Ocurrence of free gold in hydrothermally-altered volcanic rocks at Castro Basin, State of Paraná, Brazil: perspectives for new potential areas

New occurrences of free gold were identified during fieldwork at outcrops located in the western part of the Castro Basin, state of Paraná. These are associated with silicified and sulfide-rich zones in hydrothermally-altered volcanic rocks. The aerogeophysical data indicate that the areas of the new targets show high K and eU relative to eTh, suggesting intense hydrothermal alteration. The stream sediment geochemistry shows anomalies with up to 60 ppb of Au and whole-rock geochemical results confirm the presence of up to 54 ppb of Au in rock samples. The data obtained until now are consistent with those observed in mineralized targets previously described in the same basin, in which an epithermal setting was suggested for the origin of the gold mineralization. Ongoing studies of the new occurrences may indicate an increase in the mineral potential of the Castro Basin.