Late Paleozoic–Early Mesozoic southward subduction-closure of the Paleo-Asian Ocean: Proof from geochemistry and geochronology of Early Permian–Late Triassic felsic intrusive rocks from North Liaoning, NE China

Abstract

Many studies have confirmed the existence of Late Paleozoic–Early Mesozoic accretionary arc and subduction complex belt to the south of the Solonker-Xar Moron-Changchun-Yanji Suture (SXCYS) zone. Nevertheless, since the suture from the east is covered by the Songliao Basin, until now there have been no completed reports focused on the Late Paleozoic–Early Mesozoic intrusive rocks of this area. Recently, a sequence of granitoid intrusions was identified in the Faku area, northern Liaoning. Zircon (SHRIMP) U-Pb dating results show that there are eight groups of felsic intrusions in the study area, and the intrusions formed at 283–227 Ma (Early Permian to Late Triassic). Together with study of regional events, A four-stage tectonic evolution scenario was recommended during Permian-Triassic in the Faku area: Early Permian magmatism in an activity continental margin setting (293–274 Ma); Middle-Late Permian magmatism in a setting where subduction is translated into collision (270–255 Ma); Early-Middle Triassic magmatism in a setting where collision is translated into detachment of the oceanic slab (255–242 Ma); and Middle to Late Triassic magmatism recorded procedure of post-collision orogeny transformed into extensional environment (241–215 Ma). The Early Permian–Late Triassic felsic intrusions documented the extension-collision of the convergent continental margin and the subduction-extinction of the Paleo-Asian Ocean. Zircon Hf isotopic analyses yield εHf(t) values of −2.03–15.80, almost all of which are positive (with two points being negative), indicating the depleted characteristics of the source area. According to emplacement time and occurrence location, the plutons are interpreted to have been generated by the subduction-collision of the Paleo-Asian oceanic crust beneath the North China Craton (NCC). This study provides strong evidence for Late Paleozoic–Early Mesozoic tectonic evolution and the characterization of the eventual closure of the Paleo-Asian Ocean in the Songliao Basin overlying the northern margin of the NCC.