Abstract

Physical models of convergent boundary processes can provide insights into compressional orogens such as those studied by Lithoprobe. We summarize the qualitative tectonic style of a series of models designed to explore behaviour in subduction, collision, and obliquely convergent settings. The model results are represented by a series of diagrams which emphasize the main controls and behaviours in each case. Models are categorized in terms of the three main types of control: B, the boundary conditions assumed to operate on crust from surrounding lithosphere; I, the internal properties such as rheology and temperature distribution; and T, the redistribution of thickened crust or excess mass by gravitational forces (flexural compensation) and by surface processes such as erosion and deposition. The model templates for each setting are used to interpret some of the orogens studied by Lithoprobe, where there are sufficient temporal and spatial data for such a comparison to be meaningful. The purpose is to examine conceptual evolutions proposed by geologists and geophysicists in a process-based way. We compare the evolution of the Cascadia subduction margin with templates for oblique subduction; the eastern Trans-Hudson Orogen with models of the transition from subduction to collision; the Appalachian Transect in Lithoprobe East with models that involve a weak interior (“vise” models); the Torngat and New Quebec orogens with templates of subduction, transition to collision, and vise models; and the evolution of the Abitibi–Opatica granite–greenstone belt with models of subduction and collision. Comparison between models and seismic transects also highlights some of the potential pitfalls in interpreting compressional structures using reflectivity fabric.

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