DISCLAIMER: This English version is translated from the original French. In case of any discrepancy, the French version shall prevail.
The Nunatak Suite was introduced in the Sirmiq Lake area (Vanier and Lafrance, 2020) to group late granitic intrusive rocks of the Kovik Lithotectonic Domain.
Granite of the Nunatak Suite is most commonly observed as intrusions and dykes within other units of the Kovik Domain. It represents the main lithology only on a few outcrops, where it is generally observed in the summit part.
Unit pPnat1 is leucocratic (2-4% ferromagnesium minerals), massive to very slightly foliated. The rock has a monzogranitic or syenogranitic composition. It is homogeneous, medium grained, even grained and light pink to pink. However, it includes a coarser-grained, even pegmatitic phase in more or less diffuse contact. This coarse-grained phase locally takes on a beige or white colour, which gives it an appearance similar to the leucosome observed in migmatized paragneisses of the Crony Suite.
Microscopic observations confirm the intrusive appearance of granite. However, a few textures indicate some deformation. More specifically, quartz displays subgrain or chessboard undulatory extinction and twinned feldspar grains are deformed in places. These are dominated by microcline; also, there are smaller amounts of slightly sericitized plagioclase, some perthitic orthose and myrmekites. Ferromagnesian minerals consist of moderately chloritized biotite. Small scattered muscovite flakes are also present, as well as hornblende very locally. Other accessory phases are sparse and include magnetite and zircon.
Thickness and distribution
The Nunatak Suite has only been observed as a few intrusions hectometre wide and 1 km to 4 km long in the southern part of the Sirmiq Lake area (Vanier and Lafrance, 2020). Some units of the Kovik Complex will eventually be reassigned to the Nunatak Suite as mapping work in the Kovik Lithotectonic Domain progresses.
Granite of the Nunatak Suite seems to represent the latest unit of the Kovik Domain. It cuts units of the Nanuk Complex and Gastrin, Arviq and Crony suites. Enclaves of monzonite and speckled quartz monzonite (Gastrin Suite) and diatexite (Crony Suite) have been observed in granite.
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Publications Available Through SIGÉOM Examine
VANIER, M.-A., LAFRANCE, I., 2020. Geology of the Sirmiq Lake area, Ungava Orogen, Nunavik, Quebec, Canada. MERN. BG 2020-02, 1 plan.
Ministère de l’Énergie et des Ressources naturelles (MERN). Nunatak Suite. Quebec Stratigraphic Lexicon. https://gq.mines.gouv.qc.ca/lexique-stratigraphique/province-du-churchill/suite-de-nunatak_en [accessed on Day Month Year].
Mehdi A. Guemache, P. Geo., Ph.D. (coordination); Benoit Charette, P. Geo., M.Sc. (critical review); Simon Auclair, P. Geo., M.Sc. (editing); Céline Dupuis, P. Geo., Ph.D. (English version); André Tremblay (HTML editing).