Pre-Variscan Ba enrichment in rocks adjacent to the Sardic unconformity (SW Sardinia, Italy)

Rocks from the Cabitza and Monte Argentu Fms, adjacent to the Sardic Unconformity (SU), are characterized by anomalously high concentrations of Ba. Very high Ba contents had been previously observed only in the late Variscan mineralization of the "Quartzite" horizon. This horizon is located between the Gonnesa and the Portixeddu Fms, in a reduced sequence due to the complete erosion of the Cabitza and Monte Argentu Fms. High Ba contents, with six values exceeding 1000 ppm, up to 4363 ppm, indicate that even in its early tectonic movements, before the Late Variscan mineralizing event, the SU acted as a major pathway for the circulation of Ba-rich fluids. Ba contents significantly decrease with the distance from the SU, with local maxima in correspondence of more heterogeneous and frequent permeable layers.