SHRIMP U-Pb Dating of Zircon from the Fenghuangshan Quartz Monzodiorite and Granodiorite in Tongling Area,Anhui Province and Its Geological Implication

Abstract

In order to study the magmatic evolution and relationship between magmatism and mineralization,the SHRIMP U-Pb dating of zircon in Fenghuangshan quartz monzodiorite and granodiorite in Tongling area,Anhui Province are carried out.The SHRIMP U-Pb age of zircon from the quartz monzodiorite changes from (136.0±2.0) to (143.0±2.4) Ma,and the weighted mean age is (139.4±1.2) Ma (n=15,MSWD=0.76).Results of SHRIMP U-Pb zircon dating of granodiorite is from (136.7±2.0) to (145.3±2.4) Ma,and the weighted mean age is (141.0±1.1) Ma (n=17,MSWD=1.5).The emplacing age of the Fenghuangshan intrusion is the Late Jurassic.Moreover,the molybdenite Re-Os isochrone age is accordant with that of the granodiorite and older than the age of quartz monzodiorite.The copper mineralization has the closer relationship with the granodiorite and they are formed contemporaneously.Isotopic data indicate that the mineralization is related to the deep fluids derived from mantle magma differentiation.The extensional process resulted from the whole lithosphere thickening and the basaltic magma approaching,caused by from the aesthenosphere mantle and upper crust decompression and melting,played an important role in forming of the Fenghuangshan intrusion.