Deflected Mantle Flow and Shearing-Aligned Lithospheric Melt Under the Strike-Slip Dead Sea Rift

Abstract

Continental rifting is one of the fundamental tectonics of the Earth evolution while our current understandings on the dynamic mechanism of the strike-slip ones are relatively limited. Here, we have utilized three kinds of core-refracted shear waves (including PKS, SKKS, and SKS) and employed the shear-wave splitting technique to systematically investigate the azimuthal anisotropy of the upper mantle under the typical strike-slip Dead Sea rift. There are a total of 1,855 well-determined anisotropic measurements from 187 stations with dominantly N-S fast orientations. We have proposed a new model from a joint analysis of multiple newly available geophysical observations to interpret the resulting anisotropy as mainly due to the absolute-plate-motion-driven mantle flow deflected by the thick lithosphere of the eastern Arabian plate. Relatively larger splitting times are locally revealed at the rift zone and attributed to additional lithospheric anisotropy from the shearing-oriented melt pockets whose existence further induces complex anisotropy with slight difference of fast orientations between the upper and lower layer anisotropy. The overall rift-parallel fast orientations, when combined with the absence of low-velocity and hot thermal anomalies in the mantle transition zone, rule out the role of mantle plume or edge-driven convection in the rift development and further infer the Dead Sea rift to evolve in a passive mode.