Lac Doré granophyric zone
Stratigraphic label: [narc]ldg
Map symbol: nAldg

First published: 1 February 2019
Last modified:











Translation of original French




Informal subdivision(s)
Numbering does not necessarily reflect the stratigraphic position.
nAldg2 Quartz gabbro
nAldg1 Quartz-rich granophyric granitoid


Author: Allard and Caty, 1969
Age: Neoarchean
Reference section: None
Type area: The Ramsay mineralized zone, located NW of David Lake (unit nAldg1), and a hill to the NW of Clark Lake (unit nAldg2) are easily accessible areas for the study of the granophyric zone.
Geological province: Superior Province
Geological subdivision: Abitibi Subprovince
Lithology: Gabbro, quartz-rich granitoid
Type: Lithodemic
Rank: Lithodeme
Status: Informal
Use: Active




The unit was originally known as the « tonalite zone » by Allard and Caty (1969), followed by the « sodic granophyre zone » (Allard, 1976) and the « granophyre zone » (Daigneault and Allard, 1990). It was first included in the “Upper Series” (Daigneault and Allard, 1990); it now consists of an informal lithodeme within the Lac Doré Upper Unit (Leclerc et al., 2017).




Lac Doré granophyric zone 1 (nAldg1): Quartz-Rich Granophyric Granitoid

White granophyre displays very homogeneous structures and colour. Crystals range in size from 5 mm to 7 mm, but can exceed 1 cm. Plagioclase sericitization in deformation corridors highlights the presence of local bluish quartz.



Lac Doré granophyric zone 2 (nAldg2): Quartz Gabbro

To the north and west of Clark Lake, quartz becomes less abundant and granophyre gradually changes to quartz gabbro. This fine-grained leucocratic gabbro contains 1 to 5% millimetric quartz crystals.


Thickness and Distribution

The granophyric zone has been recognized on the northern flank of the Chibougamau Anticline for a distance of >53 km. On the southern flank of the same anticline, the granophyric zone outcrops for >30 km. The thickness is estimated between 150 m and 900 m (Daigneault and Allard, 1990).


A granophyre sample from the granophyric zone yielded an age of 2727 ±1.3 Ma (Mortensen, 1993).

Isotopic System Mineral Crystallization Age (Ma) (+) (-) Reference(s)
U-Pb Zircon 2727 1.3 1.3 Mortensen, 1993

Stratigraphic Relationship(s)

Rocks of the granophyric zone are overlying those of the Lac Doré Layered Unit. They cut volcanic rocks of the Obatogamau and Waconichi formations (Roy Group‘s first volcanic cycle). They are unconformably overlain by sedimentary rocks of the Opemisca Group.


Does not apply.


Author(s) Title Year of Publication Hyperlink (EXAMINE or Other)
ALLARD, G.O. Doré Lake Complex and its importance to Chibougamau geology and metallogeny. Ministère des Richesses naturelles, Québec; 486 pages, 2 plans. 1976 DPV 368
ALLARD, G.-O. – CATY, J.-L. Géologie du Quart nord-est et d’une partie du Quart sud-est du canton de Lemoine, comtés d’Abitibi-Est et de Roberval. Ministère des Richesses naturelles, Québec; 25 pages, 1 plan. 1969 RP 566
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; 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; 97 pages, 6 plans. 2017 RG 2015-03
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



16 janvier 2020