Subduction Controls on Tibetan Plateau Deformation: Insights from Numerical Modelling

Abstract:

The formation of the Tibetan plateau is intimately related to the collision of Indian and Asian plate and the ensuing large-scale continental tectonics. To date, the mechanisms driving the growth of the plateau remain unknown, thus leaving the role of the Tibetan plateau in the collision largely debated. Using three-dimensional numerical models we investigate the controls of subduction dynamics on the deformation in the upper plate interiors and focus on the relation among thickening, shearing/faulting and lateral extrusion. The models illustrate the formation of lithospheric-scale shear zones as an effect of the breakoff of part of the oceanic slab from the continental lithosphere. The localized deformation pattern in the upper plate interiors profoundly controls the structural grain of the continent interiors, accommodating further deformation driven by far field forces. The emerging picture illustrates plateau-like thickening and shearing in front of the indenting down-going plate within a plate-scale extrusion tectonics, providing the frame to investigate the role of plateau formation in the wider tectonic context. The comparisons with various observables, such as strain axes and GPS motions, support the discussion on the possible processes at work, allowing inferences on the driving mechanisms of Tibetan plateau formation within the coupled plate margin-interiors tectonics. Our conclusions allow confuting some of the proposed models, supporting the view that the Tibetan plateau is best explained within the large-scale tectonic context.