Tengchong volcanic field is characterized by post-collisional high-K calc-alkaline series. Basaltic trachyandesites and trachyandesites formed by assimilation-fractional crystallization of mantle-derived magmas. The assimilants may mainly come from the lower crust. Relatively primitive trachybasalts formed by partial melting of a mantle source enriched by subducted clay-rich sediments. Tengchong magmas were generated by continental subduction of Indian slab coupled with recent regional extension.