The Gada’Ale volcano-tectonic structures: Implications for the geodynamics of the Erta’Ale1 Volcanic Range, Northern Afar Depression, Ethiopia

The volcano-tectonic history of the Danakil Depression represents the complete succession of rifting processes, spanning from incipient crustal rupture to the onset of sea-floor spreading. The Erta’Ale Volcanic Range (EVR), located in the central part of the Danakil Depression, is a subaerial segment of nascent oceanic crust and hosts well exposed magmatic and tectonic features. In this study, we investigate the tectonic processes shaping rift-floor structures and the development of magmatic sill-induced domes within the volcanic range, using field observations, satellite image interpretations, digital elevation model (DEM) analysis, structural analysis, geophysical (seismic profile) interpretation, and borehole data analyses. The integrated results indicate that a variety of surface and sub-surface volcano-tectonic processes are very active within the thin crust of Danakil Depression. Magmatic intrusions and/or sills are emplaced at the interface between thick evaporite deposits specifically at the boundary between upper and lower rock salt units. These intrusions uplift the upper halite layers by ~130 m, forming a well-defined dome. Further analysis of the western sector of the volcanic range shows that large off-axis volcano-tectonic structures including sill-induced domes, collapse calderas, and composite volcano are linearly distributed exclusively along the western side of the rift floor, coincident with inherited structural weaknesses, and interpreted here as paleo-rift axes. Thus, our results demonstrate that the western side of the rift floor is more intensely faulted and intruded by magmatic bodies, resulting in a more fractured and more porous crust compared to its eastern counterpart.