THREE-DIMENSIONAL MODELLING OF LAURENTIA IN SOUTH-CENTRAL CANADA: UNDERSTANDING CRUSTAL-SCALE STRUCTURES AND RELATED CRITICAL MINERAL ACCUMULATIONS

The Saskatchewan Geological Survey has developed a three-dimensional (3-D) model of Archean cratons centred on Saskatchewan that helps viewers to visualize the building blocks of Laurentia’s core. The model will guide future geoscience initiatives and address questions relating to critical-mineral systems.

The entire Hearne, Wyoming and Sask cratons, and Medicine Hat block were modeled, whereas only relevant parts of the Superior and Rae cratons were completed. All the cratonic elements were modeled to the Mohorovičić discontinuity. The modeling inspired several novel geological interpretations. The spatial extent of the Hearne and Sask cratons has been modified based on similarities in patterns in the regional aeromagnetic and Bouguer gravity maps. The Sask craton was merged with the Dakota block, which was defined in the northern U.S.A., and was extended into northeast Manitoba. Furthermore, Alberta’s Vulcan negative geophysical anomaly was extended into southwest Saskatchewan, where it separates the Hearne craton and the Medicine Hat block.

The crustal-scale architecture of Saskatchewan’s crystalline rocks has implications for evaluating the distribution of the province’s non-renewable resources, including several materials included in Canada’s critical minerals list. Recent core logging of Phanerozoic rocks of the Western Canada Sedimentary Basin (WCSB) and subjacent crystalline basement rocks in southern Saskatchewan has resulted in the generation of new analytical data. These data suggest the need to modify, and possibly expand, a region of radiometrically elevated igneous rocks known as the Swift Current Anorogenic Province, which are a possible source for Saskatchewan’s helium. Helium accumulations in the WCSB form due to migration of radiogenic alpha particles from basement rocks to traps in the overlying strata. Basement-rooted fractures are plausible migration pathways for helium-concentrated fluids. Moreover, knowledge of structural architecture in and/or near to a potash deposit may have important implications for project design as migrating fluids can dissolve potash and lead to significant consequences at a mining operation. As part of this improved understanding of potash distribution, we have used 3D modeling to determine Saskatchewan’s potash resource more accurately.