Zircon U-Pb geochronology and geochemistry of the Xinxikou pluton in Shexian County,Southern Anhui Province and its prospecting significance

The Xinxikou pluton is mainly consists of medium-to fine-grained granite, was emplaced at 121.31± 0.67 Ma. The granites have high SiO₂(75.97%～76.49%)and K₂O(4.84%～5.28%)contents with K₂O/Na₂O ratios from 1.61 to 2.05, and show weakly peraluminous nature with A/CNK values from 1.05 to 1.06. The granites have high total REE contents ranging from 261.90 to 329.83 ppm. On the chondrite-normalized patterns, they all show markedly LREE-enriched patterns with(La/Yb)_N ranging from 3.26 to 5.15 and significant troughs of Eu anomalies(δEu=0.018～0.063). Normalized to primitive mantle, the granites are enriched in large ion lithophile elements(e.g. Rb)and high field strength elements(e.g. Th and U)but depleted in Ba and Sr showing affinity to A₂ granites. Together with the regional geology, the granites formed in a extensional environment, related to asthenospheric mantle upwelling triggered by roll-back of the Paleo-Pacific oceanic slab. The Xinxikou pluton is widely exposed and have a shallow denudation. These granites are rich in metallic elements(W, Sn, Bi and etc)which diffused into surrounding rocks by high temperature gas-liquid alteration such as greisenization, indicating a good prospect of ore exploration.