Several names have been given to the Narsajuaq Domain over time, such as Ungava Terrane (St-Onge et al., 2001), Sugluk Terrane or Block (Hoffman, 1985; St-Onge and Lucas, 1990; Corrigan et al., 2009), or Narsajuaq Terrane (Lucas and St-Onge, 1991; St-Onge et al., 2009). The area north of the Ungava Trough was first mapped by Taylor (1982), who assigned an Aphebian (Paleoproterozoic) age to intrusive rocks in this area. The works of Parrish (1989), St-Onge and Lucas (1990) and Lucas and St-Onge (1991) characterise this plutonic (and sedimentary) assemblage as two entities: one of Archean age, the Kovik Antiform (now the Kovik Lithotectonic Domain), and the other of Paleoproterozoic age, the Narsajuaq Arc. The term “Narsajuaq Arc” was defined as a mapping unit in the synthesis of the Ungava Orogen (Lamothe, 2007). Given that this is more of a lithotectonic domain, this definition of the Narsajuaq Arc was abandoned by Charette and Beaudette (2018). The unit was formally renamed the Narsajuaq Lithotectonic Domain by Vanier and Lafrance (2020). Charette and Beaudette (2018) also introduced the Narsajuaq Complex to describe geological units mapped during historical work. In areas mapped at scale 1:100 000 by the Ministère since 2017, lithologies of the western part of the Narsajuaq Domain have instead been divided into complexes and suites (see table in the Geology section).

The Narsajuaq lithotectonic domain forms an E-W oriented strip of 13 to 65 km wide over at least 245 km long in the northern portion of the Ungava Orogen at the northern tip of Quebec. The southern contact with the Kovik Lithotectonic Domain is marked by the Sugluk Shear Zone. Its lateral and northerly extension is poorly defined as rocks of the domain extend under Hudson Bay to the west and Hudson Strait to the east and north.

The Narsajuaq Domain is a lithotectonic division of the Churchill Province. It consists of gneissic, intrusive and metasedimentary units with metamorphic facies ranging from granulites to amphibolites. Paragneiss klippes are generally limited in thickness within the domain, with the exception of the northern portion of the Cape Wolstenholme region where larger strips were observed. In this area, Charette and Beaudette (2018) report that orthogneiss is distinguished from the rest of the domain by its amphibolite facies metamorphic assemblages and intense deformation. These authors believe the presence of folded mylonites would indicate a polyphase evolution and therefore a tectonometamorphic signature different from the rest of this domain’s units.

Relationships between the units are usually obliterated by the E-W regional fabric, which induces fine imbrication of lithologies on an hectometric to kilometric scale. However, it is possible to recognize the emplacement of intrusive rocks, synchronous or posterior to the Ungava Orogen, such as granulitic felsic intrusions (Navvaataaq Suite), likely polyphase potassic granitoids (Tasialuk Allipaaq Complex and Sanningajualuk Suite) and intermediate and mafic intrusions (Ivitaruq Suite).

Geological units mapped during the pre-summer 2017 work (Charette and Beaudette, 2018) are grouped within the Narsajuaq Complex. The Ministère’s mapping progress is expected to eventually lead to the abandonment of this unit. New units introduced since the summer of 2017 are shown in the table below, from the youngest to the oldest unit.

Geological Evolution

The Narsajuaq lithotectonic domain was historically interpreted as a magmatic terrane comprising three phases of intrusions (Dunphy and Ludden, 1998 and references cited), namely the ancient plutonic suite (1863-1844 Ma), the recent plutonic suite (1836-1821 Ma) and the anatectic plutonic suite (also called the late suite; 1803-1800 Ma). According to the authors, the geological evolution of this terrane is polyphase.

First, the ancient plutonic suite would have intruded around 1860 Ma, possibly into an Archean craton. This hypothesis is based on: 1) Sm-Nd model ages obtained from samples belonging to the ancient plutonic suite (extraction age of the depleted mantle varying from 1.97 to 3.11 Ga; Dunphy and Ludden, 1998); and (2) on Rb-Sr isochrone timelines of metasedimentary rocks of the Sugluk Group that indicate their source is possibly Paleoproterozoic to Archean (Doig, 1987). For example, several authors have defined an Archean to Paleoproterozoic terrane that includes intrusions of the magmatic arc, sedimentary rocks and possibly the Archean bedrock. Several names have been given to this terrane, such as the Ungava Terrane (St-Onge et al., 2001), the Sugluk Terrane or Block (Hoffman, 1985; St-Onge and Lucas, 1990; Corrigan et al., 2009) or the Narsajuaq Terrane (Lucas and St-Onge, 1991; St-Onge et al., 2009).

According to this interpretation, only intrusive rocks of the ancient plutonic suite would have recorded an intra-arc tectonometamorphic event (D₁-M₁) associated with granulite facies metamorphic conditions (Lucas and St-Onge, 1992). These conditions would have developed during accretion of the magmatic terrane in the Meta Incognita Peninsula around 1.85 Ga (Corrigan et al., 2009). The recent and anatectic plutonic suites, sometimes denoted Narsajuaq Arc sensu stricto, intrude into the ancient plutonic suite and Meta Incognita block.

Collision between the Narsajuaq-Meta Incognita assemblage and the Superior Province would have occurred during the Ungava Orgenesis, approximately 1.82 to 1.80 Ga. This collision would have resulted in regional deformation and metamorphism to the amphibolite facies affecting all of the Narsajuaq domain lithologies, with the exception of post-tectonic intrusions.

Five crystallization ages between 2800 Ma and 2550 Ma (Davis and Sutcliffe, 2018) were obtained in the Cape Wolstenholme area, within large units that consist mostly of Archean rocks.

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