VOLCANOGENIC MASSIVE SULPHIDE (VMS) DEPOSITS IN THE LOWER CRETACEOUS LOS PASOS FORMATION, SANTA CLARA REGION, CENTRAL CUBA
The Antonio deposit is a past open pit producer. Three stacked mineralized bodies occur in highly altered felsic rocks stratigraphically below their contact with overlying basalt. The deposit has been traced 300 m along strike, 190 m vertically and averages 11 m thick. A thin barite-rich exhalite caps the massive sulphides. A debris flow containing abundant massive sulphide clasts occurs adjacent to the pit. Three types of mineralization are recognized at Antonio; massive pyrite in the upper part of the deposit; central VMS mineralization with high Cu-Zn grades; and, the poorly explored underlying disseminated and vein type of mineralization.
The Santa Rosa prospect was accessed by 2 short adits and tested by several shallow drill holes to a vertical depth of 50 m. The mineralization occurs in silicified basalt and is associated with high contents of barite. Recent sampling has yielded high gold and silver grades (2.3 m grading 9.65 g/t Au and 600.16 g/t Ag). These high gold and silver grades in association with barite suggest a shallow water depositional environment where the hydrothermal fluids likely boiled during exhalation onto the sea floor.