Abstract
AbstractA 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 continental 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 (SWS) measurements. We recover a change of ∼90° (from approximately WNW to nearly NS) 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 in our SWS parameters for localized fossil deformation in the lithospheric mantle underlying the UAE‐Oman mountain range, possibly related to stress‐induced tectonism triggered by north‐east oriented underthrusting of the proto‐Arabian continental margin beneath the overriding Semail ophiolite. Shear‐wave‐splitting anisotropy orientations along two transects across the northern Musandam peninsula, averaging 15° anticlockwise from the north, provide the first geophysical verification of previous geological evidence that suggests a NE polarity of the Late Cretaceous Oman subduction zone system.
Highlights
The northeastern corner of the Arabian plate, from the Oman-United Arab Emirates (UAE) mountains around the Strait of Hormuz syntaxis to the Zagros Mountains in Iran, provides an excellent framework for understanding plate kinematics and geodynamics during the transition from ophiolite obduction to early continent-continent collision (Carminati et al, 2020; Glennie et al, 1973; Searle, 2007, 2019)
We find evidence in our shear-wave splitting (SWS) parameters for localized fossil deformation in the lithospheric mantle underlying the UAE-Oman mountain range, possibly related to stress-induced tectonism triggered by north-east oriented underthrusting of the proto-Arabian continental margin beneath the overriding Semail ophiolite
We argue that the persistent fast-polarization orientations localized in the UAE-Oman mountains region derive from the frozen-in deformation inherited from the continental lithospheric mantle during the NE-directed underthrusting of the Arabian passive margin (Figure 10)
Summary
The northeastern corner of the Arabian plate, from the Oman-UAE mountains around the Strait of Hormuz syntaxis to the Zagros Mountains in Iran, provides an excellent framework for understanding plate kinematics and geodynamics during the transition from ophiolite obduction to early continent-continent collision (Carminati et al, 2020; Glennie et al, 1973; Searle, 2007, 2019). Tectonic processes that affected the northeastern Arabian margin include (i) continental accretion during the Precambrian-Cambrian, multiple rifting events with accompanying basin subsidence and shelf carbonate deposition from Early Permian to Early Jurassic, post-rift stable sedimentary conditions (see Stern & Johnson, 2010, for a review of the Arabian plate), (ii) emplacement of the Semail ophiolite in Late Cretaceous and uplift of the UAE-Oman mountains (see Searle, 2019, for a review), and (iii) continental collision between the former Arabian passive margin and central Iran from Early Eocene (see Agard et al, 2011, for a review). A series of allochthonous thrust sheets (Haybi and Hawasina complex thrust sheets) were emplaced structurally beneath the ophiolite to the southwest
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