COMPARATIVE STUDIES OF THE GEOLOGY, MINERALOGY, AND GEOCHEMISTRY OF SOME U-MINERALIZATION IN THE EASTERN DESERT, EGYPT

Abstract

This work first characterizes the petrographical and geochemical features of Gabal Qattar, North Eastern Desert and Gabal Urn Ara, South Eastern Desert. It also describes and discusses and discusses the genesis of their spatially associated small-sized epigenetic fault-controlled U-mineralizations. The unaltered rocks of the two plutons comprise peraluminous biotite granites which are classified as leucocratic exhibiting subsolvus textures. Their major oxides chemistry is very similar to low calcium granites. These granitic rocks are also depleted in the compatible trace elements (Ni,Sr,Ba and Pb), and enriched in the incompatible ones (Rb,Y,Zr,Nb,Th and U), which suggest originating from calc­ alkaline peraluminous magmas developed in a within-plate (A-type) anorogenic tectonic setting. such magmas were probably formed by high temperature partial melting of deep residual sources which suffered extraction of granitoid liquids before, in the presence of volatile rich fluids. These melts alter underwent significant crystal-liquid fractionations.

The peripheral zones where the U-mineralizations occur show the effects of late- to post-magmatic hydrothermal alterations by F-rich fluids causing abundant appearance of fluorite, F-rich mica,_topaz, zircon and Nb-Ta-Sn oxides. Uranium nd thorium were remobilized and enriched exhibiting a low-Th high-U type characteristic of low temperature hydrothermal type deposits dominated by epigenetic secondary U-minerals uranophane and P-uranophane.

Combining the bove characteristics with the estabilished ones for other granitic plutons (Al-Missikat Al Aradiya, Al Atawi and Abu Garadi) in the Centeral Eastern Desert, the following recognition criteria of a Uranium Province in Egypt can be identified: 1- Discordant individual or cluster of plutons, epizonally emplaced and sometimes associated with major faults.