Mechanical behaviour of warm continental lithospheres Evolution of the Neoarchaeans and Paleoproterozoics cratons of Terre Adélie (East Antarctica) and Gawler (South Australia)

• Main Author: Duclaux, Guillaume
• Other Authors: Laboratoire Transferts Lithosphériques (LTL), Centre National de la Recherche Scientifique (CNRS), Université Jean Monnet - Saint-Etienne, René-Pierre Ménot, IPEV, The Univeristy of Sydney
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2007
• Subjects: Neoarchaean; Paleoproterozoic; craton; polyphased tectonic; warm lithosphere; transpression; rheology; Terre Adélie; Antarctica; Gawler; Australia; rhéologie; Néoarchéen; Paléoprotérozoïque; tectonique polyphasée; lithosphère chaude; Antarctique; Australie; [SDU.STU.AG]Sciences of the Universe [physics]/Earth Sciences/Applied geology; Antarctic; East Antarctica; Southern Ocean; Terre-Adélie; Antarc*; Antarctique*
• Online Access: https://tel.archives-ouvertes.fr/tel-00206311; https://tel.archives-ouvertes.fr/tel-00206311/document; https://tel.archives-ouvertes.fr/tel-00206311/file/TheseDuclaux-version_finale.pdf

The East Antarctic Shield is made of several geological domains amalgamated at about 530 Ma, during the Ross orogeny. All this domains but one recorded Grenvillian and Pan-African events : the Terre Adelie Craton. The Terre Adelie Craton and its northern extension, the Gawler Craton (in South Australia), are both parts of a same block : the Mawson continent. Also, they display identical geological histories prior the opening of the Southern Ocean basin at around 90 Ma. These cratons are made of a polymetamorphic basement structured during two main orogenesis dated to Neoarchaean (∼ 2.5 Ga) and Paleoproterozoic (∼ 1.7 Ga) times. The present work deals with the study of the tectonic mechanisms responsible for the structuration of the Mawson Paleo-continent. Field investigations and laboratory work (petrology, Ar–Ar and U–Th–Pb geochronology) on samples from both cratons allowed (1) to precise the age and the origin of the Neoarchaean deformation and the mechanical behaviour of the continental lithosphere at that time, and (2) to quantify the magnitude of the Paleoproterozoic deformation within the Archaean crust and in adjacent Paleoproterozoic domains. This work provides new constraints regarding Precambrian tectonics. Our results allowed us to evidence and to numerically model in 3D at the lithospheric-scale, the strain evolution during waning of convergence force into a warm Archaean lithosphere. We show that tectonic and gravitationnal forces compete in order to drive horizontal constrictive flow of the continental lithosphere, in a direction perpendicular to the convergence. Furthermore, we illustrate rheological duality between a stabilized cratonic domain and its autochtonous sedimentary cover during later tectonic reactivation. Le bouclier Est Antarctique est constitué de nombreux domaines géologiques accrétés autour de 530 Ma. Tous ces domaines enregistrent la trace des événements Grenvillien et Pan-Africain à l'exception d'un seul : le Craton de Terre Adélie. Le Craton de Terre Adélie et son ...