Influence of hot spots on the initiation (rifting) and evolution of sedimentary basins.

Our study is motivated by the desire to quantify the impact of a hotspot on the continental lithosphere and to better understand the relationship between hotspot and lithospheric deformation. We have developed a referential related to hotspots up to 300 Ma, by associating continental surface markers (volcanism, uplift) with the hotspot that caused them, in order to establish the trajectory of hotspots over time. From these trajectories, we observed that future rift zones leading to the fragmentation of Pangea were impacted by at least one hotspot. Thus, we sought to understand whether the impact of a hotspot can localize deformation by permanently weakening the lithosphere. A numerical model, taking into account the stresses created by the mantle mass anomalies, has been established and tested on a natural analogue, the Red Sea, such that the East-Africa hotspot follows and precedes the axis of this future rift. The results show that the Red Sea rift is constrained to initiate at t=30 Ma and evolve in a zone prefigured by the East-Africa hotspot impact. Furthermore, we demonstrate that the weakening of the lithosphere by a hotspot is efficient, long-lasting and lasts for several tens of millions of years. Finally, we propose that thermal weakening by a hotspot allows us to locate weak zones, which following the action of a stress field, can evolve into a rift system.