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

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.