Zircon U-Pb age of intrusive rocks and molybdenite Re-Os age for Lianzigou Au deposit in Xiaoqinling area and its geological significance

The Lianzigou gold deposit is located in the west of Xiaoqinling Au ore concentration area. The orebodies are hosted in the upper strata of Taihua Group and controlled by fault fracture zone or quartz veins. The wall rock alteration is dominated by potassium alteration and silicification. Au (Mo) orebodies have been discovered in the depth of the deposit. To constrain its petrogenic and metallgogenic ages, the authors carried out LA-ICP-MS zircon U-Pb dating on syenite porphyry and Re-Os dating on molybdenite, respectively. LA-ICP-MS zircon U-Pb dating of syenite porphyry gave a weighted average age of 1802.9±9.9Ma, which is clearly older than the age of large-scale gold mineralization in the Xiaoqinling area. Re-Os dating on molybdenite from the Au orebodies gave an isochron age of 128.8±6.5Ma, indicating that the Au and Mo mineralization occurred in Early Cretaceous. The Re-Os age is younger than the petrogenic ages of granites in the Xiaoqinling area, showing that there is no direct relationship between the known granitic magmatism and the mineralization of the Lianzigou Au deposit. Deep fluids or concealed magmatic intrusion probably played an important role in mineralization.