内蒙古扎拉格阿木铜矿床成矿岩体地质地球化学及其成矿学意义  

Geological and Geochemical Characteristics of Ore-forming Granite Porphyry and Its Metallogenic Significance in the Zhalageamu Copper Deposit,Inner Mongolia

作　　者：宋彦博 王建平[1] 沈存利 车东[1] 杨文华 郭海蛟 SONG Yanbo;WANG Jianping;SHEN Cunli;CHE Dong;YANG Wenhua;GUO Haijiao(School of Earth Sciences and Resources,China University of Geosciences(Beijing),Beijing 100083,China;Nonferrous Geological Bureau of Inner Mongolia,Hohhot,Inner Mongolia 010010,China)

机构地区：[1]中国地质大学(北京)地球科学与资源学院,北京100083 [2]内蒙古自治区有色地质勘查局,内蒙古呼和浩特010010

出　　处：《现代地质》2023年第6期1482-1494,共13页Geoscience

基　　金：内蒙古自治区自然资源厅项目“内蒙古北山成矿带黑鹰山-石板井地区铁铜钼多金属成矿系统研究与找矿预测”(2022-TZH03)。

摘　　要：扎拉格阿木铜矿床位于锡林浩特古老地块东北部边缘,是内蒙古自治区也是大兴安岭中南段西坡富Zn-Pb-Ag成矿带新近发现的一处与花岗斑岩相关的中等规模热液型铜矿床,研究其成岩成矿机制能为区域找铜提供理论基础,并拓宽勘查方向。为查明花岗斑岩形成时代、岩浆源区特征及其与矿化之间的关系,本文对该岩体进行了岩相学、全岩元素组成、锆石U-Pb年代学和全岩Sr-Nd同位素组成研究。结果表明,岩体具高SiO_(2)和Al_(2)O_(3)含量、低MgO含量,轻稀土元素富集、重稀土元素亏损,弱Eu负异常,亏损Ta、Nb、Ti和P等高场强元素,富集Rb、K、La和Th等大离子亲石元素。这些特征表明其属高钾钙碱性I型花岗岩。ε_(Nd)(t)值为较小的正值,变化范围为2.1~3.3,对应的Nd同位素模式年龄T_(DM)值在980~740 Ma之间,显示花岗斑岩岩浆的形成与壳幔物质的混合有关。岩浆锆石U-Pb年龄为(254.51±2.13)Ma,指示成岩及与其相关的成矿作用发生于晚二叠世。综合分析认为,扎拉格阿木铜矿床形成于晚二叠世岛弧构造环境,可能与贺根山洋盆俯冲作用有关。The Zhalageamu copper deposit is located in the northeastern margin of the ancient Xilinhot Block,and is a recently discovered medium-sized hydrothermal copper deposit in the Zn-Pb-Ag metallogenic belt(western slope of the south-central Greater Khingan Range)in Inner Mongolia.Studies on its magmatic and metallogenic mechanism provides the theoretical basis for copper exploration and broadens the exploration direction.The granite porphyry is closely space-time associated with Cu mineralization of the Zhalageamu copper deposit.To clarify the formation age and source characteristics of the granite porphyry from Zhalageamu,and to address the magmatic-metallogenic relationship,the granite porphyry was collected for petrography and geochemical analysis,zircon U-Pb dating and Sr-Nd isotope analysis.The result shows that the granite porphyry from Zhalageamu is characterized by high SiO_(2)and Al_(2)O_(3),low MgO,and enrichments in Rb,K,La,and Th and depletions in Ta,Nb,Ti,and P.All of the samples are characterized by the enrichment of LREEs relative to HREEs,and weak negative Eu anomaly.This indicates that the granite porphyry belongs to high-K calc-alkaline I-type granite.The granite porphyry hasε_(Nd)(t)=2.1 to 3.3 and young Nd model age of 980-740 Ma,indicating that the primary magma of the granite porphyry is derved from the mixture of crust and mantle materials.The magmatic zircon age of the granite porphyry is 254.51±2.13 Ma,indicating that the granite porphyry and relevant Cu mineralization generated in the Late Permian.A comprehensive analysis supports that the Zhalageamu copper deposit was formed in a Late Permian volcanic arc setting,which may be closely related to the subduction of the Hegenshan oceanic Plate.

关 键 词：扎拉格阿木铜矿床 花岗斑岩 岩石地球化学 锆石U-Pb定年 SR-ND同位素 

分 类 号：P595[天文地球—地球化学] P597.3[天文地球—地质学] P618.41P588.121