Late Proterozoic extensional collapse in the Arabian-Nubian Shield

A structural and petrological study of the Late Proterozoic rocks in the Wadi Kid area, Sinai. Egypt indicates the presence of an extensional metamorphic core complex in the northern Arabian-Nubian Shield. Gneissic domes throughout the Arabian-Nubian Shield resemble the core complex of the Wadi Kid area and as a result, they are interpreted as extensional metamorphic core complexes. The presence of a widespread phase of extension at the end of the Pan-African period in the Arabian-Nubian Shield requires a new interpretation of the tectonic history of this shield. Three main tectonic phases are recognized in the Late Proterozoic of the Arabian-Nubian Shield. Ophiolites and island-are remnants are relicts of an oceanic phase, the oldest one. This phase was followed by arc-accretion, well established in the Arabian-Nubian Shield from the presence of individual terranes bordered by sutures, which was responsible for lithospheric thickening. The Late Proterozoic ended with widespread NW-SE extension. The metamorphic core complexes, late-orogenic extensional basins and large strike slip zones were formed during this phase. Similarity of the tectonic evolution of the Arabian-Nubian Shield with the Mesozoic and Early Cenozoic evolution of western North America lead us to conclude that gravitational instability at the final stages of the arc-accretion phase caused the collapse and resulted in extension at the latest stages of the Pan-African orogeny in the Arabian-Nubian Shield.