La Tuque Anorthosite
Stratigraphic label: [mpro]tuq
Map symbol: mPtuq

First published: 17 January 2018
Last modified:

























Translation of original French



Informal subdivision(s)
Numbering does not necessarily reflect the stratigraphic position.
Author: Klugman, 1976
Age: Mesoproterozoic
Reference section: Anorthosite outcrop 17-MR-4064
Type area: Haut-Saint-Maurice (NTS sheet 31P10)
Geological province: Grenville Province
Geological subdivision: Allochton
Lithology: Mafic intrusive rocks
Type: Lithodemic
Rank: Lithodeme
Status: Formal
Use: Active




The La Tuque Anorthosite was introduced by Klugman (1976). Then Rondot (1978) described it as an intrusive body resembling the Langelier Anorthosite. Summer 2017 fieldwork (Moukhsil and Côté, 2018) observed it on the southern edge of NTS sheet 31P10. This intrusion consists of anorthosite and minor amounts of gabbronorite.



The La Tuque Anorthosite forms an orthopyroxene mafic intrusion with local iron oxides.



Anorthosite is white and weakly deformed. It is composed of biotite, clinopyroxene, orthopyroxene, amphibole, opaque minerals and accessory quartz. Amphibole is biotitized and plagioclase is slightly sericitized.


Gabbronorite is greyish in fresh exposure and is composed of amphibole, clinopyroxene, orthopyroxene, plagioclase, pyrrhotite, magnetite and biotite. Accessory minerals are apatite and zircon.

From a geochemical perspective, SiO2 contents range from 49.5% to 52.6% and the rare earth element (REE) diagram is more or less flat, with a slight enrichment of light REE compared to heavy REE. There is a positive europium (Eu) anomaly due to high plagioclase content. Plagioclase is of labradorite type.






Thickness and Distribution

The La Tuque Anorthosite forms a small mass (12 km2) located on the boundary between sheets 31P10 and 31P07.




Stratigraphic Relationship(s)

The unit intrudes into the Vermillon Plutonic Suite. 


Does not apply.


Author(s) Title Year of Publication Hyperlink (EXAMINE or Other)
KLUGMAN, M.A.  La Tuque Area: West half (Comte de Laviolette). Ministère des Richesses naturelles, Québec, 49 pages. 1976 DPV 370
RONDOT, J. Géologie de la région du Saint-Maurice. Ministère des Richesses naturelles, Québec, 91 pages, 2 cartes. 1978 DPV 594

Levé géologique dans la Province de Grenville, au nord de La Tuque, régions de la Mauricie et du Saguenay-Lac-Saint-Jean (région du lac Borgia). Ministère de l’Énergie et des Ressources naturelles, Québec.

2018 Bulletin géologiQUE


29 octobre 2018