Grenville age deformation of the Sudbury impact structure: evidence from magnetic modelling of the Sudbury diabase dyke swarm

Terra Nova, 24, 213–220, 2012 Abstract The Sudbury Structure is located <10 km from the Grenville Front; the northern boundary of the Grenville metamorphic terrane. Previous geological studies have suggested that late Grenvillian deformation (1000–1070 Ma) of the Sudbury Structure was limited to minor brittle deformation. Olivine diabase dykes, which were intruded at 1238 Ma, before the last pulse of Grenville deformation, cross much of the Sudbury Structure. Any Grenville age deformation of the Sudbury Structure therefore should produce systematic displacements in the geometry of the dykes. This study uses information derived from an aeromagnetic survey of the Sudbury Structure to map and measure fault displacements. Lateral displacements of dyke segments define a progressive increase in fault rotation from NE to SW across the basin. A two-dimensional inversion modelling of magnetic anomaly profiles across segments of the dykes outlines a series of fault blocks with common dip. The dyke dip detected by the inversion models suggests that displacement on the faults included rotation about an axis perpendicular to the trend of the fault. The resulting model of scissor, or splay faults is compatible with previously published palaeomagnetic studies of the olivine dykes in the Sudbury region.