Detailed Architecture of the Manda Hararo Magmatic Segment in Afar, Ethiopia:

Abstract

The Afar depression at the northern end of the East African Rift system is the only analog on earth where magmatic continental rifting and associated ongoing break-up processes are exposed onshore. This unique active system presents the key advantage to expose extensional structures related to ocean-continent transition, with magmatic rift segments characterized by contrasted morphologies, and magmato-tectonic styles. The main goal of this study is to identify the location and investigate the functioning and persistence of magma reservoirs at the active magmatic segments in the central Afar depression (Manda Hararo, northern Tendaho grabben), in order to (i) highlight their relationships and potential control with the first- and second-order local segmentation, and (ii) understand the interplay between magmatic and tectonic processes during the generation of such magmatic crust. We combine remote sensing, field investigations, precise and comprehensive mapping of volcanic and tectonic structures, cosmogenic (36Cl) exposure dating of lava surfaces, and geochemical analysis to constrain the temporal frame and the dynamics of magmatic and tectonic processes. The first result of remote sensing analysis allows us to identify two active and self-consistent axial rift subsegments within this extensional system, map detailed lava flow fields which form these segment surfaces and investigate their relationships with caldera formation and focussed fissural activity. Geochemical analysis and dating of lava flows from this Manda Hararo rift system will be conducted to test the integrity of this model of contiguous subsegments.