Petrogenesis of the Gaofengshan granite in Gejiu area, Yunnan Province: Zircon U-Pb dating and geochemical constraints
云南个旧高峰山花岗岩成因:锆石U-Pb年代学及地球化学约束

The Gaofengshan granite is located in the eastern part of the Gejiu ore district,Yunnan Province.The lithology of the granitoid is mainly medium grained biotite monzonitic granite.In this paper,zircon U-Pb dating and geochemistry of the Gaofengshan granite is studied to constrain its geochronology and petrogenesis.Zircon LA-ICP-MS dating yields an emplacement age of 85.76±0.58Ma,which suggests that this granite formed in the Late Cretaceous.Geochemically,this granite is silica riched in composition, with high content of alkali(Na 2 O+K2 O).It’s a metaluminous to peraluminous granite and belongs to the high-K calc-alkaline series, and characterized by enrichment of Rb,U,Ta,Pb,Nd and depletion of Ba,Nb,Sr,P,Zr,Eu,Ti.The abundance of∑REE varies in the range of 146.7×10 -6 to 236.1×10 -6 ,and it has intensely negative Eu abnormality(δEu=0.03～0.11).What’s more,it reflects a tetrad-like effect with a shape of"M".These features are coincident with A2 granite.Geochemical characteristics show that the parental magma of the Gaofengshan granite was derived from the partial melting of crust,and experienced a strong crystal fractionation process.New data of this study indicate that the Gaofengshan granite was one component of the large scale Late Cretaceous magmatism in western Cathaysia block,which viewed as under a regional lithospheric extension tectonic setting.