The late Pan-African granites of Gabal Abu Harba area occur in the North Eastern Desert of Egypt. Field and mineralogical studies indicate that the granites comprise coarse-grained biotite granite and mediumgrained leucogranite. The geochemical characteristics categorize these rocks as syenogranite and alkali feldspar granite according to the Ab-Or-An normative values. The syenogranite, as compared with the alkali feldspar granite, possesses lower A/CNK ratio values, higher P 2 O 5 , CaO, TiO 2

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... , Sr and Ba contents, and is depleted in Rb, Nb, Th, U. The U contents of the alkali feldspar granite (average=12.3ppm) suggest fertile-U source to constitute a suitable setting for uranium minerals formation by later hydrothermal fluids. The alkali feldspar granite was affected by hydrothermal solutions along its fault planes, causing a series of zones of wall-rock chloritization, sericitization, kaolinitization, carbonatization and hematitization as well as highly enrichment of U and slight mobilization for Th. The secondary uranium minerals, locally identified in these altered parts, comprise chiefly beta-uranophane and kasolite. Whole-rock geochemistry shows that the altered alkali feldspar granite experienced both sodic and potassic metasomatism. Mass balance calculations, with reference to unaffected alkali feldspar granite, evidenced loss for SiO 2 , TiO 2 , FeO, MgO, CaO and K 2 O and LREE contents, and gain of both the HREE (Tm, Yb and Lu) and most of the trace elements (Sr, U, Zn and Pb).