Recent detailed geological mapping and UPb geochronological studies in the Torngat, Ungava and Baffin orogens of Northeast Laurentia have provided new information regarding the tectonic assembly of this region between ∼1.92 and 1.74 Ga. In contrast with an earlier hypothesis whereby the geometry of Archean continental fragments was thought to have resulted entirely from northerly indentation of the Superior Province and consequent extrusion tectonics, interpretation of recently acquired data shows that Superior Province indentation was the last of multiple collisional events during the formation of Northeast Laurentia. In the present model, we propose that Southeast Rae and North Rae provinces were separate prior to ∼1.92 Ga, when regional tectonism changed from extension to contraction. Westerly subduction and westward translation of the Archean Disko terrane and Nain Province between the North Rae and Southeast Rae provinces resulted in the development of a continental magmatic arc in the Cumberland batholithic complex and in the Torngat orogen, and deposition of the upper sequences of the Penrhyn-Piling-Karrat sequences in the Foxe and Rinkian belts of the Baffin orogen (1880-1895 Ma). Continental collision between the Disko terrane and North Rae Province produced shortening across the Rinkian and Foxe belts at, or before, 1876 Ma. Meanwhile, early arc magmatism in the Ungava orogen (1861-1898 Ma) accompanied foredeep or transtensional basin formation in the New Quebec orogen (∼1870-1883 Ma) and the onset of deformation in the southeastern Nagssugtoqidian orogen (∼1883 Ma). Nain-Southeast Rae provinces collision at ∼1860 Ma across the Torngat orogen caused renewed granitic magmatism and metamorphism in the Cumberland batholithic complex between 1857 and 1853 Ma. Initiation of felsic volcanism in the Makkovik-Ketilidian orogen at this time indicates a shift in the locus of plate subduction from the Southeast Rae Province to the southern margin of the Nain Province. In the Ungava orogen, northerly subduction changed to southerly subduction resulting in the generation of a second arc suite at between 1844 and 1826 Ma. Formation of the de Pas batholith in the hinterland of the New Quebec orogen at ∼1840 Ma accompanied arc-continent and Superior-Southeast Rae collision from 1845 to 1829 Ma. At this time, accretion of arc material in the Makkovik-Ketilidian orogen was contemporaneous with high-grade sinistral shearing along the reactivated Torngat orogen and the northwestern Nagssugtoqidian orogen. Southeast-directed thrusting along the southeastern margin of the Cumberland batholithic complex, and reactivation of the Rinkian belt is predicted to have also occurred at this time. At ≤1826 Ma, the onset of arc-continent collision across the Ungava orogen initiated closure of the North Rae-Southeast Rae provinces juncture and generation of the Ford Lake plutonic suite. Subsequent Superior-Southeast Rae continental collision (∼1810 Ma) resulted in dextral "escape tectonics" in the Foxe and Rinkian belts, and thick-skinned folding of basement and cover sequences in the Ungava orogen. High-grade metamorphism and granitoid magmatism in the Makkovik-Ketilidian orogen also occurred. Reactivation of the Nain-Southeast Rae (east-directed thrusting) and Superior-Southeast Rae (west-directed thrusting) margins at ∼1790 Ma resulted in "pop-up" of the Southeast Rae Province between its more rigid neighbors. Final cooling and the emplacement of post-tectonic granitoid rocks took place at ∼ 1740-1790 Ma.
ASJC Scopus subject areas
- Geochemistry and Petrology