Geochronology and geochemistry of the Late Cretaceous Xinpeng granitic intrusion, South China: Implication for Sn-W mineralization

Large-scale Late Cretaceous granitic intrusions are developed in the southernmost margin of South China block. They constitute an EW-trending magmatic rock and mineralization belt from Guangdong to Yunnan province. Some of these Late Cretaceous granitic intrusions are associated with Sn-W mineralization, but the mineralization potential of other intrusions in this belt remains unclear due to intensive weathering and thick sediment covers. The Xinpeng intrusion is the largest Late Cretaceous granitic intrusion in the Yangchun basin, situated in Guangdong province, which mainly comprises of medium- to coarse-grained biotite granite. Previous geological surveys showed that the Xinpeng intrusion has undergone extensive alteration. Stream sediments around the Xinpeng intrusion displayed Sn and W geochemical anomalies. In addition, greisen-type and quartz vein-type tin occurrences have been discovered in the Xinpeng intrusion, which preliminarily shows a certain mineralization potential of tin and tungsten. However, little information is known about the geochronological and geochemical characteristics of the Xinpeng intrusion, and this limits our further assessment of its Sn-W mineralization potential. Here we summarize the geochemical characteristics of Late Cretaceous ore-forming granites in South China and report the geochronological and geochemical characteristics of the Xinpeng granitic intrusion for the first time. LA-ICP-MS zircon U-Pb dating yielded a weighted mean Pb-206/U-238 age of 77.4 +/- 0.8 Ma for the Xinpeng granitic intrusion, linking it with the Late Cretaceous magma activity. The Xinpeng intrusion is high-K calc-alkaline and slightly peraluminous. Chondrite-normalized REE elements of the Xinpeng intrusion show seagull-like patterns with strong negative Eu anomaly. High Rb/Sr ratios and low Nb/Ta, Zr/Hf ratios indicate the Xinpeng granitic intrusion experienced highly magmatic differentiation, attributed to high volatile F contents that can dramatically reduce the viscosity and solidus of magma. The intrusion shows whole-rock initial Sr isotope of 0.717703-0.718420 and Nd isotope of - 5.6-5.7 and zircon I-If isotope of - 3.28-0.62, indicating crust-derived source with some input of mantle materials. Taking into account all the characteristics, the Xinpeng intrusion agrees well with the common geochemical characteristics of Late Cretaceous Sn-W-bearing granites in the Yangchun basin, indicating that the Xinpeng granitic intrusion has a great potential of Sn-W mineralization.