结晶锆石的定年结果为313.9±2.6Ma,表明包古图地区的岩体形成于晚石炭世.包古图地区小岩体的岩石富Na、高Sr,贫Y和Yb,无明显的Eu异常,具有埃达克岩特征,同时有些岩石富集MgO(3.93%～4.78%),具有高的Mg#(68～74),类似高镁安山岩.结合区域地质和岩浆岩的资料,认为:(1)包古图地区的小岩体形成于晚石炭世的岛弧环境,并可能与石炭纪的洋脊俯冲有关,其中埃达克质岩为俯冲洋脊两侧的板片熔融而形成,而高镁闪长岩类为俯冲板片熔体与地幔橄榄岩相互作用的产物;(2)包古图地区的铜金矿床也很可能与洋脊俯冲有关,高氧逸度的板片熔体上升并与地幔橄榄岩相互作用,这使得地幔中的金属硫化物不稳定,释放出金属成矿物质,从而使得Cu、Au等在熔体中不断富集而形成矿床.The small porphyry plutons or dikes in the Baogutu area, western Junggar, have attracted wide attentions owing to the close association between them and Cu-Au mineralization. This paper presents new LA-ICP-MS zircon U-Pb age and geochemical data of ore-bearing porphyries in the Baogutu area. The quartz diorite porphyry bodies Ⅱ and Ⅴand diorite porphyry body Ⅲ have crystallization ages of 314.9±1.7 Ma, 309.9±1.9 Ma, and 313.9±2.6 Ma, respectively, suggesting they were generated in Late Carboniferous. They are characterized by high Na2O/K2O and high Sr values but low Y and Yb contents, and negligible Eu anomalies, similar to adakites. In addition, some samples have high MgO（3.93%-4.78%） and Mg#（47-74） values, similar to high-Mg andesite. Taking into account the data of regional geology and magmatic rocks, we suggest that （1）The Baogutu intrusive rocks were possibly formed in an island-arc setting linking to ocean ridge suduction in Late Carboniferous, the adakitic magmas have likely formed by partial melting of the leading edge of the subducted ridge, and high-Mg diorites possibly originated from the interaction between adakitic melts and mantle peridotite; （2） The Baogutu Cu-Au mineralization might occur above a slab window during ocean ridge suduction, and the interaction between high oxygen fugacity slab melt and mantle peridotite caused the decomposition of metal sulfides and the Cu and Au mineralization.

关 键 词：锆石U-Pb定年 埃达克岩 高镁闪长岩 洋脊俯冲 板片窗 西准噶尔 中亚造山带 

分 类 号：P581[天文地球—岩石学]