扬子西缘摩挲营新元古代高分异花岗岩年龄、成因和锡钨成矿潜力OA北大核心

The Mosuoying granite pluton is situated in the Kangdian Axis in the western Yangtze Block,where tin-tungsten mineralization has developed in the contact zone between granite and carbonate rocks.This study aims to investigate the petrogenesis and ore potential of the pluton through geochronology,whole-rock geochemistry,and zircon Hf isotopic analysis.The LA-ICP-MS zircon U-Pb ages of the porphyritic biotite granite and fine-grained biotite granite are 842±6 Ma and 841±7 Ma,respectively,with zircon εHf(t)values ranging from-10.0 to-2.5 and-16.9 to-3.8 and two-stage model ages(TDM2)ranging from 2.35 to 1.89 Ga and 2.29 to 1.96 Ga.These indicate that the magma were derived from re-melting of ancient crust.The Mosuoying granites are peraluminous and high-K calc-alkaline,with high light rare earth element/heavy rare earth element ratios and pronounced negative Eu anomalies.They are enriched in Sn,Be,W,Rb,K,and Th and depleted in Ba,Nb,Sr,P,and Ti.Low whole-rock K/Rb,Nb/Ta,and Zr/Hf ratios,coupled with high Rb/Sr ratios,suggest intense fractional crystallization.Based on these geochemical characteristics,the Mosuoying granites are classified as highly fractionated S-type granites.The calculated relative oxygen fugacity values and zircon Ce4+/Ce3+ratios range from-5.84 to-0.93(average of-3.72)and 0.23 to 14.02(average of 2.55),respectively,indicating low oxygen fugacity.The occurrence of greisenization,tourmalinization,and fluoritization in the Mosuoying granites indicates hydrothermal fluid activity.During ocean-continent subduction,upwelling of the asthenosphere triggered re-melting of ancient crust and the formation of volatile-rich,highly-fractionated reduced granites,providing conditions favorable for tin-tungsten mineralization.The Neoproterozoic highly fractionated granites in the Mianning-Huili area are thus considered to be a key target for further tin-tungsten exploration.