Structures and deformations correlated to the activation of a major shear zone : multi-scale study of the Eastern boundary of the Neoarchean-Paleoproterozoic Terre Adélie craton (Mertz shear zone, East Antarctica)

• Main Author: Lamarque, Gaëlle
• Other Authors: Laboratoire Magmas et Volcans (LMV), Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Institut de Recherche pour le Développement et la société-Université Clermont Auvergne 2017-2020 (UCA 2017-2020 )-Centre National de la Recherche Scientifique (CNRS)-Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), Institut national des sciences de l'Univers (INSU - CNRS)-Université Clermont Auvergne 2017-2020 (UCA 2017-2020 )-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Clermont Auvergne 2017-2020 (UCA 2017-2020 )-Centre National de la Recherche Scientifique (CNRS), Université Jean Monnet - Saint-Etienne, Jérôme Bascou
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2015
• Subjects: Shear zone; Mechanisms of deformation; Lithospheric structures; Geodynamic; Craton; Paleoproterozoic; Mertz shear zone; Terre Adélie; Antarctica; Zone de cisaillement; Mécanismes de déformation; Structures lithosphériques; Géodynamique; Paléoprotérozoïque; Antarctique; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; East Antarctica; Southern Ocean; Tac; Terre-Adélie; Antarc*; Antarctique*
• Online Access: https://theses.hal.science/tel-01560841; https://theses.hal.science/tel-01560841/document; https://theses.hal.science/tel-01560841/file/These-LAMARQUE-Gaelle-2015.pdf

The study of the behavior and the structure of large shear zones, as well as their evolution in space and times is essential because shear zones accommodate the main deformation in intermediate and deep crust as well as in the mantle.The Mertz shear zone (MSZ; longitude 145°East, Antarctica) is a key target for the study of the deformation localization. The MSZ is located on the eastern boundary of the Neoarchean to Paleoproterozoic Terre Adélie craton (TAC) and it separates the TAC from a Paleozoic granitic domain to the east. Previous studies suggest that this strike slip structure was probably continuous with the Kalinjala shear zone (KSZ, South Australia) before the opening of the Southern Ocean. Outcrops indicate that the MSZ was formed in the intermediate crust during a transpressive event at 1.7 Ga. The structure of the MSZ was studied from terrain to micrometric scales. The field structural study shows that the Paleoproterozoic deformation is mainly accommodated by localized shear zones that are extremely anastomosed at the MSZ and become more scattered elsewhere in the TAC. Microstructures and crystallographic preferred orientation (CPO) of minerals (quartz, feldspaths, biotite, amphibole and orthopyroxene) of the MSZ indicate similar characteristics that can be interpreted in terms of conditions, cinematic and rate of deformation, which are distinct from those of the the tectonic boudins from the TAC. These tectonic boudins reveal microstructures and CPO including a large variety of mechanisms of deformation developed during their formation at 2.5 Ga. The seismological study (receiver functions and SKS-waves anisotropy) permits the characterization of the deep structure on the MSZ area. Receiver functions results show that crustal thickness is about 40 to 44km in the TAC, 36km above the MSZ and 28km in the Paleozoic domain to the east. Analysis of SKS-waves anisotropy suggests that the mantle structures below the craton (ϕ≈N90°E, δt=0,8-1,6s) are different from the ones below the Paleozoic domain ...