Linking the deep structures of the cratons of Africa and South America by integrated geophysical modelling

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In the proposed study, we are going to integrate gravity, seismic, geothermal and mineral physical data for investigations of the lithosphere of the regions of Africa and South America. For both continents, compositional changes reflecting the tectonothermal age have been proposed previously, which largely affect geophysical observables as seismic velocities and densities. The comparison between the continents allows to decipher the similarities and differences in the evolution of the cratonic interior.Analysis of a single geophysical technique does not allow to distinguish clearly between compositional and additional thermal effects in the upper mantle. Furthermore, sources in the crust limit the detection of upper mantle sources, especially in gravity studies. For the two regions, crustal models exist from seismic and seismological studies and we will make use of the newly available gravity gradients from the GOCE satellite mission. Satellite gravity gradients have the advantage that their main sensitivity is limited to a depth of less than 100 km, so they can be used to validate the density structure in the (lower) crust and upper mantle. The novel data set allows further to discriminate with a higher confidence than in previous studies between lithospheric and sub-lithospheric components in the gravity field. The gravity residuals are then exploited to estimate dynamic topography and the role of mantle dynamics on the present state of the cratonic interior, e.g the evolution of sedimentary basins, of the continents. In addition, the results will be used to model mantle flow by converting the temperature variations to viscosity variations, while the density heterogeneity drives convection. Models of mantle flow velocities will be established that are analysed jointly with the obtained structural models to characterize the processes that affect the compositional structure of the lithosphere.