Exhumation during oblique transpression: The Feiran–Solaf region, Egypt

Abstract

The Feiran-Solaf metamorphic complex of Sinai, Egypt, is one of the highest grade metamorphic complexes of a series of basement domes that crop out throughout the Arabian-Nubian Shield. In the Eastern Desert of Egypt these basement domes have been interpreted as metamorphic core complexes exhumed in extensional settings. For the Feiran-Solaf complex an interpretation of the exhumation mechanism is difficult to obtain with structural arguments as all of its margins are obliterated by posttectonic granites. Here, metamorphic methods are used to investigate its tectonic history and show that the complex was characterized by a single metamorphic cycle experiencing peak metamorphism at 700-750°C and 7-8 kbar and subsequent isothermal decompression to 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 D 2 , while the compressive D 2 and D 3 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 15 km depth must have occurred due to an unrelated mechanism.

Nd–Sr–Hf–O isotope provinciality in the northernmost Arabian–Nubian Shield: implications for crustal evolution

“…The older MCs in this region include orthogneisses, and meta-sedimentary and -volcanic sequences, all metamorphosed at greenschist to amphibolite facies conditions (ElShafei and Kusky 2003;Eyal et al 1980;Jarrar et al 1983;Katz et al 1998;Matthews et al 1989;Shimron 1984;Blasband et al 2000;Abu-Alam and Stüwe 2009). In the study area of Sinai and southern Israel, these are grouped into four complexes: the Elat-, Feiran-, Sa'al-, and KidMCs (Fig.…”

Calc-silicates from Wadi Solaf region, Sinai, Egypt

“…2a). In the center metamorphic grade is reported to have reached upper amphibolite facies and locally granulite facies conditions from 700°C to 750°C at pressure from 6 kbar to 8 kbar during the Pan-African Orogeny around 600 Ma (Akaad et al, 1967a,b;El-Gaby and Ahmed, 1980;Hashad et al, 2001;Eliwa et al, 2008;Abu-Alam and Stüwe, 2009). In contrast, the metamorphic grade of the rocks at higher structural level is reported to be around 600-650°C at the same pressure condition (Abu-Alam and Stüwe, 2009).…”

“…It has evolved and was exhumed in close connection with the activity of this shear zone system (Abu-Alam and Stüwe, 2009). The complex can be divided into two zones: the Feiran zone in the northwest and the Solaf zone ( Fig.…”

The pegmatitic rocks of El-Hudi and Um Hibal areas, Southeastern Desert, Egypt: genesis and petrological characteristics

“…The structural basement experienced high-grade metamorphism and deformation with peak P-T conditions around 680°C and 0.8 GPa (Neumayr et al 1998;Loizenbauer et al 2001;Abd El-Naby et al 2008;Abu-Alam and Stüwe 2009). This suggests detachment between deeply buried island arc roots and volcanosedimentary cover nappes that remained at shallow crustal levels.…”

“…Gneissic domains in Sinai are intruded by large volumes of late tectonic plutons that frequently preclude recognition of structures along the contact between high-grade gneiss terranes and the volcanosedimentary carapace. Early thrust sheets may have been transported SSE-ward and are later transposed by sinistral shear (El- Shafei and Kusky 2003;Abu-Alam and Stüwe 2009;Fowler et al 2010a, b).…”