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 south
and 2) granodiorite-quartz monzodiorite form two separated elongated and parallel bodies extending
in N-S direction. At the contact between the two types there are some enclaves and ferromagnesian
minerals.
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. Secondary
minerals 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 granite
due to the presence of high titanium content which derived from granodiorite-quartz monzodiorite, the
presence of zircon included in biotite and both of them mantled with hornblende and the presence of
different 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 low
content of Ba and Sr in granite as compared with granodiorite-quartz monzodiorite, low Zr content in
granite but high in granodiorite-quartz monzodiorite, presence of high Zn and Pb in granite and the
presence of small gab between the two rock samples which may be attributed to absence of complete
spectrum of samples to causes such gabs.
This study revealed that the uranium content in granite is lower than that of granodiorite-quartz
monzodiorite and the thorium content in granite is greater than that of granodiorite-quartz monzodiorite
which give an indication for the mixing magma. On the other hand, the uranium content in both types
are suitable for using this granite as ornamental stones.