The most recent volcanic activity of the Manda Hararo rift segment (Central Afar, Ethiopia): new dating and petrological processes associated with the eruption sequences

Yafet Gebrewold Birhane, Raphaël Pik, Nicolas Bellahsen, Sarah Gommery, Irene Schimmelpfennig, Lydéric France, Simon Daout, Jessica Flahaut, Dereje Ayalew, Gezahegn Yirgu

Journal of Volcanology and Geothermal Research, Volume 480, December 2026, 108755

Voir en ligne : https://doi.org/10.1016/j.jvolgeores.2026.108755

The Manda Hararo rift segment in the Afar depression (Ethiopia) represents a key location to study the timing, style, and evolution of volcanic activity within an active continental rift close to the Ocean-Continent Transition (OCT) stage. Despite its importance, the southern part of this segment has remained poorly documented. In this study, we provide a detailed mapping based on a combination of medium-resolution spectral imagery and a unique dataset of very-high-resolution Pléiades images. We combine this map with volcanological observations, major and trace element analyses, and cosmogenic 36Cl surface exposure dating to investigate the very last eruptions and volcanic history of two sub-segments (Gumat Mali and Gablaytu). Our results show that the last volcanic activity occurred at Gablaytu between ~3.20 and 1.50 ka and at Gumat Mali between ~1.90 and 0.60 ka. Petrological data indicate that the Gumat Mali sequence was driven by reservoir recharge with new, less differentiated magma that hybridized with a more evolved mush, enhancing magma mobilization. The Gablaytu sequence records progressive magma differentiation accompanied by plagioclase assimilation and/or accumulation. For both sub-segments, these processes control magma evolution prior to eruption and indicate a complex transcrustal plumbing system characterized by magma storage, recharge, and interaction within vertically connected reservoirs. Our volcanological observations also provide the first evidence for late Holocene explosive activity in the southern Manda Hararo rift segment. The documentation of the most recent volcanic activity provides new geological constraints for future volcanic hazard assessments in Central Afar. Our results show that future hazard scenarios should consider not only effusive fissure eruptions but also potentially high-energy phreatomagmatic eruptions, as documented at the onset of the Gumat Mali eruptive sequence. Our observations support the recognition of two self-consistent sub-segments within the wide Central Afar magmatic system with their own associated plumbing system: the Gumat Mali sub-segment located in the direct prolongation of the Dabbahu segment corridor and the en-échelon lateral Gablaytu sub-segment along the Manda Hararo and Unda Hararo axis. This illustrates the intimate links between tectonic structures, magma storage and upward migration in controlling the expression of first and second order segmentation in such zones of the Afar depression close to the OCT.