BREAKING NEW GROUNDS IN METALLIC MINERAL EXPLORATION IN BRAZIL
Brazil has historically been one of the world most important iron ore producers, a global player in niobium, graphite, and aluminum (as bauxite), but has also recorded an increasing commercialized production ofmanganese, copper, nickel, tin and gold.
In this context, it is noteworthy that the geological distribution of most of the known reserves for these metals and mines with annual ROM production above 1,000,000 t are strongly skewed toonly two well-endowed multi-commodities districts, the Carajás Mineral Province (Amazonian Craton) and Iron Quadrangle (QuadriláteroFerrífero – São Francisco Craton).
This becomes a paradoxal scenario when taking into account Brazil´s continental size and its geological framework comprised of two large Precambrian cratons and smaller cratonic fragments,surrounded by extensive Neoproterozoic-Early Cambrian orogenic belts, all partially covered by Paleozoic sedimentary basins.
If, on the other hand, known deposits or occurrences are now added to this picture, then an important scenario becomes apparent from the exploration standpoint: the metallic mineral deposits are mostly concentrated within these major Precambrian geotectonic units, which indicates vast possibilities to identify attractive geological environments with potential to contain economic ore deposits. Within this scenario, several attractive geological domains in Brazil are currently underexplored and a few examples are provided here.
The Tapajós and the Alta Floresta/Juruena-TelesPires Provinces, in the southern sector of the Amazonian Craton have been important gold-producing regions, with an historical output estimated at 20 Moz and 4 Moz of Au, respectively, mostly from artisanal miners called “garimpeiros”. Both provinces consist predominantly of non-metamorphosed calc-alkaline – alkaline plutono-volcanic sequences that formed in continental magmatic arc environments in the Paleoproterozoic. Recents works conducted by research groups from the Brazilian Universities have demonstrated that both provinces are not gold-only, but have potential to be polymetallic. At Tapajós and Alta Floresta, calc-alkaline volcanic rocks host epithermal Au and base metal mineralization, whereas Cu-Au and Cu-Mo ± Auporphyry-type mineralization is associated with sub-volcanic felsic rocks.
Potential for Cu-Au porphyry and epithermal base metal systems have also been recognized in the Neoproterozoic age Goiás Magmatic Arc, Central Brazil, as well in the Neoproterozoic – Cambrian Dom Feliciano Belt, in southern Brazil.
On the other hand, exploration challenges in the Borborema Province, a Neoproterozoic orogenic belt in northeast Brazil include potential for iron oxide-copper-gold deposits, as revealed by prospects of quartz-hematite breccias, involved bystrong sodic, calcic-potassic and potassic-ferric alteration; (2) shear zone-hosted amphibolite – facies orogenic goldsystems in Paleoproterozoic metavolcano-sedimentary in liers; and in Neoproterozoic metasedimentary sequences of the Seridó Group; and (3) Au-W-Fe skarn-type deposits.
Therefore, Brazil indeed stands out as a country still very much open for exploration opportunities and waiting for the treasure chest to be opened.