Last modified: 14 May 2018
Translation of original French
Author: | Beauchamp and Massei, 2018 |
Age: | Neoarchean |
Reference section: | |
Type area: | Bohier Island area (NTS sheet 33A08) |
Geological province: | Superior Province |
Geological subdivision: | Opatica Subprovince |
Lithology: | Diorite |
Type: | Lithodemic |
Rank: | Suite |
Status: | Formal |
Use: | Active |
None
Background
The Gaël Intrusive Suite was introduced by Beauchamp and Massei (2018) following mapping work conducted by MERN in 2017. The suite consists of a series of dioritic plutons observed on outcrop or described by Eastmain Resources as “felsic intrusive” in its campaign reports (Gerber and Robinson, 2012).
Description
In the literature, rocks belonging to the Gaël Intrusive Suite are poorly documented. They are described as a fine to medium-grained diorite containing hornblende and feldspar (Drouin and Thiboutot 1983; Knowler and Thiboutot 1988).
In outcrop, it is a medium grey diorite, locally brownish and slightly lighter in fresh exposure. It is fine to medium-grained and foliated. Some outcrops show a L-tectonite. The unit has up to 15-20% biotite-epidote clusters and clusters and veins of chloritic alteration that show intense chloritization. In addition to biotite, the rock contains 10% amphibole, 10% epidote, 5% carbonate and opaque minerals often associated with ferromagnesian clusters. Sphene and apatite are accessories. Alterations that affect the rock are intense chloritization, weak to moderate carbonatation with disseminated carbonates and moderate to strong sericitization of plagioclases.
The mineralogical assemblage, the disposition of biotite grains in clusters, and the presence of disseminated carbonates are reminiscent of certain characteristics of the Île Bohier Pluton, which is located a few kilometres north.
Thickness and Distribution
The Gaël Intrusive Suite consists of 8 mapped plutons, the smallest being 130 m x 160 m and the largest being 2 km x 0.8 km. They are located between Érasme and Gaël lakes at distances between 1 and 4 km west of the Eastmain mine.
Dating
None.
Stratigraphic Relationship(s)
The Gaël Invasive Suite cuts the Érasme Formation and the Roman Formation, both members of the René Group. In the event that the Gaël Intrusive Suite is affiliated with the Île Bohier Pluton, it would be contemporaneous to the Roman Formation.
Paleontology
Does not apply.
References
Author(s) | Title | Year of Publication | Hyperlink (EXAMINE or Other) |
---|---|---|---|
BEAUCHAMP, A.-M. – MASSEI, F. | Géologie de la région de l’île Bohier, au contact entre les sous-provinces d’Opatica, d’Opinaca et le bassin d’Otish, au nord de Mistissini, municipalité Eeyou Istchee Baie-James, Québec, Canada. Ministère de l’Énergie et des Ressources naturelles, Québec. | 2018 | Bulletin géologiQUE |
DROUIN, M. – THIBOUTOT, H. | Drilling and geological report, Eastmain river project. Placer Development, rapport statutaire déposé au ministère de l’Énergie et des Ressources naturelles, Québec; GM 41013, 165 pages, 29 plans. | 1983 | GM 41013 |
GERBER, W. – ROBINSON, D.J. | Report on 2010 drilling and mapping programs, Eastmain mine project. Eastmain Resources, rapport statutaire déposé au ministère de l’Énergie et des Ressources naturelles, Québec; GM 66611, 3242 pages, 83 plans. | 2012 | GM 66611 |
KNOWLES, R.J. – THIBOUTOT, H. | Geological report, F grid extensions 1, 2, 3 – 87, Eastmain river project. Milner Consolid Silver Mines L, Placer Dome, rapport statutaire déposé au ministère de l’Énergie et des Ressources naturelles, Québec; GM 47887, 38 pages, 8 plans. | 1988 | GM 47887 |