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Viau Suite
Stratigraphic label: [narc]via
Map symbol: nAvia

First published: 6 June 2018
Last modified:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Translation of original French

 

 

Informal subdivision(s)
Numbering does not necessarily reflect the stratigraphic position.
 
nAvia3 Alkaline granite
nAvia2 Syenogranite and monzogranite
 
Author:Leclair et al., 1998
Age:Neoarchean
Reference section:None
Type area:Bermen Lake area (NTS sheet 23F)
Geological province:Superior Province
Geological subdivision:Ashuanipi, La Grande and Opinaca subprovinces
Lithology:Granite
Type:Lithodemic
Rank:Suite
Status:Formal
Use:Active

 

 

Background

The Viau Suite was introduced by Leclair et al. (1998) in the Bermen Lake area to describe two biotite-fluorine-magnetite syenogranite post-tectonic intrusions. Subsequently, several other intrusions were assigned to the Viau Suite in the Nitchequon Lake (Lamothe et al., 2000), Hurault Lake (Thériault and Chevé, 2001), Caniapiscau Reservoir (Simard et al., 2009) and Lake Léran (Talla-Takam et al., in preparation) areas. The Viau Suite is also described in the Ashuanipi Subprovince geological and metallogenic synthesis (Simard et al., 2015).

 

Description

The Viau Suite groups several subcircular anorogenic granite intrusions (Simard et al., 2015). It has been divided into two units: nAvia2 and nAvia3. This nomenclature is retained to facilitate the link between the synthesis map and maps of the various previously published reports. Thus, the Viau Suite does not have a nAvia1 unit (Simard et al., 2015).

The Viau Suite consists of pinkish biotite-titanite-magnetite ± hornblende syenogranite and monzogranite displaying a porphyraceous or pegmatitic texture, which generally form the pluton edge phase (nAvia2). The core of plutons is occupied by alkaline granite (nAvia3) which is distinguished from the edge phase by a redder colour and the presence of interstitial fluorine (Simard et al., 2015). Rocks are characterized by very high contents of rare earth elements and other incompatible elements (i.e. Hf, Nb, Rb, Th, Y). The presence of fluorine, combined with the very high enrichment in incompatible element, suggests that these intrusions are A-type granites (i.e., anorogenic; Thériault and Chevé, 2001).

 

Viau Suite 2 (nAvia2): Syenogranite and Monzogranite

Unit Avia2 is the most common. It consists of homogeneous and massive pinkish biotite-titanite-magnetite ± hornblende syenogranite and monzogranite. The rock is medium to coarse grained and generally displays a porphyraceous or pegmatitic texture (Simard et al., 2015). Myrmekitic textures between quartz and plagioclase are also common (Thériault and Chevé, 2001). This unit usually forms the edge phase of Viau Suite intrusions (Simard et al., 2015).

In thin section, K-feldspar occurs as subhedral phenocrystals and euhedral interstitial grains. Subhedral olive-green biotite is partially chloritized. Titanite forms subhedral to anhedral crystals often associated with magnetite, biotite and apatite. Locally, euhedral allanite crystals reach 3 mm in length (Thériault and Chevé, 2001).

 

Viau Suite 3 (nAvia3): Alkaline Granite

Unit Avia3 usually occupies the central part of plutons, is a biotite-magnetite alkaline granite that differs from rocks of unit Avia2 by a more reddish colour and the presence of interstitial fluorine (Simard et al., 2015). Allanite is also observed in this unit (Talla-Takam et al., in preparation). 

 

Thickness and Distribution

The Viau Suite groups several subcircular granite intrusions corresponding to strong positive aeromagnetic anomalies located in the southwestern Ashuanipi Subprovince. These intrusions are concentrated along a NE-oriented corridor ~80 km by 200 km, extending from Naopocane Lake to Caniapiscau Reservoir (Thériault and Chevé, 2001). Some intrusions are also located directly to the south, in the Opinaca Subprovince (Simard et al., 2015).

 

Dating

A U-Pb dating returned a crystallization age of 2571 ±2 Ma in a fluorine syenogranite of the Bermen Lake area (David and Parent, 1997). Another U-Pb dating gave a crystallization age of 2572 ±1 Ma in a fluorine granite of the Nitchequon Lake area (Parent, 1998). The Viau Suite is thus the youngest Archean unit known to date in the Ashuanipi Subprovince.

Isotopic SystemMineralCrystallization Age (Ma)(+)(-)Reference(s)
U-PbZircon257122David and Parent, 1997
U-PbZircon257211Parent, 1998

Stratigraphic Relationship(s)

The Viau Suite intrudes into several geological units of the Ashuanipi Subprovince and, to a lesser extent, into the La Grande and Opinaca subprovinces, including the Grosbois Complex, the Opiscotéo, Gamart and Lataignant suites, and the Mercator Formation.

Paleontology

Does not apply.

References

Author(s)TitleYear of PublicationHyperlink (EXAMINE or Other)
DAVID, J. – PARENT, M.Géochronologie U-Pb du projet Moyen Nord. Ministère des Ressources naturelles, Québec; GM 59903, 90 pages.1997GM 59903
LAMOTHE, D. – THÉRIAULT, R. – LECLAIR, A.,Géologie de la région du lac Nitchequon (SNRC 23 E). Ministère des Ressources naturelles, Québec; RG 99-14, 43 pages.2000RG 99-14
LECLAIR, A. – LAMOTHE, D. – CHOINIÈRE, J. – PARENT, M.Géologie de la région du lac Bermen (SNRC 23F). Ministère des Ressources naturelles, Québec; RG 97-11, 40 pages.1998RG 97-11
PARENT, M.Géochronologie U-Pb du projet Moyen Nord. Phase II. Ministère des Ressources naturelles, Québec. GM 59904, 63 pages.1998GM 59904
SIMARD, M. – PAQUETTE, L. – PARENT, M.Synthèse géologique et métallogénique de la partie québécoise de la Sous-province d’Ashuanipi, Province du Supérieur. Ministère des Ressources naturelles, Québec; MM 2015-01, 96 pages.2015MM 2015-01

SIMARD, M. – PARENT, M. – PAQUETTE, L.

Géologie de la région du réservoir Caniapiscau (SNRC 23N et 23K). Ministère des Ressources naturelles et de la Faune, Québec; RG 2009-04, 37 pages.2009RG 2009-04
TALLA-TAKAM, F. – BEAUCHAMP, A.-M. – MASSEI, F.Géologie de la région des lacs Emmanuel et Léran (SNRC 33A et 23D). Ministère de l’Énergie et des Ressources naturelles, Québec.In preparation
THÉRIAULT, R. – CHEVÉ, S.Géologie de la région du lac Hurault (SNRC 23L). Ministère des Ressources naturelles, Québec; RG 2000-11, 49 pages.2001RG 2000-11

 

 

15 octobre 2019