Geodynamic evolution of the Deseado Massif (Patagonia) : contribution of a new low-temperature multi-thermochronological approach

• Main Author: Derycke, Alexis
• Other Authors: Géosciences Paris Saclay (GEOPS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Université Paris-Saclay, Cécile Gautheron, Massimiliano Zattin
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2021
• Subjects: Thermochronology; (U-Th)/He; Geodynamic; Shield; Patagonia; Thermochronologie; Géodynamique; Craton; Patagonie; [SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics; [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry; Argentina; Argentine; South Atlantic Ocean
• Online Access: https://theses.hal.science/tel-03357660; https://theses.hal.science/tel-03357660/document; https://theses.hal.science/tel-03357660/file/94657_DERYCKE_2021_archivage-2.pdf

The main objective of this PhD thesis is the reconstruction of the geological history and geodynamics of the Deseado Massif, located in the central Patagonia foreland (Argentina). This goal, apart from its regional aspect aiming to constrain a poorly known area’s history, is also linked to a more global scientific question. Indeed, the Deseado Massif is a cratonic area, which its dynamic is linked to large scale processes (Gondwana fragmentation, Andean subduction.), and thus the understanding of its history allows to learn more about the mechanisms that trigger the dynamics of cratonic and stable zones over a long time, with more than a hundred million years.This study is based on a low temperature thermochronometers approach, which allow constraining the rocks evolution through time and space. The particular aspect of this study relies on the combination of multiple thermochronometers (fission tracks and (U-Th)/He on apatite and (U-Th)/He on iron and manganese oxides), the calibration of a helium diffusion model and the use of data inversion methods. This study allows the quantitative reconstruction of the burial and exhumation history of the Deseado Massif over the last 200 million years, and thus for the first time provide relevant calendar of its geodynamics. The results of this PhD thesis also demonstrate the unique dynamics of the Deseado Massif during the Gondwana break-up and the South Atlantic Ocean opening, compared to the other part of Patagonia.Finally, apart from its regional contributions, this thesis contributes to establish a new thermochronology methodologies adapted to study stable geodynamic areas over long periods of time. L’objectif de ce travail de thèse est la reconstruction de l’histoire géologique et plus particulièrement géodynamique du Massif du Deseado, situé dans l’avant-pays de la Patagonie centrale (Argentine). Cet objectif, en dehors de son aspect régional visant à contraindre l’histoire d’une zone peu investiguée, est aussi à rattacher à une problématique scientifique plus ...