Abstract

Basement exposed on the perimeter of the Red Sea was created during the Pan-African event at the end of the Precambrian. Pre-Pan-African crust in the northern part of this region has not yet been identified. This paper reports the results of Rb–Sr whole-rock and U–Pb zircon dating of gneisses and related basement units from the Wadi Feiran area in the Sinai peninsula, where the existence of such older basement has previously been suggested. A post-tectonic extensional dyke gives a Rb–Sr age of 591 ± 9 Ma with an initial 87Sr/86Sr ratio of 0.7034 ± 0.0002. Rb–Sr whole-rock and thin slab dating of paragneisses gives ages of c. 610 Ma with an initial 87Sr/86Sr ratio of 0.7035. A U–Pb zircon age of 632 ± 3 Ma is interpreted as either the time of formation of these gneisses or the age of the crust sampled by protolith sediments. Granodiorite to the east gives a U–Pb zircon age of 782 ± 7 Ma and is interpreted as representing the westernmost extent of a 780 ± 50 Ma terrane that extends across Sinai into Jordan. Uplift and erosion of the 780 ± 50 Ma terrane supplied detritus to flanking terranes in N and SE Sinai. This region thus acted as a foreland to the younger accretionary and extensional units to the south and west that were active later in the Pan-African event. There is still no evidence for pre-Pan-African basement in the Precambrian units around the northern Red Sea east of the Nile.

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