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Lablois Suite
Stratigraphic label: [narc]slb
Map symbol: nAslb

First published: 3 April 2018
Last modified:

 

 

 

 

 

 

 

 

 

 

 

 

 

Translation of original French

 

 

 

 

 

Informal subdivision(s)
Numbering does not necessarily reflect the stratigraphic position.
 
nAslb2 Actinote-tremolite metawebsterite
nAslb1 Phlogopite and actinolite-tremolite metawebsterite
nAslb Olivine ± phlogopite metawebsterite, usually orthopyroxene and anthophyllite porphyroblastic

 

 
Author:Goutier et al., in preparation
Age:Neoarchean
Reference section: 
Type area:The southeast portion of NTS sheet 33F01, approximately 10 km east of Lablois Lake. The most differentiated facies outcrops in the suite are located 3 km west of Pelletan Lake (sheet 33H04, Pelletan Ultramafic Intrusion, Goutier et al., in preparation) and 21 km northeast of the Éléonore Mine facility (sheet 33B13, Giard Ultramafic Intrusion, Bandyayera et al., 2010). The sample taken for U-Pb isotopic dating in a felsic dyke cutting the Giard Ultramafic Intrusion (2008-PR-6037) gives the minimum age of the Lablois Suite.
Geological province:Superior Province
Geological subdivision:La Grande and Opinaca subprovinces
Lithology:Olivine metawebsterite and metawebsterite
Type:Lithodemic
Rank:Suite
Status:Formal
Use:Active

 

 

Related unit(s)
  • Lablois Suite
    • Pelletan Ultramafic Intrusion
    • Giard Ultramafic Intrusion

 

 

 

 

Background

Ultramafic intrusions in the La Grande and Opinaca subprovinces have been observed since the early mapping of this area (e.g., Eade Unit 9, 1966; Ub on Sharma Map 1878, 1977). During the 2012 geological mapping, several orthopyroxene porphyroblast or anthophyllite-rich ultramafic intrusions were mapped in several portions of sheet 33H (Chartier-Montreuil, 2013; Hammouche et al., 2016; Goutier et al., in preparation). In 2013, an honours thesis was undertaken to characterize these intrusions and divide them into several groups (Grezla, 2014). As a result, the Lablois Suite was defined based on the results of Chartier-Montreuil (2013), Grezla (2014), the geological mapping work of 2015 (sheets 33F01 and 33F02, Goutier et al., in preparation) and the visit of the Giard Ultramafic Intrusion outcrops by Goutier in 2015. Hammouche and Burniaux (in preparation) divided this suite into two units, depending on the abundance of micas in the rock; unit nAslb1 combines intrusions rich in phlogopite and biotite, while unit nAslb2 is composed of intrusions lacking or very poor in micas.

 

Description 

 

Lablois Suite (nAslb): Olivine ± Phlogopite Metawebsterite, Usually Orthopyroxene and Anthophyllite Porphyroblastic

Unit nAslb of Lablois Suite consists of an olivine metawebsterite, with or without phlogopite, commonly orthopyroxene and anthophyllite porphyroblastic. These intrusions are generally small (<2 km²). They are characterized by a high magnetic susceptibility that allows for easy identification on the magnetic gradient map. Unit nAslb corresponds to ultramafic intrusions without distinction of the presence of phlogopite.

 

At the scale of the outcrop, the rocks form rounded hills a few metres high. The rock patina is brown to greenish and the fresh surface is dark green to black. Olivine metawebsterites of the Lablois Suite usually contain phlogopite. Rock typically has a porphyroblastic texture due to orthopyroxene recrystallization. This corresponds to a “ball” facies with porphyroblasts ranging in diameter from 0.5 to 10 cm. These rocks may show weak foliation or even banding. The typical mineralogical assemblage consists of orthopyroxene, partially serpentinized olivine, tremolite, phlogopite, magnetite and traces of spinel.

These rocks are also characterized by weak preservation of primary orthopyroxene and olivine, which are replaced by tremolite/cummingtonite, orthopyroxene and anthophyllite porphyroblasts. The “needle” facies is associated with anthophyllite-rich rock (>15%) with crystals up to 7 cm long. Carbonate, talc and chlorite alterations are also observed. A number of these are located near shear corridors. Locally, they contain anomalous levels of gold (> 300 ppb Au, 1906020351), platinum group elements or chromium (2013056557).

 

 

Lablois Suite 1 (nAslb1): Phlogopite and Actinolite-Tremolite Metawebsterite

Unit nAslb1 in the Lablois Suite meets the same criteria as those in the undifferentiated Lablois Suite (nAslb), except for a high percentage of phlogopite (≥5%).

 

Lablois Suite 2 (nAslb2): Actinolite-Tremolite Metawebsterite

Unit nAslb2 meets the same criteria as the undifferentiated Lablois Suite (nAslb), except for the absence or very low amounts of phlogopite in the rock (<5%). 

Thickness and Distribution

The intrusions belonging to the Lablois Suite are small (area less than 2 km² with an average of 0.32 km², Duvernois, 2017). Altogether, the 80 bodies surveyed cover a total area of 22 km². They are primarily located in the Opinaca Subprovince, or at the interface between the La Grande and Opinaca subprovinces (sheets 33H01, 33H02 and 33H03). In many cases, they follow or are adjacent to shear zones, which can be mapped or locally present as boudinaged metric dykes. Some of these dykes are adjacent to gold-bearing zones (e.g., Quentin Index, 2012-QD-2133, sheet 33H04). 

Dating

The age of 2619.6 +1.9/-1.4 Ma was obtained from a felsic dyke cutting the Giard Ultramafic Intrusion which is related to the Lablois Suite (outcrop 2008-PR-6037). It is therefore a minimum age. 

Isotopic SystemMineralCrystallization Age (Ma)(+)(-)Reference(s)
U-PbZircon2619.61.91.4David et al., 2011

Stratigraphic Relationship(s)

Ultramafic intrusions cut almost every unit in the Opinaca Subprovince. They are intrusive into the rocks of the Trieste and Rivière Solomon formations. These rocks are less deformed than those of the Laguiche Complex, but have undergone significant metamorphism which resulted in the recrystallization of orthopyroxene and olivine. They are cut by dykes from the Vieux Comptoir Granitic Suite, as well as diabases of the Lac Esprit Dykes. 

Paleontology

Does not apply.

References

Author(s)TitleYear of PublicationHyperlink (EXAMINE or Other)
CHARTIER-MONTREUIL, W.Minéralogie et géochimie d’une intrusion ultramafique du Laguiche, Baie James. Université Laval, projet de fin d’études, 68 pages.2013
DUVERNOIS, A. Étude des intrusions ultramafiques des sous-provinces de La Grande et d’Opinaca. Étude des faciès à anthophyllite et phlogopite. Université UniLasalle, Beauvais, France. Mémoire d’ingénieur géologue, 89 p.2017

GIGON, J. – GOUTIER, J.

Géologie de la région du lac Richardie, Eeyou Istchee Baie-James. Ministère de l’Énergie et des Ressources naturelles, Québec; RG 2016-04, 45 pages, 2 plans.2017RG 2016-04
GOUTIER, J. – GIGON, J. – BURNIAUX, P. – DION, C. – TALLA TAKAM, F. – CHARTIER-MONTREUIL, W. – BANDYAYERA, D.Géologie de la région du lac de la Corvette, Eeyou Istchee Baie-James. Ministère de l’Énergie et des Ressources naturelles, Québec.In preparation
GRZELA, D.

Étude pétrographique et géochimique des intrusions ultramafiques de la région du lac Richardie, Baie-James, Québec. Université d’Ottawa, projet de fin d’études, 48 pages.

2014
HAMMOUCHE, H. – BURNIAUX, P.

Géologie de la région du lac Joubert (23E03, 23E04, 33H01) Eeyou Istchee – Baie-James. Ministère de l’Énergie et des Ressources naturelles, Québec.

In preparation
DAVID, J. – VAILLANCOURT, D. – BANDYAYERA, D. – SIMARD, M. – GOUTIER, J. – PILOTE, P. –  DION, C. – BARBE, P.Datations U-Pb effectuées dans les sous-province d’Ashuanipi, de La Grande, d’Opinaca et d’Abitibi en 2008-2009. Ministère des Ressources naturelles et de la Faune, Québec; RP 2010-11, 37 pages.2011RP 2010-11
EADE, K. E.Fort George and Kaniapiskau river (west half) map-areas, New Quebec. Geological Survey of Canada; memoir 339, 84 pages.1966Source
SHARMA, K.N.M.Région de La Grande Rivière. Ministère des Richesses naturelles, Québec; RG-184, 75 pages, 3 cartes.1977RG 184

 

 

 

8 novembre 2018