| Titre | Widespread poly-metamorphosed Archean granitoid gneisses and supracrustal enclaves of the southern Inukjuak Domain, Québec (Canada) |
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| Auteur | Greer, J; Caro, G; Cates, N L; Tropper, P; Bleeker, W ; Kelly, N M; Mojzsis, S J |
| Source | Lithos vol. 364-365, 105520, 2020 p. 1-19, https://doi.org/10.1016/j.lithos.2020.105520  Accès ouvert |
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| Année | 2020 |
| Séries alt. | Ressources naturelles Canada, Contribution externe 20200063 |
| Éditeur | Elsevier |
| Document | publication en série |
| Lang. | anglais |
| DOI | https://doi.org/10.1016/j.lithos.2020.105520 |
| Media | papier; en ligne; numérique |
| Formats | pdf; html |
| Province | Québec |
| SNRC | 34K/02; 34K/03; 34K/04; 34K/05; 34K/06; 34K/07 |
| Région | Inukjuak; Nunavik |
| Lat/Long OENS | -78.0000 -76.7500 58.5000 58.0000 |
| Sujets | Archéen; structure de la croûte; géologie du substratum rocheux; lithologie; roches métamorphiques; gneiss granitiques; roches ignées; roches intrusives; roches sédimentaires; formations ferrifères;
pétrographie; datation radiométrique; datations au uranium-plomb; datations au zircon; géochimie des roches totales; rapports sur le terrain; géochimie des éléments en trace; Domaine d'Inukjuak ; Bloc de Minto ; Province de Superior ; Bouclier
Canadien; géochronologie; géochimie; Nature et environnement; Sciences et technologie; Précambrien |
| Illustrations | cartes de localisation; cartes géolscientiques généralisées; photographies; photomicrographies; diagrammes ternaires; graphiques géochimiques; diagrammes Concordia; graphiques |
| Diffusé | 2020 04 06 |
| Résumé | (disponible en anglais seulement)
The ~12,000 km2 Inukjuak Domain in northern Québec is part of the Archean Minto Block in the northwestern Superior Province of Canada. Eoarchean (ca. N3800-3780
Ma) rocks of the Nuvvuagittuq supracrustal belt (NSB) are the best known occurrence of otherwise abundant b1 m to km-scale supracrustal enclaves dispersed throughout the Innuksuac Complex. The supracrustals are dominantly amphibolites, with
subordinate intermediate-, mafic- and ultramafic schists, quartzo-feldspathic (trondhjemitic and granodioritic) sills, dikes and sheets, banded iron-formations and quartz-pyroxene ± magnetite rocks, and (detrital) fuchsitic quartzites. Supracrustal
assemblages are in turn hosted by variably deformed granite-granitoid gneisses metamorphosed to amphibolite facies. Locally, retrogression is expressed as pervasive chloritization and development of jaspilite box veinings. This metamorphic history
precludes preservation of original fragile microfossil shapes. Despite its importance as one of the few terranes to host Eoarchean supracrustal assemblages, limited geochronology was previously available for rocks beyond the ~8 km2 NSB. Here, we
report new major-, minor-, and trace-element geochemistry and metamorphic petrology coupled with U-Pb zircon geochronology, from rocks within and surrounding the NSB. These include the little-studied but volumetrically significant Voizel suite
gneisses. Results show that intra-NSB fold belt rocks of the Central Tonalitic Gneiss (CTG) preserve mainly ca. 3650Ma zircons. Beyond the NSB, the Voizel gneisses - previously considered contemporaneous with the CTG - are instead about 100 Myr
younger (~3550 Ma). Tonalitic (ortho) gneisses at the margin of the NSB were previously assigned a ca. 3650 Ma age, and the surrounding Boizard suite gneisses may be about 2700 Ma. We find the Boizard rocks contain inherited zircon cores up to ca.
3700 Ma, with younger overgrowths dated at ca. 2700 Ma. A tonalitic gneiss that transects another highly deformed supracrustal enclave north of the NSB - dubbed the Ukaliq Supracrustal Belt - yields maximum concordant zircon ages of 3653 ± 16 Ma
(2sigma). Detrital zircons from Ukaliq and Nuvvuagittuq quartzites and quartz-biotite schists define a maximum age of ca. 3780 Ma. No indication of U-Pb zircon ages older than about 3800 Ma exist in this terrane from our geochronological surveys. New
reconnaissance sampling of gneisses to the west of the NSB fold belt yielded more zircon-bearing rocks with ages of ca. 3760Ma. This discovery of more pre-3700 Ma rocks beyond the NSB outcrops calls attention to the existence of hitherto unidentified
but widespread scattered occurrences of Eoarchean and Paleoarchean rocks throughout the region. |
| GEOSCAN ID | 326112 |
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