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Nunatak Suite
Stratigraphic label: [ppro]nat
Map symbol: pPnat
 

First published: 23 October 2020
Last modified:

 

 

 

  DISCLAIMER: This English version is translated from the original French. In case of any discrepancy, the French version shall prevail. 

Informal subdivision(s)
Numbering does not necessarily reflect the stratigraphic position.
 
None
 
Author: Vanier and Lafrance, 2020
Age: Paleoproterozoic
Stratotype: None
Type area: Guichaud River area (NTS sheet 35K01)
Geological province: Churchill Province
Geological subdivision: Ungava Orogen / Kovik Lithotectonic Domain
Lithology: Granite
Category: Lithodemic
Rank: Suite
Status: Formal
Use: Active
Related unit(s)

None

 

Background

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.

 

Description

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.

Dating

None.

Stratigraphic Relationship(s)

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.

 

Paleontology

Does not apply.

References

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.

 

Suggested Citation

Ministère de l’Énergie et des Ressources naturelles (MERN). Nunatak Suite. Quebec Stratigraphic Lexicon. http://gq.mines.gouv.qc.ca/lexique-stratigraphique/province-du-churchill/suite-de-nunatak_en [accessed on Day Month Year].

Contributors

First publication

Isabelle Lafrance, P. Geo., M.Sc. isabelle.lafrance@mern.gouv.qc.ca; Marc-Antoine Vanier, Jr. Eng., M.Sc. marc-antoine.vanier@mern.gouv.qc.ca (redaction)

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).

 
19 novembre 2020