Geophysical transect across a Paleoproterozoic continent–continent collision zone: The Trans-Hudson Orogen

Abstract

A summary and comparison of geophysical data and models for the Trans-Hudson Orogen in northern Manitoba and Saskatchewan are presented. Magnetic total field and Bouguer gravity maps are used to define the along-strike extension of geological domains of the orogen exposed on the Canadian Shield, and a two-dimensional density model is produced, which accounts for the observed variations of the Bouguer gravity field across the orogen. An 800-km-long crustal section across the entire continent–continent collision zone, including the edges of the bounding cratonic blocks, is presented. It incorporates seismic reflectivity, seismic velocities, resistivity, and density models. Key results include (1) evidence for west-vergent crustal stacking and exhumation in the eastern Trans-Hudson Orogen in the form of preserved Moho topography and the presence of higher grade (higher velocity) rocks in the hanging wall of an east-dipping crustal stack; (2) definition of the eastward extent of the Archean Sask craton in the subsurface based on distinct lower crustal properties; and (3) 400 m of present-day surface topography and 6–8 km of relief on the Moho are isostatically compensated mainly within the upper mantle by a westward increase in upper mantle temperatures by 40–155 °C and (or) 16–107 km of thinning of the mantle lithosphere.