Abstract
AbstractDuring the breakup of continents in magmatic settings, the extension of the rift valley is commonly assumed to initially occur by border faulting and progressively migrate in space and time toward the spreading axis. Magmatic processes near the rift flanks are commonly ignored. We present phase velocity maps of the crust and uppermost mantle of the conjugate margins of the southern Red Sea (Afar and Yemen) using ambient noise tomography to constrain crustal modification during breakup. Our images show that the low seismic velocities characterize not only the upper crust beneath the axial volcanic systems but also both upper and lower crust beneath the rift flanks where ongoing volcanism and hydrothermal activity occur at the surface. Magmatic modification of the crust beneath rift flanks likely occurs for a protracted period of time during the breakup process and may persist through to early seafloor spreading.
Highlights
During the breakup of continents, stretching and thinning of the plate commonly causes decompression melting and volcanism
We present phase velocity maps of the crust and uppermost mantle of the conjugate margins of the southern Red Sea (Afar and Yemen) using ambient noise tomography to constrain crustal modification during breakup
Our velocity maps suggest that the magmatic systems beneath the rift flanks that were active during the onset of rifting remain magmatically active throughout the breakup process either through continued minor accumulation of partial melt in reservoirs, dike intrusion, and/or ongoing conductive cooling leading to release of fluids such as water [Keir et al, 2009; Holtzman and Kendall, 2010]
Summary
During the breakup of continents, stretching and thinning of the plate commonly causes decompression melting and volcanism. In the resultant magmatically active rift valleys it is widely thought that extension is initially accommodated mainly by border faulting and progressively localizes to relatively narrow axial volcanic segments as the rift valley widens [e.g., Ebinger and Casey, 2001]. It is becoming increasingly more recognized that magma intrusion and volcanism can occur on the rift flanks at an early stage of rifting [e.g., Maccaferri et al, 2014]. These rift flank magmatic systems accommodate extension through diking [Rooney et al, 2014], and thermally and compositionally modify the lithosphere [Daniels et al, 2014].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
