Archaean Rae craton

The northern half of Baffin Island (Fig. 2) is underlain by the Archaean Rae craton (Hoffman 1988), which comprises: (1) banded granodioritic to monzogranitic orthogneiss (Fig. 5); (2) an overlying clastic sedimentary rock sequence with quartzite and banded iron formation, and dominantly mafic tholeiitic, subordinate intermediate, and minor felsic metavolcanic rocks (Mary River Group); (3) a second volcanic-dominated supracrustal sequence (Prince Albert Group) comprising tholeiitic and isotopically depleted amphibolite (including komatiite), quartzite, and calc-alkaline mafic and intermediate metavolcanic rocks; and (4) younger granodioritic to monzogranitic and rare tonalitic calc-alkaline plutonic rocks (Scott & de Kemp 1998; Jackson 2000; Jackson & Berman 2000; Bethune & Scammell 2003; Scott et al. 2003; Johns & Young 2006; St-Onge et al. 2006b; Young et al. 2007). The felsic orthogneiss is c. 2.9–2.78 Ga in age, including a 2868 +13/−12 Ma age determination and the metavolcanic rocks of the Mary River Group have been dated at c. 2829 Ma (c. 3.3–2.9 Ga Sm–Nd model ages). The Prince Albert Group yields ages that cluster between 2732 +8/−7 and 2718 +5/−3 Ma (c. 2.85–2.7 Ga Sm–Nd model ages) and the younger felsic plutons range in age between c. 2.73 Ga and 2658 +16/−14 Ma (Jackson et al. 1990; Jackson 2000; Wodicka et al. 2002b, 2007a; Bethune & Scammell 2003; Johns & Young 2006; Young et al. 2007).

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Fig. 5.

Archaean granodioritic to monzogranitic orthogneiss, Rae craton, central Baffin Island. Length of hammer is 35 cm.

In northern West Greenland, the coastal areas of Inglefield Bredning, Kap York, and Melville Bugt (Rae craton; Fig. 3) are underlain by tonalitic to granitic orthogneiss and quartzofeldspathic paragneiss of the Thule mixed gneiss complex (c. 2.91 Ga Sm–Nd model age), gabbro–tonalite–granite units of the Kap York metaigneous complex (c. 2.7 Ga Rb–Sr age), and tonalitic to granitic gneiss and granite of the Melville Bugt orthogneiss complex (c. 2.7 Ga Rb–Sr age) (Dawes 1991, 2006; and references therein). Based on lithological characteristics and associations, the Archaean, dominantly felsic, metaigneous units of the Rae craton in Greenland are correlated with the metaplutonic units of northern Baffin Island (Hoffman 1988). Along the north shore of Melville Bugt, c. 2.7–2.6 Ga (Rb–Sr and U–Pb ages; Dawes et al. 1988) quartzofeldspathic to pelitic paragneiss and schist (including ironstone), magnetite-bearing quartzite, mafic schist, amphibolite, and ultramafic rocks of the Lauge Koch Kyst supracrustal complex (Dawes 1991, 2006) are similar to the Mary River Group (Jackson 2000) and/or Prince Albert Group of northern Baffin Island (Young et al. 2007) and Melville Peninsula (Scott & de Kemp 1998), thus providing an additional basis for the correlation of units belonging to the Rae craton between West and northern West Greenland and northern Baffin Island (Figs 2 and 3).

Palaeoproterozoic northern margin of the Rae craton

The Precambrian basement of southeastern Ellesmere Island and eastern Devon Island comprises highly deformed, granulite facies, metasedimentary and metaigneous rocks of the Ellesmere–Devon terrane (Frisch 1988), which are overlain by the unmetamorphosed strata of the late Mesoproterozoic Thule basin and early Palaeozoic Franklinian basin (Fig. 2). The metasedimentary rocks of the Ellesmere–Devon terrane include quartzofeldspathic gneiss, migmatitic pelitic gneiss, marble and quartzite that are interpreted to represent a metamorphosed continental margin sequence of shale, greywacke, shallow-water carbonate and volcanogenic rocks (Frisch 1988). The plutonic rocks mainly comprise pyroxene-bearing tonalite, quartz norite and several varieties of granite, including peraluminous S-type granite. Lithological and gneissic trends are predominantly north–south on Ellesmere Island but east–west on Devon Island (Frisch 1988). Age determinations (Frisch & Hunt 1988) yield 1960±5 to 1912±2 Ma for the metaplutonic rocks and indicate the presence of Archaean crust on southernmost Devon Island (Fig. 2; north margin of Rae craton?).

Polydeformed and granulite facies rocks of the Inglefield mobile belt in northern West Greenland (Fig. 3; Frisch & Dawes 1982; Dawes 1988; Dawes & Garde 2004) can be divided into two main assemblages (Dawes et al. 2000; Dawes 2004); namely, high-grade Palaeoproterozoic paragneiss (Etah Group) and a polyphase igneous suite (Etah metaigneous complex) that intrudes the Etah Group on all scales. Recently, Nutman et al. (2008) described the mobile belt as also comprising a northern and a southern part, with the two separated by a late shear zone that they called the Sunrise Pynt straight belt.

The Etah Group comprises pelitic to quartzofeldspathic paragneiss and schist, as well as voluminous S-type granite, marble and calc-silicate, amphibolite, and ultramafic units. The Etah metaigneous complex is composed of intermediate to felsic orthogneiss, megacrystic monzogranite, quartz diorite, syenite, and subordinate metagabbro and magnetite-rich rocks. The available geochronological data are complex (Nutman et al. 2008), but regional subsidence and deposition of the Etah Group has been bracketed between c. 1.98 and 1.95 Ga, with the age of the Etah metaigneous complex constrained between 1949±13 and 1915±19 Ma by ion probe U–Pb ages on zircon. Correlations between the metasedimentary rocks of the Ellesmere–Devon terrane and the Etah Group of the Inglefield mobile belt, as well as between the metaplutonic rocks of Ellesmere and Devon Islands and those of Inglefield Land, were made by Frisch & Dawes (1982), Dawes (1988), and Dawes et al. (1988), based on similarities in lithology, metamorphic grade, and tectonic history.

Palaeoproterozoic southern margin of the Rae craton

On central Baffin Island, the southern margin of the Rae craton is unconformably overlain by the Palaeoproterozoic Piling Group (Morgan et al. 1975, 1976; Scott & de Kemp 1998; Scott et al. 2003), as well as by the stratigraphically correlative Hoare Bay Group on Cumberland Peninsula (Fig. 2; Jackson & Taylor 1972; St-Onge et al. 2006b). In the type Piling Group area of west–central Baffin Island, the stratigraphically south-facing continental margin sequence comprises (Scott et al. 2003): (1) shallow marine, continental margin clastic (Dewar Lakes Fm) and carbonate platform (Flint Lake Fm; Fig. 6) strata (younger than 2159±16 Ma); (2) stratigraphically younger mafic intrusive, extrusive, and sedimentary rift units (younger than 1980±11 Ma, with a feeder dyke of intermediate composition yielding an age of 1935±25 Ma) (Bravo Lake Fm) and rusty-weathering sulphide schist, black shale, and sulphide-facies iron formation (Astarte River Fm) associated with foundering of the carbonate platform; and (3) foredeep turbidites younger than 1915±8 Ma (Longstaff Bluff Fm). Analysed sedimentary strata are dominated by 3.61–2.72 Ga detrital zircons (lower and middle Dewar Lakes Fm), 3.02–2.16 Ga detrital zircons (upper Dewar Lakes Fm), 3.31–1.98 Ga detrital zircons (Bravo Lake Fm), and 2.95–1.91 Ga detrital zircons with a preponderance of 2.03–1.91 Ga ages (Longstaff Bluff Fm). The above geochronological constraints on the deposition of the Piling Group are based on ion probe U–Pb ages on detrital zircon in clastic rocks and igneous zircon in a volcanic dyke from Wodicka et al. (2007b). The interbedded mafic volcanic and sedimentary rift units of the Bravo Lake Formation occur at the interface between the lower clastic unit (Dewar Lakes Fm) and the overlying black shale and turbidites (Astarte River and Longstaff Bluff Fms), where the marble of the Flint Lake Formation is not present (Scott et al. 2003).

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Fig. 6.

Flat-lying Palaeoproterozoic carbonate strata of the Flint Lake Formation, lower Piling Group, central Baffin Island. Front of helicopter for scale.

Various felsic plutonic rocks, ranging in age from 1897 +7/−4 to 1823 +7/−4 Ma (Wodicka et al. 2002b; Bethune & Scammell 2003) and including the northernmost components of the dominantly hypersthene-bearing 1865+ 4/−2 to 1848±2 Ma Cumberland batholith (Jackson et al. 1990; Wodicka & Scott 1997; Scott & Wodicka 1998; Scott 1999), intrude the southern and western strata of the Piling and Hoare Bay groups, respectively, on Baffin Island. The Cumberland batholith has been interpreted as the base of a continental margin arc emplaced above a north-dipping subduction system following accretion of the Meta Incognita microcontinent to the Rae craton (see below; Thériault et al. 2001; St-Onge et al. 2006c, 2007), although this conflicts with the interpretation of the contemporaneous Prøven igneous complex in adjacent northern West Greenland (see below; Thrane et al. 2005).

Palaeoproterozoic units in central and northern West Greenland have traditionally been considered as belonging to two distinct belts, the Rinkian fold belt in the north and the Nagssugtoqidian orogen farther south (Fig. 3), largely because of their contrasting structural styles (see below; Pulvertaft 1973; Escher & Pulvertaft 1976; Escher et al. 1976b; Grocott & Pulvertaft 1990). Following a recent integration of fieldwork in 2001 to 2003 by Adam Garde and coworkers with previously published field observations, new U–Pb geochronology from the intervening region around Disko Bugt (Fig. 3), and regional tectonostructural considerations, the two belts are now considered to represent the northern and southern parts of a single, composite orogen more than 1100 km wide resulting from the collision of the Rae craton with a medial Aasiaat domain (microcontinental fragment?) of Archaean age and the North Atlantic craton to the south (van Gool et al. 2002; Garde et al. 2003, 2007; Thrane et al. 2003; Connelly & Thrane 2005; Connelly et al. 2006; Sidgren et al. 2006).

In the Inussulik Bugt to Uummannaq Fjord area of the Rinkian fold belt in northern West Greenland (Fig. 3), c. 2.86–2.57 Ga (Rb–Sr and U–Pb ages; Kalsbeek 1981, 1986; Andersen & Pulvertaft 1985) tonalitic to granodioritic gneiss of the Rae craton (Fig. 7) is overlain unconformably by the metamorphosed supracrustal units of the Palaeoproterozoic Karrat Group (Garde 1978; Escher 1985; Grocott & Pulvertaft 1990). The Karrat Group in the type Karrat Fjord area (Henderson & Pulvertaft 1967, 1987) comprises a lower sequence of shallow marine, shelf-type metasedimentary rocks, including quartzite, semipelitic to pelitic gneiss and schist (Qeqertarssuaq Fm), and marble (Mârmorilik Fm), overlain by black shale and a thick, uniform, arenaceous turbidite flysch sequence (Nûkavsak Fm; Fig. 8) that is younger than 1946±13 Ma (ion probe U–Pb age of youngest detrital zircon; Kalsbeek et al. 1998). Samples of quartzite from the lower Qeqertarssuaq Formation yield detrital zircons up to 3.65 Ga (laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses, Thrane et al. 2003), whereas a sample of metagreywacke from the Nûkavsak Formation analysed by Kalsbeek et al. (1998) has yielded 3.04–1.95 Ga detrital zircons with a preponderance of 2.10–1.95 Ga ages (ion probe U–Pb ages). A maximum age for deposition of the Qeqertarssuaq and Mârmorilik formations is constrained at c. ≤2150 Ma (K. Thrane, pers. comm.). A mafic volcanic member comprising both pillowed lava flows and pyroclastic rocks is found at the interface between the lower clastic and marble units (Qeqertarssuaq and Mârmorilik Fms) and the overlying turbidites (Nûkavsak Fm) (Grocott & Pulvertaft 1990; Thomassen 1992). Based on the similarity in distribution and association of the sedimentary and volcanic lithologies, stratigraphic sequences, overall tectonic context, and recent detrital zircon analytical data (Kalsbeek et al. 1998; Thrane et al. 2003; Wodicka et al. 2007b), and following previous suggestions, the correlation between the Piling–Hoare Bay groups of central Baffin Island and the Karrat Group of West Greenland is retained (Figs 2 and 3; Jackson & Taylor 1972; Escher & Pulvertaft 1976; Taylor 1982; Henderson & Pulvertaft 1987).

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Fig. 7.

Recumbent isoclinal folds of Archaean orthogneiss (pink) and thin tectonic panels of Palaeoproterozoic supracrustal rocks (black), Uummannaq Island, Rinkian fold belt, West Greenland. Cliff is c. 1200 m high.

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Fig. 8.

Palaeoproterozoic graded metaturbidite of the Nûkavsak Fm, upper Karrat Group, Rinkian fold belt, West Greenland. Lower amphibolite facies, with abundant andalusite porphyroblasts visible in the tops of the graded beds. Coin is 2.8 cm in diameter.

South of Uummannaq Fjord, the peninsula of Nuussuaq (Fig. 3) is underlain by Archaean orthogneiss (2947±23 Ma; LA-ICP-MS Pb–Pb age), diorite (3030 +8/−5 Ma), a large anorthosite complex, and metavolcanic-dominated supracrustal sequences (2847±4 Ma) (Garde & Steenfelt 1989, 1999a; with ages from Connelly et al. 2006). Low-grade Palaeoproterozoic cover rocks in the northern part of the peninsula have been correlated with the Karrat Group to the north (Garde & Steenfelt 1999a).

South of Nuussuaq, supracrustal units also correlative with the Karrat Group crop out in the Torsukattak–Ataa Sund area (Fig. 3; Anap nunâ Group of Escher & Burri 1967; Escher 1971; see updated correlation by Garde & Steenfelt 1999a; Higgins & Soper 1999). The Anap nunâ Group consists of platform and tidal flat sedimentary rocks that include basal, cross-bedded and ripple-marked mature quartz sandstone overlain by marble that is capped by tidal and deeper-water siltstone and fine-grained sandstone (Garde & Steenfelt 1999a). A sample collected near the base of the Anap nunâ Group has 3.22–1.93 Ga detrital zircons with a preponderance of 2.96–2.46 Ga ages (LA-ICP-MS Pb–Pb, Connelly et al. 2006). In contrast, another sample collected by the same workers from the upper part of the sequence yielded 2.94–1.89 Ga detrital zircon ages, with a dominant component between 2.10 and 1.89 Ga. The clastic and carbonaceous supracrustal strata unconformably overlie 2835±4 to 2758±2 Ma orthogneiss and supracrustal rocks (ion probe U–Pb ages, Nutman & Kalsbeek 1999, see also Connelly et al. 2006).

In the northern part of the southern Nagssugtoqidian orogen (Fig. 3), Palaeoproterozoic psammitic and pelitic schist and gneiss, with banded iron formation, metagreywacke, fine-grained metavolcanic rocks, and marble (Nunatarsuaq supracrustal rocks of Garde & Steenfelt 1999a; Naternaq supracrustal belt of Østergaard et al. 2002; Thrane & Connelly 2006; Nordre Strømfjord supracrustal suite of Marker et al. 1999) are dominated by 2.20–1.95 Ga detrital zircons with very little to no Archaean input (ion probe U–Pb and LA-ICP-MS Pb–Pb ages; Scott et al. 1998; Nutman et al. 1999; Connelly et al. 2006; Thrane & Connelly 2006). Deposition of the Nunatarsuaq supracrustal rocks is constrained to being in part younger than c. 1.89 Ga (Connelly et al. 2006). Accumulation of the Naternaq supracrustal belt is constrained to younger than 1904±8 Ma (ion probe U–Pb age; Thrane & Connelly 2006), whereas deposition of the Nordre Strømfjord supracrustal suite is bracketed between 1.95 and 1.92 Ga (van Gool et al. 2002). These restricted (dominantly Palaeoproterozoic) age ranges for detrital zircons are in contrast to those of the Karrat Group (and correlative Anap nunâ Group) to the north. The composite lithostratigraphies of these assemblages also appear to be different. Whereas the former belts are dominated by mafic to ultramafic metavolcanic and pelitic rocks indicative of rifting (and possibly deep marine) environments (Garde & Steenfelt 1999a; Marker et al. 1999; Østergaard et al. 2002), the Karrat and Anap nunâ groups largely consist of shelf-type metasedimentary rocks deposited unconformably on Archaean basement and draped by a thick turbidite flysch sequence (Henderson & Pulvertaft 1967, 1987).

The present correlation of supracrustal units within West Greenland is critical and needs to be further tested because, in conjunction with structural and isotopic studies, it may provide the best method for determining the southern extent of the Rae craton versus the occurrence of separate cratonic domains to the south. That in turn will further constrain the location of the crustal suture (or sutures) that necessarily separate(s) the Rae craton from the North Atlantic craton to the south within the tectonic framework of the Rinkian fold belt and Nagssugtoqidian orogen (van Gool et al. 2002; Connelly et al. 2006; Garde et al. 2007).

Based on geometric, structural, and isotopic data and arguments presented by van Gool et al. (2002), Connelly & Thrane (2005), and Connelly et al. (2006), two south-dipping sutures are shown separating the Rae craton from the North Atlantic craton in Figure 3 (see also Garde et al. 2007). The northern suture, labelled ‘Disko Bugt suture’, separates the Anap nunâ Group and underlying Archaean basement in the north from the Nunatarsuaq supracrustal rocks and underlying basement units in the south. The southern suture roots in the Nordre Isortoq steep belt (van Gool et al. 1996, 2002) after Kalsbeek et al. (1987) and separates the North Atlantic craton in the south (see below) from a small cratonic domain to the north, which was heated but not deformed by the Nagssugtoqidian orogeny. For ease of reference and to avoid confusion with previous designations, we utilize the term ‘Aasiaat domain’ for the area bound by the two sutures in Figure 3. The Aasiaat domain thus comprises part of the northern and north–central Nagssugtoqidian domains of van Gool et al. (2002), the Nunatarsuaq and southern Rodebay domains of Garde & Steenfelt (1999a), and the southern domain or block of Connelly & Thrane (2005) and Connelly et al. (2006). Lastly, the recent discovery of tholeiitic metavolcanic rocks, pelitic metasedimentary rocks, chert and banded iron formation on islands north of Aasiaat (southern Disko Bugt, Fig. 3), which are lithologically similar to the Naternaq supracrustal belt but much better preserved, would corroborate the idea that the transitional area east and south of Disko Bugt, between the Rinkian fold belt and the central Nagssugtoqidian orogen, may contain one or more microcontinents, as well as relicts of intervening pieces of oceanic crust including deformed and metamorphosed mafic pillow lava and pelagic sedimentary strata (Garde et al. 2007).

In the Tasiussaq Bugt area (Fig. 3), metasedimentary rocks of the Karrat Group are intruded by K-feldspar megacrystic, hypersthene-bearing, granite of the Prøven igneous complex, which has recently been dated at 1869±9 Ma (Thrane et al. 2005). A-type geochemical signatures and Sm–Nd, Lu–Hf and Rb–Sr isotopic compositions show that it is a crustal melt derived largely from Archaean continental crust (Kalsbeek 1981; Thrane et al. 2005). Thrane et al. (2005) also suggested that the Prøven igenous complex formed in response to massive underplating related to collisionally induced delamination of the overthickened upper lithosphere at an early stage of the Nagssugtoqidian–Rinkian orogenic collision.

Similarities in major element geochemistry of the constituent plutonic rock types, the stratigraphy of the encasing host-rocks, and available geochronology suggest that the Prøven igneous complex may be viewed as an eastern correlative to the Cumberland batholith of Baffin Island (Hoffman 1990a; Figs 2 and 3). However, geochemical and isotopic compositions of the complex preclude it from being interpreted as a continental margin arc, as has been suggested for the Cumberland batholith by Thériault et al. (2001) and St-Onge et al. (2006c, 2007).

Archaean to Palaeoproterozoic Meta Incognita microcontinent

Archaean and Palaeoproterozoic units of the Meta Incognita microcontinent (Fig. 2; St-Onge et al. 2000) comprise (Scott et al. 1997; St-Onge et al. 2002; Sanborn-Barrie et al. 2009): (1) 3019±5 to 2784±9 Ma (Scott 1998, 1999, pers. comm.; N. Rayner, pers. comm.; N. Wodicka, pers. comm.) crystalline basement exposed in the Foxe and Hall Peninsulas (Fig. 9); (2) an overlying succession of relatively homogeneous arenaceous rocks (Lona Bay sequence and Blandford Bay assemblage); (3) a heterogeneous volcanic-bearing supracrustal assemblage (Schooner Harbour sequence) of mainly basaltic composition and including lapilli tuff and variolitic units; (4) a stratigraphically north-facing 1934±2 to c. 1880 Ma (Scott 1997; Scott et al. 2002), continental margin shelf and foredeep succession (Fig. 10; Lake Harbour Group); and (5) an extensive suite of 1865 +4/−2 to 1848±2 Ma (Jackson et al. 1990; Wodicka & Scott 1997; Scott & Wodicka 1998; Scott 1999) continental margin quartz diorite to monzogranitic arc plutons (southern portion of the Cumberland batholith) that intrude units (1) to (4). At this point, it remains unclear whether the Meta Incognita microcontinent was initially rifted from the Superior craton (described below) as suggested by St-Onge et al. (2000), whether it constitutes a rifted fragment of the Rae craton, or whether it represents crust that is exotic with respect to both bounding cratons.

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Fig. 9.

Disrupted and folded Archaean tonalitic to granodioritic gneiss, with late monzogranitic seams, Meta Incognita microcontinent, Foxe Peninsula, Baffin Island. Pen is 15 cm long.

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Fig. 10.

Tonalitic gneiss (background) tectonically overlying Palaeoproterozoic marble of the middle Lake Harbour Group in the foreground, Meta Incognita microcontinent, southern Baffin Island. Cliff in background is 250 m high.

As suggested by Jackson & Taylor (1972), supracrustal rocks of the Lake Harbour Group are correlated with similar-named supracrustal sequences on the southeastern side of Ungava Bay, based on lithological similarities (Fig. 4). St-Onge et al. (2002) utilized residual total magnetic field signatures to further strengthen the correlation and project the boundaries of the Meta Incognita microcontinent from Baffin Island to the SE shore of Ungava Bay. In this correlation, the distinctive aluminous Tasiuyak paragneiss of eastern Labrador and northeastern Quebec (Fig. 4; Wardle 1983) may represent a lateral, deeper water equivalent of the shelf-facies Lake Harbour Group (Goulet & Ciesielski 1990). The Lac Lomier complex (Fig. 4; Ermanovics & Van Kranendonk 1998; Wardle et al. 2002) may correspond to the southern extension of the Cumberland batholith (R. Wardle 2005, pers. comm.). Detrital zircons from both the Lake Harbour Group and the Tasiuyak paragneiss show a similar Palaeoproterozoic-dominated source (2.10–1.94 Ga, Scott & Gauthier 1996; Scott 1997; Scott et al. 2002) and distinct REE and Nd-isotopic signature (Thériault et al. 2001), supporting suggestions based on lithological similarities and tectonostratigraphic context that these units may have been part of a single depositional system developed along the northeastern and eastern side of the microcontinent (see also Van Kranendonk et al. 1993; Scott 1998). Alternatively, Wardle & Van Kranendonk (1996) utilized the relatively juvenile isotopic character of the Tasiuyak paragneiss to suggest deposition within an accretionary prism environment (see also Rivers et al. 1996), associated with the Burwell arc (see below) subduction system (Van Kranendonk & Wardle 1997). More recently, Wardle et al. (2002) proposed accumulation in an oceanic arc setting in an attempt to reconcile the juvenile nature of the detrital zircon population and the Archaean input suggested by the Nd-isotopic signature of the Tasiuyak gneiss.

Archaean and Palaeoproterozoic units correlative to those of the Meta Incognita microcontinent possibly occur within central West Greenland (Aasiaat domain in Fig. 3; Scott 1999; Hollis et al. 2006b; Thrane & Connelly 2006). However, the pursuit of a definite correlation would require further field-based research, as well as geochronological and geochemical data on basement and cover units of the Hall Peninsula on eastern Baffin Island, to link central West Greenland with southern Baffin Island and the southeastern side of Ungava Bay.

Archaean North Atlantic craton

The Archaean North Atlantic craton of eastern Canada, Greenland and NW Scotland (Sutton et al. 1972; Bridgwater et al. 1973b; Bridgwater & Schiøtte 1991; Wasteneys et al. 1996) is bounded to the north and west by segments of Palaeoproterozoic orogenic belts that are tectonically related to the accretional–collisional Trans-Hudson orogen, including the Nagssugtoqidian orogen and Rinkian fold belt on the north side and the Torngat orogen on the west side of the craton (Figs 3 and 4). On its south side, the craton is bounded by the Palaeoproterozoic accretionary Makkovik–Ketilidian orogens (Figs 3 and 4).

In northern Labrador, the North Atlantic craton (known in Labrador as the Nain craton or Nain Province; Stockwell 1963; Taylor 1971, 1972, 1977) comprises the isotopically distinct Saglek block in the north and Hopedale block in the south. These two crustal blocks are separated by Mesoproterozoic plutonic suites (Fig. 4), which include the Nain plutonic suite dated at 1343±3 to c. 1295 Ma (Fig. 4; Simmons et al. 1986; Connelly & Ryan 1994). The two Archaean blocks in Labrador are characterized predominantly by deeply exhumed, early to late Archaean orthogneiss, greenstone belts, and late Archaean granitoid intrusions. The southern Hopedale block contains c. 3.3 Ga to 3105 +6/−9 Ma (Loveridge et al. 1987; Finn 1989; James et al. 2002), high-grade tonalite, granodiorite and granite orthogneiss (Maggo Gneiss; Ermanovics 1993), c. 3.1–2.98 Ga (James et al. 1998) supracrustal belts dominated by mafic metavolcanic rocks and local occurrences of metasedimentary rocks, and c. 2.89–2.82 Ga (Wasteneys et al. 1994, 1996) tonalitic to granitic plutonic rocks (Kanairiktok plutonic suite). North of the Mesoproterozoic plutonic suites, the Saglek block (Bridgwater et al. 1976; Bridgwater & Schiøtte 1991) comprises c. 3.7–3.3 Ga tonalitic to granodioritic metaplutonic rocks (Uivak gneisses; Schiøtte et al. 1989a; Collerson et al. 1991; Collerson & Regelous 1995; Wasteneys et al. 1996), subordinate >3.9 Ga supracrustal (Nulliak) and plutonic (Nanok) remnants or inclusions, and metasedimentary and metavolcanic rocks (Upernavik supracrustal rocks; Schiøtte et al. 1989a, b, 1992), and deformed gabbro–dolerite intrusions and dykes (Saglek dykes). It is assumed that the boundary between the Hopedale and Saglek blocks is tectonic, and that the amalgamation of the two blocks occurred at c. 2.7 Ga following distinct magmatic and tectonic histories for each block (James et al. 2002, and references therein).

In southern West Greenland, recent and current detailed studies of the Archaean magmatic and tectonic evolution in the greater Nuuk region (Fig. 3) have documented the complex and composite nature of this segment of Archaean crust (Friend et al. 1988, 1996; Nutman et al. 1989, 2005; Garde et al. 2000; Crowley 2002; Friend & Nutman 2005; Hollis et al. 2006a; Garde 2007a; van Gool et al. 2007; Hölttä et al. 2008). These studies suggest that the North Atlantic craton in Greenland comprises a still unknown number of distinct tectonostratigraphic terranes or microplates, varying in size from tens of kilometres to at least a couple of hundred kilometres, and having independent histories prior to amalgamation in the late Archaean eon at c. 2.7 Ga (e.g. Friend & Nutman 2005; overview by Garde 2003; Hollis et al. 2006a; and references therein). The northwestern Akia terrane consists of a c. 3.2 Ga core of mafic tonalitic–dioritic gneiss, surrounded by mafic supracrustal rocks including a c. 3071±1 Ma disrupted oceanic island arc complex (Garde 2007a) and younger orthogneiss (3.05–2.97 Ga) metamorphosed at amphibolite- to granulite-facies conditions at c. 2.98 Ga. Several complexly interfolded terranes occur SE of the Akia terrane. Two of these, the Færingehavn and Isukasia terranes, contain at least two different groups of c. 3.8–3.5 Ga supracrustal and plutonic rocks, including the well-known Isua supracrustal belt (Nutman et al. 1996, 2000; Furnes et al. 2007), as well as c. 2.8 Ga orthogneiss. The 3.075–2.96 Ga Kapisilik terrane (Friend & Nutman 2005) is contemporaneous with the Akia terrane and may be regarded as having been rafted off the latter. The Tre Brødre terrane is dominated by uniform, c. 2.82 Ga, largely granodioritic orthogneisses with a simple crustal history (Ikkattoq gneisses; Friend et al. 1988, 1996). The southern Tasiusarsuaq terrane largely comprises c. 2.92–2.86 Ga orthogneiss with c. 2.80 Ga granulite-grade metamorphism.

Archaean terranes outside the Nuuk region are poorly defined (van Gool et al. 2004). They mainly comprise 3.0–2.7 Ga rocks (Connelly & Mengel 2000; Friend & Nutman 2001), and the small 3.78–3.55 Ga Aasivik terrane (only orthogneiss, Rosing et al. 2001) near the Nagssugtoqidian front. Windley & Garde (2009) show that the entire North Atlantic craton in SW Greenland can be described in terms of six tilted crustal blocks, which preserve relics of volcanic arcs in their upper, greenschist to amphibolite facies parts (Garde 2007; Polat et al. 2007), and arc roots with anorthosite-gabbro complexes (e.g. the Fiskenæsset complex, Windley et al. 1973; Myers 1985) in their lower, amphibolite to granulite facies parts. Windley & Garde (2009) also reinterpreted three terranes in the Kvanefjord region (Friend & Nutman 2001) as a major refolded nappe structure.

Given an unexposed, pre-drift distance of c. 300–400 km, correlations of single blocks and terranes between the Canadian and Greenlandic components of the North Atlantic craton are considered highly speculative by van Gool et al. (2004) and are referenced here only for completeness. Friend & Nutman (1994) suggested a correlation between the Akia terrane in Greenland and the Hopedale block in Labrador, based on c. 3.0 Ga metamorphism and plutonism in both, whereas an unnamed terrane south of Kangerlussuaq–Søndre Strømfjord was correlated with the Saglek block, based on a common granulite facies metamorphism at c. 2.74 Ga. More recently, James et al. (2002) highlighted the significant difference in the timing of metamorphism of the Hopedale block compared with the Akia terrane, and proposed a correlation between the Hopedale block and the Tasiusarsuaq terrane, and the Saglek block with the Færingehavn and Isukasia terranes.

The correlation of the North Atlantic craton from Labrador to southern West Greenland follows that of Bridgwater et al. (1973b, 1990), Korstgård et al. (1987), Bridgwater & Shiøtte (1991), Garde et al. (2002), James et al. (2002), and van Gool et al. (2002, 2004). It is consistent with the dating of offshore well cores by Wasteneys et al. (1996), which added additional constraints to the correlation of Precambrian bedrock units across the Labrador Sea.

Western and northern margins of the Archaean North Atlantic craton

The Torngat orogen of northwestern Labrador and northeastern Quebec, and the Nagssugtoqidian orogen of central West Greenland are Palaeoproterozoic collisional orogenic belts that developed respectively along the western and northern margins of the North Altantic craton (Figs 3 and 4). The correlation of the two orogenic belts is based on a similarity in constituent lithotectonic units, coeval tectonic history including igneous, structural and metamorphic events, aeromagnetic data, and complementary kinematics, as proposed and documented by Bridgwater et al. (1973a, 1990), Korstgård et al. (1987), Hoffman (1990a), Van Kranendonk et al. (1993), Park (1994), Wardle & Van Kranendonk (1996), Connelly et al. (2000), van Gool et al. (2002, 2004), and Wardle et al. (2002).

In northern Labrador, basaltic dykes indicate that rifting along the western margin of the North Atlantic craton occurred at c. 2.2–2.0 Ga, and was accompanied by the contemporaneous emplacement of anorthosite–granite suites at 2.1–2.0 Ga (Connelly & Ryan 1994, 1999; Wardle & Van Kranendonk 1996; Hamilton et al. 1998). Along the eastern coast of Labrador, these rocks are unconformably overlain by Palaeoproterozoic rocks of the Ramah, Mugford, and Snyder groups (Fig. 4), each representing an upward progression from shallow- to deep-water environments (Wardle et al. 2002) and dominated by detritus of Archaean provenance in the lower part of the sequence (Scott & Gauthier 1996). To the west, the Tasiuyak gneiss (see above) comprises migmatitic pelitic and psammitic rocks, inferred to be metaturbidites, with minor mafic and ultramafic material, and as noted interpreted either as continental slope deposits off the eastern margin of the orogenic core zone to the west (i.e. deeper-water equivalent to the platformal Lake Harbour Group of Meta Incognita microcontinent) or as a distal accretionary wedge sequence that accumulated on the western margin of the North Atlantic craton.

Along the northern margin of the North Atlantic craton within the southern Nagssugtoqidian orogen, Archaean dioritic, granodioritic, tonalitic and granitic orthogneiss of the North Atlantic craton predominate, albeit in a reworked state (Fig. 11; Kalsbeek et al. 1984, 1987; Kalsbeek & Nutman 1996; Connelly & Mengel 2000; van Gool et al. 2002). The orthogneiss are generally 2.87–2.81 Ga in age, with the plutonic protoliths deformed and metamorphosed between 2.81 and 2.72 Ga, immediately after their emplacement (Kalsbeek & Nutman 1996; Connelly & Mengel 2000). The orthogneiss are cut by several sets of mafic dykes, the most voluminous of which is the north–south- to NE–SW- trending, 2.05–2.04 Ga Kangâmiut dyke swarm (Windley 1970; Escher et al. 1975, 1976a; Korstgård 1979; Bridgwater et al. 1995; Nutman et al. 1999; Connelly et al. 2000; Cadman et al. 2001; Mayborn & Lesher 2006). The Kangâmiut dyke swarm, which extends from the Archaean foreland into the centre of the orogen, becomes reworked across an abrupt transition at the southern Nagssugtoqidian front (Fig. 12). Its northern extent is abruptly terminated by the Ikertôq thrust zone (Fig. 3), a south-vergent ductile shear zone. In this zone, metasedimentary rocks with a relatively high proportion of psammite interpreted as continental‐margin deposits (Maligiaq supracrustal suite of Marker et al. 1999) are interleaved with Archaean orthogneiss (Fig. 13). The clastic strata have a large proportion of Archaean detrital zircons (c. 2.85 Ga) but also contain a Palaeoproterozoic population that constrains their deposition to after 2.1 Ga (Scott et al. 1998; Marker et al. 1999; Nutman et al. 1999). The Maligiaq supracrustal suite (Fig. 13) is interpreted to document the northern reaches of the North Atlantic craton (a rift basin or continental margin, comparable with the Ramah Group in northern Labrador; van Gool et al. 2002). The suite provides an ultimate southern constraint on the position of the Aasiaat domain–North Atlantic craton suture discussed above, with the Aasiaat domain sandwiched between the two main (northern Rae and southern North Atlantic) cratons in the Disko Bugt area.

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Fig. 11.

Nagssugtoqidian reworking of older rocks in the northern Nagssugtoqidian orogen. Palaeoproterozoic mafic dykes were emplaced into grey Archaean orthogneiss during pre-Nagssugtoqidian rifting. The dykes were subsequently rotated and deformed with their Archaean host during the Nagssugtoqidian orogeny, and subsequently cut by postkinematic pegmatites. Aasiaat region, West Greenland. Boat for scale.

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Fig. 12.

Deformed and boudinaged dykes of the Palaeoproterozoic Kangâmiut swarm in the southern Nagssugtoqidian orogen, within Archaean orthogneiss of the North Atlantic craton, West Greenland. Dykes in the centre of the photograph are c. 30 m wide.

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Fig. 13.

Panel of Palaeoproterozoic metasedimentary rocks of the Maligiaq supracrustal suite (two buff-coloured zones on either side of a grey sheet of mafic supracrustal rocks) interleaved with Archaean orthogneiss (grey) within the Ikertoq thrust zone, West Greenland. Dark layers within the Archean gneiss are deformed Kangâmiut dykes. Cliff is c. 300 m high. Photograph provided by F. Mengel.

Two overlapping phases of arc magmatism preceding the Nagssugtoqidian orogen (described below) have been documented in the core of the belt. In the Arfersiorfik fjord and Nordre Strømfjord area (Fig. 3), quartz diorite preserved as tectonic slivers and a larger body (the 1921±15 to 1885 +6/−3 Ma Arfersiorfik intrusive suite of calc-alkaline affinity; Kalsbeek et al. 1987; Kalsbeek & Nutman 1996; Whitehouse et al. 1998; Connelly et al. 2000; van Gool et al. 1999, 2002; Sørensen et al. 2006) was intruded into metavolcanic and metasedimentary rocks of the Nordre Strømfjord supracrustal suite. All these rocks are tectonically interleaved with reworked basement rocks of Aasiaat domain and/or North Atlantic craton parentage in the subsequent collisional phase (Fig. 14). The Arfersiorfik intrusive suite occurs south of the proposed northern suture running through Disko Bugt and its origin has been related to subduction of oceanic crust beneath the Aasiaat domain (Garde et al. 2007).

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Fig. 14.

Palaeoproterozoic metasedimentary rocks of the Nordre Strømfjord supracrustal suite (brown, layered middle section of the cliff) and orthogneiss of the Arfersiorfik intrusive suite (homogeneous grey top section) in tectonic contact with Archaean gneisses (white bottom section) in the Nordre Strømfjord region, West Greenland. Cliff is c. 150 m high.

South of the proposed southern suture (Fig. 3; van Gool et al. 2002), calc-alkaline continental arc rocks of the 1921±10 to 1873 +7/−4 Ma Sisimiut intrusive suite (equivalent to the Burwell arc in Labrador) (Kalsbeek et al. 1987; Kalsbeek & Nutman 1996; Connelly et al. 2000; Campbell & Bridgwater 1996; Whitehouse et al. 1998) were emplaced into Archaean ortho- and paragneisses, consistent with the proposed location of the second south-dipping suture (van Gool et al. 2002; Garde et al. 2007) and the interpretation of the North Atlantic craton as the local overriding plate within the Nagssugtoqidian collisional orogen (see below).

South margin of the Archaean North Atlantic craton

The Makkovik orogen in central Labrador and the Ketilidian orogen along strike in South Greenland together define the southern margin of the North Atlantic craton (Figs 3 and 4). This margin was initiated as a passive continental margin at c. 2.24–2.13 Ga and became the locus of subduction, arc magmatism and juvenile crustal accretion in an overall transpressional environment within a continental margin arc setting between c. 1.89 and 1.80 Ga (see Kerr et al. 1996; Culshaw et al. 2000a, b; Garde et al. 2002; Ketchum et al. 2002; and references therein). However, in spite of long being considered along-strike segments of the same orogenic belt, the correlation of Makkovikian and Ketilidian events is complex (Garde et al. 2002; Ketchum et al. 2002; and references therein) and hindered by the 300–400 km wide pre-late Cretaceous drift gap between mainland Greenland and Labrador.

The Makkovik orogen appears much narrower than the Ketilidian orogen, which includes a major batholith (see below). The apparent eastward widening of the Makkovik orogen continues offshore, as documented by data from offshore wells and seismic lines (Kerr et al. 1996, 1997; Wasteneys et al. 1996; Hall et al. 2002). Overall, the belt records c. 300–600 Ma of convergent continental margin activity, including the accretion of several arc and back-arc units, as well as possibly a small Archaean terrane, punctuated by evidence of intra-accretion quiescent periods (Gower et al. 1990; Kerr 1994; Kerr et al. 1997; Culshaw et al. 2000b; Ketchum et al. 2001a, b, 2002). In contrast, supracrustal and plutonic units within the Ketilidian orogen record c. 450 Ma of relatively continuous magmatic and tectonic activity, which does not seem to involve the accretion of allochthonous crustal terranes to the southern margin of the North Atlantic craton (Chadwick & Garde 1996; Garde et al. 1998, 2002).

The onset of rifting of the southern margin of the North Atlantic craton in Labrador is marked by the 2235±2 Ma age of the Kikkertavak mafic dykes (Cadman et al. 1993; Ermanovics 1993). Deposition of overlying continental margin sedimentary strata (quartzite, iron formation, shale, dolostone and greywacke) and pillowed mafic volcanic rocks (Moran Lake, Aillik and Post Hill groups; Ketchum et al. 2002; and references therein) is constrained to post-date the age of the Kikkertavak dykes, and to have begun prior to 2178±4 Ma, the age of an intermediate tuff layer within the Post Hill Group (Culshaw et al. 2000b; Ketchum et al. 2001b). Overlying micaceous psammite with minor pelite and graphitic paragneiss (Metasedimentary formation; Marten 1977) has yielded both Archaean and Palaeoproterozoic detrital zircons and was deposited after 2013±3 Ma, possibly in a foredeep setting (Ketchum et al. 2001b).

In South Greenland, rifting of the North Atlantic craton is poorly constrained by an Rb–Sr age of 2130±65 Ma (Kalsbeek & Taylor 1985) on doleritic dykes of the Iggavik suite (Berthelsen & Henriksen 1975) west of Midternæs (Fig. 3). The mafic dykes were emplaced into Archaean quartzofeldspathic orthogneiss, with deposition of continental margin sedimentary rocks (Vallen Group; Bondesen 1970; Higgins 1970) loosely constrained by this age. Shallow marine quartz-pebble conglomerate, quartzite, dolomite, mudstone, chert and a banded iron formation characterize the lower part of the group, whereas deeper marine greywacke predominates in the upper part (Fig. 15). The Vallen Group is structurally overlain by the possibly laterally equivalent Sortis Group (Bondesen 1970), which comprises metabasaltic pillow lava, pillow breccia and sills, intercalated with minor mudstone and calcareous rock. Alternatively, the Sortis Group may represent an obducted component of a rifted basin to the south of the North Atlantic craton (Garde et al. 2002). Unpublished U–Pb ages of detrital zircons from a Vallen Group quartzite point to a late Archaean basement provenance (Garde et al. 2002). The Vallen and Sortis groups have been generally correlated with, and have apparent tectonostratigraphic equivalents to, the Moran Lake and Post Hill groups of Labrador (Wardle & Bailey 1981).

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Fig. 15.

Palaeoproterozoic arkosic metasediment displaying boudinaged ultramafic dyke, folding and abundant partial melting. Ketilidian forearc, southern East Greenland. Coin near centre is 2.8 cm in diameter.

Finally, it is uncertain if the onshore part of the Makkovik orogen preserves sedimentary sequences equivalent to those found in the classic psammite and pelite zones of the Ketilidian orogen (Garde et al. 2002; and references therein). Offshore, strongly reflective components of the ECSOOT seismic line (Kerr et al. 1997; Hall et al. 2002) might correspond to a westerly continuation of the psammite–pelite zones as illustrated in figure 3 of Garde et al. (2002).

Narsajuaq island-arc terrane

South of the Meta Incognita microcontinent (described above) and in the footwall of a crustal suture exposed along the southern coast of Baffin Island (Soper River suture, Fig. 2; see below), the Narsajuaq arc terrane (Dunphy & Ludden 1998) is exposed on both sides of Hudson Strait. At c. 1845 Ma, the arc formed the leading edge of the Churchill domain (St-Onge et al. 2007). It includes forearc siliciclastic rocks (Spartan Group), a dominantly volcanic sequence (Parent Group), and a dominantly plutonic assemblage (Narsajuaq arc). The volcanic and plutonic units of the arc terrane can be grouped into two temporally and petrologically distinct suites (Dunphy & Ludden 1998). An older 1863±2 to 1845±2 Ma suite includes calc-alkaline layered diorite–tonalite gneiss (Fig. 16) and tholeiitic to calc-alkaline basaltic andesite to rhyolite (St-Onge et al. 1992; Machado et al. 1993; R. Parrish 1994, pers. comm.). It is interpreted as an island-arc assemblage built on Palaeoproterozoic oceanic crust (Watts Group) and a rifted sliver of Archaean continental crust (Thériault et al. 2001). Accretion of the island-arc assemblage to the composite Churchill domain across the Soper River suture is constrained to have occurred at c. 1845 Ma (St-Onge et al. 2007; see below). The younger, 1842 +5/−3 to 1820 +4/−3 Ma suite comprises crosscutting, gneissic to massive, monzodiorite to granite plutons (Parrish 1989; Machado et al. 1993; R. Parrish 1994, pers. comm.; Scott 1997; Scott & Wodicka 1998) and is interpreted as having been emplaced in a continental margin arc setting (Dunphy & Ludden 1998; Thériault et al. 2001) following accretion of the arc terrane to the northern Churchill domain. St-Onge et al. (2002) have correlated the younger suite of Narsajuaq arc rocks in northern Quebec and Baffin Island with the 1.84–1.81 Ga de Pas batholith south of Ungava Bay (van der Leeden et al. 1990; Dunphy & Skulski 1996; James & Dunning 2000), based on strong similarities between bedrock geology units and residual total magnetic field data, available geochronological constraints, and petrological characteristics.

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Fig. 16.

Palaeoproterozoic calc-alkaline diorite (dark)–tonalite (light) gneiss complex, older suite of Narsajuaq arc, northern Quebec. Hammer is 35 cm in length.

Plutonic, volcanic and sedimentary units correlative with those of the Narsajuaq arc terrane are not known to occur in West and South Greenland.

Archaean Superior craton; northern and eastern margins

In northern and northeastern Quebec and in western Labrador the Archaean Superior craton (Fig. 4) predominantly comprises felsic orthogneiss and plutonic units ranging in age between 3220 +32/−23 and 2654±5 Ma (Fig. 17; Machado et al. 1989; Mortensen & Percival 1989; Parrish 1989; St-Onge et al. 1992; R. Parrish 1994, pers. comm.; Scott & St-Onge 1995; James & Dunning 2000). In the Cape Smith belt of northern Quebec (St-Onge et al. 2006a; and references therein), a suite of parautochthonous basal clastic sedimentary units, carbonatitic volcaniclastic rock, continental tholeiitic flood basalt (Fig. 18), and rhyolite of the Povungnituk Group is associated with initial Palaeoproterozoic rifting of the northern Superior craton. These units have yielded ages between 2038 +4/−2 and 1958.6 +3.1/−2.7 Ma (Parrish 1989; Machado et al. 1993). Disconformably overlying the initial-rift sedimentary and volcanic rocks is a younger succession of predominantly komatiitic to tholeiitic basalt (Chukotat Group) accumulated during renewed rifting along the northern continental margin and dated between 1887 +37/−11 and 1870±4 Ma (R. Parrish 1994, pers. comm.; Wodicka et al. 2002a). The ages of the younger volcanic succession indicate that c. 150 Ma elapsed between the onset of initial continental rifting and the subsequent rifting event (St-Onge et al. 2000).

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Fig. 17.

Archaean biotite–hornblende±orthopyroxene granodiorite (light) with abundant mafic enclaves (dark), lower plate Superior craton, northern Quebec. Hammer is 35 cm in length.

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Fig. 18.

Palaeoproterozoic pillowed basalt in a continental tholeiite flow, Povungnituk Group, Cape Smith belt, northern Quebec. Hammer is 34 cm in length.

Along the eastern margin of the Superior craton within the New Quebec orogen (Fig. 4), the tectonostratigraphic record (Hoffman 1990b; Rohon et al. 1993; Skulski et al. 1993; Clark & Wares 2004; and references therein) includes a parautochthonous succession of: (1) basal fluvial redbeds and mildly alkalic mafic lava (Seward subgroup) that are associated with initial Palaeoproterozoic rifting of the craton; (2) marine-shelf quartzite and dolostone (Pistolet Subgroup) that mark the establishment of a platform-type continental margin; (3) interstratified black shale and turbidite (Swampy Bay Subgroup) that interfinger eastward with tholeiitic basalt, gabbro sills, and rhyolite (Bacchus Formation) and are interpreted as a foredeep sequence; (4) a regressive peritidal carbonate reef complex (Denault and Abner formations). Age constraints on deposition range between 2169±2 and 2142 +4/−2 Ma (Clark 1984; Rohon et al. 1993). The initial-rift assemblage is overlain by a succession of transgressive quartzite (Wishart Formation), which is in turn overlain by shale (Ruth Formation), banded iron formation (Sokoman Formation), coeval alkalic mafic to felsic volcanic rock, tholeiitic sills, basalt, and turbidite (Menihek Formation), all of which are intruded by layered peridotite–gabbro–diorite sills and collectively accumulated in pull-apart basins during renewed rifting along the established continental margin (Skulski et al. 1993). Ages for this package range between c. 1884±1.6 and 1870 Ma (Findlay et al. 1995; Machado et al. 1997), and consequently c. 292 Ma separate the older and younger successions (see Skulski et al. 1993) and the establishment and subsequent rifting of the eastern margin of the Superior craton.

Plutonic, volcanic and sedimentary units correlative with those of Superior craton are not known to occur in West Greenland or South Greenland.

Ellesmere–Devon terrane and Inglefield mobile belt

The oldest deformation zone in northeastern Laurentia is the one that outlines the northern margin of the Rae craton in northern Canada (Ellesmere–Devon terrane) and in northern West Greenland (Inglefield mobile belt). The plutonic rocks of the Ellesmere–Devon terrane (Fig. 2) are dominated by arc-type pyroxene-bearing tonalite, quartz norite and several varieties of granite, and show evidence of penetrative to gneissic fabric development (Frisch 1988). A minimum age for the granulite‐facies metamorphism was determined as c. 1930 Ma (Frisch & Hunt 1988). Hoffman (1988, 1990b) utilized available ages, similarities in lithotectonic units, and the occurrence of distinctive aeromagnetic anomalies as a basis for correlation of the Ellesmere–Devon terrane with the upper plate, 2.0–1.9 Ga Taltson–Thelon magmatic zone (northwestern boundary of the Rae craton; Hoffman 1988, 1989; Thériault 1992), which is exposed south of the Queen Maud Gulf in the northwestern Canadian Shield (Wheeler et al. 1996). The inferred upper plate setting for the northern margin of the Rae craton is shown with a line marking the southern limit of upper plate arc magmatism and labelled ‘Ellesmere–Inglefield belt’ in Figure 19.

The tectonomagmatic history of the Inglefield mobile belt of northern West Greenland (Fig. 3) is complex, with most rock units having been repeatedly deformed under low- to medium-pressure granulite‐facies conditions with several episodes of anatectic melting (Dawes 2004; Nutman et al. 2008). Coring the Inglefield belt, the Etah metaigneous complex is composed of continental margin arc-type intermediate to felsic orthogneiss, megacrystic monzogranite, quartz diorite, and syenite. At least two episodes of isoclinal folding produced map-scale structures involving Etah Group supracrustal units, with at least one episode post-dating the Etah metaigneous complex, and the major, late-kinematic Sunrise Pynt shear zone that separates the northern and southern parts of the belt. Granulite-facies metamorphism is constrained at 1923±8 Ma by ion probe U–Pb ages on zircon (Dawes 2004; Nutman et al. 2008). The polydeformed, high-T character of the Inglefield mobile belt and the arc-type granitoids of the Etah metaigneous complex are interpreted as indicative of an upper plate setting for the northern margin of the Rae craton in Greenland (Fig. 19).

Foxe fold belt

Deformation along the southern margin of the Rae craton within the Foxe fold belt of central Baffin Island (Fig. 2) is characterized by early north-verging, thin-skinned imbrication and tight intrafolial isoclinal folding of the Piling Group, followed by NE–SW-trending upright folding of both Palaeoproterozoic cover and Archaean basement, and subsequent open NW–SE-trending, thick-skinned cross-folding (Scott et al. 2003). Metamorphic grade increases from greenschist facies at higher structural levels to granulite facies at lower structural levels and in proximity to the plutonic units of the Cumberland batholith. As noted, the Cumberland batholith has been interpreted as a continental margin arc emplaced above a north-dipping subduction system following accretion of the Meta Incognita microcontinent to the northern Rae craton.

The proposed Baffin suture (St-Onge et al. 2006c) separating the Archaean Rae craton and its flanking, southern Palaeoproterozoic continental margin sedimentary and volcanic sequences (Piling and Hoare Bay groups) from accreted tectonic elements to the south trends east from the Foxe Basin to the head of Cumberland Sound (Fig. 2). Closing across the proposed suture is thought to post‐date the youngest dated unit in the Piling Group (1883±5 Ma) and predate emplacement of the Cumberland batholith at 1865 +4/−2 to 1848±2 Ma (St-Onge et al. 2006c). However, new field-based research is required to further characterize the suture in terms of its structural context, tectonothermal history, and crustal geometry. Consequently, the proposed suture is shown without an upper or lower plate connotation in Figure 19.

Rinkian fold belt and Nagssugtoqidian orogen

Deformation in the Rinkian fold belt of northern West Greenland (Fig. 3) is characterized by first NE- and then WNW-directed ductile thrusts and fold-nappes (Fig. 20), and terminated by crustal-scale open, upright folding with broad domes and narrow cusps (Pulvertaft 1986; Grocott & Pulvertaft 1990; Escher et al. 1999; Garde et al. 2003; Lahtinen et al. 2009). Metamorphic grade increases from greenschist facies at Mârmorilik, is at lower to middle amphibolite facies over wide areas of central West Greenland, and reaches granulite facies in proximity to the Prøven igneous complex (Garde 1978; Crocott & Pulvertaft 1990). Collision across the Rinkian fold belt occurred at 1881±20 Ma (Taylor & Kalsbeek 1990), based on Pb–Pb dating of an amphibolite-facies Karrat Group marble.

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Fig. 20.

Part of Kigarsima nappe structure in the central Rinkian fold belt, West Greenland. Pale Archaean orthogneiss in the upper part of the c. 1600 m high mountain tectonically overlies Palaeoproterozoic metagreywacke of the Nûkavsak Fm, upper Karrat Group.

The earliest Palaeoproterozoic, collision-related, deformation documented within the Nagssugtoqidian orogen of central West Greenland (Fig. 3) is NW-directed thrusting and imbrication of Archaean and Palaeoproterozoic units at a scale of hundreds of metres to several kilometres (van Gool et al. 1999, 2002; and references therein). Thrust imbrication started after intrusion of the youngest arc rocks at 1873 Ma and lasted at least until 1837+9/−8 Ma (Kalsbeek et al. 1987; van Gool et al. 2002). It was followed by isoclinal folding of large-scale tectonic contacts, and subsequent belt-parallel, thick-skinned, folds of basement and cover units at c. 1825±1 Ma (Connelly et al. 2000) and emplacement of steep, NNE–SSW-trending pegmatites at 1837±12 Ma (Thrane & Connelly 2006), both during post-collisional convergence. This phase coincides with left-lateral shearing in the Abloviak shear zone in Labrador (see below). Late strike-slip deformation in the Nordre Strømfjord shear zone and Nordre Isortoq steep belt occurred at c. 1775 Ma (Connelly et al. 2000). The granulite-facies thermal peak of metamorphism in the core of the orogen was dated at c. 1.86–1.84 Ga (Taylor & Kalsbeek 1990; Kalsbeek & Nutman 1996; Connelly et al. 2000; Willigers et al. 2001). This age interval coincides with the timing of thrusting and is interpreted as documenting the main phase of collision across the Nagssugtoqidian orogen.

As noted, the Rinkian fold belt and Nagssugtoqidian orogen are interpreted as being associated with the closure of two south-dipping Palaeoproterozoic sutures (see above; Connelly & Thrane 2005; Connelly et al. 2006; Garde et al. 2007): (1) a northern suture, the Disko Bugt suture that separates the lower plate Rae craton from the medial Aasiaat domain; and (2) a southern suture rooting in the Nordre Isortoq steep belt that separates the upper plate North Atlantic craton from the Aasiaat domain (Fig. 19).

Torngat orogen

Palaeoproterozoic crustal deformation within the Torngat orogen is interpreted to have resulted from the collision of the North Atlantic craton in the east with the Meta Incognita microcontinent in the west, locally described as the core zone, of northeastern Quebec (Fig. 19). The collision resulted in a narrow, north–south-trending, doubly vergent orogen (Rivers et al. 1996; Wardle & Van Kranendonk 1996; and references therein), with the crustal suture corresponding to the eastern margin of the Tasuiyak gneiss (Fig. 4). The collision was preceded by emplacement of the continental, calc-alkaline Burwell arc in northernmost Labrador, dated between 1910±2 Ma and 1869 +3/−2 (Scott & Machado 1995; Van Kranendonk & Wardle 1996). The collision itself is recorded by peak granulite‐facies metamorphism within the core of the orogen during west-directed thrusting within the Tasiuyak gneisses and east-directed thrusting at the North Atlantic craton margin between c. 1870 and 1845 Ma (Bertrand et al. 1993; Rivers et al. 1996; Van Kranendonk 1996; Scott 1998; Connelly 2001). Continued deformation is manifest as sinistral transpressional shear between 1844±3.6 and 1822 Ma along the north–south-trending Abloviak shear zone (Bertrand et al. 1993), which developed mainly in the Tasiuyak gneiss. Younger shear deformation (related to indentation of the composite Churchill domain by the lower plate Superior craton?; see below) continued to c. 1780 Ma (Van Kranendonk & Wardle 1996, 1997).

The west-directed thrusting documented within the Tasiuyak gneiss and the location of the Burwell arc plutonic rocks suggest that the North Atlantic craton occupied an upper plate position with respect to the Meta Incognita microcontinent to the west during convergence across the Torngat orogen (Fig. 19).

Dorset fold belt

Convergence between the southern margin of Meta Incognita microcontinent and crustal domains to the south led to development of the Dorset fold belt and formation of the north-dipping Soper River suture (Fig. 3). Closing of the suture is bracketed between 1845±2 Ma, the age of the youngest unit associated with the intra-oceanic phase of the accreted Narasajuaq arc (Fig. 3; Dunphy & Ludden 1998) and 1842 +5/−3 Ma (Scott 1997), the age of the oldest plutonic unit of the continental margin arc phase of the Narsajuaq arc (St-Onge et al. 2007).

Deformation in the Dorset fold belt includes: (1) structural repetition and truncation of distinct tectonostratigraphic units yielding an overall SW-verging ramp-flat fault geometry (Scott et al. 1997); (2) associated tight to isoclinal folding during SW- to south-directed deformation (Sanborn-Barrie et al. 2009); (3) development of a penetrative granulite-facies compositional fabric; (4) formation of ribbon mylonites and transposition of cross-cutting intrusive units into parallelism in the vicinity of the Soper River suture; and (5) later open cross-folding and localized dextral transcurrent shearing. Syntectonic, granulite-facies, regional metamorphism associated with emplacement of the Cumberland batholith and closure of the Soper River suture is bracketed between c. 1849 and 1835 Ma (St-Onge et al. 2007).

The SW- to south-verging thrusting and folding documented within the Dorset fold belt and the location of the Cumberland batholith continental margin arc rocks in the northern hanging wall of the suture suggest that the Meta Incognita microcontinent occupied an upper plate position with respect to the Narsajuaq arc to the south (Fig. 19) during convergence across the Soper River suture.

Makkovik and Ketilidian orogens

Early foreland-directed thrusting and dextral transpression in the Makkovik orogen of Labrador at c. 1895–1870 Ma (Culshaw et al. 2000b) may be contemporaneous with Ketilidian thrusting of the Sortis Group and dextral transpression along the steep, ENE–WSW-trending, Kobberminebugt shear zone in South Greenland. Deformation along the Kobberminebugt shear zone is constrained by the 1848±2 Ma age of crosscutting augen granite (Hamilton et al. 1999; Garde et al. 2002).

In the Makkovik orogen, early continental calc-alkaline plutonism is manifest by the c. 1893±2 to 1870 Ma Island Harbour Bay plutonic suite (Ryan et al. 1983; Kerr et al. 1992; Culshaw et al. 2000a, b; Barr et al. 2001). There appears to be no direct plutonic counterpart in the Makkovik orogen to the voluminous continental margin arc of the Julianehåb batholith (Fig. 21) in South Greenland, which largely comprises 1854–1795 Ma plutons of granodiorite and granite, with minor gabbro, diorite, quartz monzodiorite, tonalite and rare quartz syenite (Chadwick et al. 1994; Chadwick & Garde 1996; Garde et al. 2002; Garde 2007b). The felsic volcanic Aillik Group dated at c. 1860–1807 Ma (Schärer et al. 1988; Ketchum 1998) is close in age to the Julianehåb batholith and, like the latter, it contains evidence of synmagmatic sinistral transpression. The Aillik Group has been interpreted as having been erupted in an extensional back-arc setting, but it might instead be a high-level equivalent of the Julianehåb batholith (Culshaw et al. 2000b).

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Fig. 21.

Juvenile, 1792 Ma arc-type granite cut by synkinematic mafic dykes emplaced during sinistral transpression. Late-stage Julianehåb batholith, southeastern Ketilidian orogen, South Greenland. Hammer is 35 cm in length.

The continental calc-alkaline plutonism (and possible related felsic volcanism) documented in both the Makkovik and Ketilidian orogens, as well as the geometry of thrusting and transpressional deformation within these orogens, points to an upper plate setting for the southern margin of the North Atlantic craton during the time interval 1.89–1.80 Ga (Fig. 19). The upper plate setting for the southern margin of the North Atlantic craton established during the middle Palaeoproterozoic appears to have been maintained during the late Palaeoproterozoic (1.71–1.60 Ga) Labradorian orogeny, which involved formation and closure of a small ocean or back-arc basin, and formation and accretion of offshore terranes (Gower 1996; and references therein).

New Quebec orogen

Within the New Quebec orogen (Fig. 4) parautochthonous sedimentary and volcanic strata along the eastern margin of the Superior craton are imbricated by thrust faults above a regional basal décollement (Wares & Goutier 1990). Fault displacement was in a west to SW direction, with thin-skinned imbrication and associated open to tight, large-scale, upright to overturned folds occurring in a piggyback sequence toward the western foreland.

A trailing fan of break-back thrusts or ‘out-of-sequence’ faults younging toward the eastern hinterland of the orogen re-imbricate the cover units of the Superior craton (Wares & Goutier 1990). As in the case of the Cape Smith belt (Lucas 1989; see below), out-of-sequence thrusting in the New Quebec orogen seems to be the dominant mechanism responsible for crustal shortening based on degree of imbrication and juxtaposition of domains.

Regional metamorphic grade increases from greenschist and lower amphibolite facies in the Palaeoproterozoic cover strata of the western foreland, to amphibolite and granulite facies in the Archaean basement and Palaeoproterozoic metasedimentary and metavolcanic rocks in the eastern hinterland (Perreault & Hynes 1990).

The west-verging geometry of the broad thin- to thick-skinned thrust–fold belt preserved within the New Quebec orogen and the systematic eastward increase in metamorphic grade within the tapered thrust-stack document the lower plate position of the Superior craton during its collision with the eastern portion of the composite Churchill domain (Fig. 19).

Cape Smith belt

Within the Cape Smith belt of northern Quebec (Fig. 19) parautochthonous sedimentary and volcanic strata along the northern margin of the Superior craton are imbricated by thrust faults above a regional basal décollement (Lucas 1989). Fault displacement was in a southerly direction, with thin-skinned imbrication and associated folding occurring in a piggyback sequence toward the southern foreland. Thrust deformation was initiated after 1870±4 Ma, the age of the youngest unit within the parautochthonous Superior craton cover sequence.

A distinct suite of late or ‘out-of-sequence’ thrust faults that post-date the thin-skinned structures re-imbricate the cover units of the Superior craton (Lucas 1989). These younger south-verging structures are thick-skinned (involving both crystalline basement and Palaeoproterozoic cover units) and are collisional in origin as they can be linked to terrane boundary faults within the Churchill domain (St-Onge et al. 2001). The late faults truncate the metamorphic isograds within the Cape Smith belt (see below) and thus must postdate c. 1820 +4/−3 to 1815±4 Ma (Bégin 1992). They predate the age of emplacement of post-kinematic syenite plugs and syenogranite dykes at 1795±2 to 1758.2±1.2 Ma (St-Onge et al. 2006c).

Regional, Barrovian-facies, kyanite–sillimanite-grade, medium-pressure metamorphism is associated with early thin-skinned thrusting of cover units along the north margin of the Superior craton (Bégin 1992). Metamorphism is bracketed between 1820 +4/−3 and 1815±4 Ma and is interpreted as a consequence of the relaxation of isotherms in the tectonically thickened thrust belt (St-Onge & Lucas 1991).

A south-verging tectonic boundary or crustal suture (Bergeron suture) separates the northern Superior margin strata from allochthonous crustal elements of the composite Churchill domain to the north (Fig. 19; St-Onge et al. 1999, 2001). Associated with, and sitting in the hanging wall of, the Bergeron suture are the crustal components of an obducted 1998±2 Ma ophiolite (Watts Group; Parrish 1989; Scott et al. 1992, 1999), and the plutonic, volcanic and sedimentary components of the Narsajuaq arc (described above). Preservation of the ophiolite and the higher structural levels it represents within the Cape Smith belt are entirely a function of the late- to postcollisional, crustal-scale, orogen-parallel folding and orogen-perpendicular cross-folding that characterize the southern margin of the Trans-Hudson orogen in northern Quebec (Lucas & Byrne 1992). Closure of the Bergeron suture and collision of the composite Churchill domain with the Superior craton, is bracketed between 1820 +4/−3 Ma (youngest component of Narsajuaq arc) and 1795±2 Ma (the age of an undeformed crosscutting syenogranite pegmatite dyke) (St-Onge et al. 2006c).

The architecture of the foreland thin- to thick-skinned thrust–fold belt, the geometry of the Bergeron suture, and the regional Barrovian metamorphism documented within the Cape Smith belt document the lower plate position of the Superior craton during its collision with the northern Churchill domain (Fig. 19).