Tectonic evolution of the Liupan Shan fold-and-thrust belt, NE Tibetan Plateau during the late Cenozoic: numerical simulations

Abstract

SUMMARY The propagation of Tibetan Plateau high-elevation towards the Asian interior remains poorly understood. We conduct a series of 2-D viscoelastic plastic finite element models addressing the development of the Liupan Shan fold-and-thrust belt with multiple detachments in the NE Tibetan Plateau. We focus on the spatio–temporal relations of the Liupan Shan fold-and-thrust belt and dynamic mechanisms of growth in the NE margin of Tibetan Plateau during the late Cenozoic. Our models, consisting of a seismically-constrained two-layer-crust (of variable thicknesses) plus lithospheric mantle consider tectonic horizontal contraction and the influence of elastoplastic materials, including Model 1 (only the upper crust is elastoplastic), Model 2 (both the upper crust and the middle part of the lower crust are elastoplastic) and Model 3 (the whole lithosphere is elastoplastic). The results show that Model 1 can only reflect the properties of shallow detachment layer. Models 2 and 3 can better reflect the properties of multidetachment layers and approximately represent the process of fold-and-thrust belt formation and evolution; thus suggesting the importance of plastic rheology in the deep crust. In addition, Model 3 suggests that the pre-existing fault near the Moho below Liupan Shan is activated during the evolution process of ∼8 Ma. In summary, the results embody that the initiation and evolution of the fold-and-thrust belt depend on detachment structures: the deep and shallow detachments control the evolution of surface deformation and fold-and-thrust belt altogether. The simulated surface deformation is generally consistent with actual surface elevation distribution. Moreover, the growth of the Liupan Shan range may represent an expansion of the NE Tibetan Plateau toward the Ordos basin vicinity. Additionally, the tectonically driven uplift of Liupan Shan area supports the general crustal shortening tectonic mechanism of the Tibetan Plateau.