We have begun to investigate mid-crustal ductile flow (infrastructure), and its effect on upper crustal (superstructure) deformation style, through centrifuge modelling. Analogue centrifuge models are used to investigate contrasting deformation styles in the superstructure and infrastructure observed in continental collision zones. Models are designed to simulate the structural evolution of horizontal shortening in a superstructure/infrastructure package, followed by vertical thinning and horizontal stretching and ductile flow of the melt-weakened infrastructure due to focused erosion and a lithostatic pressure gradient in a manner akin to channel flow.
Emphasis in our research is placed on examining: 1) coeval and dynamically linked deformation (coupling) between the superstructure and infrastructure; 2) the formation of drag folds along the interface between the superstructure and infrastructure during infrastructure horizontal flow; 3) the effects of varying the slope steepness of the orogenic topographic front, which drives extrusion of the ductile infrastructure, on the development of deformation features in the superstructure, 4) the role of low-viscosity melts in strain partitioning of the orogenic edifice, and 5) the role basement faults may have in influencing the efficiency of crustal-scale mid-crustal flow.
A high-acceleration centrifuge is used to dynamically scale gravitational forces deemed important to the evolution of orogen-scale structures, especially those developed during channel flow. We collaborate with colleague Lyal Harris (INRS-centre – Eau Terre Environnement), who has a PR-7000 centrifuge at the Institut National de la Recherche Scientifique in Quebec City capable of subjecting models up to 200 mm x 80 mm in plan view to accelerations exceeding 1000 g (where g is the local acceleration due to gravity).