Integrated Geophysical‐Petrological 3D‐Modeling of the West and Central African Rift System and Its Adjoining Areas

Abstract This study addresses the lithospheric structure of the West and Central African rift system (WCARS) and explores its origin and development in relation to the enigmatic Cameroon volcanic line (CVL). Based on a recent seismic tomography model, we subdivide the areas in tectonic domains. We perform integrated 3D geophysical and petrological forward modeling. By exploring the thickness and composition of different domains, we compare the model response to the observed topography and gravity anomalies, under consideration of the available seismic Moho depth points. Our model reveals three distinct domains within the study area: The WCARS is predominantly underlain by a Phanerozoic‐type lithospheric mantle, surrounded by the West African and the Congo Cratons, where the lithospheric mantle has a Proterozoic‐type signature. Between these domains, we identify a transition area where lithospheric thickness changes rapidly. Our preferred model shows significant variability of crustal thickness from 20 km in the rift area to 50 km beneath the cratons accompanied by thin lithosphere of 80 km in the rift area to thick lithosphere of up to 240 km beneath the cratons. The final model confirms that the WCARS' origin is passive, and suggests that the origin of the CVL, particularly its continental part, is the result of two tectonic events: (a) V‐shaped opening of the lithospheric mantle beneath the WCARS, resulting in (b) a strong variation of the lithosphere thickness at the transition between the rift zone and the northwestern part of the Congo craton.