Scaled 3-D analogue modelling using viscous and granular materials

The 1.85 Ga Sudbury Igneous Complex is located in the Southern Province of the Canadian Shield, specifically at the junction between the Eastern Penokean Orogen (EPO) and the Cobalt Plate. The complex is the relic of an originally horizontal impact melt sheet that was geometrically modified by thrusting and folding during Paleoproterozoic orogenesis. The cause for non-cylindrical folding of the SIC under uniform NW-SE shortening is unknown. Unravelling the kinematics of this folding requires an understanding of the generation of cylindrical structures in the EPO and, by contrast, of domes and basins in the Cobalt Plate. In order to resolve the evolution of structures on the scale of these regions, analogue experiments using layered viscous and granular materials scaled to density, viscosity and thickness of major lithological units are proposed. Experimental set-ups will be designed to take into account kinematic boundary conditions of Paleoproterozoic deformation and the influence of the pre-deformational geometry of individual rock units on the evolution of structures. The geometry of structures observed in model orogens will be quantitatively compared to those observed in the natural prototype. Elucidating the formation of dome-and-basin structure, an ubiquitous, yet kinematically little understood structural pattern in orogenic belts of all ages, is of general geodynamic importance.