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Crustal Evolution and Deformation in a Non-Plate-Tectonic Archaean Earth: Comparisons with Venus.

Harris, Lyal B. et Bédard, Jean H. (2014). Crustal Evolution and Deformation in a Non-Plate-Tectonic Archaean Earth: Comparisons with Venus. In: Evolution of Archean Crust and Early Life. Modern Approaches in Solid Earth Sciences, 7 . Springer, New York, pp. 215-291. ISBN 978-94-007-7614-2

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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.

Type de document: Chapitre de livre
Mots-clés libres: Archaean tectonics; mantle plumes; crustal evolution; mantle flow; cratonic mobilism; Venus; Ishtar Terra; Lakshmi Planum; Superior Craton; Abitibi; aeromagnetics; gravity; seismic tomography
Centre: Centre Eau Terre Environnement
Date de dépôt: 08 mai 2018 17:43
Dernière modification: 08 mai 2018 17:43
URI: https://espace.inrs.ca/id/eprint/3598

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