阿吾拉勒山琼布拉克铜矿床流体包裹体及碳氧同位素研究

Fluid inclusion and carbon oxygen isotope studies of Qiongbulake copper deposit in Awulale Mountains,Xinjiang

琼布拉克铜矿床位于新疆伊宁县境内,前人对该矿床的成因一直存在争议。文章通过对琼布拉克铜矿床方解石中的流体包裹体进行系统的岩相学、显微测温学和碳氧稳定同位素分析研究,探讨了成矿流体的来源及演化。研究表明:琼布拉克铜矿床的流体包裹体主要为气-液两相包裹体,另有少量的气相包裹体,未见富CO2和含子矿物的流体包裹体,显示出张性构造环境流体包裹体组合的特征;琼布拉克铜矿床流体包裹体的均一温度和盐度变化范围较大,分别介于92~356℃和w(NaC1eq)0.88%~16.89%之间,成矿流体的密度从0.62 g/cm3变化到1.04 g/cm3;琼布拉克铜矿床方解石中δ13CPDB为-7.37‰^-4.19‰,与地幔碳同位素组成(-5‰±2‰)基本相同;δ18OSMOW为9.63‰~11.91‰,与火山岩氧同位素组成值(5‰~15‰)相似,表明成矿流体主要来自于地幔,暗示成矿作用与区内二叠纪火山活动有关。

Located in Yining County of Xinjiang,the Qiongbulake copper deposit was formed in relation to magmatic hydrothermal fluids.These fluids formed a stockwork of calcite veinlets.The distribution of veins and fluid inclusions in these veins records the progressive pressure,temperature,and compositional evolution of the hydrothermal fluids that formed this copper deposit.This paper aims to characterize the temporal and spatial evolution of the mineralizing system and to understand the mechanism that controlled the accumulation of this large,massive Cu deposit.On the basis of the studies by means of inclusion petrography,microthermometry and carbon,oxygen stable isotope,the authors systematically studied characteristics of the ore-forming fluids and the origin of the Qiongbulake copper deposit.Three types of fluid inclusions in calcite were recognized,i.e.,VL type inclusions,LVa type inclusions and LVb type inclusions,with no CO2 phrase fluid inclusions and daughter phrase fluid inclusions.Fluid inclusions associated with calcite display moderate-low homogenization temperature（92.3～355.9℃）,moderate-low salinities（w（NaC1eq） 0.88%～16.89%）and low density（0.62～1.04 g/cm3）.C and O isotope determinations of calcite show δ13CPDB values of-7.37‰～-4.19‰ and δ18OSMOW values of 9.63‰～11.91‰,suggesting that the ore-forming fluids were derived from the mantle and volcanism.On the whole,the Qiongbulake copper deposit is a moderate-low hydrothermal ore deposit.