Petrogeochemistry, zircon U-Pb age and Hf isotope of Xinping granodiorite(104Ma) in Xinfeng area, Guangdong Province

Located in the north-central part of the Fogang complex pluton, the Xinping Cu-Mo mineralization granodiorite pluton formed in late Early Cretaceous, and its LA-ICP-MS zircon U-Pb age is (104.6±1.8)Ma(MSWD=1.2). The granodiorite is characterized by medium acidity (SiO₂=63.43%-65.27%), quasi-aluminium(ACNK=0.76-0.92), medium alkali(ALK=6.09%-7.63%) and high-K Calc-alkaline. It shows enrichment in light rare earth elements Rb, U, Th and La, and the ratio of LREE/HREE is 8.26-13.20 while (La/Yb)_N is 8.17-16.64. Otherwise, it shows depletion in Nb, Ta, Ti, P, Ba and Sr, with minor loss of Eu (δEu=0.73-0.87). The ε_Hf(t) range from -3.0 to +0.2, and the two-stage model age of Hf(t_DM2) is 1.16-1.36Ga, and the index of Mg(Mg^#) is 42.64-46.95. All of these indicate that the source rocks are mainly crustal materials formed in Mesoproterozoic, with the participation of deficient mantle components. The ratio of Nb/U and Nb/La is respectively 0.20-0.38 and 1.7-2.2, which indicates that the source area is affected by the fluid metasomatism in subduction of Paleo-Pacific Plate. This study shows that the Xinping granodiorite is dominated by partial melting in process of diageneesis. The Xinping pluton formed in the extensional setting under the subduction of the Paleo-Pacific plate in late Yanshanian period, which is related to the partial melting of the Mesoproterozoic crystalline basement induced by the basaltic magma. In late Early Cretaceous, it was an important Cu-Au-Mo mineralization period in late Mesozoic in southeastern China, while the Xinping granodiorite, located in the middle east of Nanling mountains, coincide with the diagenetic age of the Zijinshan copper polymetallic rocks or ores in the southwestern Fujian Province, with similar petrochemical characteristics. Also, the obvious copper-molybdenum mineralization can be observed in the field, so it will have a good prospecting prospect for copper-molybdenum deposits.