The compositional diversity of rock types in the Yanhu area is usually considered as the tectonic setting that southward subduction of the Bangong- Nujiang Tethyan Ocean lithosphere broken off. In this paper, we report for the first time the zircon SHRIMP U- Pb age and Hf isotopic composition data, whole- rock major and trace element composition data, and Sr- Nd- Pb- Hf isotopic data from Yanhu quartz diorite. SHRIMP U- Pb dating yields a weighted mean of 118. 5±1. 9 Ma，indicating that Yanhu quartz diorite belongs to late Early Cretaceous. Geochemically, the quartz diorite from Yanhu belongs to Na- rich calc- alkali series, A/CNK=0. 84~0. 89 and are metaluminous. The quartz diorite enriched in Rb、K、Th、U and light rare earth elements (LREEs), relatively depleted in Nb、Ta、Zr、Hf、P、Ti and heavy rare earth elements (HREEs), without Eu anomalies (δEu=0. 81~0. 98). No alkaline mafic minerals and muscovite were observed duringoptical microscopy. All these features above suggest that quartz diorite belongs to metaluminous unfractionated I- type granite. The quartz diorite yielded whole- rock εNd(t) of +0. 5~+2. 1 and (87Sr/86Sr)i 0. 7045~0. 7048, the zircons εHf(t) values are +7. 9~+13, and the model ages (tDM2) range 283 Ma to 674 Ma. Based on integrated isotopic and geochemical data, we infer that the quartz diorite formed by the partial melting of juvenile lower crustal material derived from depleted mantle under amphibolite facies. Based on the above data, combined with the regional geological background, we conclude that the quartz diorite are differernt from granites in Yanhu composite body in age and geochemical characteristics, have relative low zircon saturated temperature (596~614℃), suggesting mantle- derived materials had not involved in the petrogenesis of the Yanhu quartz diorite, the parent magma may formed before the slab broke off, sustainable subducted slab of Bangong- Nujiang Tethyan ocean had returned and the subduction angle becomes steep, enter geodynamic movement of deep subduction.