Detrital zircon geochronology of Kilohigok basin: Record of Paleoproterozoic orogenesis and unroofing of the Thelon tectonic zone (Nunavut, Canada)

Abstract

The Paleoproterozoic Kilohigok foreland basin formed on the Archean Slave craton in response to 2.02–1.90 Ga collision in the adjacent Thelon tectonic zone (Ttz), the boundary between the Slave and Rae cratons within the nascent Nuna supercontinent. U-Pb and Hafnium isotopic data from detrital zircon are used to test the foreland basin model and examine the nature of crustal components within the Ttz. Changes in provenance within the basin can be linked with tectonic events in the Ttz. Platformal deposits of the Kimerot Group are derived from local Archean Slave sources, which also dominate the initial foredeep deposits of the ca. 1.97 Ga lower Bear Creek Group. Paleoproterozic 2.02––1.97 Ga detritus match ages of plutonic rocks within the overthrust Thelon tectonic zone and dominates the deposits of the upper Bear Creek Group (Beechey and Burnside River formations) within 10 Ma of foredeep initiation at 1.97 Ga. Significant populations of 2.3 Ga and 2.17–2.07 Ga detrital zircon were introduced to the basin at that time. Their relatively juvenile Hf isotopic compositions are characteristic of the Buffalo Head terrane, but not to potential sources in the western Rae, indicating that Buffalo Head-like crust extended north of the Great Slave Lake Shear zone and was involved in Slave-Thelon-Rae collision events. Basin rejuvenation occurred after 1.88 Ga with deposition of the Bathurst Group, in part coeval with basaltic magmatism correlated with the underlying Mara River sills, dated at 1.87 Ga. Magma transport within basin-wide sill-complexes indicates magma sources on the western side of the Slave, associated with contemporaneous Great Bear magmatism in the Wopmay orogen. Bathurst Group basin rejuvenation is synchronous with 1.88–1.87 Ga metamorphism and shortening in Wopmay orogen on the west side of the Slave. More diverse detrital zircon signatures in the Bathurst Group indicate a broader source region, including areas from the eastern side of the Ttz. The data are consistent with tectonic models that link Thelon tectonic zone to the Ksitusan terrane and involve a Slave-Buffalo Head terrane collision as part of the greater Slave-Rae amalgamation.