Afar triple junction fed by single asymmetric mantle upwelling

The arrival of upwellings within the mantle from Earths deep interior are commonly observed worldwide, but their role in driving volcanism during continental breakup has long been debated. Given that only a small fraction of Earth’s upwellings are situated under continents and a limited number of them are associated with active continental rifting, our understanding of these processes remains incomplete.

Here, we investigate the interplay between continental breakup and mantle upwellings using the classic magma-rich continental rifting case study of the Afar triple junction in East Africa. Some studies previously proposed that the region is underlain by mantle upwelling(s), yet others argue for limited involvement of mantle plumes.  Several discrete segments of the rift have been studied in terms of magma petrogenesis. However, until now, a paucity of high-precision geochemical data across the broader region has hampered our ability to test the models and evaluate the spatial characteristics and structure of this upwelling in the recent geologic past.

Within this study, we present extensive new geochemical and isotopic data spanning the region and integrate these with existing geochemical and geophysical datasets shedding light on the spatial characteristics of the mantle beneath Afar.  By combining geophysics and geochemistry using statistical approaches, our multi-disciplinary approach shows that Afar is underlain by a single, asymmetric heterogeneous mantle upwelling. Our findings not only validate the heterogeneous characteristics of mantle upwellings, but demonstrates their susceptibility to the dynamics of the overriding plates. This integrated approach yields valuable insights into the spatial complexity of mantle upwellings.