A geodynamic model for the distribution of the oceanic plate slivers within a Pan-African orogenic belt, Eastern Desert, Egypt

Abstract

The Gabal Meatiq-Wadi Atalla area, central Eastern Desert, Egypt, is an arc-arc collision zone, which lies within the Pan-African orogenic belt of NE Africa. This collision zone consists of a Gneiss Dome situated at the concave side of an arcuate ophiolitic mélange belt. Island arc metavolcanics bound this collision zone from both sides. Syn-collision foreland molasse troughs occur in an arcuate zone bordering the ophiolitic mélange, and uncomformably overly the mélange belt. Late-collision intermontane molasse troughs occur away from the collision zone. Oceanic plate fragments, dominantly composed of serpentinite sheets and ophiolitic complexes, occur within the subduction mélange. Widely dispersed high-grade oceanic plate slivers composed of ortho-amphibolites and talc-serpentinite lenses occur within the migmatitic gneisses of the Gneiss Dome. The dominance of the serpentinite sheets within the subduction mélange may suggest obduction of broken upper mantle fragments from the base of an overriden oceanic plate margin. The thick ophiolitic complexes in the mélange may suggest gravity slide of oceanic plate fragments from the overriding oceanic plate margin. The oceanic plate slivers within the Gneiss Dome might have resulted partly from gravity slide of broken fragments from an outer-arc ridge into a forearc basin, and partly represent protrusions from subduction mélange wedges underlying the margin of the forearc basin.