Geochronology and Petrogenesis of Granitoid Intrusions in the Feidong District, Southern Tan-Lu Fault Zone, China

The Feidong district is located in the southern segment of the Tan-Lu fault zone that separates the South China Block(NCB)from the North China Craton(NCC).We report zircon U-Pb geochronology and Hf isotope data,as well as whole-rock geochemistry for Xishanyi granodiorite and Jianshan granite in the Feidong district.Zircon U-Pb dating results show that the emplacement ages of the Xishanyi and Jianshan intrusions are 124±3 Ma and 130±1 Ma respectively,coeval with magmatic events linked to large-scale lithospheric thinning in eastern China.The whole-rock geochemistry of the Xishanyi and Jianshan intrusions demonstrate that they are peraluminous,high potassium calc-alkaline I-type granites with adakitic characteristics.Both intrusions underwent weak crustal assimilation during emplacement.The in situ zirconε(Hf)(t)values of the Xishanyi granodiorites range from-26.4 to-21.8,with T(DM2)model ages of 2552 to 2841 Ma.The in situ zirconε(Hf)(t)values of the Jianshan granite are from-27.5 to-23.0 with T(DM2)model ages of 2632 to 2904 Ma.The peak age of inherited zircon grains from the Xishanyi granodiorite and the Jianshan granite were^2.07 Ga and^1.94 Ga,respectively.After compared with the regional magmatism,we suggest that both the Xishanyi and Jianshan granitoid intrusions were derived from partial melting of the NCC lower crust.