The Liwu-type copper deposit refers to stratiform or stratiform-like or lenticular Cu-rich ore deposits occurring in the suture zone between the western margin of the Yangtze block and Songpan-Ganzi fold belt.Research of geological features,mineralization type and mineralography indicates that the Liwu-type copper deposit belongs to hydrothermal deposits.In order to accurately constrain the metallogenic age,we performed NTIMS Re-Os geochronological dating for the chalcopyrite from massive-veined ores.The results show isochron ages of chalcopyrites ranging from 150.2 ± 4.9 to 151.1 ± 4.8 Ma (2σ),indicating that the Liwu-type copper deposit formed in the Late Jurassic,distinctly later than the sedimentary time of the wall rock (Liwu Group),but roughly close to the age of the granite outcropping at the edge of Jianglang dome.Initial 187Os/188Os value of chalcopyrites is 3.65±0.29,suggesting that the ore-forming materials came mainly from the continental crust,probably from the Liwu Group.Combined with the tectonic-magmatic events of the dome,this paper proposed that the magmatic thermal uplifting caused by the early Yanshanian extension in the Songpan-Ganzi fold belt not only provided thermal forces and partial fluids for Cu mineralization,but also led to the formation of ore-inducing and orecontaining structure space.Therefore,magmatic thermal uplifting was the key factor of the formation of Liwu-type copper deposits.%川西里伍式富铜矿系指产于扬子地台西缘和松潘—甘孜造山带接合带江浪穹窿中的呈层状—似层状或透镜状的富铜矿床.矿床地质特征、矿化类型及矿相学研究表明其为热液型矿床.为精确厘定热液成矿作用发生的时间,本文对占主体的块状—脉状矿石中的黄铜矿进行了高精度NTIMS Re-Os同位素定年,获得等时线年龄为150.2±4.9～151.1±4.8Ma(2σ),说明里伍式富铜矿主要形成于晚侏罗世,明显晚于赋矿围岩新元古界里伍岩群,与江浪穹窿边部出露的花岗岩体年龄较为接近;初始187Os/188Os比值为3.65±0.29,说明其金属成矿物质来源主要为大陆地壳,很可能主要来源于赋矿岩层里伍岩群.结合成穹构造—岩浆事件,本文认为早燕山期区域伸展构造背景下的岩浆热隆作用不仅为铜富集提供了热动力和部分流体,同时为矿体最终定位提供了良好的导矿—容矿空间,是里伍式富铜矿形成的关键因素.
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