New Constrains on the Thickness of the Semail Ophiolite in the Northern Emirates

Abstract

Near-critical angle and refraction studies were performed at IFP as piggyback studies during a wider programme of crustal imagery operated by WesternGeco on behalf of the Ministry of Energy of the United Arab Emirates. The main objective is to illuminate the base of the Semail Ophiolite along part of a regional transect (D1) crossing the Northern Emirates from the Gulf of Oman in the east up to the Arabian Gulf in the west. Results confirm that the sole thrust of the ophiolite has been folded during the Miocene stacking of the underlying Arabian Platform. The thickness of the ophiolite grades from zero in the core of the Masafi tectonic window, up to a maximum of 1.7 km below the axial part of a successor basin which has been preserved on top of the serpentinite west of the current exposure of the main ultramafic bodies. Apatite grains extracted from plagiogranites of the Semail ophiolite also provide evidences for an early unroofing of the gabbros and plagiogranites during the Late Cretaceous, with cooling ages of 72-76 Ma at the top of the ophiolite in the east (not far from the Fujairah coast line), which are coeval and also consistent with the occurrence of Late Cretaceous paleo-soils, rudists and paleo-reef deposits on top of serpentinized ultramafics in the west. Younger cooling ages of 20 Ma have been also found at the base of the ophiolite near Masafi, in the core of the nappe anticline, thus providing a Neogene age for the refolding of the allochthon and stacking of underlying parautochthonous platform carbonate units. These results, together with the occurrence of a thick sedimentary pile illuminated below the metamorphic sole along the north-trending, strike-profile D2 running parallel to the axis of the Masafi window, should stimulate a renewal of the exploration in the central part of the Emirate foothills, where the ophiolite thickness is currently limited, and was already drastically reduced by the end of its Late Cretaceous obduction.

Paleo-fluids characterisation and fluid flow modelling along a regional transect in Northern United Arab Emirates (UAE)

“…2). Deeper platform duplexes are evidenced on seismic profiles, and have been locally proven to be productive (gas-condensate) further south in the Margham and Sajaa fields (Blinton and Wahid 1983;Alsharhan 1989;O'Donnell et al 1994; Fig. 2).…”

Tectono‐Stratigraphic Evolution of the Foreland Fold‐and‐Thrust Belt of the United Arab Emirates

“…Jardin et al (2013) focused on advanced seismic processing and depth migration of the deep seismic sections, whereas Tarapoanca et al (2013) applied coupled kinematic-thermal-petroleum modeling along D1 and D4 profiles. Moreover, Naville et al (2013) used the same four deep seismic profiles (D1-D4) to constrain on the thickness of the Semail ophiolite. They observed a west-dipping basal Semail thrust west of the Masafi window, which they attributed to a late-stage refolding of the Semail and Hawasina-Sumeini thrust sheets during the Neogene duplexing of the underlying Arabian margin.…”

“…Western Geco acquired four regional deep seismic profiles (D1-D4; Figure 1) in the northern UAE for the Ministry of Energy to determine crustal structures in the region (Callot et al, 2010;Jardin et al, 2013;Naville et al, 2013;Tarapoanca et al, 2013). Additionally, British Geological Survey and Fugro conducted regional geological mapping, and aerogravity and aeromagnetic surveys, respectively (Styles et al, 2006).…”