FEIRAN-SOLAF METAMORPHIC COMPLEX, SINAI: ITS RELATIONSHIP TO THE CORE COMPLEXES OF THE ARABIAN NUBIAN SHIELD

The high-grade metamorphic rocks of the Arabian-Nubian Shield are exposed in a series of tectonic windows which are exposed from underneath a low grade arc assembly. In the Eastern Desert of Egypt, these basement complexes have been interpreted as metamorphic core complexes exhumed in extensional settings. In Sinai, the exhumation mechanism of Feiran-Solaf complex is difficult to obtain with structural arguments as all of its margins are obliterated by post-tectonic granites. Here we use metamorphic methods to investigate its tectonic history and show that the Feiran-Solaf complex was characterised by a single metamorphic cycle experiencing peak metamorphism around 700 – 750 °C and 7 – 8 kbar and subsequent isothermal decompression to about 4 – 5 kbar, followed by near isobaric cooling to 450 °C. Correlation of this metamorphic evolution with the deformation history shows that peak metamorphism occurred prior to the compressive deformation phase D₂, while the compressive D₂ and D₃ deformation occurred during the near isothermal decompression phase of the P-T loop. We interpret the concurrence of decompression of the P-T path and compression by structural shortening as evidence for the Najd fault system exhuming the complex in an oblique transpressive regime. However, final exhumation from 14.5 km depth must have occurred due to an unrelated mechanism. In the Arabian part of the Arabian-Nubian shield, no metamorphic studies exist for the high-grade metamorphic complexes which have more or less the same geometry as the Feiran-Solaf complex. The Arabian complexes need further studies to draw an overview for the evolution of the high-grade metamorphic rocks of the Arabian-Nubian Shield during the Pan-African Orogen.