Mineralogy and mineral chemistry of precious metals of the Cu-Au mineralisation at the Palai-Islica deposit, Almería, SE Spain

Abstract

The Au-Cu mineralisation of Palai-Islica is hosted within strongly hydrothermally altered calc-alkaline rocks of the Cabo de Gata-Cartagena volcanic belt. Mineralisation is related to subhorizontal levels (named levels A, B, C and D, from bottom to top). Au and Cu are economically the most important elements, with Ag also being of potential interest. The Au-bearing phases of the Palai-Islica deposits are restricted to Au-Ag alloys (present at levels A, B and C) and native gold (found only at level D). The Ag-bearing minerals in levels A, B and C are fahlore, Au-Ag alloys, Ag-Bi-Pb sulphosalts, Ag sulphides, Ag tellurides, collomorphic pyrite, and galena. Within level D, the only significant values of Ag are found in some collomorphic pyrite. As deduced from textural studies and chemical features of different mineral phases, the noble metals at levels A, B and C evolved from Au-rich to Ag-rich as time progressed. Level D is a gold-rich silver-poor level and is apparently not connected with the genesis of the rest of the deposit