The Yamansu granite pluton consists of 27 intrusive rocks, which can be divided into three lithofacies units but belong to one superunit. The ellipseshaped plutonic body was the product of three intrusive activities of the same magama. Zircon LA-ICP-MS U-Pb dating result shows that the Yamansu pluton intrusion occurred in the Middle Triassic between 227 Ma and 230 Ma and was the product of the Early Indosinnian Period. Zircon insitu Hf isotopic composition analysis of the Yamansu pluton yielded the εHf(t) values between 7.7~11.5 and the two stage Hf mode age (TDM2) varying between 530~776Ma, suggesting that the magma originated from depleted mantle-derived juvenile crustal rock. Geochemically, the pluton is characterized by the high contents of SiO2 (70.73%~78.12%) and K2O+Na2O (7.17%~8.53%), the high ratios of K2O /Na2O (1.1~1.89), and the low contents of Ti, Ca, Fe and Mg, with the ratios of (K2O+Na2O)/Al2O3 varying between 0.75 and 0.91, and the ratios of A/CNK between 0.98 and 1.03. All these features indicate that the pluton belongs to high K calc-alkaline granite. The pluton is enrich in LILE (K, Rb) and HFSE (Th) but depleted in Hf, Zr, Sm, Y and Yb. The chondrite-normalised REE distribution pattern of the Yamansu pluton displayed right skewed shapes, distinct fractionation between LREE and HREE, with slightly negative Eu anomalies (δEu=0.38~0.74). The petrological and geochemical features of the Yamansu pluton indicate that the pluton originated from partial melting of Neoproterozoic new-born crust due to mantle magma intraplating. The magma intrusion was driven by northward subduction and collision of the Tethys Ocean from the Late Hercynian to Early Indosinian, and the subsequent intense intra-continental extention in the East Tianshan Mountains.