Interaction between magmatism and deformation at magma-rich rifted margins : the example of the Mozambique channel

• Main Author: Tomasi, Simon
• Other Authors: Institut de physique du globe de Strasbourg (IPGS), Université de Strasbourg (UNISTRA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université de Strasbourg, Gianreto Manatschal
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: HAL CCSD 2020
• Subjects: Magma-rich margin; Mozambique; Antarctica; Timing and budget of magmatism; Tight fit restoration; Marge riche en magma; Antarctique; Budget et timing magmatisme; Reconstruction cinématique; Marge volcanique; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; Antarc*; Antarctique*
• Online Access: https://theses.hal.science/tel-03975520; https://theses.hal.science/tel-03975520/document; https://theses.hal.science/tel-03975520/file/TOMASI_Simon_2020_ED413.pdf

When, where and how magmatism forms during the evolution of the margin and how to assess the relative volume of the magmatic addition compared to the inherited crust are still poorly understood. This study aims to understand these interactions and evaluate the magmatic budget and timing through the analysis of the Mozambique-Antarctica rift system.A new method consisting in restoring end-member scenarios is developed to estimate magmatic budget in domains. This method highlights that the Mozambique Coastal Plains (MCP) and Beira High are floored by hybrid crust (i.e, thinned continental crust with magmatic additions, which fill up the accommodation space).This MCP is analysed through geophysical methods and unify 3 main characteristics of hybrid crust, which are: 1) flat, unfaulted, top basement parallel to Moho, 2) high-density crust due to significant magmatic additions, and 3) high post-rift subsidence due to plume collapse. Integrating the budget and also the timing of magmatic processes are required to characterize of a rifted margin. Therefore, a new classification is proposed linking the first order crustal shape to the magmatic budget and timing. Où, quand, et comment le magma intervient dans la formation de la marge, et comment estimer les volumes relatifs des additions magmatiques par rapport à la croûte originelle restent aujourd’hui incompris. Cette étude vise, par l’analyse du système conjugué Mozambique-Antarctique à comprendre l’interaction entre magmatisme et déformation dans l’évolution d’un rift.Une nouvelle méthode de reconstruction cinématique de scenarios permet de mettre en évidence une zone de croûte hybride : une croute continentale amincit qui est lourdement affectée par du magmatisme syn-extension qui remplit l’espace d’accommodation créé.Cette croute hybride est analysée à l’aide de méthodes géophysiques et vérifie 3 caractéristiques majeures: 1) toit du socle plat, parallèle au Moho, 2) une densité crustale élevée à cause du magmatisme, 3) une grande subsidence thermale due à la ...