Magmatism and deformation during continental breakup

Recent observations of rifting in Afar show that magma intrusion can localize extension away from border faults to narrow axial volcanic segments fairly early during continental rifting. The 2005-2010 Dabbahu rifting episode demonstrates that the zones of crustal intrusion beneath the axial volcanic segments are emplaced by episodic lateral dike intrusion sourced from a segment-centred magma reservoir in the mid-upper crust. The magma intrusion induces faulting in the upper crust, but importantly maintains crust that is thicker than if extension took place by mechanical processes alone. Along-rift variations in rift architecture, volcanic geology and style of magmatic plumbing in Afar imply that the intruded plate undergoes plate stretching in order to rupture. The observations from Afar supplemented by numerical modelling suggest that protracted heating and weakening of the plate from previous localized magma intrusion are a primary reason for the change in extension mechanism through time. Plate thinning during late-stage breakup results in increased melt production and basaltic volcanism which fills rift valley basins at sea-level. The similarity in geology of northernmost Afar to the thick sequences of basalt flows and evaporites common at volcanic margins worldwide means that the processes active today in the Danakil depression are a modern analogue for those responsible for formation of seaward-dipping reflector sequences commonly observed at ancient rifted volcanic continental margins. © 2014 Royal Astronomical Society.