Zircon U-Pb Geochronology and Petrogenesis of Taipinggou Copper (Gold)-related Granites, South Qinling

Taipinggou copper (gold) deposit is located in Qinling orogenic belt, at the junction of the Indosinian fold belt of south Qinling and the northeastern structural magmatic belt of the Laoniushan-Yanzhiba period. The altered rock mass relating to mineralization appears to be an ellipse, with a exposed surface area of 0.12 km². The altered rock mass is mainly composed of quartz diorite and fine-grained granite, which were closely related to copper (gold) mineralization, with porphyry granite scattered. The LA-ICP-MS zircon U-Pb shows that the age of Taipinggou quartz diorite mineralization is 223.2±2.9ma, indicating that it was emplaced in late Triassic of the late Indosinian. The geochemical analysis shows that the quartz diorite is potassium-rich (Na₂O/K₂O=1.21-1.75) and alkali-rich (Na₂O+K₂O=7.31%-9.67%) and belongs to high-potassium calc-alkaline series of quasi aluminous rocks. The total amount of rare earth elements in the rocks is high, with obvious negative Eu anomaly, and the REE distribution pattern is obviously right dipping. The trace elements are characterized by the enrichment of big ion lithophile elements such as Ba, u, K, and the depletion of high field strength elements of Nb, P, Ti, belonging to type-I granite. Based on the comprehensive analysis, the authors hold that Taipinggou copper (gold) deposit is the magmatic activity of late Indosinian, suggesting some important magmatic mineralization events in late Indosinian in Ningshan-Zhen'an area of South Qinling.