Structural history and granite emplacement in the Rottenstone Domain during closure of the Trans-Hudson Orogen, Davin Lake, northern Saskatchewan

Abstract

The Rottenstone Domain at Davin Lake northern Saskatchewan, exhibits structural and granite-emplacement evidence for crustal thickening, and possible Himalayan-style extrusion, overprinted by transpressional strain increasing toward the contact with the Wathaman Batholith. Three discrete Rottenstone subdomains parallel the regional strike of the Trans-Hudson Orogen: (i) the southeast Rottenstone subdomain (SERSD) with gently northwest-dipping migmatitic straight gneiss (S1) and white granitoid rocks with pinch-and-swell structures parallel to the straight gneissosity; (ii) the central Rottenstone subdomain (CRSD), which partly preserves the same NW-dipping fabric (S1) but is overprinted at its margins by tight upright F2 folds and includes a stockwork of pink monzogranitic aplites and pegmatites; and (iii) the northwest Rottenstone subdomain (NWRSD) in which the F2 folds are generally tighter and penetrative and its network of narrow white granitoid rocks is deformed and transposed by the F2 folds; but in the northwestern part, a wide, syn-D2 complex of schlieric white tonalitic and diatexite sheets strikes parallel the orogen. The SERSD D1 straight zone may be a remnant of Himalayan-type extrusion zone although it could be the lowest member of a stack of ductile thrust sheets. The CRSD stockwork may represent fluid-assisted magma injection into extensional fractures above the postulated extrusion zone. The increasing transpressional strain northwestward expressed primarily by the F2 folds in CRSD and NWRSD defines the Davin Lake shear zone, into which the NWRSD granitoid dyke complex represents syntectonic magma injection. Both the postulated extrusion and transpression are related to oblique convergence of the Archean Sask craton with the Archean Rae–Hearne craton.