Geology and metallogeny of Neoarchean and Paleoproterozoic copper systems of the Carajas Domain, Amazonian Craton, Brazil

The copper deposits of the Carajas Domain in the southeastern Amazonian craton (Brazil) are grouped into iron oxide-copper-gold (IOCG) and Cu-polymetallic systems. These systems represent multiple ore-forming hydrothermal events that took place in the Neoarchean (2.70 Ga and 2.56 Ga) and Paleoproterozoic (1.88 Ga) during the reactivation of regional-scale shear zones. The world-class Neoarchean (2.70 Ga and 2.56 Ga) IOCG systems were emplaced at deeper crustal levels compared to the Paleoproterozoic analogues. The Neoarchean and Paleoproterozoic Cu-polymetallic deposits are typically shallow hydrothermal systems and as a contrast to the IOCGs result in lower sulfidation state and more reduced ore assemblages. Mixing of high temperature hypersaline metalliferous fluids with other fluid types is a marking feature in both copper system groups and a trigger to ore precipitation. While a magmatic fluid source still remains unclear, non-magmatic brines (e.g. bittern fluids) seem to be an important component in the Neoarchean IOCG systems. A-type magmatism, on the other hand, could have acted as source of fluids or heat to move non-magmatic brines to form the Paleoproterozoic copper systems.