The Dayana WMo deposit in Dong Ujimqin Banner of Inner Mongolia is a quartzvein type deposit newly discovered in the midwestern part of MongoliaHinggan Orogen. It is typical of quartz veintype wolframitemolybdenum ore deposit, with wolframitebearing quartz veins occurring as nearly vertical, parallel quartz veins (75°) within biotite granite or in outer contact zone between rock mass and strata. Main mineralization and alteration includes greisenization, potash feldspathization, albitization, and silicification, etc. A large amount of molybdenite formed accompanied with wolframite and occurs on both sides of wolframitebearing quartz veins or in quartz veins. Based on detailed analysis of deposit geological feature, this study carried out LAICPMS zircon UPb dating and geochemistry analysis for oreforming rock massbiotite granite. The UPb dating yielded two similar ages (134±1 Ma (MSWD=0.41) and 135±1 Ma (MSWD=0.52)) for tow biotite granite samples. Major and trace element geochemistry shows that the biotite granite is characterized by high SiO2 and K2O contents, a “rightinclined” shape of the chondrite normalized REE patterns, enrichment of large ion lithophile elements (LILEs), and depletion of high field strength elements (HFSEs) such as Nb, P, Ba. The biotite granite is highK calcalkaline, has a strong negative Eu anomaly (Eu/Eu*=0.22~0.45), low P2O5 content, A/CNK value close to 1. These characteristics define the Dayana biotite granite as a highly fractionated granite. The in situ zircon Hf isotopic data show that the 176Hf/177Hf isotopic ratio of the zircons from the biotite granite is 0.28295~0.28302, with εHf(t) values ranging from (+6.4) to (+8.8). It indicates that the source region of the biotite granite magma was derived from the juvenile Lower crust. The ReOs isotopic analysis of seven molybdenite separates from the deposit yielded an isochron age of 133 ± 3 Ma (MSWD=2.2), suggesting that the biotite granite and mineralization have the identical age within error range, are probably genetically related, and closely related to the cretaceous metallogenic events in North China.