内蒙古东乌旗沙麦钨矿床的成矿时代

The metallogenic age of the Shamai wolframite deposit in Dong Ujimqin Banner,Inner Mongolia

内蒙古东乌旗沙麦钨矿位于贺根山断裂带以北的兴蒙造山系二连-东乌旗弧盆带内,为岩浆期后高温热液黑钨矿石英脉型矿床。采用黑钨矿Sm-Nd同位素分析获得黑钨矿的形成年龄为137.9±1.7Ma,采用TIMS锆石U-Pb同位素定年获得赋矿黑云母花岗岩的形成年龄为139.1±0.93Ma,据此提出,沙麦钨矿床的形成时代为燕山晚期,这与区域上大兴安岭西坡主要金属矿床的形成年龄数据相吻合。黑钨矿的初始ε_(Nd)值为正值,与中亚造山带内大量花岗岩的εNd值均为正值的特点相一致,表明其来源于亏损地幔源。

The Shamai wolframite deposit in Dong Ujimqin Banner of Inner Mongolia is located within the Erlian- Dong Ujimqin Banner arc-basin belt in the Da Hinggan Mountains-Inner Mongolia orogenic belt south of the Ergenshan fault. It is a postmagmatic high-temperature hydrothernal deposit. In this paper,wolframite Sm-Nd isotope analysis of the deposit yielded an ore formation age of 137.9±1.7Ma,whereas TIMS zircon U-Pb dating of samples from the wall rock biotite granite yielded a petrogenetic age of 139.1±0.93 Ma. These isotopic ages indicate that the mineralization of Shamai wolframite deposit occurred in late Yanshanian,consistent with the age of the formation of the main ore deposits on the west slope of the Da Hinggan Mountains regionally. Consistent with the positive initial ε_（Nd） value of granites scattered in central Asian orogenic belt,the initial ε_（Nd） value of the wolframite is positive,indicating a depleted mantle source.