The BangonghuNujiang suture zone in Tibet of China. has been is an important porphyry copper gold metallogenic belt,with superior geological condition of mineralization, The Duolong oreconcentrated deposit, the first superlarge epithermal porphyry CuAu deposit discovered in the western BangonghuNujiang suture zone, is widely covered with plenty of effusive volcanic rocks. However, the petrogenesis, magma source and geodynamic setting of the granitoids are still constrained loosely. In this paper, LAICPMS zircon date yields UPb age of 108.2±2.6Ma(MSWD=0.39) for the dacite，regarding to the similar geochronological data of 109.3±2.2Ma(MSWD=1.70) for the rhyolite. The dacite and rhyolite are characterized by high silica(SiO2=60.89%~72.00%),potassiumrich(K2O =3.08%~5.53%),alkalirich (K2O+Na2O=6.88%~8.96%),peralkaline to peraluminous (A/CNK= 0.92~1.28) and High calcalkaline to shoshonitic. The rocks are systematically more enriched in largeion lithophile elements (LILE: Th、U、K、Pb and Rb) and LREE, relatively deplted in high strength elements (HFSE:Ta、Nb、Ti and Zr) and HREE. Total Coneentartion of REE range from 141.52×10-6 ~ 236.05×10-6, with LREE/HREE of 8.54~9.30, LaN/YbNof 10.42~11.05 and middle negative Eu anomalies(δEu=0.65~0.80).Besides, trace elements compositions indicate that the magma is contaminated by crustal mantle when it rise and The isotopes of these rocks are characterized by high(87Sr/86Sr)i(from 0.7050 to 0.7053), low (143Nd/144Nd)i(from 0.5124 to 0.5126,low εNd(t)(from -1.51 to 1.29). The positive εHf(t) values of zircons from rhyolite whose second stage Hf mode mean ages are 288.0Ma vary from +11.6 to +15.5, contrasted with εHf(t)values of +3.4~+8.0 from dacite whose second stage Hf mode mean ages are 8131Ma. Based on the above discussions, we proposed that the geochemical characteristics of these volcanic rocks are consistent with those of arctype magmas worldwide and the arc volcanic rocks magma were all generated by partial melting of mantle wedges replaced by the fluid which is formed the dehydration of the oceanic crust subduction plate, and its rockforming resulted from the mixing between the juvenile lower crustderived melts and mantlederived mafic melts under the background of BangonghuNujiang Tethys subducting northward to Qiangtang massif. In addition, the volcanic activity suggests BangonghuNujiang ocean was subducting at least during approximate 108~109Ma, and the closure time of this ocean should be later than early Cretaceous(108~109Ma), which is different from early recognition of closure time of late Jurassic to earlyCretaceous.