In this paper, we report the petrological, major and trace element geochemistry and Sr–Nd–Hf isotope data for the potassic volcanic rocks around Junan-Dadian region in the middle-south parts of Yishu deep fault zone, with aims to constrain the enrichment mechanism of the mantle source and to elucidate the petrogenesis. Potassic volcanic rocks outcropped around Junan are a set of latitic volcanic-subvolcanic rock association, and those in Dadian consist mainly of trachyte. They have consistent zircon LA-ICP-MS U-Pb ages of about 118Ma. Chemically, they show higher K2O+Na2O contents with Rittmann’s indices ranging from 4.10 to 5.07, and enriched in potassium (K2O=4.21%~5.77%). On the SiO2-K2O and K2O-Na2O plots, these volcanic rocks all fall into the field of shoshonite series. Both the latitic and trachytic volcanic rocks are enriched in LILE (e. g., Cs, Rb, Th, U, Pb) and LREE, and depleted in HFSE (e. g., Nb, Ta, Ti, P), but the trachytes show distinct negative anomalies of Ba and Eu in the primitive mantle-normalized trace element spidergrams, and have lower LREE/HREE ratios. The volcanic rocks have homogeneous and enriched Sr-Nd isotopic compositions with ISr ratios of 0.7086 ~ 0.7091 and εNd(t) values of -16.9~-18.2, and show distinct negative zircon εHf(t) values (specially -22.3~-24.3 for the latitic volcanic rocks, and -19.7~ -23.6 for the trachytes). Based on a synthesis of the elemental and isotopic geochemistry, we suggest that the mantle source of the potassic volcanic rocks might have underwent multiple enrichment events induced by source contamination of continental crustal materials both from deep subduction of the Yangtze Craton and lithospheric delamination of the North China Craton. During Early Cretaceous, the continued extension of Tanlu Fault induced the upwelling of asthenospheric mantle and led decompression partial melting of these multiple modified enriched mantle. The generated magmas subsequently suffered further differentiation, thus finally resulted in the formation of these potassic volcanic rocks.