Geophysical evidence for a pre-impact Sudbury dome, southern Superior Province, Canada
Canadian Journal of Earth Sciences
Terrestrial Impact Cratering Res., Hugh Allsopp Laboratory, School of Geosciences, Johannesburg, Wits 2050, South Africa; Department of Geology, Rhodes University, P.O. Box 94, Grahamstown 6140, South Africa; Cowan Geodata Services, Dalkeith, WA 6009, Australia; Department of Geophysics, School of Geosciences, University of the Witwatersrand, Johannesburg, WITS 2050, South Africa
New filtering of aeromagnetic images of the Sudbury area indicates the existence of a large, elliptical feature that appears to underlie the deformed Sudbury Structure in the region of the exposed Levack Gneiss Complex, such that the two features have long axes which are significantly orthogonal to one another. A north-south-oriented ellipse appears to be crosscut by that of the Sudbury Structure and does not correspond to known local lithological or structural trends. The magnetic images, combined with existing tectonic, petrological, geothermometric and geobarometric, and geochronological data, are used to suggest the existence of a pre-impact crustal dome in the southernmost Abitibi subprovince,probably related to ca.2450 Ma rifting and magmatism in the area. This is consistent with existing petrological and tectonic evidence from a variety of sources. Although the doming is itself unrelated to the ca. 1850 Ma Sudbury event, it may have affected the thermal regime existing at the time of impact, which would have profound implications for the subsequent evolution of the Sudbury Igneous Complex. © 2005 NRC Canada.
Earth sciences; Geochronology; Geophysical prospecting; Lithology; Petrology; Tectonics; Aeromagnetic images; Crustal domes; Geothermometry; Magmatism; Domes; aeromagnetic survey; dome; geological structure; Canada; North America; Ontario; Sudbury Structure; Western Hemisphere; World