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Martel Pluton
Stratigraphic label: [narc]mrt
Map symbol: nAmrt

First published: 27 February 2018
Last modified: 14 May 2018

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Translation of original French

 

 

Informal subdivision(s)
Numbering does not necessarily reflect the stratigraphic position.
None
 
Author:Beauchamp and Massei, 2018
Age:Neoarchean
Reference section: 
Type area:Bohier Island area (NTS sheet 33A01)
Geological province:Superior Province
Geological subdivision:Opinaca Subprovince
Lithology:Granite
Type:Lithodemic
Rank:Lithodeme
Status:Formal
Use:Active

 

 

Background

Rocks of the Martel Pluton were originally part of the Lac Barou Massif described by Hocq (1985). This massif was broken down into several units by Beauchamp and Massei following the summer 2017 mapping work conducted by the Ministère. They separated rocks of the Martel Pluton which, unlike other granites of the Otish Mountains, have a banded appearance and more sericite.

Description

 

 

 

The Martel Pluton entirely consists of fairly light grey-white granite, locally with tints of greenish in altered surface and light pinkish white in fresh exposure. This granite is medium to coarse-grained, massive to slightly foliated, with pegmatitic clusters in places. The Martel Pluton is distinguished from other granites in the area by the amount of white mica it contains, and by the banded aspect it gives it. It contains 1% to 4% primary and well-crystallized muscovite. Locally, muscovite is observed in thin section as symplektitic bundles (17-SB-4044), marking rapid and primary crystallization. White mica also appears as veinlets. These veinlets actually represent fractures that opened during a brittle deformation event, which were then filled with secondary sericite. Early ductile deformation is also marked by the oscillatory extinction of quartz. The rock also contains 1-2% garnet and about 1% biotite. It is not uncommon to see a graphic structure on outcrop. The main alterations are weak to moderate hematitization and damouritization, both of which affect plagioclase.

The chemical composition of the Martel Pluton rocks is very homogeneous and is marked by a low content in Fe2O3T (0.75-1.94%) and MgO (0.06-0.21%) as well as a higher K2O content (3.91-5.14%) than other felsic intrusions in the region (Barou Intrusion, Cadieux Pluton, Île Bohier Pluton, Kaaispaach Suite, Misasque Pluton). At the trace element level, the samples analyzed are distinguished by their very low contents in Sr (13 to 43 ppm), Ba (18 to 98 ppm) and V (below the detection limit). The Martel Pluton is peraluminous and similar to S-type granitoids (Maniar and Piccoli, 1989). It is primarily of transitional affinity (Ross and Bédard, 2009). In the diagram Y+Nb vs. Rb (Pearce et al., 1984), rocks of the Martel Pluton plot in the field of volcanic arc granites.

The rare earths diagram is relatively flat, except for a large negative Eu anomaly. The profiles show a slight enrichment in heavy rare earth elements because of garnet in the rock. In addition, the total concentration of rare earth elements is much lower than that of other granites in the area, with contents ranging from 18 to 39 ppm.

  

 

 

 

 

 

Thickness and Distribution

The Martel Pluton was observed in the extreme west of the terrain of the Otish Mountains, over about 15 km. It is therefore located in the western portion of NTS sheet 33A01 and likely continues in sheet 33A02. 

Dating

None.

Stratigraphic Relationship(s)

Map relationships indicate that the Martel Pluton developed after the Barou Intrusion (nAbru). It is also posterior to the Laguiche Complex (nAlgi). Contacts are intrusive with these two units. The Martel Pluton is also cut by a diabase dyke belonging to the Mistassini Dyke Swarm (Namib). 

Paleontology

Does not apply.

References

Author(s)TitleYear of PublicationHyperlink (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 Mistassini, municipalité Eeyou Istchee Baie-James, Québec, Canada. Ministère de l’Énergie et des Ressources naturelles, Québec.2018Bulletin géologiQUE
HOCQ, M.Géologie de la région des lacs Campan et Cadieux, Territoire-du-Nouveau-Québec. Ministère des Ressources naturelles, 188 pages.1985ET 83-05
MANIAR, P. D. – PICCOLI, P. M.Tectonic discrimination of granitoids. Geological Society of America Bulletin, volume 101, pages 635-643.1989Source
MCDONOUGH, W. F. – SUN, S. S.The composition of the earth. Chemical Geology, volume 120, pages 223-253.1995Source
PEARCE, J. A. – HARRIS, N. W. – TINDLE, A. G.Trace element discrimination diagrams for the tectonic interpretation of granitic rocks. Journal of Petrology, volume 25, pages 956-983.1984Source
ROSS, P.-S. – BÉDARD, J. H.Magmatic affinity of modern and ancient subalkaline volcanic rocks determined from trace-element discriminant diagrams. Journal Canadien des Sciences de la Terre, volume 46, pages 823-839.2009Source
7 novembre 2018