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Béryl Sud Pluton
Stratigraphic label: [narc]bes
Map symbol: nAbes

First published: 14 June 2019
Last modified:

 

 

 

 

 

 

 

 

 

 

Translation of original French

 

 

 

Informal subdivision(s)
Numbering does not necessarily reflect the stratigraphic position.
 
nAbes2 Leucocratic monzogranite, pegmatitic
nAbes1 Homogeneous foliated tonalite

 

 
Author: Moukhsil and Doucet, 1999
Age: Neoarchean
Reference section: None
Type area: Village Lakes area (NTS sheet 32B03)
Geological province: Superior Province
Geological subdivision: La Grande Subprovince
Lithology: Tonalite and monzogranite
Type: Lithodemic
Rank: Lithodeme
Status: Formal
Use: Active

 

 

Background

The Béryl Sud Pluton was defined by Moukhsil and Doucet (1999) in the Village Lakes area (sheet 33B03) to describe a late-tectonic intrusion cutting the Eastmain Group south of Béryl Lake. Mapping work of Bandyayera and Caron-Côté (2019) shows that this intrusion extends further south, in the NW part of sheet 32O14 and the NE corner of sheet 32O15.

 

 

Description

Moukhsil and Doucet (1999) subdivided the Béryl Sud Pluton into two separate units: nAbes1 and nAbes2. 

 

 

Béryl Sud Pluton 1 (nAbes1): Homogeneous Foliated Tonalite

Unit nAbes1 makes up 98% of the Beryl Sud Pluton. It consists of homogeneous medium-grained, locally coarse-grained, foliated tonalite and contains centimetric to decimetric pegmatitic pockets. The rock is light grey in altered surface and medium to dark grey in fresh exposure. In the Village Lakes area (sheet 33B03), unit Abes1 contains 5% locally migmatized biotite-andalusite paragneiss enclaves. To the NE of the Glas Lake area (sheet 32O14), the Béryl Sud Pluton tonalite contains metric to decametric enclaves of amphibolitized diorite (5-20%) and tonalitic gneiss (1-5%). In places, enclaves are partially assimilated, giving the rock a heterogeneous and heterogranular appearance with diffuse contact restites. In proximity to the enclaves, the tonalite grain size is coarser than in the rest of the rock. Foliated tonalite is characterized by 2-10% biotite, 1-5% hornblende and 1% magnetite.

 

 

Béryl Sud Pluton 2 (nAbes2): Leucocratic Monzogranite, Pegmatitic

Unit nAbes2 consists of leucocratic monzogranite, usually pegmatitic, showing megacrystals of plagioclase, K-feldspar and quartz. A minor amount of biotite is present. This unit was only observed in the Village Lakes area (Moukhsil and Doucet, 1999).

 

Thickness and Distribution

The Béryl Sud Pluton outcrops NE of Glas Lake (sheets 32B03, 32B02, 32O14 and 32O15). It extends in an E-W direction over a distance of 20 km and has a maximum width of 6 km.

Dating

None. 

Stratigraphic Relationship(s)

The Béryl Sud Pluton intruded in the contact zone between the Eastmain Group to the north, and the Champion Complex to the south. To the west, it is cut by the Quindèle Pluton. To the east, compilation work shows that the Béryl Sud Pluton intrudes into migmatized paragneiss of the Laguiche Complex, and that it is separated from the Lac des Montagnes Group by the Glas Shear Zone. 

Paleontology

Does not apply.

References

Publications available through SIGÉOM Examine

MOUKHSIL, A., DOUCET, P. 1999. GEOLOGIE DE LA REGION DES LACS VILLAGE. MRN. RG 99-04, 33 pages and 1 plan.

BANDYAYERA, D., CARON-COTE, E. 2019. Géologie de la région du lac des Montagnes, sous-provinces de La Grande, de Nemiscau et d’Opatica, Eeyou Istchee Baie-James, Québec, Canada. MERN. BG 2019-03.

 

 

 

11 novembre 2019