Magnetic interpretation along the Sudbury Structure Lithoprobe Transect

New high-resolution seismic reflection data has been used to provide a geometrical and lithological framework to develop a magnetic model of the Sudbury Structure, a large basin like feature that occurs at the junction of the Superior, Southern and Grenville tectonic provinces. Measured magnetic susceptibility and natural remanent magnetization values afforded an important constraint in the modelling process, and provided an valuable insight into the genesis of the various magnetic anomalies. The magnetic anomaly profile along the Lithoprobe Transect across the Sudbury Structure appears to arise from three main sources: a) a broad regional magnetic anomaly ascribed to a more magnetic layer of the Levack Gneiss Complex subjacent to the base of the Sudbury Igneous Complex; b) a prominent magnetic high associated with the southern contact between the Onwatin and Onaping Formations, believed to reflect a zone of hydrothermal mineralisation; and c) a magnetic high associated with the South Range contact of the SIC produced by the juxtaposition of rock units produced by northward directed thrusting and an enhanced remanence signature in the basal unit of the South Range Norite.