Metapelitic assemblages in the Umm Zariq schists, central western Kid Belt, Sinai Peninsula, Egypt
Abu El-Enen, Mahrous M.; Okrusch, Martin; Will, Thomas M.
published: May 12, 2003
ArtNo. ESP154017803003, Price: 29.00 €
The Kid Belt, one of the four metamorphic belts constituting the Pan-African basement of the Sinai Peninsula, underwent two main phases of ductile deformation and regional metamorphism ranging in grade from the greenschist facies in the south to the upper amphibolite facies in the northeast. In the central western part of the Kid Belt, metapelites of the Umm Zariq Formation display the following mineral assemblages (always + quartz + plagioclase An20-38 + ilmenite): (i) garnet + biotite + muscovite ± andalusite, (ii) garnet + staurolite + biotite + muscovite ± cordierite ± andalusite, (iii) garnet + cordierite + biotite + muscovite ± andalusite ± (rare) sillimanite, testifying to the low pressure type of metamorphism under PT-conditions of the lower amphibolite facies. Conventional geothermobarometry yielded peak metamorphic temperatures around 570 °C and pressures of about 4 kbar. Conformable results were obtained from a petrogenetic grid, calculated in the system KMnFMASH and applied to a sample with the low-variance assemblage (ii). The PT-area for the formation of the near-peak assemblage andalusite-staurolite-garnet-biotite extends from some 3 to 4 kbar and 540 to 590 °C. Calculations on this mineral assemblage (+ plagioclase + muscovite + quartz) with the internally-consistent thermodynamic data set of Holland & Powell (1998) yield similar PT-conditions of 4.2 ± 0.9kbar and 591 ± 28 °C (2δ).