In the 1940s, geologists at Labrador Mining and Exploration introduced the term “Laporte Series” to describe schists, gneiss and amphibolites located NE of Schefferville, in the Laporte Lake area (Frarey and Duffell, 1964). Harrison (1952) formalized this unit as the Laporte Group. In the southern portion of the Quebec part of the New Quebec Orogen, Baragar (1967) designated metamorphic rocks located east of the Labrador Trough as the Younger Complex, considering that metamorphism had obliterated primary structures of rocks and that the relative age of these units could not be established. However, this term was not used in subsequent work, as authors preferred the term “Laporte Group” (Frarey, 1967; Dimroth, 1978; Dressler, 1979; Fournier, 1985; Girard, 1995; Henrique-Pinto et al., 2017, 2019). In the Kuujjuaq area (sheet 24K), Goulet (1995) assigned metamorphosed rocks of the Laporte Group to the Thévenet Formation (Sauvé and Bergeron, 1965), a term that was not used in subsequent work. In the Déborah Lake area, Girard (1995) reassigned some of Laporte Group rocks to the Deborah Formation, considering that in this area, paraschists have a mappable extent, consistency, internal homogeneity and established stratigraphic position. Metamorphosed rocks of the Laporte Group were considered by various authors to be equivalent to several units of the Kaniapiskau Supergroup (Labrador Trough). The loss of the rocks’ primary textures by metamorphic recrystallization led Simard et al. (2013) to replace the term “Laporte Group” with “Laporte Supersuite”. This designation places this regional-scale unit among higher-ranking lithodemic units, equivalent to a supergroup, in accordance with the North American Stratigraphic Code (1983, 2005). The Laporte Supersuite thus combines all Paleoproterozoic metamorphosed supracrustal rocks of the Rachel-Laporte Lithotectonic Domain.

A regional compilation of the Southeastern Churchill Province (SECP) by the Ministère’s geologists in 2003 divided rocks of the Rachel-Laporte Lithotectonic Domain (pPLAP) into 14 informal units. In the Bonaventure Lake area, Hammouche et al. (2011) recognized units pPLAP1 and pPLAP5, and defined two new informal units (pPLAP15 and pPLAP16). As part of a SECP regional synthesis (Lafrance et al., 2018; Lafrance and Vanier, 2021), these informal units were abandoned and reassigned to the Freneuse, Klein or Secondon suites, depending on their composition and origin.

In the Déborah Lake area, Girard (1995) divided the Laporte Group (now Laporte Supersuite) into four lithodemic packages: the Deborah Formation, Grand Rosoy Formation, De Jeu Gabbro and Manereuille Complex. Henrique-Pinto et al. (2017, 2019) also extrapolated the Deborah and Grand Rosoy formations in the northern part of the Rachel-Laporte Domain, in the vicinity of the Feuilles Bay. However, ages obtained in the Grand Rosoy Formation (now redefined as the Grand Rosoy Suite) has allowed including within the Baleine Lithotectonic Domain (Lafrance et al., 2020). Located to the east of the Grand Rosoy Suite, units of the Maneureuille Complex (abandoned) were also reassigned to those of the Baleine Domain (Akiasirviup, Curot or Ralleau suites). As for the Deborah Formation and the De Jeu Gabbro, they were respectively reassigned to the Freneuse and Klein suites depending on their composition.

The Préville and Secondon suites were rather introduced in the Jeannin Lake area (Charette et al., 2016).

The Laporte Supersuite was divided into two suites by Simard et al. (2013): the Klein Suite, which includes metamorphosed mafic and ultramafic rocks of effusive or intrusive origin, and the Freneuse Suite, which groups most metasedimentary rocks. Rocks of these two suites commonly contain rusty layers mineralized in sulphides (Lafrance and Vanier, 2021). In the Jeannin Lake area, Charette et al. (2016) added the Préville Suite to group mafic calcosilicate rocks and carbonate gneiss, and the Secondon Suite that consists of meta-arkose and paraschist.

Thickness and distribution

The Laporte Supersuite, which covers ~11 660 km², is the dominant unit of the Rachel-Laporte Lithotectonic Domain, representing close to 85% of its area. It is ~550 km long and 20 km to 35 km wide, and is generally oriented NNW-SSE. It is adjacent to the eastern limit of the Labrador Trough.

Dating

The age distribution of detrital zircons recovered from the Freneuse Suite ranges from 3226 Ma to 1830 Ma (Henrique-Pinto et al., 2017; Godet et al., 2020). Paleoproterozoic and Archean population peaks are interpreted to indicate provenance from different lithotectonic domains of the SEPC, namely the George, Baleine and Mistinibi-Raude domains (Henrique-Pinto et al., 2017, 2019). The sediments’ depositional age is fairly well constrained between 1834 Ma (age of the youngest detrital zircons) and 1804 Ma (age of garnet growth).