Paleoproterozoic basement-cover infolding and thick-skinned thrusting in Hearne domain, Nunavut, Canada: intracratonic response to Trans-Hudson orogen

Enveloped by orogenic belts during the assembly of Laurentia (similar to2.0-1.7 Ga), the Rae and Hearne domains of the western Churchill Province experienced a complex sequence of tectonic events historically referred to as the Hudsonian orogeny. In Hearne domain, diverse thick-skinned intraplate structures developed in response to accretionary processes in Trans-Hudson orogen. These structures include infolds of Archean basement and Paleoproterozoic cover, and broken foreland thrusts. In central Hearne domain, an intracratonic basin succession of continental to shallow-marine strata (Hurwitz Group; <2,45- <1.91 Ga) is exposed in outliers that constitute the keels of doubly plunging basement-cover synclinoria, defining a fold train with wavelengths of 35-45 km. With the exception of local out-of-syncline shear zones, basement and Hurwitz Group are welded. Formed under greenschist facies conditions, the basement-cover infolds are open, concentric, and commonly display complex structures in their interiors. In the Poorfish-Windy outlier, southwestern Hearne domain, continental rift deposits of the Kiyuk Group unconformably overlie the Hurwitz Group. In contrast to basement-cover infolding to the north and east, Archean basement, the Hurwitz Group and the Kiyuk Group are imbricated by thick-skinned northwest-vergent thrusts and folds. Thrusting in the Poorfish-Windy belt was completed by 1815 +/- 10 Ma, as indicated by new U-Pb data from hydro thermal-metamorphic titanite recovered from recrystallized cements at the top of the Kiyuk Group. We interpret that shortening from shallow-level basement-cover infolding is balanced at depth by intrabasement faulting and distributed ductile strain, and that the geometric link between central Hearne basement-cover infolding and Poorfish-Windy thrusting is via intrabasement faults that cut to the surface. The main controls on thick-skinned deformation were: the high competency of the lower Hurwitz Group; previous thermal weakening; basement heterogeneities; and possibly, shallow subduction preceding terminal collision in Trans-Hudson orogen. (C) 2002 Elsevier Science B.V. All rights reserved.