New bedrock mapping and preliminary U/Pb geochronology in the Walmsley Lake area, southeastern Slave Province, Northwest Territories

Abstract

Bedrock mapping in the Walmsley Lake area, southeastern Slave Province has resulted in the recognition of four regional deformation events. The first predated peak metamorphism and may be correlative with D 1 deformation in the central Slave Province. The second overlapped with peak metamorphism, and its timing and nature suggest that D 2 deformation across the southern Slave Province may also be correlative; however, preliminary U/Pb geochronology indicates that the age of metamorphism and D 2 deformation vary across the map area. Metamorphism is younger in the migmatized rocks, which are characterized by recumbent F 3 folds of the main foliation, and which may typify deeper structural levels. The final phase of deformation involved upright northeast- and northwest-trending cross folding. Overturned stratigraphy and the F 4 fold pattern of the melt-in isograd, suggest the possibility of kilometre-scale, downward-facing nappes, a geometry that has not previously been reported in the Slave Province.