CONTRIBUTION TO GEOLOGY AND URANIUM DISTRIBUTION OF SOME BASEMENT ROCKS IN EL-MUEILHA AREA, SOUTH EASTERN DESERT, EGYPT

Metadacite is composed of phenocrysts of plagioclase, quartz, K-feldspar, hornblende and, in less
order, biotite. These minerals are embedded in ground mass of felsic and mafic minerals forming the
porphyroblast texture. The meta-andesite is mainly composed of plagioclase, hornblende and quartz
showing common porphyroblast texture in addition to the descriptive pilotaxitic textures. The more or
less availability of the mineral assemblage of chlorite, actinolite, epidote, sericite, zeosite, plagioclase and
quartz might support that both the metadacite and metandesite are susceptible to change in temperature
and pressure and they were affected by the low greenschist facies metamorphism.
The granitoid rocks are recognized as monzogranite, granodiorite and quartz-diorite. All of them showed
the traditional petrographic features and mineral composition. However presence of more than one
phase of some main minerals in the same rock may indicate successive magmatic crystallization history.
The REE data of the studied granitoids points to a complicated origin of these rocks and their arising from
volcanic arc-magmatism with significant role of some minerals, e.g. the orthopyroxenes, clinopyroxenes,
plagioclases and zircon, found in parent sources of these granitoids. Both the monzogranite and the
granodiorite are considered as uraniferous granites and tend to be of fertile type. The uranium seems to be
of magmatic origin, particularly in the monzogranite, and linked to the accessory minerals with probable
leaching from its bearing partial-metamectized zircon resulted in a disequilibrium state.