Abstract:

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.

Key words: ore deposits, LA-]ICP-MS zircon U-Pb age, Aershan area, ore-forming granites