Gold-rich porphyry and polymetallic epithermal deposits in the Paleoproterozoic Alta Floresta Gold Province, Amazon Craton (Brazil)

The Alta Floresta Gold Province, southern portion of the Amazon Craton, represents a tectonic unit composed primarily of plutono-volcanic sequences generated in a continental arc during the Paleoproterozoic. Particularly in the easternmost segment of this province, the plutonic and volcanic rocks are the hosts of several gold mineralizations, such as Pe Quente and Francisco deposits. The ore in the Pe Quente deposit, represented by pyrite + barite +/- hematite chalcopyrite, occurs in strong sodic pervasive alteration zones that affect (quartz-)monzodiorite to leucomonzonite rocks, whereas in the Francisco deposit the gold is associated with high concentrations of base metals (Zn+Pb +/- Cu) within quartz veins that displays huge sericitic alteration halos, that affect epiclastic sedimentary rocks. In this scenario, the Pe Quente deposit represents the roots of gold-porphyry systems. The Francisco deposit, however, would be similar to the model of polymetallic epithermal systems of intermediate-sulfidation, which have been originated in a post-collisional setting, that by being more stable have contributed its preservation from the erosion and metamorphic late events.