Depositional age and provenance of Siderian metasedimentary rocks in the Nonacho Lake area, Northwest Territories, Canada: implications for the correlation of crustal domains in the western Rae province

Migmatitic quartzofeldspathic gneisses in the Nonacho Lake area of the southwestern Rae province are interpreted as metasedimentary in origin based on geochemical criteria, a broad spectrum of apparent detrital zircon dates, and the presence of a relict heavy mineral lamella. Two samples collectively yield: rare >3.0 Ga detrital zircon; c. 2.78, 2.71, 2.59, 2.53 and 2.52 Ga detrital zircon age peaks; Yb-depleted c. 2.40–2.39 Ga metamorphic zircon and monazite; and c. 1.95 Ga metamorphic monazite. The sedimentary protoliths were deposited between c. 2.52 and 2.39 Ga. The Yb-depleted c. 2.40–2.39 Ga zircon and monazite record migmatization and garnet growth (replaced by chlorite) during a collisional phase of the Arrowsmith orogeny. The c. 1.95 Ga monazite reflect metamorphism associated with a cross-cutting c. 1.94 Ga granite dyke. The depositional age, provenance and metamorphic history of these rocks permit a broad correlation with 2.5–2.4 Ga metasedimentary rocks >750 km to the north, near Queen Maud Gulf. These findings, combined with recently published U-Pb age and isotope tracer data from plutonic rocks in the Nonacho Lake area, confirm the (semi)continuous nature of 3.3–3.0 Ga granitoid gneisses, 2.5 Ga granitoids and 2.5–2.4 Ga metasedimentary rocks along the western Rae margin. In the northwestern Rae province, the >3.0 Ga rocks and 2.5–2.4 Ga rocks occur in separate adjacent belts. In the Nonacho Lake area, the 2.5–2.4 Ga rocks occur structurally above >3.0 Ga crust, as indicated by 2.3 Ga granites that cut 2.5 Ga granitoids and have initial εNd values (–8 to –11) that require >3.0 Ga sources.