High and intermediate sulphidation environment in the same hydrothermal deposit: the example of Au-Cu Palai–Islica deposit, Carboneras (Almería)

Abstract

Two epithermal environments have been identified in the Miocene Palai–Islica Au–Cu deposit: A) Intermediate sulphidation, hosted mainly in quartz veins, comprises pyrite, chalcopyrite, sphalerite and galena as the major sulphides, which are accompanied by a variety of Ag-bearing accessory minerals. Au–Ag alloys are the only gold-bearing phase. The veins are enclosed by sericitic and chloritic alteration. Fluid inclusions in quartz, sphalerite and calcite give Th between 118–453 ºC, and salinities between 0.2–51.4 wt.% NaCl eq, with high salinities being related to high-grade mineralisation. Stable isotopes indicate magmatic and marine fluids. B) High sulphidation consists of massive host rock silicification with disseminated pyrite and minor chalcocite, covellite, native copper and native gold. The surrounding alteration is advanced argillic/argillic in style. Fluids have Th between 224–381 ºC have salinities between 0.4 and 41.1 wt.% NaCl eq. The stable isotope data demonstrate the dominance of magmatic fluids, and disproportion processes