The Makkovik Province: extension of the Ketilidian Mobile Belt in mainland North America

Abstract

The Makkovik Province of Labrador represents the extension of the Ketilidian Mobile Belt of south Greenland into mainland North America; it exhibits a threefold division into a foreland region, a fold-and-thrust belt, and an interior magmatic zone. The Kaipokok Domain is dominated by Archaean basement rocks that form an extension of the North Atlantic Craton, but Proterozoic reworking is recorded by the reorientation of a c . 2230 Ma dyke swarm. Supracrustal rocks, consisting of shallow-marine sedimentary rocks overlain by greywackes and mafic volcanic rocks, rest unconformably upon Archaean basement, but towards the interior of the belt the basal unconformity is eradicated by northwest-directed thrusting. In the Aillik Domain , highgrade supracrustal rocks of similar aspect to those of the Kaipokok Domain are separated from the basement by mylonite zones, in a thick-skinned fold-and-thrust belt ( Kaipokok Bay Structural Zone ), believed to record significant northwest-directed translation. The Aillik Domain also contains abundant felsic volcanic rocks that lack typical arc-like geochemical signatures. The Cape Harrison Domain is dominated by plutonic rocks, including suites of 1840 Ma, 1800 Ma, 1720 Ma and 1650 Ma age, but gneissic inliers apparently represent ‘juvenile’ Proterozoic crust. The dominant 1800-1720 Ma plutonic suites are late-orogenic to post-orogenic, siliceous, potassic granitoid rocks, which resemble Phanerozoic post-collisional suites, rather than subduction-related arc batholiths. Nd isotopic variations position the eastern edge of the North Atlantic Craton close to the boundary between the Aillik and Cape Harrison Domains. The structural evolution of the Makkovik Province records a shift from pre- 1800 Ma northwest-directed thrusting to post-1800 Ma tight upright folding, also northwest-verging. However, there is also evidence for earlier (pre- 1890 Ma) events in the Kaipokok Domain. Major unresolved problems include the timing of early sub-horizontal deformation (perhaps related to collisional events), the age relations and setting of supracrustal sequences, the location of suture zones, the absence of clear arc-like magmatic assemblages, and the nature and antiquity of the eastern juvenile crustal block.

U–Pb geochronologic constraints on Paleoproterozoic orogenesis in the northwestern Makkovik Province, Labrador, Canada

“…Archean crust is not documented in this domain nor inferred to underlie it based on Nd isotopic data (Kerr and Fryer 1993). The Cape Harrison Kerr et al (1996) and Chadwick and Garde (1996). Location of Fig.…”

“…1650 Ma in the Makkovik Province are temporally unrelated to Makkovikian orogenesis and likely reflect magmatism associated with the younger Labrador orogen to the south (Kerr et al 1992). Structural and Nd isotopic data indicate that the Aillik domain represents an allochthonous, northwestvergent, Paleoproterozoic fold-thrust belt that overlies the southernmost limit of buried Arckean crust (Kerr and Fryer 1993;Kerr et al 1996). Southeast of the Aillik domain, the Cape Harrison domain consists of foliated to massive plutons emplaced between 1840 and 1650 Ma (Kerr et al 1992), with lesser volumes of supracrustal rock (Upper Aillik Group?)…”

“…Location of Fig. 2 1 Grenville Province krn domain is interpreted as an interior magmatic zone of the Makkovik orogen (Kerr et al 1996). All three domains are truncated by the Grenville Front (Fig.…”

“…1). The Kaipokok domain consists of reworked Archem gneisses derived from the Nain craton, overlying Pdeoproterozoic supracrustal rocks (Lower Aillik and Moran Lake groups), and Paleoproterozoic granitoid plutons (Ermanovics and Korstg%rd 1981 ;Kerr et al 1996). It is in structural contact with the Aillik domain which contains abundant felsic volcanic and volcaniclastic rocks of the Upper Aillik Group (ca.…”

“…This paper presents U-Pb geochronological data from one of these orogenic belts, the Makkovik Province of central Labrador, Canada, where a paucity of structural studies supported by precise isotopic dating has hampered the development of well-constrained tectonic models (Kerr et al 1996). We focus here on a northwestern parautochthonous domain of Archem rocks derived from the adjacent Nain craton because this domain contains tectonic fabrics, plutonic suites, and large-scale structures that provide the most complete record of Pdeoproterozoic events.…”