The Sukaliuk Complex was introduced by Verpaelst et al. (2000) in the Koroc and Hebron River area (sheets 24I and 14L) to describe a package of orthogneiss, supracrustal rocks and mafic rocks for the most part metamorphosed to the granulite facies and part of the Torngat Orogen, i.e. the area east of the Blumath Shear Zone (ZCblm). Part of this complex was assigned to the Lomier Complex by Girard (1990) during 1:50,000 mapping of the Courdon Lake area (sheet 14E12). Granulitic rocks present west of the Pilliamet Shear Zone (ZCpil) were reassigned to the Sukaliuk Complex by Lafrance et al. (2015), as were the rocks mapped by Verpaelst et al. (2000) in the area located directly to the north.

Climatic conditions of the summer of 1998 limited the fieldwork and resulted in Verpaelst et al. (2000) not always being able to differentiate granulitic gneiss of the Sukaliuk Complex by composition. They had thus grouped much of the Sukaliuk Complex in an undifferentiated granulitic gneiss unit. This subdivision was not used by Lafrance et al. (2015, 2016) in the southbound extension as the work of these authors allowed the Sukaliuk Complex to be subdivided according to its dominant composition. Mapping in the summer of 2017 in the Koroc River and Hébron area, and staining of samples collected during the summers of 1998 and 2017 have helped to standardize the nomenclature of this unit based on its dominant composition (Mathieu et al., 2018), and to abandon the undifferentiated granulitic gneisses unit.

Subsequently, as part of a regional synthesis of the southeastern Churchill Province (SEPC; Lafrance et al., 2018), Lafrance and Vanier (2022) reassigned the metasedimentary rock units, anatectic granites, and mafic and ultramafic rocks previously included in the Sukaliuk Complex to the Lake Harbour (pPhb), Abrat (pPaba), and Nuvulialuk (pPnuv) suites respectively. These changes in nomenclature are detailed in the table below.

The Sukaliuk Complex consists of two units: 1) a hypersthene tonalitic orthogneiss unit (Asuk1); and 2) a hypersthene granitic orthogneiss unit (Asuk2).

The Asuk1 gneiss contains 5 to 20% biotite and hypersthene. Green hornblende and clinopyroxene are also commonly observed, particularly in quartz diorite horizons. Biotite shows intense pleochroism from yellowish to dark brown-red. Hypersthene is usually fresh, in places altered to serpentine or transformed into a mixture of hornblende and actinolite. Smoked quartz forms bands or discontinuous millimetric rods. In thin section, it has a strong undulatory extinction. K-feldspar (≤5%) is observed locally in interstitial crystals. Opaque minerals (especially magnetite) and apatite are present (2-5%). Other accessory minerals (epidote, garnet, sphene, allanite, zircon and calcite) are observed in small amounts.

Coarser-grained bands observed in gneiss contain centimetric euhedral orthopyroxene and well-developed quartz rods, giving them a deformed leucosome appearance. Although evidence of partial melting has been extensively identified on the outcrops visited in the Sukaliuk Complex, little evidence of this process can be seen in thin section. It is possible that most of the partial melting textures were obliterated during deformation following migmatitization. The deformation style and absence of flow textures suggest that these units did not contain significant rheological contrast during the deformation event, excluding the possibility that a large proportion of leucosome was present at that time. A migmatitization episode likely occurred in the early stage of the Torngat Orogen, during which partial melting fluid extraction was effective. This explains the preservation of granulite facies paragenesis due to anhydrous conditions generated by liquid extraction (Charette, 2016).

Sukaliuk Complex 1a (Asuk1a): Tonalitic Orthogneiss

In some areas, the tonalitic gneiss does not contain hypersthene. Many of these gneisses occur within a shear zone. Metric levels of tonalitic gneiss are also interbedded in the orthopyroxene gneiss. The presence of this tonalitic gneiss can be caused by a retrogradation of the granulitic gneiss in the vicinity of structures that allowed the transport of hydrated fluids or by a variation in the composition of the protoliths. Some protoliths would not have allowed the formation of orthopyroxene, even in the granulite facies.

The gneiss composition of subunit Asuk1a varies from tonalite to quartz diorite. The rock is grey, non-magnetic and contains between 5 and 20% centimetric to decimetric enclaves or horizons of hornblende-biotite diorite. It also contains 5 to 15% bands or conformable centimetric dykes of coarser-grained pink granite. Quartz (10-25%) forms bands near deformation zones. Ferromagnesian minerals (7–20%) consist of brown biotite with hornblende and magnetite more locally. Accessory minerals are scarce and consist of K-feldspar, apatite, chlorite, epidote, hematite and zircon.

Sukaliuk Complex 1b (Asuk1b): Banded Granulitic Orthogneiss with Alternating Tonalitic and Granitic Bands

Subunit Asuk1b is a minor component of the Sukaliuk Complex. It is composed of orthopyroxene orthogneiss showing alternating millimetric to centimetric bands of either tonalitic or granitic composition. The grey-brown sugar colour on a fresh surface and the beige patina, regardless of the composition of bands, are characteristic. Only the variable proportion of ferromagnesian minerals (~5% for granitic bands and 10-25% for tonalitic bands) allows for individualization of band types in outcrop. Rocks of unit Asuk1b unit contain the same mineral phases and have the same textures as the Asuk1 unit.

Sukaliuk Complex 2 (Asuk2): Hypersthene Granitic Orthogneiss