A review of the main tectonic settings of Neoarchaean ore deposits and mineral occurrences in the northern São Francisco Craton, NE Brazil

In this paper, a compilation of the main Neoarchaean ore deposits, and their tectonic settings, in the northern São Francisco Craton, NE Brazil is presented. The Serrinha and Gavião blocks split up in the Neoarchaean, giving rise to juvenile rocks and metavolcanic-sedimentary sequences within the so-called Mundo Novo-Caraíba-Ibicuí sea. The rocks from the southern Gavião Block served as basement for the Contendas-Mirante sequence, where the Jacaré River Vanadium mine is situated in a stratified gabbro-anorthosite mafic sill, which intruded a Neoarchaean shear zone. On the northern part of the Gavião Block, where oceanic crust was identified by the presence of the Mundo Novo greenstone belt, hydrothermal mineralizations of both lead and zinc were mapped in calc-silicate rocks, which are associated to metamorphosed tholeiitic seafloor basalts and these metabasalts are tectonically intercalated with metadacites. In the Jequié Block, occurs the Ibicuí-Iguaí Iron District, which lies in the suture zone between this tectonic unit and the Itabuna-Salvador-Curaçá belt. These are rocks comprising a sequence of metabasalts and metavolcanic tuff, metakomatiites, kinzigites, quartzites and itabirites. In this belt also occurs the southern Bahia manganese district, where the mineralization is hosted in granulitized metavolcanic-sedimentary sequences. The ore protoliths are chemical sediments composed of spessartite, pyroxmangite, rhodonite, rhodochrosite, magnetite, mesoperthite and quartz. The reducing characteristics of the primary environment are confirmed by the presence of graphite and manganese sulphide (alabandite). This mineralogy produced through supergenic processes, ores with great reserves of pyrolusite and psilomelane. In the northern part of the Itabuna-Salvador-Curaçá Belt, an island arc was identified, where mafic-ultramafic bodies (2580 Ma) intruded at its base, giving rise to the Curaçá-Caraíba Valley Cupriferous District. These bornite and chalcopyrite-rich bodies were generated from a calc-alkaline magma that originated multiple Cu-rich gabbroic and pyroxenitic intrusions.