Geoscience impact: a synthesis of studies of the Sudbury Structure

Geophysical probing results are synthesized into a three-dimensional framew ork necessary for understanding the genesis of the Sudbury Structure, based primarily on seismic reflection results centred on the Sudbury Igneous Com plex. Remnants of crustal melting from a catastrophic meteorite impact are superimposed on the juxtaposition of mid-crustal rocks exhumed during the A rchean against deformed Paleoproterozoic sedimentary rocks. Sedimentation, metamorphism, deformation, and metasomatic overprints are all part of the p ost-impact history of Sudbury and tend to dominate the geophysical response of the structure. Pre-impact deformation, although certainly preserved in some aspects of Sudbury geology, is not clearly expressed in the geophysica l data, nor are any elements of impact-induced deformation. Geophysical vie ws of the Sudbury Igneous Complex are thus somewhat biased in representing mostly the post-impact, but pre-Grenvillian history of the region, with the exception of igneous events. Establishing the proper context for integrati ng these geophysical results in the genetic interpretation of the Sudbury S tructure depends crucially upon timing constraints.