东昆仑东段杏树沟金矿化带内石英钠长斑岩LA-ICP-MS锆石U-Pb年龄及围岩地球化学特征

东昆仑成矿带是我国西部重大成(找)矿潜力的贵金属-有色金属成矿带。野外调查期间,对东昆仑东段都兰县诺木洪南下石炭统哈拉郭勒组(C₁h)杏树沟金矿(化)点进行了年代学及围岩地球化学研究。通过高精度LA-ICP-MS锆石微区原位U-Pb同位素测年,获得金矿(化)点的石英钠长斑岩 ²⁰⁶Pb/²³⁸U 年龄加权平均值为243.4±1.9 Ma,确定金矿(化)发生在早三叠世。地球化学分析表明,杏树沟金矿(化)点围岩(安山玄武岩)具有高Al₂O₃、Na₂O,低TiO₂、K₂O的特征。在Zr/TiO₂-Nb/Y图解中全部样品均落入安山玄武岩区,TFeO/Mg-SiO₂图解中全部样品均落入拉斑系列区域中,属于拉斑系列玄武岩。稀土和微量元素显示其富集LREE、LILE和部分HFSE,Nb、Ta、Nd、Zr、Hf相对亏损,REE表现为LREE/HREE明显分离的分配模式,从多种判别图解综合分析,认为该套火山岩形成于大陆裂谷环境中。

Determination of the age for the Xingshu valley gold mineralization spots in the eastern segment of Kunlun orogenic belt and the geochemical characteristics of its surrounding rocks

Eastern Kunlun metallogenic belt is the precious metal-nonferrous metal ore-forming belt that has great prospecting potential in western China.Some gold mineralization spots were studied on chronology and the surrounding rock geochemical character in Early Carboniferous Halaguoge Formation during the investigation in Nuomuhong Township Dulan County,eastern segment of Kunlun orogenic belt.The ²⁰⁶Pb/²³⁸U weighted average age of 243.4±1.9 Ma,which was obtained by in-situ LA-ICP-MS zircon dating of the quartz albite porphyry,proves that this gold deposit was formed in Early Triassic.The results of geochemical analysis show that the surrounding rock of Xingshu valley gold mineralization spots(Andesitic basalt)is characterized by high Al₂O₃、Na₂O and low TiO₂,K₂O.In diagram for Zr/TiO₂-Nb/Y and TFeO/Mg-SiO₂,all samples fall into andesitic basalt area and the tholeiitic area,respectively,this indicates that it belongs to the tholeiitic basalt.The volcanic rocks were formed in a continental rift environment judging by rich LREE,LILE and some of HFSE; depleted Nb,Ta,Nd,Zr and Hf; the allocation model for clear separation of LREE/HREE and the comprehensive analysis of discrimination diagrams.