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Boullé Complex
Stratigraphic label: [narcbue
Map symbol: nAbue

First published: 20 October 2016
Last modified: 10 December 2020

 

 

 

  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.
 
None
 
Author: Charette et al., 2016
Age: Archean; Paleoproterozoic
Stratotype: None
Type area: Jeannin Lake area (NTS sheet 24B)
Geological province: Churchill Province
Geological subdivision: Rachel-Laporte Lithotectonic Domain
Lithology: Porphyraceous monzonite and monzodiorite
Category: Lithodemic
Rank: Complex
Status: Formal
Use: Active
Related unit(s)

None

Background

The Boullé Complex was introduced in the Jeannin Lake area (Charette et al., 2016) to group a package of porphyraceous intermediate intrusions circumscribed to a thrust sheet of the Rachel-Laporte Lithotectonic Domain; hence it is a structural complex.

 

Description

The Boullé Complex consists of K-feldspar porphyritic intermediate intrusive rocks and syenogranite, all moderately magnetic and well foliated to protomylonitic. The different facies are generally observed together on outcrops and it was not possible to differentiate them at mapping scale 1:250 000.

Porphyraceous rock contains 15-20% microcline phenocrystals 0.5-2 cm long. Their composition varies from monzonite to quartz monzodiorite, including monzodiorite. Monzogranite is also locally observed. Intermediate rocks are partially recrystallized and dark grey with pink flecks in fresh exposure. They contain 25-35% ferromagnesian minerals including greenish brown biotite, locally chloritized, and hornblende. K-feldspar is also found in the matrix. Quartz is sparse (<3%) and plagioclase is variably sericitized. Myrmekitic textures are common and accessory minerals are relatively abundant. These include sphene, epidote, opaque minerals, apatite and allanite. Monzogranite is pale pink and contains up to 30% centimetric microcline phenocrystals and only 10% ferromagnesian minerals consisting of biotite.

Syenogranite is partially recrystallized, medium grained, very well foliated or lineated, and pink. It contains 3-7% greenish brown biotite, locally chloritized, which forms small millimetric to centimetric clusters. Quartz regularly forms small, discontinuous millimetric bands and exhibits undulatory extinction in thin sections. Muscovite and hematite are observed as accessory minerals. Centimetre to metre-wide layers or elongated enclaves of the porphyraceous facies are commonly observed in syenogranite.

 

Thickness and distribution

The Boullé Complex is located in the NW part of the Jeannin Lake area (Charette et al., 2016), where it forms a thrust sheet ~30 km long by 8 km wide elongated in a NW-SE direction within the Rachel-Laporte Lithotectonic Domain. It covers an estimated area of 149 km2.

 

Dating

An age of 2690 Ma was obtained in a monzonite of the Boullé Complex. Protoliths of gneiss or deformed intrusive rocks that form thrust sheets of the Rachel-Laporte Domain are all Archean (2668-2883 Ma; Lafrance and Vanier). These thrust sheets are interpreted as having overthrusted Paleoproterozoic rocks during the New Quebec Orogenesis (1.82-1.77 Ga; Machado et al., 1989).

Unit Sample Number Isotopic System Mineral Crystallization Age (Ma) (+) (-) Reference(s)
nAbue 15-MO-7075 U-Pb Zircon 2690 4 4 Rayner et al., 2017

Stratigraphic Relationship(s)

The Boullé Complex consists of Archean rocks circumscribed to a thrust sheet from the Archean basement. This sheet is believed to have been emplaced within Paleoproterozoic volcano-sedimentary rocks of the Rachel-Laporte Lithotectonic Domain during the New Quebec Orogenesis. The Boullé Complex is therefore in fault contact with volcano-sedimentary rocks of the Laporte Supersuite.

Paleontology

Does not apply.

References

Author(s) Title Year of Publication Hyperlink (EXAMINE or Other)
CHARETTE, B. – LAFRANCE, I. – MATHIEU, G. Géologie de la région du lac Jeannin (SNRC 24B). Ministère de l’Énergie et des Ressources naturelles, Québec. 2016

Electronic geological report

DIMROTH, E. Région de la Fosse du Labrador, Ministère des Richesses naturelles, Québec; RG 193, 396 pages. 1978 RG 193
LAFRANCE, I. – SIMARD, M. – BANDYAYERA, D. Géologie de la région du lac Saffray (SNRC 24G-24F). Ministère des Ressources naturelles, Québec; RG 2014-02, 49 pages. 2014 RG 2014-02
LAFRANCE, I. – VANIER, M.-A. Domaine lithotectonique de Rachel-Laporte, sud-est de la Province de Churchill, Québec, Canada : synthèse de la géologie. Ministère de l’Énergie et des Ressources naturelles. 2021 BG 2021-01
MACHADO, N. – GOULET, N. – GARIÉPY, C. U-Pb geochronology of reactivated Archean basement and of Hudsonian metamorphism in the northern Labrador Trough. Canadian Journal of Earth Sciences; volume 26, pages 1-15. 1989 Source
RAYNER, N.M. – LAFRANCE, I. – CORRIGAN, D. – CHARETTE, B. New U-Pb zircon ages of plutonic rocks from the lac Jeannin area, Quebec: an evaluation of the Kuujjuaq domain and Rachel-Laporte zone. 2017 Source
SIMARD, M. – LAFRANCE, I. – HAMMOUCHE, H. – LEGOUIX, C. Géologie de la région de Kuujjuaq et de la Baie d’Ungava (SNRC 24J et 24K). Ministère des Ressources naturelles, Québec; RG 2013-04, 60 pages. 2013 RG 2013-04

 

 

 

11 février 2020