Zircon U–Pb geochronology and petrogenesis of the Late Paleozoic–Early Mesozoic intrusive rocks in the eastern segment of the northern margin of the North China Block

Abstract

Zircon U–Pb dating and whole-rock geochemical analysis have been undertaken on Late Paleozoic–Early Mesozoic intrusive rocks of central Jilin Province, NE China, with the aim of constraining the tectonic evolution of the eastern segment of the northern margin of the North China Block (NCB) during the Late Paleozoic–Early Mesozoic. Zircon U–Pb dating indicates that Late Paleozoic–Early Mesozoic magmatic events can be subdivided into four stages: Middle Permian (~270Ma), Late Permian (259–255Ma), Early Triassic (~249Ma), and Late Triassic (~222Ma). The Middle Permian magmatic event formed peraluminous garnet-bearing monzogranites, indicative of formation under a compressional tectonic regime related to collision between the NCB and the Songnen–Zhangguangcai Range Massif. The Late Permian magmatic event formed gabbros and syenogranites, a bimodal association that is typical of magmatism within post-collisional extensional setting. The Early Triassic magmatic event formed adakitic monzogranites, suggesting that they formed from magmas derived from partial melting of a thickened mafic lower crust. The Late Triassic magmatic event formed a series of mafic–ultramafic intrusive rocks, together with coeval granitoids in adjacent regions, and make up a typical bimodal association suggesting that they formed under an extensional environment related to the final amalgamation of the NCB and the Songnen–Zhangguangcai Range Massif. Taken together, we conclude that the northern margin of the NCB underwent multiple orogenic events between the Middle Permian and the Late Triassic, with final amalgamation of the NCB and the Songnen–Zhangguangcai Range Massif occurring in the Early Triassic, an event that led to the final suturing of the Solonker–Xra Moron–Changchun zone.