GEOCHEMISTRY AND PETROGENESIS OF SIKAIT LEUKOGRANITE, EGYPT - AN EXAMPLE OF S-TYPE GRANITE IN A METAPELITIC SEQUENCE

The Sikait leucogranite (SLG) is a body of porphyritic garnet granite intruded a metapelitic sequence and interlayered orthogneisses. Multip le deformation and low- to medium-grade metamorphism of the sequence w as closely associated with pluton emplacement. Textural features of th e SLG indicate that subsolidus plastic deformation was induced during the extensive thrusting. The granite is strongly peraluminous, alkali- rich and HFS (high field-strength) elements-depleted with low contents of REE, all facts that substantiate the geochemical characteristics o f S-type granites. The geologic and geochemical features are consisten t with a dehydration melting model of the hosted metapelites to genera te the peraluminous SLG. However, geochemical modelling of trace eleme nts and REEs suggest that the anatectic partial melt was subsequently affected by fractional crystallization of feldspars. This could explai n much of the chemical attributes of SLG.