Crustal and mantle deformation inherited from obduction of the Semail
ophiolite (Oman) and continental collision (Zagros)
Abstract
A common deviation from typical subduction models occurs when thrust
sheets of oceanic-crust and upper-mantle rocks are emplaced over more
buoyant continental lithosphere. The archetypal example of ophiolite
obduction is the Semail ophiolite in the United Arab Emirates (UAE)-Oman
orogenic belt, formed and obducted onto the Arabian continental margin
during the Late Cretaceous. The Strait of Hormuz syntaxis, the northern
extent of the UAE-Oman mountains, marks the transition from
ocean-continent convergence in the Gulf of Oman to continental collision
along the Zagros Mountains. Based on new seismic data from a focused
recording network, we infer crustal and mantle deformation in the
northeastern corner of the Arabian plate (including the southern Zagros
and the UAE-Oman mountains), using observations from anisotropic
tomography and shear-wave splitting measurements. We recover a change of
~90˚ in the axis of fast-anisotropic orientations in the
crust from the Zagros to the UAE-Oman mountain belt, consistent with the
dominant strike of the orogenic belts. We also find evidence for
localized fossil deformation in the lithospheric mantle underlying the
UAE-Oman mountain range, possibly related to stress-induced tectonism
triggered by underthrusting of the proto-Arabian continental margin
beneath the overriding Semail ophiolite. These orientations, averaging
15˚ anticlockwise, provide the first geophysical verification of
geological