Background

Description

The Féron Suite is composed of two subunits: 1) quartz monzodiorite, quartz monzonite and hornblende-, biotite- and magnetite-bearing monzonite with locally foliated or migmatized potassium feldspar phenocrysts (nAfer1); and 2) diorite, tonalite and monzodiorite (nAfer2). The Féron Suite units are restricted to the Opinaca Subprovince. This distinguishes them from the Bezier Suite and Bauerman Intrusion units, which straddle the Opinaca and La Grande subprovinces.

Féron Suite 1 (nAfer1): Hornblende-Biotite-Magnetite Quartz Monzodiorite, Quartz Monzonite and Monzonite, K-feldspar Porphyritic, Locally Foliated or Migmatized

Féron Suite 2 (nAfer2): Diorite, Tonalite and Monzodiorite

Unit nAfer2 is an assemblage of diorite, tonalite and monzodiorite whose main intrusion is to the SW of sheet 33G01. The rock is heterogeneous and has light grey patina and fresh surface. It is generally weakly foliated, displaying a low deformation grade, but may be more foliated in places. In thin section, the rock is composed of feldspar (35-70%), quartz (up to 20%), hornblende (10-30%), typically chloritized biotite (5-20%), magnetite and locally hypersthene and clinopyroxene (up to 15%) (Goutier et al., 2021; Côté-Roberge et al., 2021). Accessory minerals include apatite, titanite, epidote, calcite and zircon. Plagioclase is anti-perthitic and is generally moderately to strongly sericitized. Quartz occurs as individual crystals with rolling extinction or as very fine homogeneously distributed inclusions. Hornblende and pyroxenes occur as xenomorphic, locally poikiloblastic crystals and are commonly by-products of the metamorphism of other hornblende or pyroxene crystals. The rocks located in sheet 33G01 are migmatized, as shown in the tonalitic mobilisate. This feature is also present locally in the intrusions of sheet 33B07 (Côté-Roberge et al., 2021). Some fine-grained hornblendite enclaves were observed in the diorite; they contain diopside, magnetite and biotite (Goutier et al., 2021). This unit is cut by decimetric intrusions of coarse-grained pegmatitic granite. 

Thickness and Distribution

The Féron Suite is shown in sheets 33F01, 33F02, 33G01 to 33G06 and 33H02 to 33H04. In this region, the suite covers a total area of approximately 685 km², of which 633 km² (92.4%) is unit nAfer1 and 52 km² (7.6%) is unit nAfer2. Some intrusions belonging to the Bezier Suite were reassigned to the Féron Suite because they were not in direct contact with the rocks of the La Grande Subprovince.

The Féron Suite extends southward in the Opinaca Subprovince in sheet 33B07 as E-W trending nAFer2 intrusions (Côté-Roberge et al., 2021). These intrusions range in size from 500 m to 20 km in length with a maximum width of 2 km. It is likely that they continue to the east and north of sheet 33B07, based on preliminary mapping by Simard and Gosselin (1999).

Dating

Isotopic dating was conducted on samples collected in 2014, 2017 and 2018 in the Frégate (nAplf), Casterne (nAcst) and Lakanal (nAlkl) plutons, lithodemes of the Féron Suite. The ages obtained range from 2710.4 to 2701.5 Ma and are considered to be intrusion emplacement ages (Augland et al., 2016; David, 2020a and 2020b). These ages also correspond to minimum sedimentation ages for the Laguiche Basin in their respective areas.

Stratigraphic Relationship(s)

The Féron Suite is intrusive in the Laguiche Complex, namely in units nAlgi2a, nAlgi3a and nAlgi4a. It is cut by dykes from the Vieux Comptoir Granitic Suite and diabases from the Mistassini Dyke Swarm and Lac Esprit Dykes. 

Paleontology

Does not apply.

References

Publications Available through SIGÉOM Examine

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