Geochronology and tectonometamorphic history of the Snowbird Lake area, Northwest Territories, Canada: New insights into the architecture and significance of the Snowbird tectonic zone

The results of mapping, geochronology, petrology, and geochemistry of rocks of the Snowbird Lake map sheet (NTS 65D), western Churchill Province, Canada provide new insight into the tectonometamorphic history of the southern Rae Province and significance of the Snowbird tectonic zone, western Churchill Province, Canada. U/Pb TIMS and SHRIMP data document a complex igneous and metamorphic history, with major contrasts between the Rae Province, Chipman domain, and Hearne Province. The Chipman batholith represents the oldest plutonic rock; crystallized at ∼3.4 Ga, metamorphosed at 2.85 Ga, and intruded at 11 kbar by ca. 1.9 Ga mafic dykes. Subsequent Neoarchean activity in the Rae Province involved plutonism at ca. 2.735, 2.67–2.66, and 2.55 Ga, all events that are documented in other portions of the Rae Province. In contrast, the Hearne Province shows only 2.72–2.66 igneous activity.Calcareous sediments are interpreted to have formed on the Rae Province passive margin, having been deposited on exhumed ca. 2.55 Ga basement between 2.07 Ga (youngest detrital zircon) and 1.92 Ga (metamorphic zircon). Burial to ∼7.6 kbar and heating to granulite facies at ca. 1.92 Ga document tectonic thickening in a compressional setting at ca. 1.92 Ga. This compressional setting may reflect terminal collision in the Taltson orogen or accretion of the Hearne Province during the earliest stage of the Hudsonian orogeny. Collectively, these data suggest that the Snowbird tectonic zone was not in an intracratonic setting prior to ca. 1.9 Ga orogenesis.