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Universität Graz (2010)

Metamorphic and structural evolution of the Wadi Feiran Complex, Southwest Sinai

Abu-Alam, Tamer S.

Titre : Metamorphic and structural evolution of the Wadi Feiran Complex, Southwest Sinai

Auteur : Abu-Alam, Tamer S.

Université de soutenance : Universität Graz

Grade : Doctoral Thesis (PhD) 2010

High-grade metamorphic rocks of Arabian-Nubian Shield and entire East-African Orogen are exposed as a series of tectonic windows which are surrounded by low-grade metamorphic rocks or by igneous rocks. The tectonic windows of Eastern Desert of Egypt were interpreted as core complexes formed in extension setting with strong relation to a major Proterozoic shear zone in the region : the Najd Fault System. However, one of the highest grade complexes in Egypt and the largest metamorphic one in Sinai has not been studied metamorphically : the Feiran-Solaf Metamorphic Complex. The study shows that the complex was characterised by a single metamorphic cycle experiencing peak metamorphism around 700 ?750°C and 7 ?8kbar and subsequent isothermal decompression to about 4 ?5kbar. At depth of 4-5kbar, the study area subjected to intrusion of syn-tectonic granitic magma and associated fluid infiltration processes. The fluid infiltration process and the contact metamorphism appear clearly in the calc-silicate rocks which emerge in Wadi Solaf. The rocks reached a peak contact metamorphism conditions at temperature 790 ? 828oC and XCO2 = 0.22 ?0.41. Finally, the rocks reached a temperature range 296-311oC during the isobaric cooling path. 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. In chapter three, the strain caps were discussed as a microstructure feature that has a strong links to metamorphic petrology in general and this chapter provides a conceptual aspect of the thesis. The strain cap was defined as a series of microstructures that typically form during deformation of a softer matrix around hard objects. Fluid flow that is preferentially focused parallel to the foliation planes causing only local adjustment to retrograde metamorphism in the strain cap region is the most preferable mechanism to form starin cap minerals.


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