The paper presents SHRIMP U-Pb dating results of zircon and ~ 40 Ar/ ~ 39 Ar dating results of hornblende from the Mamba granitoid cropping out in the Gangdise tectonic belt. The ages were dated to be 207 Ma and 215 Ma respectively, suggesting that they were formed during the late Triassic. Geological and geochemical studies show that the Mamba Granitoids include biotite hornblende granodiorite and biotite adamellite, which were formed in an island-arc environment. Mamba granitoid and the late Triassic calc-alkaline volcanics (the Yeba Formation) cropping out near Maizhokunggar to the south of Mamba constitute a typical rock association related to plate subduction, which suggests that the Neotethys subducted before the late Triassic.