Catching the Main Ethiopian Rift Evolving Towards Plate Divergence

Magmatism accompanies rifting along divergent plate boundaries, although its role before continental breakup remains poorly understood. For example, the magma-assisted Northern Main Ethiopian Rift (NMER) lacks current volcanism and clear tectono-magmatic relationships with its contiguous rift portions. Here we define its magmatic behaviour, identifying the most recent eruptive fissures (EF) whose aphyric basalts have a higher Ti content than those of older monogenetic scoria cones (MSC), which are porphyritic and plagioclase-dominated. Despite the similar parental melt, EF and MSC magmas underwent different evolutionary processes. While MSC magmas were stored at intermediate crustal levels, EF magmas rose directly from the Moho without contamination, even below older polygenetic volcanoes, suggesting rapid propagation of transcrustal dikes across solidified magma chambers. Whether this recent condition in the NMER is stable or transient, it highlights a transition from central polygenetic to linear fissure volcanism, indicative of increased tensile conditions and volcanism directly fed from the Moho, suggesting transition towards mature rifting.