Anatomy and orogenic history of a Paleoproterozoic accretionary belt: the Makkovik Province, Labrador, Canada

Abstract

The Makkovik Province is a segment of a Paleoproterozoic accretionary belt (the Makkovik-Ketilidian orogen) that developed on the southern margin of Laurentia at 1.9-1.7 Ga. In contrast to coeval Laurentian orogenic belts that mainly resulted from collision of Archean plates, Makkovikian-Ketilidian orogenesis was dominated by active-margin processes including continental margin arc plutonism and juvenile terrane accretion, both of which were accompanied by regional transpression. In the Makkovik Province, earliest deformation and amphibolite-facies metamorphism of Paleoproterozoic rift-drift assemblages (Post Hill and Moran Lake groups) and the Archean foreland (Nain Province) occurred at 1.9 Ga in response to accretion of a Paleoproterozoic island arc. Following this collision, cratonward-dipping subduction was established, resulting in the formation of the 1895-1870 Ma Island Harbour Bay Plutonic Suite, a calc-alkaline magmatic arc built on reworked Archean crust. Crust formation continued between ca. 1860 and 1850 Ma with deposition of the Aillik Group on a largely juvenile basement in a rifted-arc or back-arc setting. Sometime before 1802 Ma this depositional basin was tectonically inverted, with resultant northwestward thrusting of the Aillik Group over reworked Archean crust. This phase of deformation may have been driven by accretion of a second island arc potentially represented by the Cape Harrison Metamorphic Suite. Regional transpression and amphibolite-facies metamorphism at ca. 1815-1780 Ma were accompanied by widespread granitoid plutonism. These events were mainly concentrated in the juvenile domains and are thought to reflect processes in a broad continental back-arc setting. A final orogenic pulse, marked by regional greenschist-facies transpression and emplacement of A-type granitoid plutons, occurred between 1740 and 1700 Ma, with deformation and plutonism potentially linked to crust-mantle detachment and incursion of mafic magmas at the base of the crust, respectively. The record of crustal development suggests that the coeval themes of spatially and temporally linked structural and plutonic activity, oceanward migration of this activity over time, and a trend toward increasingly more localized deformation occurred throughout the orogenic history of the Makkovik Province. These characteristics are thought to broadly reflect oceanward crustal growth of the orogen over time. In the correlative Ketilidian mobile belt of southern Greenland, these themes were also operative but appear to have been less pronounced, most likely due to minimal or a complete absence of accretion of island-arc material. 730Résumé : La Province de Makkovik est un segment d'une ceinture d'accrétion paléoprotérozoïque (l'orogène Makkovikkétilidien) qui s'est développée sur la bordure sud de la Laurentia vers 1,9-1,7 Ga. Contrairement aux ceintures orogéniques contemporaines laurentiennes qui résultent principalement de la collision de plaques archéennes, l'orogène Makkovikkétilidien a été dominé par des processus de marges...

Pb Isotope Mapping of Paleoproterozoic Gneisses in the SW Grenville Province: Evidence for a Cryptic Continental Suture

“…They proposed that arc accretion was followed by subduction-flip, establishing an ensialic arc on the new margin. This model was supported by Moumblow et al [6], but they rejected a second arc accretion event suggested by Ketchum et al [14], since there is no evidence for two distinct arcs within the Cape Harrison domain.…”

“…A similar scenario is observed behind the accretionary margin of the Makkovik Province in which the supracrustal units from the Aillik Group were deposited in a retro-arc basin ca. 1.86−1.85 Ga [6,14]. Evidence for a Paleoproterozoic crustal source in the SW Grenville province is further supported by the Kiosk quartzite south of the proposed Penokean arc.…”

“…Ketchum et al [14] attributed the Makkovik Province to a 1.9 Ga arc accretion event, caused by the attempt to subduct the Archean margin under a ca. 2 Ga oceanic arc.…”

Crustal Evolution of the Northeast Laurentian Margin and the Peri-Gondwanan Microcontinent Ganderia Prior to and During Closure of the Iapetus Ocean: Detrital Zircon U–Pb and Hf Isotope Evidence from Newfoundland

“…The mixing trend at 2.1 -1.6 Ga shown by the detrital zircon pattern of Figure 5a could correspond to earlier continental arc magmatism at 1.91 -1.70 Ga that reworked Archean crust to the west of the Grenville Province (Makkovikkian; Ketchum et al 2002). The oldest mixing trend, at 2.55 -2.75 Ga (Fig.…”

Palaeoproterozoic and Archaean gneiss complexes in northern Greenland: Palaeoproterozoic terrane assembly in the High Arctic

“…This aspect is important to stress, because there are some reconstructions of the Arctic and North Atlantic regions that show North-West Greenland displaced hundreds of kilometres from neighbouring Canada. Such reconstructions -for example those figured by Roest and Srivastava (1989), Eide (2002), Ketchum et al (2002). Wardle et al (2002), Piper and Darabi (2005) and Tessensohn et al (in press) do not explain the lack of displacement in the Precambrian rock units across the Nares Strait.…”