Mineralogy, fluid inclusions and stable isotope study of epithermal Au-Ag-Bi-Te mineralization from the SE Afar Rift (Djibouti)

Abstract In this paper, the mineralogy, fluid inclusions and stable isotopes of hydrothermal veins from the SE part of the Afar Rift (Djibouti) were studied. Mineralization occurs as gold-silver in quartz/carbonate veins and is mainly associated with felsic volcanism. The morphologies and textures of quartz show crustiform colloform banding, massive and breccias. Microthermometric measurements were made on quartz-hosted two phases (liquid + vapor) inclusions. Mean homogenization temperature ranges from 150 °C to 340 °C and ice-melting temperatures range from −0.2 °C to − 1.6 °C indicating that inclusion solutions contain 0.35 to 2.7 eq. wt% NaCl. Furthermore, δ 18 O and δ 13 C values from calcite range from 3.7 to 26.6‰ and −7.5 to −0.3‰, respectively. The presence of platy calcite and adularia are consistent with boiling conditions. Our study shows that the deposit of precious-metal occurred at around 250 °C and is linked to a fluid generated by the mixture of magmatic fluid, hydrothermal fluid and seawater.