Deep electrical structure of the northern UAE: An investigation along the Dibba zone and the foreland basin using magnetotellurics

Abstract

Recent geophysical studies are focused on imaging the present-day architecture of the subsurface structures in the northern United Arab Emirates. Previous geophysical data have not fully investigated the deep structures in the middle and lower crust. The foreland basin flanking the UAE-Oman mountains to its west has been investigated by oil companies, mainly using seismic techniques. These studies have been vital in providing a constraint on the subsurface structure of the northern Emirates. This paper reports the results of using broad-band magnetotelluric (BBMT) data acquired for the first time in the UAE to map deep electrical crustal structures. The study aims at determining the geometry of the Semail Ophiolite, the underlying thrust sheets, and the basement structure beneath the allochthonous units and the foreland basin. The MT data were collected from 15 stations along an E-W profile across the Semail Ophiolite and the Dibba zone in the east and the foreland basin in the west. The MT data achieve greater crustal penetration, revealing electrical structures within the upper, mid, and lower crust. 2D and 3D inversion of the data map the high resistivity Ophiolite structure and the associated conductive Hwasina-Haybi thrust sheets in the mountain ranges and in the Dibba zone. In the foreland basin, the Quaternary and Tertiary sediments in the Pabdeh basin are characterized by low resistivity. Furthermore, the MT models detect a high resistivity zone related to the basement structure of the northern UAE in the middle and lower crust. The Ophiolite near the Dibba zone has >7 km thickness as shown in the 2D MT model, and the Hawasina-Haybi sheets have a maximum thickness of ⁓10 km beneath the Ophiolite. The allochthonous units indicate an oceanward dipping as similarly reported in the previous geophysical and geologic studies.