Mesozoic-Cenozoic Multi-Stage Intraplate Deformation Events in the Langshan Region and their Tectonic Implications

In the Langshan region, northwestern China, marked multi-stage intraplate deformation events have occurred since the Mesozoic, including(1) northeast-striking ductile left-lateral strike slip during the Middle-Late Triassic, which is closely related to the collision between the North China and the Yangtze plates;(2) top-to-the-southeast thrust with northwest-southeast trending maximum compression during the Late Jurassic;(3) nearly eastward detachment during the Early Cretaceous;(4) top-to-the-northwest thrust with northwest-southeast trending maximum compression during the Late Cretaceous and Early Cenozoic;(5) northeast-striking brittle left-lateral strike slip with nearly north-south trending maximum compression; and(6) northwest-southeast extension during the Middle-Late Cenozoic. All these deformation events belong to the intraplate deformation across the entire Central Asian region and respond to the tectonic events along the plate boundaries or deep tectonics. The structures developed in early events in the crust were the most important factors controlling the later deformation styles, and few new structures have later developed. Based on previous research and our results, the paleostress inversion in the Langshan region shows that the Mesozoic intraplate deformations in the study region mainly resulted from the tectonic events from the Paleo-Pacific region and have no or a weak relation to the Tethys region. During the Late Jurassic, the maximum compression from the Mongolia-Okhotsk region cannot be excluded. The Langshan region is the bridge between southern Mongolia and the western Ordos tectonic belt and is thus important to understand the nature and relationship between both regions.