Lac Doré Layered Unit
Stratigraphic label: [narc]cdl
Map symbol: nAcdl

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: Reference strippings of the Blackrock-Zone Armitage and Vanadium-Lac Doré deposits
Type area: SE 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 Lac Doré large stratiform and differentiated mafic to ultramafic intrusion was originally identified as the Lac Doré Complex (Allard, 1956; Allard, 1976). This name, which emphasized the analogy with Bushveld or Stillwater-type layered stratiform complexes, 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 Layered Unit includes the layered zone and the ferrodiorite zone.


Thickness and Distribution

The Lac Doré Layered Unit occurs as discontinuous klippes on the north side of the Chibougamau Anticline. On the southern flank of the same anticline, the Lac Doré Layered Unit outcrops for a distance of ~30 km. The layered zone’s thickness varies between 100 to 450 m, while that of the ferrodiorite zone is undetermined due to the structural repetition of units (Daigneault and Allard, 1990).



A quartz pyroxenite sample from the layered zone (Lac Doré Layered Unit) yielded an age of 2728.3 +1.2/-1.1 Ma (Mortensen, 1993). 

Isotopic System Mineral Crystallization Age (Ma) (+) (-) Reference(s)
U-Pb Zircon 2728.3 1.2 1.1 Mortensen, 1993

Stratigraphic Relationship(s)

Rocks of the Lac Doré Lake Layered Unit are overlying those of the Lac Doré Lower Unit. They are overlain by rocks of the Lac Doré Upper Unit. They cut mafic volcanic rocks of the Obatogamau Formation (Roy Group‘s first volcanic cycle).


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, 486 pages, 2 plans. 1976 DPV 368
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, 290 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, 6 plans. 2017 RG 2015-03


Code stratigraphique nord-américain. Ministère de l’Énergie et des Ressources, Québec; DV 86-02, 76 pages. 1986 DV 86-02
MORTENSEN, J.K. U-Pb geochronology of the eastern Abitibi subprovince. Part 1: Chibougamau – Matagami – Joutel region. Canadian Journal of Earth Sciences; volume 30, pages 11–28. 1993 Source
NORTH AMERICAN STRATIGRAPHIC COMMISSION ON STRATIGRAPHIC NOMENCLATURE (NASC) North American Stratigraphic Code. AAPG Bulletin; volume 29, pages 1547–1591. 2005 Source



16 janvier 2020