Il campo filoniano a Ni-Co del Distretto Arburese (Sardegna SW): caratterizzazione geogiacimentologica e mineralogico-geochimica di una risorsa di interesse strategico

The Southern Arburèse area (SW Sardinia) hosts a wide variety of ore deposits, including Ni- Co-As-(Pb-Zn-Cu-Ag-Bi) hydrothermal veins hosted in Ordovician/Devonian metasedimentary rocks belonging to the Variscan Foreland. The vein system is exposed for over 6 km close to the contacts with the late Variscan Arbus and M. Linas igneous complexes. Veins consist of Ni-Co sulfarsenides and arsenides with Pb-Cu-Zn sulfides and sulfosalts in quartz and siderite gangue. From ore mineralogy and EMPA studies, the mineralization is polyphasic, with textures marked by concentric crusts of sulfarsenides, diarsenides and sulfides. Cockade textures, Co/Ni ratios in the Ni-Co arsenide nodules and low-Fe contents in sphalerites suggest temperatures close to 250°C for the Ni-Co-As mineralization. Stable isotope analyses on siderite confirm this thermality and suggest deposition in reducing conditions. Ni-Co-As ores of SW Sardinia may be directly comparable to the uncommon and strategically interesting “Five Elements Veins” type of deposits.