Effects of the brittle-ductile structure and burial depth of backstop on deformation patterns of fold-and-thrust belts: Insights from analogue modelling

Fold-and-thrust belts are one of the hotspots in earth science research and a crucial area for petroleum exploration, and have been extensively studied. However, systematic and in-depth studies on the influence of plate interactions on the deformation patterns of fold-and-thrust belts remain insufficient. In this paper, based on previous research, analogue modeling is employed to design eight groups of brittle-ductile structural models with varying depths of backstop, enabling the simulation and analysis of interactions and impacts between blocks within the fold-and-thrust belt. The results show that: 1) the contact location between active blocks plays a highly critical role in controlling the deformation patterns of fold-and-thrust belts. 2) With shallow burial depths of backstop, thrust faults dominate the structural style. As the burial depth increases, the deformation patterns of fold-and-thrust belts not only include thrust faults but also develop shear faults and strike-slip faults. 3) The simulation study further indicates that inferring kinematic and dynamic processes solely from the distribution of fault systems, or using deformation-controlled multifactorial interpretations may be unreasonable. Under the influence of a single burial depth of backstop, fold-and-thrust belts can also exhibit complex deformation patterns. 4) The distribution pattern of thrust faults at the front of the Longmenshan may be related to the shallow burial depth of the Songpan-Ganzi terrane to Sichuan block. This study provides tectonic physical evidence for understanding the deformation mechanisms of fold-and-thrust belts.