Zircon U-Pb geochronology, petrogenesis and geology of lanbandeng pluton in South Qinling

Lanbandeng pluton is a part of Yanzhiba rock masses on the east side of the Wulong Rock Group in south Qinling Mountains. LA-ICP-MS zircon U-Pb dating of the meso-fine-grained granite in Jinpen area at the central Lanbandeng Pluton shows that the diagenetic age of the meso-fine-grained Granite is 211.2 ± 3.5 Ma, indicating that the emplacement age of the rock mass is the Late Triassic. Rock geochemical analysis shows that the SiO2 content of medium-fine-grained granite ranges between 73.63% and 75.22%, belonging to silicon rich granite; the content of Na2O ranges between3.54%and 4.37% and K2O ranges between 4.19% and 6.47%. It is rich in potassium（Na2O/K2O=0.55～1.04） and alkali（Na2O+K2O=8.56～10.01%）, belonging to a high potassium-calcium-alkaline series of weak overaluminum rock with the geochemical characteristics of type A granite that should be attributed to type A2 granite. Based on determination of the diagenetic age of medium-fine-grained granite in the Jinpen area, it is suggested that the formation of skarn and pegmatite type tungsten deposits in the internal and external contact zone of the Lanbandeng rock body is closely related to the late Indosinian magmatism.