PETROGENESIS OF THE YOUNGER METAVOLCANICS EXPOSED AROUND GABAL UMM DISI NORTH EASTERN DESERT, EGYPT

The exposed younger metavolcanics around Gabal Umm Disi are differentiated into: lava flows and their equivalent pyroclastics. The lava flows include: andesites, trachy-andesites and dacites. The metapyroclastics comprise tuffs and less commonly lapilli tuffs.The mineral assemblages of these metavolcanics confirmed that they are metamorphosed up to the epidote-amphibolite fades. They were comparable with the younger metavolcanics (YMV).Geochemical data indicate that the studied metavolcanics are calc-alkaline with slight tendency toward tholeiitic affinity and were formed in an island arc tectonic setting.They were probably generated under slightly different degree of partial melting of mantle derived magma above subduction zone and suffered a limited shallow depth fractional crystallization