Geochronological and geochemical characteristics of the Jingning Intrusion, Zhejiang Province

The Jingning Intrusion in Zhejiang Province is located on the active continental margin of southeast China and controlled by the Yuyao-Lishui faulted zone. The main rock types of the Jingning Intrusion distributed in S-N direction include monzonitic granite, granite, and diorite. In this paper, the authors conducted the LA-ICP-MS zircon U-Pb dating, obtained whole-rock geochemical data of the monzonitic granite and granite, and investigated lithologies of Jingning Intrusion, with the purpose of exploring the geochronology, petrogenesis, and tectonic implications. The results obtained show that the U-Pb zircon ages of the monzonitic granite and granite are 121.3±0.3Ma and 111.0±0.7Ma, respectively. The Jingning Intrusion samples are compositionally characterized by high SiO2, Na2O+K2O and low MgO. The A/CNK index ranges from 1.01 to 1.09, the fractionation between the light and heavy rare earth elements is obvious, the differentiation index varies from 84.85 to 96.35, and the Eu has an obvious negative anomaly. These geochemical features suggest that the Jingning Intrusion samples are slightly peraluminous and are of highly fractionated I-type granite. Based on the geochronological and geochemical data, the authors hold that the Jingning Intrusion was produced by the partial melting of the crust under the influence of wide lithospheric extension in the late Early Cretaceous.