Fluid inclusions in the gold-bearing quartz veins at Um Rus area, Eastern Desert, Egypt

Fluid inclusions in the gold-bearing quartz veins at the Um Rus area are of three types: H₂O, H₂O-CO₂ and CO₂ inclusions. H₂O inclusions are the most abundant, they include two phases which exhibit low and high homogenization temperatures ranging from 150 to 200°C and 175 to 250°C, respectively. The salinity of aqueous inclusions, based on ice melting, varies between 6.1 and 8 equiv. wt% NaCl. On the other hand, H₂O-CO₂ fluid inclusions include three phases. Their total homogenization temperatures range from 270 to 325°C, and their salinity, based on clathrate melting, ranges between 0.8 and 3.8 equiv. wt% NaCl. CO₂ fluid inclusions homogenize to a liquid phase and exhibit a low density range from 0.52 to 0.66 g/cm³. The partial mixing of H₂O-CO₂ and salt H₂O-NaCl fluid inclusions is the main source of fluids from which the other types of inclusions were derived. The gold-bearing quartz veins are believed to be of medium temperature hydrothermal convective origin.