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New Cosmogenic Exposure Dating of Fissural Volcanic Episodes in Afar: Implications for Magmatic Processes and Plumbing System Organisation

Yafet Gebrewold Birhane1,7, Raphael Pik1, Nicolas Bellahsen2, Irene Schimmelpfennig3, Lydéric France1,4, Juliette Pin1,5, Dereje Ayalew6, and Gezahegn Yirgu6

  • Affiliations:  1CRPG, CNRS, Universite´ de Lorraine, UMR 7358, Vandoeuvre-les-Nancy, France, 2Sorbonne Universités, UPMC Université Paris 06, CNRS, Institut des Sciences de la Terre de Paris (iSTeP), Paris, France, 3Aix-Marseille Université, CNRS, Coll France, IRD, INRAE, CEREGE, Aix en Provence, France, 4France, Institut Universitaire de France (IUF), 5Laboratoire Géo-Océan (LGO), Institut Universitaire Européen de la Mer (IUEM), Université de Bretagne Occidentale (UBO), Brest,  6School of Earth Sciences, Addis Ababa University, Addis Ababa, Ethiopia, 7Department of Geology, College of Natural and Computational Sciences, Hawassa University, Ethiopia 

  • Presentation type: Talk

  • Presentation time: Tuesday 16:15 - 16:30, Room R380

  • Programme No: 1.3.7

  • Theme 1 > Session 3

Abstract

Divergent plate boundaries offer prime sites to study crustal extension and volcanic processes. The Afar depression, where active continental break-up and the transition from continental to oceanic rifting, provides a unique natural laboratory for these investigations. The magmatic segments within Afar (Erta Ale, Dabbahu-Manda Hararo and Asal) share structural organisation analogies to those in mid-ocean ridges. These segments offers insights into the mantle and crustal processes that control magma transfer, storage, and eruption. This study focuses on the dynamics of magma transfer through the crust, the organization of the plumbing system, and the processes controlling these mechanisms. We combine high-resolution multispectral orthoimages and digital elevation model, precise geological mapping, field investigations, cosmogenic 36Cl exposure dating, and lava geochemistry to constrain the timing and evolution of magmatic events. Due to the systematic axial resurfacing along the segments, only the very last volcano-tectonic cycles are preserved and documented with exposure ages. Our results document the last rifting episodes for each segment: Gumat Mali-Manda Hararo (~ 0.5 to 35 ka), and Asal (~1 to 8 ka). The recent exposure ages reveal periodic recharge of shallow magma reservoirs that ultimately feed lateral dyke injections and surface eruptions. Our findings reveal the dynamic magma storage and transfer within the Afar axial rift, where segments are at different rifting stages. Variations in reservoir recharge and differentiation highlight distinct storage zones and potential connections between subsegments. These insights show how periodic magma transfer and differentiation cycles shape the rift magmatic evolution, with important implications for local hazards.