Late Cretaceous Ophiolite Emplacement and Cenozoic Collisional Tectonics in the Northeastern Arabian Plate: Insights From New Broadband Magnetotelluric Data

Abstract

The Late Cretaceous obduction of the Semail Ophiolite onto the rifted passive Arabian margin and the Cenozoic collisional tectonics with the final closure of the Neo-Tethys Ocean, are major contributors to the present-day crustal architecture of the northern United Arab Emirates (UAE). We acquired the first 3D grid magnetotelluric observations from 73 stations in the northern UAE in order to image deep crustal electrical structures associated with the two significant compressional episodes. Inversion of the broadband magnetotelluric data reveals the subsurface geometry of the high-resistivity ophiolite blocks, the underlying conductive thrust sheet (Haybi-Hawasina nappe), a “wedge-shaped” conductive foreland basin flanking the Hajar mountain ranges, and at depth, a high-resistivity structure associated with a fold-thrust belt adjacent to the allochthonous units, or Proterozoic crystalline basement. The ophiolite along the eastern coast (from cities Khor Fakkan to Fujairah) is more than 20 km thick and dips eastward. Across the Wadi Ham fault, the resistive ophiolite lies against less resistive materials that may represent Bani Hamid metamorphic rocks. The thin-skinned thrust sheets of the proximal-distal Tethyan sedimentary units (Haybi-Hawasina complexes) exhibit low resistivity in the Dibba zone. In contrast to its gently east-dipping geometry in the Dibba zone, the conductive Haybi-Hawasina structure in the southern portion of the study area appears nearly vertically (>20 km) beneath the dense Khor Fakkan and Aswad ophiolite blocks. This result suggests extensive deformation of the thrust sheets beneath the southerly dense ophiolite blocks.