Abstract The Neoproterozoic granite of Gabal Abu Diab,
central Eastern Desert of Egypt, comprises mainly garnetbearing
granite and alkali feldspar granite intruded into
calc-alkaline granodiorite–tonalite and metagabbro–diorite
complexes. The garnet-bearing granite is composed
mainly of plagioclase, K-feldspar, quartz, garnet and
primary muscovite ± biotite. The presence of garnet and
primary muscovite of Abu-Diab granite suggests its
highly fractionated character. Geochemically, the garnetbearing
granite is highly fractionated as indicated from
the high contents of SiO2 (74.85–77.5%), alkalis (8.27 to
9.2%, Na2O+K2O) and the trace elements association: Ga,
Zn, Zr, Nb and Y. This granite is depleted in CaO, MgO,
P2O5, Sr and Ba. The alumina saturation (Shand Index,
molar ratio A/CNK) of 1.0 to 1.1 indicates the weak
peraluminous nature of this garnet-bearing granite. The
geochemical characteristics of the Abu Diab garnetbearing
granite are consistent with either the average
I-type or A-type granite and also suggest post-orogenic or
anorogenic setting. A fluid inclusions study reveals the
presence of three fluid generations trapped into the studied
granite. The earlier is a complex CO2–H2O fluid trapped
in primary fluid inclusions with CO2 contents >60 vol.%.
These inclusions were probably trapped at minimum
temperature >400°C and minimum pressure >2 kb. The
second is immiscible water–CO2 fluid trapped in secondary
and/or pseudo-secondary inclusions. The trapping conditions
were estimated at temperature between 400°C and
170°C and pressure between 900 and 2000 bar.
The latest fluid is low-salinity aqueous fluid trapped
in secondary two-phase and mono-phase inclusions.
The trapping conditions were estimated at temperature
between 90°C and 160°C and pressure <900 bar. The
origin of the early fluid generation is magmatic fluid
while the second and third fluids are of hydrothermal and
meteoric origin, respectively.