Mesozoic contractional deformation in central East Asia: Constraints from deformation and sedimentary record of the Helanshan fold and thrust belt, North China Craton

Abstract

East Asia continent underwent complex deformation in the Mesozoic under multi-plate convergence. However, the response to the multiple plate convergence in the North China Craton remains enigmatic. The fold and thrust belt in the western margin of Ordos Basin in the west of the North China Craton, far away from the East Asian continental margin, provides an important clue to uncover the deformation process and its dynamic model in the East Asian continent. This paper focuses on kinematics and strain analysis of the fold and thrust belt in Helanshan through detailed field tectonic mapping. Combined with the Mesozoic stratigraphic and deformation records of adjacent areas, we try to comprehensively analyze the timing, styles, and processes of the Helanshan fold and thrust belt. This will provide significant constraints on the mechanisms of intraplate deformation in Asia. The Helanshan fold and thrust belt is located in the central part of North China, sandwiched between the Ordos block and Alxa block. The belt has well-developed fold and thrust structures and well-preserved Mesozoic coal-bearing sedimentary basins. The NNE-trending Helanshan fold and thrust belt is a typical thin-skinned structure developed in the western margin of the Ordos Basin. The fold and thrust belt was formed in the NW contractional strain field in the Late Jurassic in response to the westward flat subduction of the paleo-Pacific plate beneath the North China Craton along the eastern margin of the Asia continent. The contractional deformation in the Late Jurassic led to the initial uplift and formation of the Helanshan, which also became the Mesozoic western boundary of the Ordos Basin.