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Mercier Suite
Stratigraphic label: [ppro]mrc
Map symbol: pPmrc

First published: 20 October 2016
Last modified: 10 December 2020

 

 

 

  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.
 
pPmrc2 Massive pink granite
pPmrc1 Pegmatitic granite, tonalite and granodiorite
 
Author: Simard et al., 2013
Age: Paleoproterozoic
Stratotype: None
Type area: Kuujjuaq area (NTS sheet 24K)
Geological province: Churchill Province
Geological subdivision: Rachel-Laporte Lithotectonic Domain
Lithology: Massive felsic intrusive rocks
Category: Lithodemic
Rank: Suite
Status: Formal
Use: Active
Related unit(s)

None

Background

The Mercier Suite was defined in the Kuujjuak and Ungava Bay areas (Simard et al., 2013) to group all granitic intrusions of the Rachel-Laporte Lithotectonic Domain. Most of these intrusions were described by Gélinas (1958, 1965) and were not revisited during the Ministère’s 1:250 000 mapping work between 2011 and 2016. The Mercier Suite was continued southward in the Saffray Lake (Lafrance et al., 2014), Jeannin Lake (Charette et al., 2016) and Résolution Lake areas.

 

Description

The Mercier Suite consists of two units: pegmatitic granite, tonalite and granodiorite (pPmrc1), and massive pink granite (pPmrc2).

 

Mercier Suite 1 (pPmrc1): Pegmatitic Granite, Tonalite and Granodiorite

Massive felsic intrusive rocks of unit pPmrc1 occurs as decimetric to decametric intrusions oriented parallel to foliation in metasedimentary rocks and amphibolites of the Laporte Supersuite (Freneuse and Klein suites). The geochemistry of this unit suggests that it comprises several different intrusions (Lafrance and Vanier, 2021). These intrusions are depleted in ferromagnesian minerals and commonly display a well-developed graphic texture at the megascopic scale. Its colour can vary rapidly from white to pink on the same outcrop. They are composed of plagioclase, quartz (25-35%), muscovite clusters (10-20%), varying amounts of K-feldspar (3-20%), and small chloritized biotite flakes (1-3%). They also contain 1-15% millimetric to centimetric crystals of accessory minerals such as tourmaline, garnet, apatite and hematite.

In the Kuujjuaq area, Gélinas (1965) states that the amount of pegmatitic granite dykes and sills increases from west to east.

 

Mercier Suite 2 (pPmrc2): Massive Pink Granite

The Mercier Suite also includes a major intrusion (25 km x 5 km) of biotite pink granite in the Saffray Lake area (Lafrance et al., 2014). Granite is pink, very homogeneous, massive, medium to coarse grained and contains <5% biotite. It contains in places some decimetric amphibolite enclaves. Granite of unit pPmrc2 resembles that of the Dancelou Suite in the Baleine Lithotectonic Domain.

 

Thickness and distribution

The Mercier Suite covers an area of ~235 km2. Unit pPmrc1 forms small intrusions <1 km wide in the Rachel-Laporte Lithotectonic Domain, with a greater concentration in the northern part of the area. Unit pPmrc2 consists of a large-scale granitic intrusion (25 km x 5 km) that cuts Archean rocks of the Rénia and Highfall complexes, on the edge of the Lac Turcotte Fault, in the Saffray Lake area (Lafrance et al., 2014).

 

Dating

None. The lack of deformation, however, suggests a later emplacement than the New Quebec Orogen, which occurred between 1.82 Ga and 1.77 Ga (Machado et al., 1989).

Stratigraphic Relationship(s)

Intrusive rocks of unit pPmrc1 cut metamorphosed volcano-sedimentary rocks of the Rachel-Laporte Lithotectonic Domain, namely the Freneuse and Klein suites. Granite of unit pPmrc2 cuts Archean rocks of the Rénia and Highfall complexes. Its late-tectonic emplacement and location at the edge of the Baleine Lithotectonic Domain does not rule out the possibility that this unit is related to the Dancelou Suite, which comprises a similar pink granite unit within the Baleine Domain (Lafrance and Vanier, 2021).

Paleontology

Does not apply.

References

Author(s) Title Year of Publication Hyperlink (EXAMINE or Other)
CHARETTE, B. – LAFRANCE, I. – MATHIEU, G. Géologie de la région du lac Jeannin (SNRC 24B). Ministère de l’Énergie et des Ressources naturelles, Québec. 2016 Electronic geological report
LAFRANCE, I. – SIMARD, M. – BANDYAYERA, D. Géologie de la région du lac Saffray (SNRC 24G-24F). Ministère des Ressources naturelles, Québec; RG 2014-02, 49 pages. 2014 RG 2014-02
LAFRANCE, I. – VANIER, M-A. Domaine lithotectonique de Rachel-Laporte, sud-est de la Province de Churchill, Québec, Canada : synthèse de la géologie. Ministère de l’Énergie et des Ressources naturelles. 2021 BG 2021-01
MACHADO, N. – GOULET, N. – GARIÉPY, C. U-Pb geochronology of reactivated Archean basement and of Hudsonian metamorphism in the northern Labrador Trough. Canadian Journal of Earth Sciences; volume 26, pages 1-15.  1989 Source
SIMARD, M. – LAFRANCE, I. – HAMMOUCHE, H. – LEGOUIX, C. Géologie de la région de Kuujjuaq et de la Baie d’Ungava (SNRC 24J et 24K). Ministère des Ressources naturelles, Québec; RG 2013-04, 60 pages. 2013 RG 2013-04
GÉLINAS, L. Géologie de la région de Fort Chimo et des lacs Gabriel et Thévenet, Nouveau-Québec. Thèse de doctorat, Université Laval, Québec; 212 pages. 1965
GÉLINAS, L. Région du lac Gabriel (partie ouest), Nouveau-Québec. Ministère des Mines, Québec; RP 373, 11 pages, 1 plan. 1958 RP 373

 

 

12 février 2020