Background

Description

The Féron Suite consists of two informal units: 1) quartz monzodiorite, quartz monzonite and hornblende-biotite-magnetite monzonite (nAfer1); and 2) diorite, tonalite, monzodiorite and quartz monzonite (nAfer2), as well as intrusive rocks from the Frégate, Casterne, Lakanal and Cadet plutons. The Féron Suite units are restricted to the Opinaca Subprovince. This distinguishes them from the Bezier Suite (to the north) and Bauerman Intrusion (to the SW) units, which overlap the Opinaca and La Grande subprovinces, or are located close to the contact between these two subprovinces. In the case of the occurrences observed in sheet 33A06, some intrusions have nevertheless been assigned to the Féron Suite due to their strong petrochemical similarity and their small surface area.

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

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

Unit nAfer2 is an assemblage of diorite, tonalite, monzodiorite, quartz monzodiorite and monzonite, whose main intrusion is in the SW corner 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 plagioclase (25-65%), K-feldspar (0-20%), quartz (0-20%), hornblende (10-30%), typically chloritized biotite (5-20%), magnetite and locally hypersthene and clinopyroxene (up to 20%; Goutier et al., 2021; Côté-Roberge et al., 2021; Chartier-Montreuil and Saint-Laurent, 2024). Accessory minerals include apatite, titanite, epidote, calcite and zircon. Plagioclase is anti-perthitic and is in general moderately to strongly sericitized. Quartz occurs as individual crystals with undulatory extinction or as very fine homogeneously distributed inclusions. Biotite is generally idiomorphic to hypidiomorphic and homogeneously dispersed throughout the rock. Hornblende and pyroxenes occur as xenomorphic, commonly in clusters, and locally as poikiloblastic crystals.

Locally, centimetric to decimetric melanocratic clusters can be observed in the rocks of the nAfer2 unit. They are finely grained and composed of biotite, hornblende, pyroxene and magnetite. They were previously identified as hornblendite enclaves (Goutier et al., 2021). 

The nAfer2 unit is cut or locally enclaved by multi-centimetric to decimetric granite injections of varying grain size. Mixed textures can also be observed between the rocks of unit nAfer2 and the intrusive granites of the Des Antons Suite (nAant), where the texture and matrix of the granite are generally recognizable alongside the ferromagnesian minerals typical of unit nAfer2. The rocks located in sheet 33G01 are migmatized and characterized by the tonalitic mobilisate. This feature is also present locally in the intrusions of sheet 33B07 (Côté-Roberge et al., 2021).

Thickness and Distribution

The Féron Suite is mostly located in the central-northern part of the Opinaca Subprovince, with some sporadic occurrences in the south. It occurs in the form of bands and large plutons, which generally follow an E-W orientation.

To the north, the Féron Suite is found 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 have been reassigned to the Féron Suite, as they were not in direct contact with the rocks of the La Grande Subprovince (Goutier, 2018).

The Féron Suite intrusions extend to the SW of the Opinaca Subprovince, in sheets 33B06, 33B07, 33B10, 33B11, 33B12 and 33C16. In this sector, they are mainly composed of rocks from unit nAfer2 (Côté-Roberge et al., 2021; Côté-Roberge and Chartier-Montreuil, 2022). These intrusions range in size from 500 m to 25 km in length with a maximum width of 2.5 km. Unit nAfer2 intrusions have also been identified slightly further east in sheet 33A06 (Chartier-Montreuil and Saint-Laurent, 2024). This unit could continue between the two sectors (sheets 33B07 and 33A06), i.e., in sheets 33B08 and 33A05. Preliminary mapping by Simard and Gosselin (1999) also supports this hypothesis, as they identified intrusions in these sheets that belong to the Opinaca Intrusive Suite (nAoan2), a unit that has been replaced by the Féron Suite in the western sector.

Dating

Isotopic dating was conducted on samples collected in 2014, 2017, 2018 and 2022 in the Frégate (nAplf), Casterne (nAcst), Lakanal (nAlkl) and Cadet (nAcdt) plutons, lithodemes of the Féron Suite. The ages obtained range from 2710.4 Ma to 2701.5 Ma and are considered to be intrusion emplacement ages (Augland et al., 2016; David, 2020a and 2020b; David and Rochin-Banaga, 2023). 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 injected by dykes from the Vieux Comptoir Granitic Suite and the Des Antons Suite. It is also cut by diabase from the Mistassini Dyke Swarm and Lac Esprit Dykes. 

Paleontology

Does not apply.

References

Publications Available through SIGÉOM Examine

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