The protracted development of focused magmatic intrusion during continental rifting

摘要: The transition from mechanical thinning toward focused magmatic intrusion during continental rifting is poorly constrained; the tectonically active Main Ethiopian Rift (MER) provides an ideal study locale to address this issue. presence of linear magmatic-tectonic belts in relatively immature central MER may indicate that more spatially distributed and temporally protracted than has previously been assumed. Here we examine lava geochemistry vent distribution a Pliocene-Quaternary chain along western margin MER—the Akaki Magmatic Zone. Our results show limited variability parental magma evolve complex polybaric fractionation system not changed significantly over past 3 Ma. suggest following: (1) channeling plume material localization shear- or topography-induced porosity modulates melt into lithosphere. (2) Pre-existing lithospheric structures act as catalysts for magmas mantle. (3) midcrustal upper crustal strain regime dictates surface orientation volcanic vents. Therefore, although like those young progressively rift axis superficially resemble oceanic style magmatism, they actually represent prebreakup magmatism on crust. oldest observed seismically magnetically at edge ocean basins thus not, often assumed, mark onset seafloor spreading.