内蒙古阿尔山地区成矿花岗岩形成时代及其找矿意义

Age of Ore-Forming Granites in Aershan Area of Inner Mongolia and Its Significance for Prospecting

阿尔山地区是大兴安岭中南段多金属成矿带的重要地段。该区热液脉型铁锰多金属矿、热液脉型钼(铜)矿和矽卡岩型铅锌多金属矿等3种代表性矿床(点)的成矿花岗岩的形成时代一直是研究的薄弱环节。通过多种高精度的U-Pb年龄测定,区内成矿花岗岩的形成时代分别为印支早期((237.8±2.3)Ma)和燕山中期((152.2±2.9)Ma)、燕山晚期((135.1±0.4)Ma),与邻区乌兰浩特—索伦地区基本可以对应。而前人划定的海西期花岗岩,实际为燕山晚期;划定的燕山早期花岗岩,实际为印支早期、燕山中期。研究成果对于区内花岗岩浆及期后热液与多金属成矿作用在时间上的关系提供了重要依据,对确定区內相应多金属矿类型的成矿花岗岩时代亦提供了可资对比的依据。

Aershan area makes up an important section of a polymetallic metallogenic belt in the mid-southern Da Hinggan Mountain.Three types of deposits（ore occurrences） are representative in the area,including hydrothermal vein-type Fe Mn-polymetallic,hydrothermal vein-type Mo（Cu） and skarn-type lead-zinc polymetallic deposits.However,no much attention has been paid on the forming age of their related granites.According to LA-ICP-MS U-Pb isotopic dating,the forming ages of the related ore-forming granites are as the followings： Early Indosinian（（237.8±2.3） Ma） and Middle Yanshanian（（152.2 ± 2.9） Ma）,Late Yanshanian（（135.1±0.4） Ma）,which are basically comparable with the those of the adjacent Wulanhaote-Suolun region.The Hercynian granite formerly designated is actually the Late Yanshanian granite and the Early Yanshanian granites formerly thought are actually the Early Indosinian and Middle Yanshanian ones.These dating could serve as an important basis for understanding the relationship between the intrusion of the granite magmas and the following hydrothermal polymetallic mineralization both in time and space.The present study is also helpful to comprehending the ages of the ore-forming granites related to different polymetallic mineralization type in the area.