Uranium mineralization in the two mica granite of Gabal Ribdab area, SouthEastern Desert, Egypt

Among the different rock units in the Gabal Ribdab area, the two-mica leuco granite and muscovite pegmatitic granite are the most favourable host rocks for uranium and thoriurn mineralization. The muscovite pegmatitic granite shows evidence of post-magmatic alteration, e.g. Na- and K-metasomatism, wh ereas the two-mica leucogranite could be regarded as being fresh. The spect rometric survey revealed the presence of three enriched zones with a maximu m eU content of 140 ppm and the maximum eTh is 36 ppm. Uranophane, zippeite and becquerelite are the most abundant uranium minerals. The origin of the se secondary minerals is mainly related to alteration of primary minerals b y the action of oxidizing fluids, mobilization of uranium and then redeposi tion in other forms. Redistribution by circulating meteoric waters might ha ve taken place. (C) 2001 Elsevier Science Ltd. All rights reserved.