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.

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

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 various 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.