The legacy of the East African rift system in understanding continental rifts worldwide from geophysical studies (with emphasis on gravity and magnetic studies)

Abstract

The diverse geology of the African continent has provided the geoscientific community with an unparallel opportunity to examine and understand complex endogenic and exogenic processes that have shaped and are still shaping our Planet Earth. An exemplary illustration of this is the East African Rift System (EARS), which traverses the African continent from its northeastern part in the Afar Depression to its southern part in the Okavango Rift Zone. In this review, we aim to provide an overview of the notable gravity and magnetic studies that have contributed to our understanding of continental rift evolution. Our primary focus is on gravity and magnetic contributions to understanding the rifting processes from their enigmatic nucleation as incipient rift systems to their subsequent progression from continental rifting to seafloor spreading, an aspect that garnered more attention and investigation. We highlight the legacy of gravity and magnetic studies in understanding the evolution of continental rifts from eight studies starting from the most evolved segment of the EARS in the Afar Depression to the most incipient segment of the rift in the Okavango Rift Zone. These include: (1) The transitioning from continental rifting to seafloor spreading in the Afar Depression (The Tendaho graben). (2) Nucleation of a future divergent plate boundary within an overlapping propagating embryonic spreading center (The Dobi graben). (3) Transfer of extension from rift border faults to rift floor through magma-assisted rifting (The Main Ethiopian Rift). (4) The evolution of broadly rifted zones though upwelling of mantle flow resulting in an unstable dynamic topography and subsequent gravitational collapse (The Southern Main Ethiopian Rift). (5) Three-dimensional (3D) crustal density stratification and superimposed rifting events (The Turkana rifted zone). (6) The rifting of cratons that is facilitated by inherited zones of weakness presented by orogenic belts (The Eyasi basin). (7) The role of preexisting lithospheric structures in controlling continental rift evolution (The Albertine – Rhino graben). (8) The role of fluid concentration through lithospheric zones of weakness in continental rift initiation (The Okavango Rift Zone).