新疆北部喇嘛苏铜矿床成矿时代与构造背景:来自石榴子石原位LA-ICP-MS U-Pb测年的证据  

Geochronology and Tectonic Setting of the Lamasu Cu Deposit in Northern Xinjiang:Evidence from In-situ LA-ICP-MS Garnet U-Pb Dating

作　　者：王晓彤 刘军[1] 杨艳 何军成 WANG Xiaotong;LIU Jun;YANG Yan;HE Juncheng(MNR Key Laboratory of Metallogeny and Mineral Assessment,Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing 100037,China;China University of Geosciences(Beijing),Beijing 100083,China;Development Research Center of Chinese Geological Survey,Beijing 100037,China)

机构地区：[1]中国地质科学院矿产资源研究所自然资源部成矿作用与资源评价重点实验室,北京100037 [2]中国地质大学(北京),北京100083 [3]中国地质调查局发展研究中心,北京100037

出　　处：《现代地质》2023年第3期645-661,共17页Geoscience

基　　金：国家自然科学基金项目(41672066,41820104010);中央级公益性科研院所基本科研业务费项目(KK2106,KK2205);国家重点研发计划项目(2017YFC0601403)

摘　　要：石榴子石是矽卡岩型矿床中最常见的蚀变矿物,石榴子石U-Pb定年技术的发展应用为准确限定矽卡岩成矿作用时代提供了新手段。我国西天山地区发育大量矽卡岩型铜矿床,由于缺乏精确的成矿年代学数据,制约了矿床成因和成矿动力学背景认识的深入。为了精确厘定西天山地区矽卡岩型铜矿化时代,本文选取代表性的喇嘛苏大型铜矿床矽卡岩带中石榴子石为研究对象,利用电子探针和LA-ICP-MS原位U-Pb定年技术开展了矿物成分和年代学分析。根据喇嘛苏矿床石榴子石的岩相学特征,将其分为红棕色石榴子石、浅棕色石榴子石和黄绿色石榴子石三类。电子探针分析显示,三类石榴子石的端元组分均主要为钙铁榴石(56.96%~85.09%),其次为钙铝榴石(14.33%~43.85%),属于钙铁榴石-钙铝榴石系列。U-Pb定年获得3件石榴子石的加权平均年龄介于(389.1±2.0)~(387.0±2.3)Ma之间,表明成矿时间为中泥盆世。结合区域构造演化史,喇嘛苏矽卡岩型铜矿床形成于北天山洋壳的俯冲环境。Garnet,as a typical altered mineral in skarn deposits,is suggested to be an important mineral for obtaining accurate ore-forming age.There are abundant skarn Cu deposits in the Chinese Western Tianshan,yet the actual skarn Cu ore-forming ages remain controversial.This limits sufficient understanding of skarn Cu ore genesis and metallogenic dynamic background in the Chinese Western Tianshan.To obtain accurate metallogenic age of skarn Cu deposits in the Chinese Western Tianshan,we selected garnet from the Lamasu Cu deposit for systematic geochemical and geochronological study by Electron Probe X-ray Micro-Analyzer(EPMA)and LA-ICP-MS U-Pb dating.According to the hand-specimen and petrographic characteristics of the garnet minerals,the Lamasu deposit has three types of garnets,including red-brown,light-brown and yellow-green garnets.These garnets belong to the andradite-grossularite series,and occur as andradite(56.96%-85.09%)with minor grossularite(14.33%-43.85%).Three types of garnets yielded LA-ICP-MS U-Pb weighted average ages of(389.1±2.0)to(387.0±2.3)Ma,indicating that the Lamasu Cu mineralization occurred during the Middle Devonian subduction of the northern Tianshan oceanic crust.

关 键 词：LA-ICP-MS U-PB 石榴子石 矽卡岩 喇嘛苏 新疆 

分 类 号：P575.1[天文地球—矿物学] P578.947[天文地球—地质学] P597.3P611.1