Lac Doré Lower Unit
Stratigraphic label: [narc]cdi
Map symbol: nAcdi

First published: 12 December 2018
Last modified:


























Translation of original French



Informal subdivision(s)
Numbering does not necessarily reflect the stratigraphic position.
Author: Leclerc et al., 2017
Age: Neoarchean
Reference section: None
Type area: The Lac Doré Lower Unit outcrops very well along Campbell Road and Portage Island Road, north of Chibougamau Lake (northern portion of NTS sheet 32G16).
Geological province: Superior Province
Geological subdivision: Abitibi Subprovince
Lithology: Mafic to ultramafic intrusive rocks
Type: Lithodemic
Rank: Lithodeme
Status: Formal
Use: Active




The large stratiform and differentiated mafic-ultramafic Lac Doré intrusion was originally identified as the Lac Doré Complex (Allard, 1956; Allard, 1976). This name emphasized the analogy with Bushveld or Stillwater-type layered stratiform complexes and was maintained by Daigneault and Allard (1990) for historical reasons, despite the recommendations of the North American Stratigraphic Code to use the term “complex” (Articles 37d and 38; MER, 1986). The most recent version of the North American Stratigraphic Code (NASC, 2005) maintains that it is incorrect to use the term “complex” to refer to “various types of rock belonging to a single class”. For this reason, we are proposing to amend the nomenclature of the Lac Doré Complex in accordance with sections 31 to 41 of the North American Stratigraphic Code: (a) the Lac Doré Complex is renamed the Lac Doré Intrusive Suite (referred to in the rest of the text as LDIS); (b) the Lac Doré Lower Series, Lac Doré Layered Series and Lac Doré Upper Series become the Lac Doré Lower Unit, Lac Doré Layered Unit and Lac Doré Upper Unit respectively; and (c) the Layered Zone, included in the Layered Series (former nomenclature), is now referred to as the “layered zone” and is considered an informal lithodeme.



The Lac Doré Lower Unit includes the magnetitite subzone, anorthositic zone and peridotitic subzone.


Thickness and Distribution

The Lac Doré Lower Unit was identified on the northern flank of the Chibougamau Anticline over a distance of >53 km. On the southern flank of the same anticline, the Lac Doré Lower Unit outcrops for a distance of >42 km. The thickness is estimated between 2500 and 3600 m (Daigneault and Allard, 1990).



Stratigraphic Relationship(s)

Rocks of the Lac Doré Lower Unit cut volcanic rocks of the Obatogamau and Waconichi formations (Roy Group‘s first volcanic cycle). They are overlain by the Lac Doré Layered Unit and intruded by the Chibougamau Pluton. They are also cut by a granodiorite unit in the Grenville Front Transitional Zone (Bandyayera et al., 2005). 


Does not apply.


Author(s) Title Year of Publication Hyperlink (EXAMINE or Other)
ALLARD, G.O. The geology of a portion of McKenzie Township, Chibougamau District, Quebec. John Hopkins University; doctoral thesis, 168 pages. 1956
ALLARD, G.O. Doré Lake Complex and its importance to Chibougamau geology and metallogeny. Ministère des Richesses naturelles, Québec; DPV 368, 446 pages, 2 plans. 1976 DPV 368
BANDYAYERA, D. – CADÉRON, S. – HOULE, P. – SHARMA, K.N.M. Géologie de la région du lac Mitchisso (SNRC 32H13). Ministère des Ressources naturelles et de la Faune, Québec; RP 2005-04, 12 pages, 4 plans. 2005 RP 2005-04
DAIGNEAULT, R. – ALLARD, G.O. Le Complexe du lac Doré et son environnement géologique (région de Chibougamau – Sous-province de l’Abitibi). Ministère de l’Énergie et des Ressources, Québec; MM 89-03, 275 pages. 1990 MM 89-03
LECLERC, F. – ROY, P. – HOULE, P. – PILOTE, P. – BÉDARD, J.H. – HARRIS, L.B. – McNICOLL, V.J., VAN BREEMEN, O. – DAVID, J. – GOULET, N. Géologie de la région de Chibougamau. Ministère de l’Énergie et des Ressources naturelles, Québec; RG 2015-03, 97 pages, 3 plans. 2017 RG 2015-03
MINISTÈRE DE L’ÉNERGIE ET DES RESSOURCES (MER) Code stratigraphique nord-américain. Ministère de l’Énergie et des Ressources, Québec; DV 86-02, 58 pages.
1986 DV 86-02
NORTH AMERICAN STRATIGRAPHIC COMMISSION ON STRATIGRAPHIC NOMENCLATURE (NASC) North American Stratigraphic Code. AAPG Bulletin; volume 29, pages 1547–1591. 2005 Source


16 janvier 2020