A basic, mediosilicic and acidic volcanic belt with east-west-ward length about 300km exists along the southern margin of the South Tianshan orogen. Dacites attributed to Xiaotikanlike Formation of Lower Permian, outcropping near the Tiereke hot spring, are characterized by calc-lkaline (δ=1.37~1.69) and metaluminous–peraluminous (A/CNK=0.89~1.36). The dacites are enriched in LREE (La/Yb=10.45~12.77) and elements such as Th, Hf, Zr, Tb, Gd, Rb,U, and depleted in elements such as P, Ti ,Nb, Ta, Sr, Ba, and with middling negative Eu anomaly (δEu=0.57~0.62). Nd(288Ma)=-6.77, Sr(288Ma)=117.78, ISr=0.702145, TDM=1.47Ga. Zircon U-Pb LA-ICP-MS dating on the magmatic genetic zircon yields and age of 288.4±3.0Ma (MSWD=2.7), representing the formation age of the dacites. Combined with regional tectonic analysis, it is concluded that the dacites are formed under the the post-collisional extensional setting of Early Permian, and are probably derived from partial melting of middle-lower crust of Tianshan orogenic belt.