Whitefish Intrusion
Stratigraphic label: [narc]wf
Map symbol: nAwf

First published: 15 September 2017
Last modified:




Translation of original French



Informal subdivision(s)
Numbering does not necessarily reflect the stratigraphic position.
nAwf2 Monzonite
nAwf1 Purple gabbro
Author: Leclerc and Caron-Côté, 2017
Age: Precambrian / Archean / Neoarchean
Reference section:  
Type area: The Whitefish Intrusion (nAwf) outcrops mainly between the Quénonisca and Rocher lakes (NTS 32K09 and 32K10).
Geological province: Superior Province
Geological subdivision: Opatica Subprovince
Lithology: Purple gabbro, monzonite
Unit type: Lithodemic
Rank: Lithodeme
Status: Formal
Use: Active




The Whitefish Intrusion is a lithodeme introduced by Leclerc and Caron-Côté (2017) to describe an intrusion located west of Rocher Lake which belongs to the Rocher-Quénonisca Intrusive Suite. This unit is elongated in a NE-SW direction just over 25 km long by 1.5 to 5 km wide.


The Whitefish intrusion is divided into two informal units: a purple gabbro unit (nAwf1) and a monzonite unit (nAwf2). 

Whitefish Intrusion 1 (nAwf1): Purple Gabbro

The dominant unit of the Whitefish Intrusion is a homogeneous, massive, medium-grained gabbro characterized by dark gray to purple plagioclase crystals. The rock comprises 20 to 45% mafic minerals and has a well-preserved subophitic structure (Franconi, 1974). Minerals observed in thin sections are plagioclase, alkali feldspar, clinopyroxene and orthopyroxene, biotite, apatite and opaque minerals. Olivine appears only locally. Geochemical analyses indicate a calc-alkaline affinity (Bandyayera and Sharma, 2001). 

Whitefish Intrusion 2 (nAwf2): Monzonite

Monzonite is massive and medium-grained with potassium feldspar phenocrysts. It has a pinkish to greyish color (Brisson et al., 1998). It also contains 10 to 20% of mafic minerals (biotite and hornblende). Under the microscope, plagioclase and microcline form perthitic intergrowths and clinopyroxene is almost entirely replaced by hornblende. Accessory minerals include iron oxides, apatite, quartz, biotite and titanite (Franconi, 1974). 

Thickness and distribution

The Whitefish Intrusion forms an intrusive NE-SW unit a little over 25 km long by 1.5 to 5 km wide. It cuts tonalites of the Salamander Intrusive Suite (nAsam), as well as volcano-sedimentary rocks of the Rocher Complex (nAroc) and Broadback Group (nAbk). 



Stratigraphic Relationship(s)

The Whitefish Intrusion cuts both tonalites of the Salamandre Intrusive Suite and volcano-sedimentary rocks of the Rocher Complex and Broadback Group. The latter also occur as xenoliths in purple gabbro of the nAwf1 unit. The Rocher-Quénonisca Suite is thus considered a late-tectonic intrusion by Bandyayera and Sharma (2001).


Does not apply.


Author(s) Title Year of Publication Hyperlink (EXAMINE or Other)
BANDYAYERA, D. – SHARMA, K.N.M Minéralisations en Ni-Cu ± EGP dans la bande volcano-sédimentaire de Frotet-Evans (SNRC 32K). Ministère des Ressources naturelles, Québec; MB 2001-06, 74 pages. 2001 MB 2001-06
BRISSON, H. – GOSSELIN, C. – FALLARA, F. – GAULIN, R. – DION, D.-J. Géologie de la région du lac Rocher (SNRC 32K/09). Ministère des Ressources naturelles, Québec; RG 98-05, 22 pages. 1998 RG 98-05
FRANCONI, A. Géologie de la moitié ouest de la bande volcano-sédimentaire de Frotet-Evans, territoire d’Abitibi, rapport intérimaire. Ministère des Richesses naturelles, Québec; DP 265, 141 pages. 1974 DP 265
LECLERC, F. – CARON-CÔTÉ, E. Levé géologique dans la Sous-province d’Opatica au nord-est de Matagami (Région du lac Amisquioumisca). Ministère de l’Énergie et des Ressources naturelles, Québec. 2017
Bulletin géologiQUE



27 février 2018