The petrology, geochemistry, zircon U-Pb geochronology, and Hf isotopes of Duobagou diorite and Karatashtage diorite were studied to establish the evolution of Palaeozoic orogeny in the Dunhuang area in Western China. The weighted mean 206 Pb/ 238 U age of 448 ± 2 Ma in zircon grains from Duobagou diorite indicated an origin in the late Ordovician Period; age-corrected ε Hf (t) values of −0.98 to +4.46 correspond to a two-stage zircon Hf model age (T DM2 ) of 1,145 Ma to 1,477 Ma. Karatashtage diorite has a weighted mean 206 Pb/ 238 U age of 436 ± 3 Ma, indicating an origin in the early Silurian Period; age-corrected ε Hf (t) values of −1.13 to +7.96 correspond to a two-stage zircon Hf model age (T DM2 ) of 718 Ma to 1,301 Ma. These findings indicate that Duobagou and Karatashtage diorites were derived from ancient crust. Duobagou diorite has high levels of Al 2 O 3 (15.76%~17.64%), MgO (2.18%~5.44%), Mg # (40~51), Na 2 O (2.78%~4.19%), Sr (466~1,160 ppm), and Ba (523~892 ppm), low levels of K 2 O (1.29%~3.13%) and TiO 2 (0.64%~1.0%), variable levels of Cr (73.4~253 ppm) and Ni (42.2~98.8 ppm), and depleted HREEs. Karatashtage diorite is characterized by high levels of Al 2 O 3 (16.33%~17.59%), MgO (4.15%~7.10%), Mg # (50~59), Na 2 O (3.39%~4.41%), Cr (73.4~253 ppm), Ni (42.2~98.8 ppm), Sr (466~1,160 ppm), and Ba (523~892 ppm), low levels of K 2 O (1.29%~3.13%) and TiO 2 (0.64%~1.0%), and depleted HREEs. The Duobagou pluton and the Karatashtage pluton display arc signa-tures, suggesting that they were formed by the partial melting of a subducted slab under garnet-amphibolite facies in an active continental margin, and an interaction between melt and mantle materials during emplacement. Subduction of the oceanic plate in the Dunhuang terrane occurred during the Early Silurian Period (435-430 Ma), which is close to that of the Beishan orogenesis but later than the formation of the Hongliugou-Lapeiquan ophiolitic belt. We suggest that the Dunhuang terrane underwent an orogenic process related to the Palaeo-Asian Ocean during the Early Palaeozoic Era, and that it belongs to the Central Asian Orogenic Belt (CAOB).