Formation mechanism of the Dabashan foreland arc-shaped structural belt
Institute of Geomechanics, Chinese Academy of Geological Sciences
Abstract:Based on field observations and structural measurements, this paper describes basic features of the Dabashan foreland arc-shaped structural belt, its distribution pattern, zonation, segmentation, vertical stratification, deformation pattern, superimposed folding and paleostress field, then discusses main factors controlling the formation of this structural arc. It pointed out that the formation and development of the Dabashan foreland arc are different from classical model of collisional mountain built-up; it was shaped through three different stages: original boundary conditions formed during Paleozoic extension and rifting along the marginal zone of the Yangze; initiation during Middle-Late Triassic collisional orogen; and final formation during Middle-Late Jurassic intra-continental orogen. The arc-shaped Chengkou-Fangxian fault zone not only controls the Early Paleozoic deposition and magmatism, but also played key role in the foreland arc formation, and the basement uplifts at the two syntax acted as important boundary conditions. Sandbox modeling was carried out in the laboratory to model the formation and boundary condition of the Dabashan foreland arc. The model was set-up according to the real geologic data.