1. College of Earth Sciences, Jilin University, Changchun 130061, China; 

 Kaiyuan area of Liaoning Province is located in the northern margin of North China Craton, in which a set of medium?to?low metamorphic rock series is exposed along the Qinghe fault. It was successively named as “Liaohe Group”, “Qinghezhen Group”, “Kaiyuan rock group”, and “Qinghe tectonic mélange”, and a unified understanding about its composition and age has not yet been reached. By systematically summarizing the zircon U?? Pb dating results and geochemical data with different lithologies, this set of metamorphic rock series is composed of geological bodies with different ages from Neoarchaean, through Paleoproterozoic to Late Permian??Middle Triassic, among which the Early Triassic marine sedimentary covers and the large area of Late Permian??Middle Triassic arc? type blocks formed within an active continental margin indicate the closure process of the Paleo??Asian Ocean. The collision?related metamorphosed dacite (244 Ma) constrained the final closure time of the Paleo??Asian Ocean at the Middle Triassic. A comprehensive comparison of regional geological data shows that the subduction and closure of the Paleo??Asian Ocean in the Kaiyuan area resulted in the formation of a set of mélange series with different degrees of metamorphism, including the Neoarchean basement rocks of the North China Craton, the Late Permian ??Middle Triassic volcanic rocks as “rock blocks” and metamorphic clastic rocks such as metamorphic leptynite and leptits as “matrix”.