Mechanisms of Continental Extension and Africa-Arabia separation: Constraints from Laboratory Experiments

We study the mechanisms of continental extension and rifting through the example of Africa-Arabia separation. The influence of the Zagros-Makran subduction and of the Afar hot-spot on the geometry and kinematics of rifting in the Aden-Red Sea region are investigated through laboratory experiments. Our goal was to unravel the effect of the dynamics of the subduction on the deformation of the subducted (Arabic) plate. We used a three-layer analogue model where sand and silicone represent respectively the brittle and ductile lithosphere, and where honey represents the viscous upper mantle. The negative buoyancy of the sand/silicone unit is the main driving force for subduction, while the bending resisting force of the sand/silicone unit tends to slow down subduction. Preliminary models were realized to characterize the effect of the boundary conditions and the effect of an additional circular weakness corresponding to the Afar hot spot. In more complex models, we simulate the deformation of Northeast Africa during the Tethyan lithosphere subduction and Zagros collision simultaneously with the activity of the Afar hot spot. These models contribute to explain the presence of distributed extensional deformation in northeast Africa before rifting and the final Africa-Arabia separation. They explain the timing of these extensional events. Subduction has been active since the Mesozoic and provides forces which lead to extension within the subducting plate. The Eurasia-Africa collision changes the boundary conditions and triggers the localization of rifting 30-35 Ma ago. These models also explain the location and the geometry of the rifting in the Gulf of Aden and in the Red Sea. The Afar hot spot localizes extension acting as a lithospheric weakness and constrains the rift geometry. The obliquity between the rift direction and the direction of extension explains the internal fault geometry.