The Rivière aux Feuilles Suite was defined by Percival and Card (1994) during their mapping work in the Lac Minto-Rivière aux Feuilles area. This unit takes its name from the Feuilles River located in sheet 24L. Although mainly consisting of biotite granodiorite, it then included pyroxene-hornblende granodiorites, tonalites, granites and smaller amounts of diorite, gabbro and pyroxenite. In the Dupire Lake area (sheet 34H03), Lamothe (1997) identified four informal units: a biotite granodiorite and tonalite unit (Arfe1) and three units of granitic intrusions of different composition (Arfe1 to Arfe4). Subsequently, in the Nedlouc Lake area (sheets 34H and 24E), Parent et al. (2000, 2001) reassigned these different lithologies to several lithodemic suites and restricted the Rivière aux Feuilles Suite to an informal unit of biotite-hornblende granodiorite and biotite-pyroxene granodiorite (Arfe1), and an informal tonalite unit (Arfe2). The redefined Rivière aux Feuilles Suite was extended eastward in the Aigneau Lake area (sheets 24E and 24F04; Berclaz et al., 2001, 2002) and to the NE in the Dufreboy Lake area (sheet 24L; Leclair et al., 2003).

In the La Potherie Lake area (sheet 34I), Leclair et al. (2001, 2002) reduced the Rivière aux Feuilles Suite to a unit of biotite-hornblende-magnetite granodiorite. This unit was extended westward in the Vernon Lake area (sheet 34J; Parent et al., 2002, 2003) and to the SW in the Minto Lake area (sheet 34G; Simard et al., 2005). To comply with this new definition, Simard et al. (2008) reassigned tonalites that had been incorporated in the Rivière aux Feuilles Suite to the Favard and Rochefort tonalitic rock suites. Simard et al. (2008) also assigned heterogeneous biotite-hornblende granodiorites of the Monchy and Lac Minto suites to the Rivière aux Feuilles Suite. These amendments resulted in abandonment of the Monchy Suite. Finally, during the Ministère’s geological compilation work (MNRF, 2010a-i; Simard et al., 2011), the Rivière aux Feuilles Suite was divided into three informal units, mainly based on the nature of ferromagnesian minerals observed in granodiorite.

Granodiorite usually contains a granitic facies in diffuse contact with the granodiorite facies. In many areas, granitic intusions and numerous enclaves give a heterogeneous appearance to the unit. Decimetric to metric enclaves are composed of amphibolite and diorite and, more sparsely, diatexite and paragneiss. The amount of these enclaves rarely exceeds 5% of the outcrop area, but can reach 30% locally. Granitic intusions and the alignment of ferromagnesian minerals mark an obvious foliation, but the latter is difficult to observe when the rock is massive and homogeneous.

The Rivière aux Feuilles Suite is divided into three informal units (MRNF, 2010a-i; Simard et al., 2011): undifferentiated homogeneous biotite ± hornblende ± pyroxene ± magnetite (nArfe), biotite-hornblende granodiorite (nArfe1), and heterogeneous hornblende-biotite granodiorite (nArfe2).

This undivided unit of the Rivière aux Feuilles Suite consists of homogeneous light grey biotite-hornblende-pyroxene-magnetite granodiorite (5-25%), medium to coarse-grained and foliated to locally gneissic. This unit also contains mafic rock enclaves, and granite and pegmatite intrusions, pinkish white to pinkish grey.

Rivière aux Feuilles Suite 1 (nArfe1): Homogeneous Biotite ± Hornblende ± Magnetite Granodiorite

Unit nArfe1 consists of granodiorite containing 5-25% biotite, hornblende and magnetite. This rock is homogeneous, foliated to locally gneissic, light grey to pinkish grey, of massive to slightly foliated appearance, medium to coarse grained, locally slightly porphyritic, containing <10% centimetric ferromagnesian mineral clusters. The unit contains mafic rock enclaves, a coarse-grained granitic phase in diffuse contact with granodiorite, and a pegmatitic phase, pinkish white to pinkish grey.

Rivière aux Feuilles Suite 2 (nArfe2): Heterogeneous Biotite-Hornblende-Magnetite Granodiorite

Unit nArfe2 granodiorite is composed of 10-20% hornblende, biotite and magnetite. It is heterogeneous, foliated to locally gneissic, migmatitic and coarse to medium grained. It has a heterogranular and locally porphyritic texture with a diatexite appearance. This rock contains up to 40% enclaves of tonalite, light grey granite and, locally, paragneiss, and granitic pegmatite intrusions.

Thickness and distribution

The Rivière aux Feuilles Suite covers a large area in the central part of the Minto Subprovince (Simard, 2008). Granodiorite forms several kilometric, generally oriented NW-SE intrusive bodies, mostly in sheets 34G, 34H, 34J, 34I, 24E, 24L, as well as in sheets 34O, 34P and 24F. These cover an area ~350 km long by 220 km wide. Unit nArfe1 occurs primarily in sheets 34G to 34J, unit Arfe2 follows a NW-SE oriented strip in the NW quarter of sheet 24E, NE corner of sheet 34H and west half of sheet 34I.

Dating

Several dating of Rivière aux Feuilles Suite granodiorite samples yielded ages between 2733 Ma and 2721 Ma (Percival et al., 1992; Percival and Card, 1994; Skulski et al., 1996; David et al., 2009).