Impacts of strength heterogeneity on thrust belts: Insights from analogue experiments

The strength and rheology of the lithosphere are critical factors controlling strain concentration and partitioning, and hence affect the deformation propagation sequence of thrust belts. In this study, we used analogue experiments consisting of materials with different mechanical properties to model strength heterogeneity and investigate the specific impact of lithosphere heterogeneity on the structural evolution sequence of thrust belts. The results showed that the structural evolution sequence is sensitive to strength heterogeneity: (1) the variations in the strength of different materials were conducive to strain concentration along the strength contrast surface and controlled the position of the potential deformation structure; and (2) the spatial configuration of the lower decollement and upper heterogenous brittle layer controlled deformation propagation. The distribution of the weak decollement constrained the deformation propagation range, and the strength heterogeneity in the overlying brittle cover disturbed the deformation evolution sequence. We applied the insights from analogue models to interpret the factors controlling the Eastern Tibetan Plateau lateral growth. The strong complexes along northern Longmenshan and the weak and ductile layer at 20 km depth in the interior plateau jointly controlled the extension behavior of the Eastern Tibetan Plateau. They lead to the retracement of deformation propagation from the Longmenshan Thrust Belt to the Longriba Fault. The intense convergence in the Eastern Tibetan Plateau is eventually accommodated in the interior plateau, resulting in a silent thrust belt front in northern Longmenshan.

Automated summary

The strength and rheology of the lithosphere play a critical role in the deformation propagation sequence of thrust belts. The study showed that strength heterogeneity controls the location and concentration of strain, while the spatial configuration of different layers influences deformation propagation. These insights can be applied to understand and predict the evolution of geological structures.