新疆元宝山金矿床锆石U-Pb、全岩Rb-Sr年代学及其地质意义

摘要

元宝山金矿床位于新疆鄯善县境内,属于东天山康古尔塔格金矿带,受秋格明塔什-黄山韧性剪切带控制.为探讨元宝山金矿床的成矿时代及其地质意义,本次研究开展了矿石石英Rb-Sr年代学、含矿围岩Rb-Sr、Sm-Nd及锆石U-Pb同位素年代学分析.(255.6±1.0) Ma的含矿围岩Rb-Sr同位素等时线年龄以及(256±14) Ma的石英Rb-Sr等时线年龄,限定了该矿床的形成时代,而(334.7±9.8) Ma的含矿围岩锆石U-Pb年代学数据表明,该矿床的含矿围岩为中石炭统.Sr、Nd同位素特征表明,成矿物质来源具有幔源特征并有壳源物质参与,而区内韧性剪切带右行走滑剪切及随后的抬升作用导致的压力和温度的降低应是元宝山金矿床形成的动力学背景.%The Yuanbaoshan gold deposit,located in Shanshan County of Xinjiang,belongs to the Kanggurtage gold belt of eastern Tianshan Mountains.The deposit is controlled by the Qiugemingtashi-Huangshan ductile shear zone.In order to investigate the ore-forming age of the Yuanbaoshan gold deposit and its geological significance,the authors analyzed the Rb-Sr isotope composition of fluid inclusions in quartz and the ore-bearing rock.The Sm-Nd isotope composition of mineralized whole rock and U-Pb dating of zircon from the rock were all carried out.The ore-bearing rock yielded an Rb-Sr isochron age of (255.6± 1.0) Ma,which is in agreement with the (256 ± 14) Ma obtained by quartz within error,indicating that the Yuanbaoshan gold deposit was formed at 256 Ma.The U-Pb dating of the mineralized whole rock yielded an age of (334.7 ± 9.8) Ma,revealing that the orebearing rock belongs to middle Carboniferous strata.The characteristics of Sr and Nd isotope indicate that the metallogenic material had the mantle-derived attribute with the addition of some crust matters.The decrease of pressure and temperature caused by the dextral strike-slip and subsequent uplift action constituted the main dynamic mechanism for the formation of the Yuanbaoshan gold deposit.