The Trans-Hudson Orogen is the only fully preserved Early Proterozoic orogenic belt in North America. It is the principal element of a network of such belts that formed by Proterozoic crustal accretion and the collision of pre-existing Archean continents. In the case of the THO, the Archean continents are the Superior Province to the southeast and the Hearne-Rae provinces to the northwest. In northern Saskatchewan and Manitoba, the 500 km wide orogen includes four major lithotectonic zones:

• a southeast foreland zone;
   
• an internal zone of juvenile Proterozoic crust;
   
• an Andean-type magmatic arc batholith;
   
• a northwest hinterland zone (divided into smaller domains).

Figure 1. Geological map of the exposed Trans-Hudson Orogen and boundary locations. LITHOPROBE seismic reflection lines along which data were collected are shown in red, purple and dark blue.

Seismic survey results indicate prominent, pervasive east-dipping reflectors (not west-dipping as expected) throughout the crust in the foreland zone where the orogen bounds the Superior Province. Such results require major revision of current geotectonic models of the boundary zone and perhaps of the orogen as a whole. In the western segment of the orogen (in the internal zone), a crustal scale culmination coincides with the surface-defined arc-granitoid Glennie domain penetrated by Archean basement "windows". This culmination is interpreted as a previously unknown Archean microcontinent.

Figure 2. Migrated line drawing of seismic reflection data collected along line 9 (see Fig. 1). Base of reflections (yellow dots) represents the crust-mantle transition (reflection Moho). The thickest crust (45 km; marked Root) is interpreted as a trapped Archean microcontinent.

Figure 3. Geologic cross-section showing the principal tectonostratigraphic units of the THO as constrained by reflection profiles, potential field maps, and surface and drillcord geology.

Ongoing work is focussed on:

• a corridor across the foreland boundary zone to characterize its lateral variability in a region of significant interest to the mining industry;
   
• corridors along and across the Glennie domain and the magmatic arc to better define the newly discovered microcontinent;
  
• studying controversial aspects of individual domains and their boundaries;
   
• corridors across the hinterland zone into the Hearne-Rae provinces to investigate the northwest boundary region and the Snowbird Tectonic Zone.

Publications

Transect Reports