Geochemistry Characteristics of Xihuashan Granite and Structural Environment Discussion

There are five granitic intrusions which are biotite monzogranite in the district of Xihuashan.They are divided into three phases,show high Si,alkaline,poor Ti,Fe,Mg,Ca,P,belong to strongly-peraluminous high-K calc-alkaline series,ACNK1.1.All this imply that the granites are S-type granite.Zircon U-Pb dating age is(150~153)Ma.The average of TREE is 237.15×10-6,higher than Naling granite(229.68×10-6).γ2-1a5,γ2-1b5,γ2-35 represent a LREE-rich curve while γ2-2a5,γ2-2b5 show a HREE-rich curv,but Eu negative anomaly are obvious in all granites.The granites geochemical characteristics and regional tectonic evolution background indicate that the rocks were formed in a post-orogenic extension environment,lithospheric thinning and extension tectonic background.