浙江平水铜矿含硫化物石英脉锆石U-Pb定年及其地质意义

LA-ICP-MS U-Pb dating of zircons from sulfide-bearing quartz veins in the Pingshui copper deposit, Zhejiang Province, and its geological implications

平水铜矿是位于扬子板块和华夏板块结合带(即钦杭结合带)北东段的典型火山岩型块状硫化物矿床,其铜矿主要形成于石英-黄铁矿-黄铜矿-闪锌矿阶段。本文对其块状矿体下部发育的含硫化物石英脉中锆石进行了LA-ICP-MSU-Pb精确测年,CL图像和Th/U比值显示锆石多为岩浆成因,测年数据可分为5组:981～988Ma、(950±15)Ma、(926±13)Ma、(899±21)Ma和93～120Ma。地质证据和定年结果表明平水铜矿的成矿年龄为新元古代早期(～899Ma),白垩纪的热事件(93～120Ma)对矿体进行了叠加改造作用。这一认识对深入了解平水铜矿的成因、形成和演化具有重要地质意义,同时提供了在钦杭结合带寻找火山岩型块状硫化物矿床的年代学信息。

The Pingshui copper deposit in Zhejiang Province is a typical volcanics-hosted massive sulfide deposit （VHMSD） in the northeast part of Qinzhou-Hangzhou collision belt between Yangtze and Cathaysia blocks. Its copper mineralization occurred mainly in the quartz-pyrite-chalcopyrite-sphalerite stage. This paper reports LA-ICP-MS U-Pb ages of zircon from sulfide-bearing quartz veins beneath the.massive ore body. The results of dating are （981～988） Ma, （950±15） Ma, （926±13） Ma, （899±21） Ma and （93～120） Ma. CL images and Th/U ratios of the zircons show that both Neoproterozoic and Cretaceous zircons are almost of magmatic origin. Geological evidence and the findings indicate that the ore deposit was formed in the Neoproterozoic （～899 Ma） and the ores were affected by Cretaceous （93～120 Ma） thermal event. These results are of great significance for further researches on the genesis, formation and evolution of the Pingshui copper deposit and also provide chronological information in search for contemporaneous VHMSD along the Qinzhou-Hangzhou collision belt between Yangtze and Cathaysia blocks.