|Titre||Evidence for ~40 MA transition from a forearc to a foreland basin in eastern part of Labrador Trough|
|Auteur||Henrique-Pinto, R; Guilmette, C; McNicoll, V; Bilodeau, C; Corrigan, D|
|Source||GSA Annual Meeting in Denver, Colorado, USA - 2016; Geological Society of America, Abstracts With Programs vol. 48, no. 7, 204-6, 2016 p. 1, https://doi.org/10.1130/abs/2016AM-285515|
|Séries alt.||Ressources naturelles Canada, Contribution externe 20190408|
|Éditeur||Geological Society of America|
|Réunion||GSA annual meeting; Denver, CO; US; Septembre 25-28, 2016|
|Document||publication en série|
|Media||en ligne; numérique|
|Sujets||géochronologie; Sciences et technologie; Nature et environnement|
|Programme||GEM2 : La géocartographie de l'énergie et des minéraux Zone centrale de la région d'Hudson/Ungava|
|Diffusé||2016 09 01|
|Résumé||(disponible en anglais seulement)|
The New Quebec Orogen (NQO) is a Paleo-Proterozoic supra-crustal belt that underwent reworking when the Superior Craton collided with the Core Zone, during the
Trans-Hudson Orogeny. Within the NQO, the Labrador Trough regroups greenschist-facies sedimentary and volcanic sequences (Kaniapiskau Supergroup) inferred to represent the rifted margin of the Superior and a potential oceanic domain, whereas the
Laporte Group, composed of similar successions but metamorphosed to higher grades, remains of unclear origin. Competing models purport that the Laporte Group is either a deeper, higher grade exposure of the Labrador Trough, or an exotic terrane.
Large scale sampling, petrography and U-Pb detrital zircon geochronology provide insights to elucidate the sedimentary provenance and depositional environments for both zones.
New results reveal a different sedimentary architecture for both units.
In particular, the majority of metarenites from Kaniapiskau Supergroup have medium to high textural and compositional maturity, such as meta-quartzarenites and meta-subarkoses; whereas the metarenites from Laporte Group suggest photoliths with low to
medium textural/compositional maturity, like feldspathic and some lithic meta-wackes.
A total of 343 zircon analyses from the Kaniapiskau Supergroup yield ages older than 2.5 Ga (2565 ±12 Ma, youngest zircon), with typical Archean Superior-type
signature as the main source area and a main statistical age peak at 2722 Ma. There is more than a 150 Ma gap between detrital zircon ages and the interpreted depositional age, suggesting a divergent environment like a rifted and/or passive
In contrast, detrital zircons from the Laporte Group (a total of 234 analyses) yield ages older than 1.8 Ga, with the youngest zircon dated at 1827 ± 25 Ma and a dominant statistical age peak at 1843 Ma. Metamorphic monazite ages from
Laporte Group previously dated at 1793 ± 2 Ma suggest a relative short depositional time period (around 40 Ma). The presence of detrital zircon age peaks at 2.2- 2.4 Ga suggests an exotic terrain compatible with the Core Zone as the main source area.
The presence of the orogenic-type De Pas Batholith suggests eastward subduction at 1840-1830 Ma and the time period between detrital ages and deposition may represent a transition between forearc to foreland basin.