Abstract: A set of Late Triassic granite is exposed in the Hongshuihe area of the eastern section of the East Kunlun Orogenic
Belt, which has typical adakite granite characteristics and is of great significance for the study of the time constraint on the closure process of the Paleo-Tethys Ocean on the northern margin of the Gondwana continent. A detailed petrology, zircon U-Pb chronology, and geochemical study of the granite in the area was carried out in this study. The results show that the weighted average ages of granodiorite and diorite inclusions in this area are 225±1 Ma and 223±1 Ma, indicating a Late Triassic age. Geochemical analysis shows that the SiO2 content of the granodiorite is 63.85%-65.87%, the value of Na2O/K2O is 0.99-1.42, the value of Mg# is 42.76-49.15, and the value of A/CNK is 0.90-1.03. The fractionation of light and heavy rare earths in rocks is obvious, and it has the characteristics of enrichment in light rare earths and loss of heavy rare earths. The trace elements show high Sr (360.10×10-6-483×10-6), low Y (8.54×10-6-14.3×10-6), Yb (0.97×10-6-1.23×10-6), high Sr/Y (27.05-36.65) ratio, and weak positive or no Eu anomaly, with the characteristics of adakitic granite. The content of diorite inclusions in SiO2 was
59.15%-61.80%, the average value of Na2O/K2O was 1.84, the value of Mg# was 46.12-48.02, and the value of A/CNK was 0.85- 0.92. The diorite inclusions also show the right-dipping characteristics of light rare earth element enrichment and heavy rare earth element loss, and their trace elements also display the characteristics of high Sr (447.30×10-6-482.70×10-6), low Y (8.54×10-6 - 10.36×10-6), low Yb (0.67×10-6-0.78×10-6) and high Sr/Y (43.18-56.52). Petrogenetic studies indicate that the granodiorite in the Hongshuihe area of the eastern East Kunlun Orogen originated from partial melting of amphibolite in the thickened lower crust, with subsequent contamination by mantle-derived magmas. Combined with the regional data and the discriminant diagrams of tectonic environments, it is believed that the Hongshuihe granodiorite mass was formed in the post-collisional tectonic
environment, which further indicates that the East Kunlun orogenic belt had entered the post-collisional tectonic evolution stage in the Late Triassic. 

Key words: East Kunlun Orogenic Belt, adakitic granite, geochemistry, Paleo Tethys, Indosinian, Hongshuihe