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Coigny Pluton
Stratigraphic label: [narc]coi
Map symbol: nAcoi

First published: 15 November 2018
Last modified:

 

 

 

 

 

 

 

 

 

 

Translation of original French

 

 

 

Informal subdivision(s)
Numbering does not necessarily reflect the stratigraphic position.
 
None
Author:Guemache, in preparation
Age:Neoarchean
Reference section:Sonic drillings RO-240 and RO-241
Type area:Coigny River area (NTS sheet 32E01)
Geological province:Superior Province
Geological subdivision:Abitibi Subprovince
Lithology:Diorite
Type:Lithodemic
Rank:Lithodeme
Status:Formal
Use:Active

 

 

Background

This dioritic intrusion is little known due to the lack of outcrops resulting from the relatively large Quaternary cover. Deschênes and Allard (2014) initiated their description based on data from the Octave River sonic drilling project. Based on the reanalysis of available data, Guemache (in preparation) proposes the name Coigny Pluton after a river located ~2 km further north.

 

 

Description

 

Using the two sonic drillings RO-240 and RO-241 that intercepted the pluton – which are the only direct observation of this intrusion to date – Deschênes and Allard (2014) described a massive dioritic unit (lithological label I2Ja), which is coarse-grained at the centre and generally medium-grained towards the edge. According to Guemache (in preparation), this unit has a dioritic to monzodioritic composition and is massive to foliated, banded in places. The greenish grey melanoratic rock is mainly composed of plagioclase, hornblende and minor K-feldspar. It locally shows a porphyraceous texture associated with the presence of plagioclase phenocrystals. Clinopyroxene and biotite are ubiquitous and associated with amphibole. Under the microscope, the mineralogical assemblage includes more or less sericitized plagioclase, scarce microcline (<15%), hornblende (10-40%), biotite (10-20%) and clinopyroxene (5-10%). Quartz is scarce (<5%). Pyroxene grains are commonly surrounded by an amphibole rim (poikiloblastic actinolite or green hornblende), indicating an uralitization process. The rock contains relatively abundant epidote and titanite, as well as apatite, zircon and magnetite as accessory minerals. Calcite (<5%) is relatively abundant in some areas. Amphibolite enclaves are present, as are small felsic intrusions. The latter are unlikely to be associated with the Bernetz Intrusion as suggested by Deschênes and Allard (2014), due to the syntectonic nature of this large neighbouring intrusion (Guemache, in preparation).

 

 

Thickness and Distribution

This pluton occupies the eastern end of NTS sheet 32E01. Its near-circular geometry (3 km x 4 km) is clearly visible on high-resolution aeromagnetic maps (Keating et al., 2010; Keating and d’Amours, 2010) due to its high magnetic susceptibility.

 

Dating

None. 

Stratigraphic Relationship(s)

The Coigny Pluton’s geometry favours a late-tectonic to post-tectonic intrusion within the Rivière Octave Formation, dated 2726.3 ±2.4 Ma (Deschênes et al., 2014; Augland et al., 2015). 

Paleontology

Does not apply.

References

Author(s)TitleYear of PublicationHyperlink (EXAMINE or Other)
GUEMACHE, M.A.Synthèse géologique de la région de rivière Octave, Abitibi. Ministère de l’Énergie et des Ressources naturelles, Québec.In preparationRG 2018-01
DESCHÊNES, P.-L. – ALLARD, G. – GUEMACHE, M.A.

Révision de la géologie de la région de la rivière Wawagosic (parties des SNRC 32D15 et 32E02). Ministère de l’Énergie et des Ressources naturelles, Québec; RP 2014-04, 20 pages.

2014RP 2014-04
AUGLAND, L.E. – DAVID, J. – PILOTE, P. – LECLERC, F. – GOUTIER, J. – HAMMOUCHE, H. – LAFRANCE, I. – TALLA TAKAM, F. – DESCHÊNES, P.-L. – GUEMACHE, M.A.

Datations U-Pb dans les provinces de Churchill et du Supérieur effectuées au GEOTOP en 2012-2013. Ministère de l’Énergie et des Ressources naturelles, Québec; RP 2015-01, 43 pages.

2015RP 2015-01
DESCHÊNES, P.-L. – ALLARD, G.

Révision de la géologie de la région de la rivière Octave (SNRC 32D16 et 32E01). Ministère de l’Énergie et des Ressources naturelles, Québec; RP 2014-02, 14 pages.

2014RP 2014-02
KEATING, P. – LEFEBVRE, D. – RAINSFORD, D. – ONESCHUCK, D.

Série des cartes géophysiques, parties des SNRC 31, 32, 41 et 42, Ceinture de roches vertes de l’Abitibi, Québec et Ontario. Ministère des Ressources naturelles et de la Faune, Québec; DP 2010-05, 8 pages, 2 plans.

2010DP 2010-05
KEATING, P. – D’AMOURS, I.Réédition des données numériques en format Géosoft (profils) des levés aéroportés de l’Abitibi, au Québec. Ministère des Ressources naturelles et de la Faune, Québec; DP 2010-09, 6 pages, Digital data.2010DP 2010-09

 

 

15 octobre 2019