Zircon U-Pb age, Hf isotope composition, and magma source of Mo-bearing granite porphyry in the Wenquan Mo deposit from West Qinling

The Wenquan Mo ore deposit, the only one porphyry-type Mo deposit in the West Qinling, is located on the northern margin of the West Qinling orogenic belt. The ore bodies are mainly distributed within the granite porphyry and the contact zone between the granite porphyry and its surrounding rocks. The zircon U-Pb dating and Hf isotope studying of the ore deposit have great significance to define the forming age of the granite porphyry, reveal the evolution of the magma, and furthermore to clarify genesis of the ore deposit. The zircon LA-ICP MS U-Pb dating method was used to constrain the forming age of Mo-bearing granite porphyry in the Wenquan mine. Zircons from the granite porphyry have clear zonal texture and large value of Th/U ratio (0.41~0.88). The LA-ICPMS U-Pb dating of zircons from the Mo-bearing granite porphyry and its intruding porphyritic monzogranite yield ages of 212.43~213.4Ma and 219.9Ma respectively, indicating Late Triassic magmatic product. The hafnium isotope of the granite porphyry has a negative value between-1.89 and-1.63, with an average value of-1.59. On the ε_Hf(t)-t diagram, the sampling points are plotted below the chondrite and the deficit mantle line, which indicates a unitary magmatic source. This source is the partially melting product of the modified earth crust. The age of the second stage (T_DM2) model ranges from 1291 to 1408 Ma, which indicates that the magma was probably derived from the partiall melting of Mesoproterozoic earth crust.