Objectives:This paper focuses on the study of petrology and geochemistry of the newly discovered bimodal volcanic rock assemblage in Bailinshan area,Yanyuan,Sichuan,and discusses its petrogenesis and tectonic geological background,which provides new clues and geological basis for further research on the formation mechanism, tectonic evolution and mineralization of Emeishan large igneous province. Methods:On the basis of field investigation,representative samples of basic and acid volcanic rocks were collected,and the bimodal volcanic rocks were studied by microscopic observation,analysis of major elements,trace elements and rare earth elements,and the petrogenesis and tectonic environment of the bimodal volcanic rocks were discussed. Results:A bimodal volcanic rock composed of alkali-rich high-titanium basalt and pantellerite was newly discovered in the Bailinshan area of Yanyuan County.It belongs to a part of the Emeishan large igneous province and was formed in the late Permian.Both basalt and pantellerite are characterized by light rare earth enrichment.The rare earth content and fractionation degree in pantellerite are significantly higher than those in basalt,and pantellerite shows obvious negative Eu anomaly.The basalts are relatively enriched in high field strength elements such as U,Th,Nb and Ta, and relatively depleted in large ion lithophile elements such as Rb,K and Sr.The pantellerite are significantly enriched in high field strength elements such as U,Th,Nb,Ta,Zr and Hf, and severely depleted in Ba,K,Sr,P,Ti,Ni and Cr.Basalt is the product of partial melting of mantle peridotite to a small extent.Pantellerite is mainly formed by acidic residual magma after extreme separation and crystallization of basaltic magma.The basalt were formed in the oceanic island environment,and the pantellerite were formed in the intracontinental extensional environment.The tectonic environment is related to the activity of the Emeishan mantle plume and the intracontinental rift extension by it. Conclusions:The definition of the late Permian bimodal volcanic rocks in the Bailinshan area is of great significance for the study of regional tectonic evolution and mineralization and the expansion of prospecting ideas.