Geological characteristics and molybdenite Re-Os ages of Baituyingzi Mo-Cu field, eastern Inner Mongolia and their geological implications

The recently discovered Baituyingzi porphyry-quartz vein type Mo-Cu orefield from the Xilamulun Mo belt in the north margin of the North China Plate, is genetically related to magmatic hydrothermal activity. On the basis of detailed geologic research, molybdenite samples were selected from the three important Mo-Cu deposits for Re-Os isotopic analysis, and results are: 1) molybdenite samples from Baituyingzi porphyry ores yield an isochron age of 248.0±10Ma (MSWD=0.52, 2σ); 2) samples from Baimashigou quartz vein ores yield an isochron age of 248.6±6.7Ma (MSWD=1.06, 2σ); 3) samples from Kulitu quartz vein type Mo-Cu deposit yield an isochron age of 245.0±4.3Ma (MSWD=0.71, 2σ). These ages indicate that the Mo-Cu mineralization in Baituyingzi area occured in Early Triassic. The Baituyingzi mineralization system was formed during the late stage of continental collision between North China Plate and Siberian Plate in Early Triassic, and the ore-forming fluids originated from the monzogranite porphyry, as indicated by UST (Unidirectional Solidification Texture). The Early Triassic Mo-Cu mineralizations extensively occured in the northern margin of the North China Plate and its adjacent areas, and are potential for future exploration.