Geochronology and geochemistry of the Triassic intrusive rocks in the Faku area, northern Liaoning, China: Constraints on the evolution of the Palaeo‐Asian Ocean

This study reports petrography, geochemistry, geochronology, and Lu–Hf isotopic analyses of Xiaofangshen, Lingshansibei, and Shidonggou plutons, which are located in the northern Liaoning Province, eastern segment of the northern margin of the North China Craton. In this study, we discuss their formation ages, petrogenesis, and tectonic environment. Petrographic characteristics suggest that these plutons are composed mainly of granitic rocks and are widely altered by later deformation. Zircon U–Pb dating results suggest formation ages of 248.2 ± 1.4 Ma, 245.1 ± 1.5 Ma, and 230.6 ± 2.5 Ma for the Xiaofangshen, Lingshansibei, and Shidonggou plutons, respectively. The geochemical characteristics indicate that both the Xiaofangshen and Lingshansibei plutons are metaluminous, high‐K calc‐alkaline‐shoshonitic granites that formed in a crustal thickening environment; the Shidonggou pluton is peraluminous, calc‐alkaline I‐type granite that formed in a post‐orogenic environment. All granitic plutons in the study area are enriched in large‐ion lithophile elements and light rare earth elements (REEs) and depleted in high‐field‐strength elements and heavy REEs. Combined with geochemical characteristics of the plutons and previous studies on the region, we conclude that the eastern part of the Palaeo‐Asian Ocean closed in the Late Permian to Early Triassic. The orogeny of the eastern segment of the northern margin of the North China Craton continued until the early Late Triassic. The evolution of the study area can be divided into three stages during the Triassic. First, the region entered the stage of Palaeo‐Asian Ocean extinction and oceanic plate detachment. Second, a transition stage from post‐collisional orogeny to extensional collapse took place. Third, the environment changed from collisional orogenic to post‐orogenic tectonic.