PETROLOGICAL STUDY OF WADI MAGRISH MIGMATITES, NE SINAI, EGYPT

A detailed petrological study was carried out on migmatites of Wadi Magrish (Taba, Sinai) to constrain the P-T conditions of metamorphism and partial melting. On the basis of their field appearance, migmatites are subdivided into undifferentiated (massive) and stromatic types. The latter is typified by a layered structure. Most layers of leucosomes are concordant or discordant by a few degrees to the host rock foliation. Others are clearly discordand. The host rock is interpreted to have metasedimentary origin.

Leucosomes are trondhjenitic in composition (quartz + plagioclase + biotite). The K-poor composition of this product could imply melting under high H2O activity conditions. The migmatite mesosomes contain assemblage of biotite + quartz + plagioclase + garnet + sparce sillimenite. Melanosomes with higher biotite content occur sometimes adjacent to leucosome layers.

Assemblages of garnet + plagioclase + quartz + biotite as well as garnet + biotite are used to provide information for pressure and temperature calculations, respectively. Preliminary findings suggest that the migmatites formed at low/medium pressure condition and at temperatures near 750 degree.