Druillon Suite
Stratigraphic label: [narc]dru
Map symbol: nAdru

First published: 16 August 2019
Last modified:




  DISCLAIMER: This English version is translated from the original French. In case of any discrepancy, the French version shall prevail. 

Informal subdivision(s)
Numbering does not necessarily reflect the stratigraphic position.
nAdru2 Amphibole granite
nAdru1 Monzodiorite and diorite
Author(s): Thériault et Chevé, 2001
Age: Neoarchean
Stratotype: None
Type area: Hurault Lake area (NTS sheet 23L)
Geological province: Superior Province
Geological subdivision: La Grande Subprovince
Lithology: Monzodiorite, quartz monzodiorite, quartz monzonite
Category: Lithodemic
Rank: Suite
Status: Formal
Use: Active


The Druillon Suite was introduced by Thériault and Chevé (2001) to describe a few small intrusions of monzodiorite, quartz monzodiorite and quartz monzonite, all porphyraceous, located in the NW corner of the Hurault Lake area (NTS sheet 23L). Simard et al. (2008) reassigned to the Druillon Suite the three small monzodiorite, diorite and monzonite intrusions of the Turbar Suite and the two small amphibole granite intrusions of the Ossant Suite, located SE of the Bienville Lake area (sheet 33P), just NW of the Hurault Lake area (sheet 23L). According to Simard (2008), these intrusions are similar to other Druillon Suite intrusions. Simard et al. (2008) interpreted granites of the Ossant Suite as a felsic phase linked to intermediate rocks of the Turbar and Druillon suites. These changes led to the abandonment of the Ossant and Turbar suites.



Simard (2008) describes the Druillon Suite as consisting of monzodiorite, quartz monzodiorite, diorite, monzonite and quartz monzonite forming small intrusions in the NE La Grande Province. Rocks are homogeneous, of various colours, massive to slightly foliated and characterized by a porphyraceous texture. They contain varying amounts of ferromagnesian mineral clusters composed mainly of hornblende, biotite, clinopyroxene and, locally, orthopyroxene. The unit also includes some homogeneous, massive to slightly foliated porphyraceous granite intrusions characterized by the presence of sodic amphibole (formerly the Ossant Suite).


Druillon Suite 1 (nAdru1) : Monzodiorite and Diorite

According to Gosselin et al. (2002), unit nAdru1 consists of coarse-grained antiperthitic feldspar monzodiorite, monzonite and diorite. Thériault and Chevé (2001) noted that monzonitic and monzodioritic rocks are generally composed of plagioclase (50-60%), K-feldspar (20-35%), quartz (10-15%), hornblende (5-15%), clinopyroxene (5-10%) and biotite (5%). The rock has a characteristic satin appearance, although its colour varies widely; the most common colours being bluish grey, beige and pink (Gosselin et al., 2002). In addition, it is distinguished by its coarse grain size and antiperthitic feldspar porphyraceous texture visible in staining. This unit is massive or has a slight foliation marked by tabular minerals, mainly feldspar and amphibole.

In thin sections, monzodiorite and diorite are composed mainly of feldspar with fine antiperthitic to perthitic exsolution textures that indicate crystallization at high temperature (Gosselin et al., 2002). Thériault and Chevé (2001) noted that plagioclase forms subhedral crystals and phenocrystals that are slightly recrystallized and moderately sericitized. In addition, K-feldspar crystals occur in two different habits, namely, as anhedral grains interstitial to plagioclase and quartz, or forming centimetric phenocrystals. Quartz is typically interstitial and partially granoblastic. Ferromagnesian minerals (5-35%) form compact, interstitial grains to coarse feldspars (Gosselin et al., 2002). According to Thériault and Chevé (2001): “poikilitic (or poikiloblastic) crystals of clinopyroxene highly retromorphosed to bluish green hornblende constitute the two main ferromagnesian phases, while brownish to olive-green biotite is partially altered to chlorite.” The most abundant ferromagnesian minerals are hornblende and biotite, while clinopyroxene and orthopyroxene occur in lower amounts. Hornblende forms the core of ferromagnesian mineral clusters. Biotite occurs as inclusions or rims around other ferromagnesian minerals. Magnetite, ilmenite, titanite, apatite and sulphides are also associated with these clusters (Gosselin et al., 2002).


Druillon Suite 2 (nAdru2) : Amphibole Granite

Unit nAdru2 forms kilometric amphibole granite intrusions emplaced and confined within the Brésolles Suite (Gosselin et al., 2002). The old Ossant Suite is recognized by its pink and grey colour, which gives it a spotted appearance. Granite is homogeneous, massive to very slightly foliated and porphyraceous. The rock is composed mainly of perthitic feldspar phenocrystals in a quartz-plagioclase matrix.

According to Gosselin et al. (2002), this unit contains 5-10% ferromagnesian minerals, mostly sodic amphibole (5-8%) in clusters. Biotite and chlorite rim or replace amphibole. Clusters also include epidote, allanite, apatite, titanite and iron oxides.


Thickness and distribution

Druillon Suite intrusions extend ~100 km along a NW-SE axis and over width of ~50 km along a NE-SW axis.



Stratigraphic Relationship(s)

According to Simard (2008): “The Druillon Suite was not dated. Gosselin et al. (2002) considered intrusions of the Turbar and Ossant suites to be relatively young due to their massive, homogeneous and minimally deformed appearance. Thériault and Chevé (2001) mentioned that Druillon Suite intrusions could be associated with the same magmatic event responsible for the formation of the Maurel Suite (2707-2685 Ma). Simard et al. (2008) associate an age between 2705 Ma and 2680 Ma to the Druillon Suite.”


Does not apply.


Publications available through SIGÉOM Examine

GOSSELIN, C., ROY, P., DAVID, J., 2002. GEOLOGIE DE LA REGION DU LAC BIENVILLE (33P). MRN; RG 2002-11, 40 pages, 1 plan.

SIMARD, M., 2008. Lexique stratigraphique des unités archéennes du nord-est de la Province du Supérieur. MRNF; DV 2008-03, 107 pages.


THERIAULT, R., CHEVE, S., 2001. GEOLOGIE DE LA REGION DU LAC HURAULT (23L). MRN; RG 2000-11, 51 pages, 1 plan.


Suggested Citation

Ministère de l’Énergie et des Ressources naturelles (MERN). Druillon Suite. Quebec Stratigraphic Lexicon. [accessed on Day Month Year].


First publication

Sarah Blais (redaction)

Mehdi A. Guemache, P. Geo., Ph.D. (coordination and critical review); Simon Auclair, P. Geo., M.Sc. (editing); Céline Dupuis, P. Geo., Ph.D. (English version); Ricardo Escobar Moran (HTML editing). 

12 mai 2021