Geothermobarometric evidence for a metamorphic core complex in Sinai, Egypt

Blasband et al. [Geologie en Mijnbouw 76 (1997) 247, J. Geol. Soc. Lond. 157 (2000) 615] postulated a metamorphic core-complex model for the Wadi Kid area, south Sinai, Egypt. This core complex was formed in an extensional setting after gravitational collapse of the East African Orogen in the Late Proterozoic. Arc-accretion was responsible for the closure of the Mozambique Ocean. Blasband et al. [Geologie en Mijnbouw 76 (1997) 247, J. Geol. Soc. Lond. 157 (2000) 615] based their theory mainly on structural data. In order to justify this model geothermobarometric evidence is crucial. Therefore, the metamorphic rocks of the Wadi Kid area were the subject of a detailed metamorphic study. metamorphic phase is characterized by greenschist-facies conditions and is related to arc-accretion. The M2 metamorphic phase is the main subject of this paper. The petrologic characteristics of pelitic and mafic rocks that were metamorphosed during M2 show that the lower crustal rocks in the Wadi Kid area were subjected to upper greenschist to upper amphibolite conditions of the low-pressure/high-temperature type at the end of the Late Proterozoic. Garnet-biotite and amphibole-plagioclase geothermometry reveal temperatures of 488–684 °C. Plagioclase-biotite-muscovite-garnet geothermometry and amphibole-plagioclase geobarometry indicate pressures of 3.42–4.28 kbar. metamorphic phase is associated with a D2 deformation phase. This phase is a relict of gravitational collapse during the final stages of the collision of East and West Gondwanaland.