| Titre | Crustal evolution and deformation in a non-plate-tectonic Archaean Earth: comparisons with Venus |
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| Auteur | Harris, L B; Bédard, J H |
| Source | Evolution of Archean crust and early life, modern approaches in solid Earth sciences; par Dilek, Y (éd.); Funes, H (éd.); Modern approaches in solid Earth sciences vol. 7, 2014 p. 215-291, https://doi.org/10.1007/978-94-007-7615-9 9 |
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| Année | 2014 |
| Séries alt. | Secteur des sciences de la Terre, Contribution externe 20120436 |
| Éditeur | Springer Netherlands |
| Document | livre |
| Lang. | anglais |
| DOI | https://doi.org/10.1007/978-94-007-7615-9 9 |
| Media | papier; en ligne; numérique |
| Formats | pdf |
| Province | Ontario; Québec |
| SNRC | 31; 32; 33; 41I; 41J; 41O; 41P; 42; 43 |
| Région | Abitibi; Venus |
| Lat/Long OENS | -88.0000 -72.0000 56.0000 46.0000 |
| Sujets | interpretations structurelles; études de la croûte; evolution de la croûte; structure de la croûte; Archéen; déformation; tectonique; géologie structurale; Précambrien |
| Illustrations | cartes géologiques généralisées |
| Programme | Initiative géoscientifique ciblée (IGC-3), 2005-2010
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| Diffusé | 2013 11 27 |
| Résumé | (disponible en anglais seulement)
Evidence for modern plate tectonics in the Archaean is equivocal to absent, and alternative environments for formation and deformation of greenstone sequences
are summarized. We focus on proposals for an unstable stagnant lid basaltic plateau crust, with cratonization occurring initially above major mantle plumes. Archaean continental drift initiated as a result of mantle traction forces acting on
newly-formed subcontinental mantle keels, with further cratonic growth occurring as a result of terrane accretion to the leading edges of the migrating cratonic nuclei.
Venus is presented as an analogue for a non-plate-tectonic Archaean Earth.
Despite the absence of evidence for characteristic plate tectonic environments on Venus (i.e. subduction=trenches and volcanic arcs; seafloor-spreading=volcanic ridges and transforms), the form, scale, and geometry of folds, brittle-ductile shear
zones, and faults interpreted on the surface of Venus from radar imagery are comparable to mid-upper crustal structures on Earth. Anastomosing rifts link coronae interpreted to form above upwelling mantle plumes. The Lakshmi Planum highland plateau
in the western Ishtar Terra region of Venus lacks extensive, regional-scale internal deformation structures, but a fold-thrust belt produced mountains on its northern margin, folds and sinistral strike-slip faults occur on its NW margin, and both
regional dextral and sinistral strike slip belts occur in a zone of lateral escape to its NE. Rift zones are present along the southern margin to Lakshmi Planum. The scale and kinematics of structures in western Ishtar Terra closely resemble those of
the Indian-Asia collision zone, and we propose that lateral displacement of some coronae and 'craton-like' highlands or plana result from mantle tractions at their base in a stagnant lid convection regime, i.e. a similar regime as interpreted to have
preceded development of plate tectonics on Earth.
In the Wawa-Abitibi Subprovince of the Superior Craton in Canada, the formation of granite greenstone sequences in a plume-related volcanic plateau and subsequent deformation can be generated
through geodynamic processes similar to those on Venus without having to invoke modern-style plate tectonics. 3D S-wave seismic tomographic images of the Superior Province reveal a symmetrical rift in the sub-continental lithospheric mantle (SCLM)
beneath the Wawa-Abitibi Subprovince, with no evidence for 'fossil' subduction zones. Major gold deposits and kimberlites are located above rift-bounding faults in the SCLM. Early rift structures localized subsequent deformation and hydrothermal
fluid flow during N-S shortening and lateral escape ahead of a southwardly moving indenter (the Northern Superior Craton - Hudson's Bay terrane) in the ca. 2696 Ma Shebandowanian orogeny. The geometry of reverse and strike-slip shear zones in the
Abitibi Subprovince of the SE Superior Province is similar to that of shear zones developed in western Ishtar Terra, Venus, which also formed ahead of a rigid indenter whose displacement is attributed to mantle tractions. Similarly, shortening and
rift inversion in the Abitibi is ascribed to cratonic mobilism where displacement of the N Superior Province 'proto-craton' resulted from mantle flow acting upon its deep lithospheric keel. Deformation in other Archaean cratons previously interpreted
in terms of plate tectonics may also be the result of similar, mantle-driven processes. |
| Sommaire | (Résumé en langage clair et simple, non publié)
Les données de Venus NASA sont interprétées pour produire une carte structurelle ; montrant que la dérive des continents se produisait, malgré
l'absence d'environnements tectoniques des plaques comme l'étalement et la subduction du fond marin. Vénus est considérée comme un analogue de la Terre archéenne (avant 2500 ans). Nous utilisons le modèle structurel de Vénus avec les cartes
structurelles et les résultats de la tomographie pour le craton/écran supérieur, afin de réinterpréter la géologie de la ceinture de roches vertes de l'Abitibi. Nous proposons qu'un ancien bouclier S Supérieur a été désagrégé suite à l'arrivée d'une
remontée de manteau chaud à environ 2750-20 my, avec des fragments séparés par rafales. Les régions d'extension maximale (Abitibi) ont vu leur manteau fossile entier détruit. Plus tard (2720-2500 my), des courants mantéliques poussant sur la racine
mantélique du bouclier N Supérieur l'ont fait se déplacer vers le sud, réassemblant le bouclier Supérieur. Le modèle structurel du S Supérieur est donc le résultat de l'indentation des terranes à la Vénus. |
| GEOSCAN ID | 292352 |
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