PETROGRAPHICAL , GEOCHEMICAL AND RADIOACTIVITY STUDIES ON GRANITE AND GRANODIORITE ASSOCIATIONS IN ASWAN CATARACTS, EGYPT

Aswan granites are divided into two types: 1) granite extends from Aswan north to El Shellal southand 2) granodiorite-quartz monzodiorite form two separated elongated and parallel bodies extendingin N-S direction. At the contact between the two types there are some enclaves and ferromagnesianminerals.Aswan granite is composed mainly of alkali-feldspars, plagioclase, quartz, biotite, hornblende. Allanite,zircon , monazite, fluorite, apatite, titanite and opaques are the main accessory minerals. Secondaryminerals are muscovite, chlorite and carbonates. Two generations of quartz which included in hornblende,microclinization of plagioclase, presence of skeletal apatite, presence of secondary titanite in granitedue to the presence of high titanium content which derived from granodiorite-quartz monzodiorite, thepresence of zircon included in biotite and both of them mantled with hornblende and the presence ofdifferent types of textures, all the previous are some criterias for magma mixing.There are some criteria in the geochemistry of the trace elements for magma mixing, presence of lowcontent of Ba and Sr in granite as compared with granodiorite-quartz monzodiorite, low Zr content ingranite but high in granodiorite-quartz monzodiorite, presence of high Zn and Pb in granite and thepresence of small gab between the two rock samples which may be attributed to absence of completespectrum of samples to causes such gabs.This study revealed that the uranium content in granite is lower than that of granodiorite-quartzmonzodiorite and the thorium content in granite is greater than that of granodiorite-quartz monzodioritewhich give an indication for the mixing magma. On the other hand, the uranium content in both typesare suitable for using this granite as ornamental stones.