GEOCHEMISTRY OF THE WADI-HAWASHIA GRANITE COMPLEX, NORTHERN EGYPTIAN SHIELD

The Hawashia Complex is comprised of calc-alkaline granitic rocks of p eraluminous character. The bulk of the complex is composed of biotite granite, while the other intrusive phases, namely the ''leucocratic- a nd alkali feldspar'' granites, only constitute a minor proportion of t he exposed surface area of the complex. Fractional crystallization is the dominant mechanism, which is necessary to explain the chemical att ributes within the complex. Geochemical modelling reveals that an earl y stage of crystallization, which was controlled by plagioclase and am phibole separation, is necessary to generate the biotite granite. Late r stages are dominated by K-feldspar crystallization, which evolves in to the alkali feldspar granite. In contrast with the leucocratic grani te, the alkali feldspar granite displays a significant enrichment in H FS elements (Nb, Y, Th, Zr) and a strong depletion in Ba and Sr. The s mall volume and the restriction of the alkali feldspar granite to the roof of the pluton, together with the specialized chemical signature, all substantiate the role of the volatile enhancement in the upper por tion of the magma chamber This volatile fraction was efficient in remo ving highly charged cations from the leucocratic granite and re-enrich ing them in the alkali feldspar granite.