Upper mantle structure beneath the arabian peninsula from regional body wave tomography: implications for the origin of cenozoic uplift and volcanism in the arabian shield

Abstract

We investigate upper mantle structure beneath the Arabian Shield, and parts of the Arabian Platform and Red Sea by modeling P and S travel time residuals from teleseismic events recorded on the Saudi Arabia National Digital Seismic Network, the 1995-1997 Saudi Arabian PASSCAL Experiment, and three permanent stations (RAYN, EIL and MRNI). Relative travel time residuals were obtained using a multi-channel cross-correlation method and inverted for upper mantle structure using VanDecar’s method. The resulting images reveal a broad low velocity region (~1.5% for the P model and ~3% for the S model) generally trending N-S beneath much of the Arabian Shield. The region with the largest amplitude anomaly is located beneath the southern part of the Arabian Shield, but resolution tests indicate that differences in the amplitude of the anomaly across the Shield could result from variations in resolution. We attribute the low velocities to a mantle thermal anomaly that could be as large as 330 K, and that is associated with Cenozoic uplift of and volcanic centers on the Shield. Our tomographic images are not consistent with models invoking separate mantle upwellings beneath the northern and southern regions of the Shield and instead favor single plume or superplume models. We also find little evidence for low velocities beneath the parts of the Red Sea where upper mantle structure can be resolved in our model. This result is not congruent with a geodynamic connection between Red Sea rifting and the plateau uplift and volcanism in the Shield.