Post-Archean diabase dykes and sills were recognized during the first geological mapping campaigns of the Canadian Shield in Quebec and Ontario (e.g., Murray et al., 1897). The Rivière Payne Dyke unit was introduced by Fahrig and West (1986) from their compilation map and interpretation of aeromagnetic surveys. They illustrated the distribution of the Canadian Shield diabase dyke swarms and their chronologies based on isotopic ages. On this map, the northern Quebec NNW dykes are attributed to the Rivière Payne Swarm. The Rivière Payne Dykes were plotted from outcrops and the magnetic field vertical gradient map. They have a straight-line signature for kilometres with a NNW orientation. The Rivière Payne Dykes were mapped in NTS sheets 24M (Madore et al., 1999), 25D, 25C, 25E and 25F (Madore and Larbi, 2000), 35A and 35H (Madore et al., 2001), 24E (Berclaz et al., 2001), 34P (Cadieux et al., 2002), 35B and 35G (Madore et al., 2002), 34O (Berclaz et al., 2002), 35C and 35F (Maurice et al., 2003), and 34N and 34M (Maurice et al., 2004).

The Rivière Payne Dykes are similar in location to the Klotz Dykes. They have therefore been documented in the same work with similar descriptions, since they show several mineralogical and petrographic affinities (Madore et al., 1999; Madore and Larbi, 2000; Madore et al., 2001; Madore et al., 2002; Maurice et al., 2003; Maurice et al., 2005). In some areas, the Rivière Payne River Dykes have some characteristics that differentiate them from the Klotz Dykes (Berclaz et al., 2001; Berclaz et al., 2002; Cadieux et al., 2002).

The Rivière Payne Dykes consist of gabbro; they have a subophitic to ophitic texture and are medium to coarse-grained. In some areas, these dykes have a greater variety of petrographic facies. They are fine grained to aphanitic and have ophitic to trachyoidal textures due to a magmatic flow structure (Berclaz et al., 2001; Berclaz et al., 2002; Cadieux et al., 2002). Rock is bluish grey in fresh exposure and greenish brown in altered patina (Berclaz et al., 2001; Berclaz et al., 2002; Cadieux et al., 2002). Gabbro is composed of euhedral plagioclase crystals surrounded by a matrix of clinopyroxene and locally, anhedral to subhedral orthopyroxene. Dykes have aphanitic chilled margins of decimetric thickness, containing euhdral microcrystals of plagioclase and augite aligned with contact with the host rock (Madore et al., 1999). Common accessory minerals are quartz, iron and titanium oxides and biotite.

Deformation and metamorphism of dykes cutting the Troie and Qimussinguat complexes are generally null, while intrusions in the northeastern portion of the Faribault-Thury Suite show deformation and metamorphism that intensifies eastward towards the Labrador Trough (Madore et al., 1999). The amphibolite metamorphic facies is thus reached within the Diana Complex, as evidenced by the loss of their original igneous characteristics (Madore and Larbi, 2000). Metamorphic and alteration minerals include chlorite and amphibole partially replacing ferromagnesian minerals, as well a sericite-epidote assemblage replacing plagioclase. Dykes located near large brittle faults are also altered and contain chlorite, hematite and epidote veins (Madore et al., 2001).