Dominique Ultramafic Suite
Stratigraphic label: [narc]dmq
Map symbol: nAdmq

First published: 4 December 2020
Last modified:









  DISCLAIMER: This English version is translated from the original French. In case of any discrepancy, the French version shall prevail. 

Informal subdivision(s)
Numbering does not necessarily reflect the stratigraphic position.
Author: Beauchamp, 2020
Age: Neoarchean
Stratotype: None
Type area: Cadieux Lake area (NTS sheet 33A02)
Geological province: Superior Province
Geological subdivision: Opatica and Opinaca subprovinces
Lithology: Ultramafic rocks
Category: Lithodemic
Rank: Suite
Status: Formal
Use: Active




Hocq (1985) mapped a number of ultramafic intrusions in NTS sheet 33A02. During mapping of the Bohier Island project (Beauchamp et al., 2018), several other small, rounded intrusions were identified in the field using magnetic anomaly maps. They have been grouped into a lithological unit of undifferentiated ultramafic intrusive rocks (Beauchamp et al., 2018). The Dominique Ultramafic Suite was created following the summer 2018 work in the Cadieux Lake area to group these intrusions (Beauchamp, 2020).



The Dominique Ultramafic Suite consists of a series of isolated rounded ultramafic intrusions. On geophysical maps, these intrusions are associated with strong positive magnetic anomalies that are particularly visible within the Laguiche Complex, which is very weakly magnetic. The following description is based solely on a few observation sites (outcrops 17-MC-3010, 17-MC-3116, 17-SB-4115, 17-JF-5015 and 18-WM-3170), since circular magnetic anomalies associated with the Dominique Ultramafic Suite are very little exposed.

Ultramafic intrusions consist of peridotite and pyroxenite that are fine to medium grained, homogeneous and highly magnetic. Rocks are also characterized by a grey-black to dark greenish alteration patina. Locally, the alteration patina is light grey. These intrusions are generally massive, although slightly foliated in some places. They contain actinolite, tremolite, serpentine, talc, magnetite, clinopyroxene and locally orthopyroxene. Orthopyroxene outcrops show orange-red zones in altered patina. Peridotite typically contains serpentinized olivine pseudomorphs. Cumulate textures are also commonly observed. Magnetite-serpentine veinlets are common in peridotite facies.


Thickness and Distribution

The various intrusions belonging to the Dominique Ultramafic Suite are located in the north part of sheets 33A01 and 33A02, and in the SE corner of sheet 33A07. They are rounded and correspond to strong circular magnetic anomalies. There are more than 20 such intrusions, generally measuring between 100 m and 1.5 km, except the larger intrusion of 2.5 km x 3 km located 3 km south of Clément Lake.



Stratigraphic Relationship(s)

The Dominique Ultramafic Suite intrudes mainly into rocks of the Laguiche Complex. In addition, two intrusive bodies from the suite intrude into volcanic rocks of the Clément Formation, which belongs to the Upper Eastmain Greenstone Belt. Hence, the suite cuts both the Opinaca and Opatica subprovinces. It is possible that the Sorbier Mafic-Ultramafic Suite may be a deformed equivalent of the Dominique Ultramafic Suite.


Does not apply.


Publications Available Through Sigéom Examine

BEAUCHAMP, A.-M. 2020. Géologie de la région du lac Cadieux, sous-provinces d’Opatica et d’Opinaca, Eeyou Istchee Baie-James, Québec, Canada. MERN. BG 2019-02, 2 plans.
BEAUCHAMP, A.-M., MASSEI, F., DAOUDENE, Y. 2018. 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, Eeyou Istchee Baie-James, Québec, Canada. MERN. BG 2018-02, 2 plans.


Suggested Citation

Ministère de l’Énergie et des Ressources naturelles (MERN). Dominique Ultramafic Suite. Quebec Stratigraphic Lexicon. [accessed on Day Month Year].



First publication

Anne-Marie Beauchamp, Eng., M.Sc. (redaction)

Mehdi A. Guemache, P. Geo., Ph.D. (coordination); Patrice Roy, P. Geo., M.Sc. (critical review); Simon Auclair, P. Geo., M.Sc. (editing); Céline Dupuis, P. Geo., Ph.D. (English version); André Tremblay (HTML editing). 




1 février 2021