Constraining timescales of focused magmatic accretion and extension in the Afar crust using lava geochronology

As continental rift zones mature the tectonic and volcanic processes associated with crustal
extension become confined to narrow magmatic rift zones, reminiscent of oceanic spreading
ridges. The formation of these rift zones and the development of ocean-ridge type topography
is a significant milestone in rift evolution as it signifies the localization of crustal extension
and rift-related volcanism. Here we show that lavas, which erupted since B200 ka along part
of the on-land Red Sea rift system in Afar, Ethiopia, have a consistent age-progression from
the rift axis outwards, indicating that axial dyke intrusion has been the primary mechanism of
segment growth and that focused magmatic accretion and extension in the crust have
remained stable here over this period. Our results suggest that as this rift segment has
formed, in thinned and intruded continental crust, the time-averaged surface opening rate has
closely approximated the total extension rate between Africa and Arabia.