Geotectonic setting and metallogeny of the northern São Francisco craton, Bahia, Brazil

Abstract

a b s t r a c tThis paper aims at establishing a tectonic and temporal framework to characterize the metallogenic processes that contributed to the origin of the mineral provinces in the northern São Francisco Craton. Many Archean mineralizations (eg. massive sulfide zinc, lead, zinc and copper, besides magnesiteetalc, ironetitaniumevanadium, iron, chromite and manganese) were generated before the assembly of the Craton. Deposits of chromite, nickel, gold and emerald were produced during the Paleoproterozoic orogenic cycle, when the Craton was amalgamated into the Atlantica paleocontinent. An extension event is recorded in the Neoproterozoic, during the breakup of Rodinia, associated with deposits of phosphorite and uranium. Kimberlite diamond and gold mineralization were generated during the Brasiliano orogenic cycle, coeval with the amalgamation of West Gondwana. A long-lasting and rather uniform crustal stress is recorded in the area during the Cambrian period. Resetting of the isotopic and magnetic systems that affected the Neoproterozoic sediments of the Irecê Basin at about 520 Ma was attributed to the regional-scale fluid migration and mineralization in the aftermath of the Brasiliano orogenic cycle.Ó 2010 Elsevier Ltd. All rights reserved. r e s u m oEste artigo visa estabelecer um quadro tectônico e temporal para caracterizar os processos metalogenéticos que contribuíram para a origem das províncias minerais no setor norte do Cráton São Francisco. Muitas mineralizações arqueanas (por ex. sulfeto maciço de zinco, chumbo, zinco e cobre, além de magnesitaetalco, ferroetitânioevanádio, ferro, cromo e manganês) foram geradas antes da formação do Cráton. Depósitos de cromo, níquel, ouro e esmeralda foram produzidos durante a orogênese paleoproterozóica, quando o cráton foi amalgamado dentro do paleocontinente Atlântica. Um evento extensional é registrado no Neoproterozóico, durante a fragmentação do paleocontinente Rodinia, associado a depósitos de fosforita e urânio. Kimberlitos diamantíferos e mineralizações de ouro foram geradas durante o ciclo orogenético Brasiliano, contemporâneo com a aglutinação do paleocontinente Gondwana Ocidental. Um regime de tensão crustal bastante uniforme e de longa duração foi registrado na região durante o período Cambriano. A reconfiguração dos sistemas isotópico e magnético que afetou os sedimentos neoproterozóicos da bacia de Irecê há cerca de 520 Ma foi atribuída ao evento tectônico de escala regional, à migração de fluidos e mineralização, como consequência do ciclo orogenético Brasiliano.

Geological and isotopic characteristics of granites from the Western Pernambuco-Alagoas Domain: implications for the crustal evolution of the Neoproterozoic Borborema Province

“…The Entremontes Complex and metaplutonic bodies from RSN show Archean U-Pb and Sm-Nd ages, similar to rock units identified in the Congo and São Francisco Cratons (Bizzi et al 2003;Teixeira et al 2010), implying a correlation with the cratonic rocks.…”

Linking Gold Systems to the Crust-Mantle Evolution of Archean Crust in Central Brazil

“…The presence of deformed clasts of Au-bearing quartz-veins, disseminated sulphides in carbonaceous schist, and gold within a fine-grained matrix suggest the paleoplacer post-dates the main Au-related hydrothermal event [135]. This is consistent with other Paleoproterozoic paleoplacer deposits, such as in the Jacobina greenstone belt in the São Francisco craton [136].…”

“…Older model ages of up to 3500 Ma obtained in previous studies [147] from samples with high 147 Sm/ 144 Nd ratios may reflect fractionation of the Sm-Nd system during metamorphism [28]. In the northern GAB, volcanic sequences of the Crixás greenstone belt reveal spinifex textures [92,136] typically associated with komatiite flows [150]. Ultramafic flows are overall characterized by smoothly sloping, LREE-rich patterns, whereas basalts show flat REE patterns and slight depletion in both LREE and HREE [150].…”

Accretion Tectonics in Western Gondwana Deduced From Sm‐Nd Isotope Mapping of Terranes in the Borborema Province, NE Brazil

“…Based on the obtained and available data, it is possible to speculate on possible correlative crustal segments to the studied terranes. Archean and Paleoproterozoic crusts in the São Francisco and Congo cratons, including the Itabuna‐Salvador‐Curaçá Belt and adjacent blocks, share evolution similarities with the Alto Moxotó Terrane, including TTG rocks as well as calc‐alkaline subduction‐related granites (e.g., Barbosa & Sabaté, ; Teixeira et al, ). Reworking of Archean crust by Paleoproterozoic convergent events, such as those observed in the Alto Moxotó Terrane, is also present in these cratons, as well as their adjacent fold belts, collectively known as Eburnean Orogeny (Baratoux et al, ; Feybesse et al, ; Hein, ; Lompo, ).…”