Geology of the Henik, Montgomery, and Hurwitz groups, Sealhole and Fitzpatrick lakes area, Nunavut

Abstract

Bimodal mafic-felsic volcanic rocks, consistent with rift and back-arc tectonic settings, form lenses in the lower Henik Group (Neoarchean). Emplacement of granitic bodies within the Henik Group was syn- to post-tectonic. Montgomery Group (age uncertain) conglomerate beds unconformably overlie Archean basement and are voluminous, suggesting fault-generated relief during sedimentation. Lower Hurwitz Group continental strata record Paleoproterozoic intracratonic basin expansion; locally preserved dolostone beds near the base of the predominantly fluvial Maguse Member (Kinga Formation) reflect a short-lived marine incursion. Pebbly arkose units between mature arenite beds of the Maguse and Whiterock members signify slope failure from basement monadnocks. Unusual feldspar megacryst-bearing gabbro sills in the Hurwitz Group were likely fed by hitherto unreported dykes which cut basement. Well foliated basement clasts in Montgomery and Hurwitz group conglomerate units imply deformation (likely Archean) before Paleoproterozoic dome-and-basin basement-cover infolding. Variably oriented folds and faults, including a duplex-like structure, accommodated constrictions arising from Paleoproterozoic concentric infolding.