LA-ICP-MS U-Pb zircon ages and whole rock geochemical data are reported for tonalites from the Ashele Cu-Zn deposit on the southern margin of Altay. The zircons from tonalite samples yielded mean ²⁰⁶Pb/²³⁸U ages of 375.3±2.1 Ma and 386.2±3.8 Ma, suggesting that the intrusion took placed between Early Devonian and Middle Devonian. These tonalites have high SiO₂(74.72% to 77.72%), moderate Al₂O₃ (12.06% to 13.5%) and total alkali (Na₂O+K₂O) (5.84% to 6.59%), and low P₂O₅ (<0.04%) and CaO (0.34% to 1.65%). In addition, they are enriched in Na (Na₂O/K₂O=3.3 to 10.9) with high A/CNK values (1.10 to 1.18), implying low-K peraluminious granites. They display negative anomalies of Nb, Ta, Ti, Sr, Ba and P and obvious enrichment of LREE and LILEs (Th, U and Pb) with significant Eu (0.47～0.81) negative anomalies. Combined with the tectonic evolution of the southern margin of the Altay, the authors hold that these tonalities were generated from the melting of continental crust in an island arc tectonic setting.