Français
 
Qimussinguat Complex
Stratigraphic label: [narc]qim
Map symbol: nAqim
 

First published: 30 May 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.
 
nAqim2  Hornblende gabbronorite and biotite gabbronorite
nAqim1 Gneissic or foliated orthopyroxene-clinopyroxene tonalite

 

 

 

 
Author(s): Madore et al., 1999
Age: Neoarchean
Stratotype: None
Type area: Peters Lake area (NTS sheet 24M)
Geological province: Superior Province
Geological subdivision: Minto Subprovince
Lithology: Orthopyroxene intrusive and metamorphic rocks
Category: Lithodemic
Rank: Complex
Status: Formal
Use: Active

 

 

Background

The Qimussinguat Complex was introduced by Madore et al. (1999, 2000) in the Peters Lake area (sheet 24M) to describe lithological assemblages corresponding to a strong subcircular magnetic anomaly within the Douglas Harbour Domain. It takes its name from Qimussinguat Lakes about 40 km away to the NW of Peters Lake. The complex then consisted mainly of orthopyroxene intrusive and metamorphic rocks (gneissic orthopyroxene-clinopyroxene tonalite [Aqim4], and hornblende gabbronorite and biotite gabbronorite [Aqim6]), but also included migmatitic granite (Aqim5), granodiorite and granite intrusions (Aqim5a), small ultramafic bodies (Aqim3a), klippes of granulitic supracrustal rocks (mafic gneiss/granulitic metavolcanics [Aqim3] and biotite-garnet paragneiss [Aqim2]), and iron formation layers (Aqim1). The Qimussinguat Complex thus defined had been extended in the Arnaud River (sheet 25D; Madore and Larbie, 2000, 2001) and Klotz Lake (sheet 35A; Madore et al., 2001, 2002) areas. Simard et al. (2008) redefined the Qimussinguat Complex to retain only orthopyroxene rocks within the unit. Supracrustal rocks, ultramafic rocks and iron formations were assigned to the Arnaud Complex, whereas granodiorites and granites were assigned to the Leridon Suite.

 

Actual Unit Simard (2008) Simard et al. (2008) Madore et al. (2001, 2002) Madore and Larbie (2000, 2001) Madore et al. (1999, 2000)
nAqim1 Aqim Aqim

Aqim4

Aqim4 Aqim4
nAqim2   Aqim6 Aqim6
nAlrd1 (Leridon Suite)       Aqim5a Aqim5
mAarn1 (Arnaud Complex)       Aqim3a  
mAarn2     Aqim3   Aqim3
mAarn4         Aqim1
mAarn5         Aqim2

 

 

Description

The Qimussinguat Complex consists of orthopyroxene orthogneiss and charnockitic intrusions mainly of tonalitic composition and more rarely of granodioritic, granitic and dioritic composition (Madore et al., 1999, 2000; Madore and Larbie, 2000, 2001; Madore et al., 2001, 20002; Simard, 2008; Simard et al., 2008). It has been divided into two informal units (Simard, 2002a, b; MNRF, 2008): gneissic or foliated orthopyroxene-clinopyroxene tonalite (nAqim1, formerly Aqim4 [Madore et al., 1999, 2000; Madore and Larbie, 2000, 2001; Madore et al., 2001, 2002]), and hornblende gabbronorite and biotite gabbronorite (nAqim2, formerly Aqim6 [Madore et al., 1999, 2000; Madore and Larbie, 2000, 2001]).

 

 

Qimussinguat Complex 1 (nAqim1) : Gneissic or Foliated Orthopyroxene-Clinopyroxene Tonalite

Gneissic or foliated tonalite (granulitic orthogneiss) characterized by the presence of two pyroxenes (clinopyroxene and orthopyroxene) is the main lithology of the Qimussinguat Complex. It is inserted between centimetre-thick dioritic layers that represent 1-25% of the rock. This type of gneiss constitutes ~70% of the unit. Tonalite also contains trondhjemitic, granodioritic and granitic phases. It contains 1-10% small mafic enclaves (<2 m2) consisting of metagabbro, amphibolite or mafic gneiss. In outcrops, the rock is heterogeneous, migmatized and made up of 10-60% felsic mobilisate, which is present as centimetre-to-decametric-thick discontinuous veins.

In thin sections, gneissic or foliated tonalite and its associated phases are granoblastic and medium grained (0.5-2.0 mm). Despite recrystallization, these rocks locally exhibit a more massive and coarser-grained (1-4 mm) relic texture of magmatic origin. In gneissic facies, ferromagnesian minerals tend to concentrate as porphyroblasts in dioritic bands. These ferromagnesian minerals are reddish biotite, clinopyroxene, orthopyroxene and green hornblende. Garnet porphyroblasts (<2%) are observed in a few places. Between 1 and 10% of opaque minerals, mostly magnetite, are disseminated in the rock. The most common secondary minerals are apatite and zircon.

 

Qimussinguat Complex 2 (nAqim2) : Hornblende Gabbronorite and Biotite Gabbronorite

A few small gabbronorite intrusive bodies, not exceeding 20 km in diameter, are found mainly inside gneissic or foliated tonalite (unit nAqim1) as metric enclaves surrounded by felsic mobilisate, thus defining an agmatitic texture. These gabbronorite bodies are also found as enclaves in granulitic rocks. Based on petrographic and geochemical observations, two types of gabbronorite can be identified: hornblende gabbronorite and biotite gabbronorite. In thin sections, these rocks display a heterogranular granoblastic texture with grain sizes ranging from 1 to 5 mm. Locally, remnants of subophitic textures are observed, but primary igneous textures are usually replaced by recrystallization textures.

Both types of gabbronorite are mainly composed of clinopyroxene (10-35%), orthopyroxene (5-30%) and plagioclase (40-55%). Hornblende gabbronorite contains 15-30% green hornblende partially replacing pyroxenes and a small amount of biotite (1-5%). This first type of gabbronorite is usually deformed and displays a well-developed foliation. Biotite gabbronorite contains 5-15% biotite and <5% hornblende. This second type of gabbronorite is less deformed than the previous and locally forms dykesdisplaying  an igneous porphyraceous texture. Secondary minerals observed in both types of gabbronorite are apatite (1-3%) and quartz (1-2%). These rocks contain 5-15% disseminated opaque minerals, mainly magnetite and ilmenite.

 

Thickness and distribution

The Qimussinguat Complex is a subcircular unit that covers a large area, corresponding to a magnetic high, in the Douglas Harbour Domain (Madore et al., 1999, 2000; Simard et al., 2008; Simard, 2008). It forms a strip 45-50 km wide at the ends to 90 km in the centre which begins in the northern part of sheet 24M and continues towards the NNW over 150 km.

 

Dating

U-Pb dating on zircons of a massive granulitic charnockitic gneiss from the Peters Lake area yielded crystallization ages of 2734 ±3 and 2738 ±7 Ma, as well as an inherited age of 2798 ±15 Ma (David et al., 2009).

Unit Sample Number Isotopic System Mineral Crystallization Age (Ma) (+) (-) Inherited Age (Ma) (+) (-) Reference(s)
nAqim1

1998-JB-3230-A

Pb-Pb Zircon

2734

3

3

2798 15 15 David et al., 2009
2738 7 7

 

Stratigraphic Relationship(s)

The Qimussinguat Complex has lithological, geochronological and magnetic characteristics comparable to the Troie Complex, located just to the south (Madore et al., 1999, 2000; Simard et al., 2008; Simard, 2008). It is likely that the two complexes are genetically linked. The period of intrusive rocks’ emplacement for these two complexes is approximately 2740 to 2720 Ma. This period also corresponds to the emplacement of several intrusive orthopyroxene rock units in the Minto Subprovince (Simard et al., 2008). However, the Qimussinguat and Troie complexes contain much more metamorphic rocks than other pyroxene units of the Minto Subprovince.

Paleontology

Does not apply.

References

 

Publications Available Through SIGÉOM Examine

DAVID, J., MAURICE, C., SIMARD, M. 2009. DATATIONS ISOTOPIQUES EFFECTUEES DANS LE NORD-EST DE LA PROVINCE DU SUPERIEUR – TRAVAUX DE 1998, 1999 ET 2000. MRNF. DV 2008-05, 92 pages.

MADORE, L., BANDYAYERA, D., BEDARD, J H., BROUILLETTE, P., SHARMA, K.N.M., BEAUMIER, M., DAVID, J. 1999. GEOLOGIE DE LA REGION DU LAC PETERS (24M). MRN. RG 99-07, 43 pages and 1 plan.

MADORE, L., BANDYAYERA, D., BEDARD, J H., BROUILLETTE, P., SHARMA, K N M., BEAUMIER, M., DAVID, J. 2000. GEOLOGY OF THE LAC PETERS AREA (24M). M R N. RG 99-16, 43 pages and 1 plan.

MADORE, L., LARBI, Y. 2000. GEOLOGIE DE LA REGION DE LA RIVIERE ARNAUD (SNRC 25D) ET DES REGIONS LITTORALES ADJACENTES (SNRC 25C, 25E, 25F). MRN. RG 2000-05, 39 pages and 4 plans.

MADORE, L., LARBI, Y. 2001. GEOLOGY OF THE RIVIERE ARNAUD AREA AND ADJACENT COASTAL AREAS. MRN. RG 2001-06, 35 pages and 4 plans.

MADORE, L., LARBI, Y., SHARMA, K.N.M., LABBE, J Y., LACOSTE, P., DAVID, J., BROUSSEAU, K., HOCQ, M. 2001. GEOLOGIE DE LA REGION DU LAC KLOTZ (35A) ET DU CRATERE DU NOUVEAU QUEBEC (1/2 SUD DE 35H). MRN. RG 2001-09, 46 pages and 2 plans.

MADORE, L., LARBI, Y., SHARMA, K N M., LABBE, J Y., LACOSTE, P., DAVID, J., BROUSSEAU, K., HOCQ, M. 2002. GEOLOGY OF THE LAC KLOTZ (35A) AND THE CRATERE DU NOUVEAU-QUEBEC (SOUTHERN HALF OF 35H) AREAS. MRN. RG 2002-05, 45 pages and 2 plans.

MRNF 2008. COMPILATION GEOLOGIQUE 1/250 000, 35A – LAC KLOTZ. In MRNF. 2010. CARTE(S) GÉOLOGIQUE(S) DU SIGEOM – feuillet 35a. CG SIGEOM35A, 1 plan.

SIMARD, M. 2002a. GÉOLOGIE 1/250 000, 24M – LAC PETERS. In MRNF. 2010. CARTE(S) GÉOLOGIQUE(S) DU SIGEOM – feuillet 24m. CG SIGEOM24M, 5 plans.

SIMARD, M. 2002b. GÉOLOGIE 1/250 000, 25D – RIVIÈRE ARNAUD-PAYNE. In MRNF. 2010. CARTE(S) GÉOLOGIQUE(S) DU SIGEOM – feuillet 25d. CG SIGEOM25D, 6 plans.

SIMARD, M. 2008. LEXIQUE STRATIGRAPHIQUE DES UNITES ARCHEENNES DU NORD-EST DE LA PROVINCE DU SUPERIEUR. MRNF. DV 2008-03, 107 pages.

SIMARD, M., LABBE, J Y., MAURICE, C., LACOSTE, P., LECLAIR, A., BOILY, M. 2008. SYNTHESE DU NORD-EST DE LA PROVINCE DU SUPERIEUR. MRNF. MM 2008-02, 198 pages and 8 plans.

 

 

Suggested Citation

Ministère de l’Énergie et des Ressources naturelles (MERN). Qimussinguat Complex. Quebec Stratigraphic Lexicon. https://gq.mines.gouv.qc.ca/lexique-stratigraphique/province-du-superieur/complexe-de-qimussinguat_en [accessed on Day Month Year].

 

Contributors

First publication

Céline Dupuis, P. Geo., Ph.D. celine.dupuis@mern.gouv.qc.ca (redaction, French and English versions)

Mehdi A. Guemache, P. Geo., Ph.D. (coordination); Charles St-Hilaire, GIT, M.Sc. (critical review and editing); Ricardo Escobar Moran (HTML editing). 

 

 

 

23 août 2021