Volcanism records plate thinning driven rift localization in Afar (Ethiopia) since 2-2.5 million years ago

Magma-rich continental rifting and breakup commonly show complex distributions of volcanism, potentially due to both plume and rifting controls. As such, interpreting the main controls on the spatial evolution of magmatism is debated, as is the point at which continental rifting transitions to oceanic spreading. Here we present new argon-argon dating of 16 lava flows from the Stratoid and Gulf series of the Afar rift. We reconstruct the spatio-temporal evolution of the rift from widely distributed to localised along narrow magmatic segments (i.e., rift localisation). Our results rule out an ocean spreading-like style of rifting. We show that over 2–2.5 million years since the early Pleistocene, the rift progressively narrowed by asymmetric in-rift localisation and propagated along-rift. Concurrently, the mantle partial melting and the crustal magmatic system shallowed. While mantle plume-related elevated temperatures influence overall melt volumes, our results suggest that the rapid and localised changes in plate thinning caused by rifting are the primary control on the spatio-temporal distribution of volcanism.