1. College of Earth Sciences, Jilin University, Changchun 130061, China;
2. Bureau of Land and Resources, Qionglai 611530, Sichuan, China;
3. Tianjin Institute of Geology and Mineral Resources, China Geological Survey, Tianjin 300170, China

In order to reveal the relationship between volcanic rocks and mineralization in the Erentaolegai silver deposit, the ore-hosting volcanic rocks were selected for systematic studies of zircon U-Pb geochronology and whole-rock geochemical analysis. The results show that (1) the ore-hosting trachyandesites yielded a zircon U-Pb age of (173.4±4.6)Ma, (2) the trachyandesites are characterized by the enrichment of large ion lithophile elements and depletion of high field strength elements with slightly negative Eu anomalies. Compared with the oceanic crust components, the ore-forming elements are characterized by strong depletion of V,Cr,Ni,Co,Mo and Cu elements,but enrichment in W,Bi and Pb elements,relative enrichment in Au,As,Sb and Te elements, with similar contents of Zn,Ag and B elements. In combination with previous studies, it is suggested that the volcanic rocks were formed at the early stage of mineralization. The magma of trachyandesites could be originated from the lithosophere mantle which had suffered fluid metasomatism. During the magma evolution, magma underwent slightly fractional crystallization(e.g.plagioclase) and continental crust contamination. The volcanic rocks were formed at the early stage of extensional environment after the convergence or collision among the North China plate, the Mongolian plate and the Siberia plate. Moreover, the volcanism at this episode did not provide the ore-forming fluid directly, the magmatism that provided the ore-forming fluid should be the quartz-monzonite porphyry magma in the Early Cretaceous (138 Ma).