EARLY CRETACEOUS INTRUSIVE ROCKS IN XIUYAN-FENGCHENG AREA, EASTERN LIAONING: Geochronology, Geochemistry and Geological Implication

The paper studies the geochronology and geochemistry of Qinjialing granodiorite and Hongqiling quartz diorite in Xiuyan-Fengcheng area, eastern Liaoning Province. The LA-ICP-MS zircon U-Pb dating yields the weighted average ages of 127.5±0.9 Ma for Qinjialing granodiorite and 126.5±0.8 Ma for Hongqiling quartz diorite, both of which were formed in the Early Cretaceous. The lithogeochemical analysis results show that the content of SiO₂ in Qinjialling granodiorite is 70.40%-72.28%, with the A/CNK and A/NK values of 0.99-1.06 and 1.44-1.61, respectively. The granodiorite is characterized by relatively enriched LREEs, depleted LILEs (Ba and Sr) and HFSEs (Nb, P and Ti), and enriched Rb, Th, La, Nd, and Hf, with the zircon saturation temperature ranging from 755℃ to 816℃, belonging to peraluminous Ⅰ-type granite, formed by the partial melting of lower crust. The content of SiO₂ in Hongqiling quartz diorite is 56.42%-57.22%, with the A/CNK and A/NK values of 1.04-1.09 and 1.70-1.83, respectively. The quartz diorite is characterized by obvious negative Eu anomaly, depleted Sr, Nb, Ta, Ti and P, and enriched Ba, Rb, K, Zr, Hf and Th. The source material is derived from the crust with minors of mantle-derived component. The Qinjialing granodiorite and Hongqiling quartz diorite were formed in the Early Cretaceous extensional environment of eastern Liaoning, which are closely related to the destruction of North China Craton and lithospheric thinning.