From oblique arc-continent collision to orthogonal plate subduction in the southeastern central Asia Orogenic Belt during Paleozoic: Evidence from superimposed folds at the northern margin of the north China Craton

Accretionary kinematic history of the Central Asia Orogenic Belt (CAOB) remains unclear in previous geological studies. Based on detailed structural analysis of newly identified folds on the northern margin of the North China Craton (NCC), we propose a tectonic model suggesting that Paleozoic accretion of the orogenic belt includes two phases of deformation. The first phase of deformation is oblique collision of the Bainaimiao Arc and the NCC, which was followed by orthogonal subduction of the Paleo-Asian Ocean in the second phase of deformation. The change of plate kinematics is supported by two generations of folding, namely D-1 (DB) and D-2 (DA). Both D-1 (DB) and D-2 (DA) folds developed in the Bayan Obo Group (BOG), a Meso- and Neoproterozoic rift sequence deposited on the passive continental margin of the NCC. D-1 (DB) folds were superimposed by the east-west trending D-2 (DA) folds. The D-1 (DB) folds developed as a result of oblique collision of the Bainaimiao arc and the NCC. The D-2 (DA) folds developed in response to the southward orthogonal subduction of the Paleo-Asian Ocean Plate. They formed between latest Silurian and Early Permian, coeval with the two accretion events at the northern edge of the NCC. Our study suggests that multiphase deformation of sedimentary layers on the subducting plates provide important constraints for kinematic evolution of plate tectonics.