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Spliting continental lithosphere during early rifting in the South Atlantic with emphasis on the role of magmatism

Principal Investigator: Dr. Thorsten Nagel

One of the largest problems in rifting and breakup is that the available force might not be sufficient to part normal continental lithosphere (force paradox). Most present-day continental margins are associated with massive volcanic outflows during initial rifting. A rising plume of hot buoyant mantle would explain thermal weakening of the lithosphere in a confined area above the plume head but not rifting and continental breakup along a rift axis that might extend thousands of kilometers away from the plume. This proposal follows the working hypothesis that besides thermal reduction of mantle viscosity two further processes are important in parting the lithosphere. (1) Diking events might propagate into continental lithosphere allowing for magmatic accommodation of extension at much lower extensional stresses that faulting and (2) stress concentrations at the tip of a rift might allow for continuous propagation of the rift. I would like to study whether massive plume-related igneous provinces and associated huge diking events are required to solve the force paradox or if stress concentrations and diking associated with passive upwelling at a rift tip might suffice. The Southern Atlantic is a classic area for this controversy. Here, I propose a series of numerical 2D- and 3D-experiments to study this problem. Predictions of the experiments in terms of margin architecture, subsidence evolution and magmatic history will be compared with the same data from the South Atlantic. Vice versa, the situation in the South Atlantic will help to build the experiments.