Crustal and upper mantle structure beneath south‐western margin of the Arabian Peninsula from teleseismic tomography

Abstract

We image the lithospheric and upper asthenospheric structure of western continental Yemen with 24 broadband stations to evaluate the role of the Afar plume on the evolution of the continental margin and its extent eastward along the Gulf of Aden. We use teleseismic tomography to compute relative P wave velocity variations in south-western Yemen down to 300 km depth. Published receiver function analysis suggest a dramatic and localized thinning of the crust in the vicinity of the Red Sea and the Gulf of Aden, consistent with the velocity structure that we retrieve in our model. The mantle part of the model is dominated by the presence of a low-velocity anomaly in which we infer partial melting just below thick Oligocene flood basalts and recent off-axis volcanic events (from 15 Ma to present). This lowvelocity anomaly could correspond to an abnormally hot mantle and could be responsible for dynamic topography and recent magmatism in western Yemen. Our new P wave velocity model beneath western Yemen suggests the young rift flank volcanoes beneath margins and on the flanks of the Red Sea rift are caused by focused small-scale diapiric upwelling from a broad region of hot mantle beneath the area. Our work shows that relatively hot mantle, along with partial melting of the mantle, can persist beneath rifted margins after breakup has occurred.

Uppermost mantle velocity from Pn tomography in the Gulf of Aden

“…On the western margin of Yemen, around the city of Aden, two high-velocity anomalies are visible (8.2-8.4 km/s). These anomalies are consistent with the teleseismic tomography fi ndings of Korostelev et al (2014) showing high-velocity anomalies of ~4% at depths of 45 km and 70 km along the western margin of Yemen. Drawing on insights from receiver functions analysis (Ahmed et al, 2013b) on October 2, 2014 geosphere.gsapubs.org Downloaded from showing spatial coincidence between regions of overthickened crust with a high Vp/Vs ratio and thick basalt fl ows (seaward dipping refl ectors) suggestive of underplated ultramafi c bodies under the crust of the Red Sea and Aden margins, we interpret our low-velocity anomalies as underplated magmatic material.…”

Upper mantle velocity structure beneath the Arabian shield from Rayleigh surface wave tomography and its implications

“…The fast polarization direction of shear wave splitting for teleseismic SKS waves has a roughly north‐south orientation across the shield [ Wolfe et al ., ; Hansen et al ., ; Elsheikh et al ., ] indicating strong lattice preferred alignment due to north‐directed shearing deformation. Some studies also investigated the seismic structure beneath Cenozoic volcanic region and margin of the Arabian plate [e.g., Koulakov and Sobolev , ; Hansen et al ., ; Korostelev et al ., , ; Koulakov et al ., ] and find evidence for dike intrusions within the crust.…”

Multiple mantle upwellings in the transition zone beneath the northern East‐African Rift system from relative P‐wave travel‐time tomography

“…Over the past 20 years, motivated by the ongoing rifting, a large number of regional seismic networks, spanning the East African Rift system (including the Red Sea‐Gulf of Aden) from Mozambique to Saudi Arabia, have been deployed. These have yielded very detailed images of the upper 400 km of the mantle along sections of the EAR [e.g., Slack et al ., ; Ritsema et al ., ; Benoit et al ., ; Weeraratne et al ., ; Benoit et al ., ; Benoit et al ., ; Bastow et al ., ; Hammond et al ., ; Jakovlev et al ., ; Korostelev et al ., ]. A few studies merged data from several of these networks to yield images into the deeper mantle [e.g., Chang and Van der Lee , ; Hansen et al ., ].…”