The Igarapé Bahia Cu-Au Mineralization, Carajás Province

Abstract

The Igarapé Bahia Cu-Au mineralization is hosted by an Archean, low-grade metavolcano-sedimentary sequence. The orebodies define an ellipsoidal structure and are associated with subvertical breccia units located at the contact between two distinct units of the host sequence. Mineralized breccias include fragments of both footwall and hanging wall, which are cemented by variable amounts of chlorite, siderite, magnetite, chalcopyrite, K-bearing phases and minor U-REE-minerals. Quartz diorite dikes that disrupt the host rocks show a variety of textures, ranging from weakly altered granophyric terms to intensely venulated and brecciated rocks. Hydrothermal alteration of dikes includes propylitization, potassification and local albitization. Based on ore petrology and geochemical data (major elements, REE, oxygen and carbon stable isotopes) it is proposed that the progressive interaction of a hot saline and acid, deep-seated fluid with a low-temperature less saline and oxidizing meteoric solutions is the most likely depositional mechanism of the Igarapé Bahia mineralization. The resemblance of the alteration styles of mineralized breccias and dioritic dikes suggest that both have interacted with the same hydrothermal fluid. Thus, the dioritic dikes could have been the source of heat and of magmatic fluids during the final stages of epicrustal emplacement.

Dating and isotopic characteristics (Pb and S) of the Fe oxide–Cu–Au–U–REE Igarapé Bahia ore deposit, Carajás mineral province, Pará state, Brazil

“…Some Abbreviations are the same as in Table 2. Table 7. veinlet arrays are described as stockwork and pointed to as evidence of the epigenetic character of the mineralization, with an implicit analogy to the Australian Olympic Dam deposit (Huhn and Nascimento, 1997;Tallarico et al, 1998Tallarico et al, , 2000Tallarico et al, , 2005Oliveira et al, 1998;Lindenmayer et al, 1998;Tazava, 1999). In addition, some authors postulate that the Paleoproterozoic granitic intrusions played a decisive role in not only the mineralizing processes but also breccia formation (Lindenmayer et al, 1998;Tallarico et al, 2000).…”

“…Both syngenetic (Ferreira Filho, 1985;Althoff et al, 1994;Almada and Villas, 1999;Dreher andXavier, 2001, 2005) and epigenetic (Huhn and Nascimento, 1997;Tallarico et al, 1998Tallarico et al, , 2000Tallarico et al, , 2005Oliveira et al, 1998;Lindenmayer et al, 1998;Tazava, 1999) models have been proposed for the Igarapé Bahia mineralization. In addition, some epigeneticists postulate a genetic link of the mineralization with Paleoproterozoic granitic magmatism (Lindenmayer et al, 1998;Tallarico et al, 2000). This paper presents Pb isotopic data of sulfide minerals that occur in the rocks of the Igarapé Bahia Group, with the purpose of constraining the timing and origin of the primary and remobilized ores.…”

“…Owned by the Companhia Vale do Rio Doce (CVRD), mining operations in this deposit started in late 1980, with most efforts directed toward producing gold from 40 to 100 m thick lateritic-gossanic crust that developed above the primary sulfide-rich ores. Ore reserves are estimated at 219 Mt, with average grades of 1.4% Cu and 0.86 g/t Au (Tallarico et al, 2000). Approximately 140 t of gold have been produced from the supergene-enriched zone, which is now practically exhausted.…”

Spinifex-textured komatiites in the south border of the Carajas ridge, Selva Greenstone belt, Carajás Province, Brazil

“…1) are particularly abundant close the Selva belt and grouped in the southern copper belt of the Carajás Mineral Province, including several large (e.g., Sossego, 118, Cristalino) and medium-size (e.g., Bacaba, Castanha, Visconde, Bacuri) deposits (Moreto et al, 2015). Despite several differences among CuAu deposits in Carajás, most deposits are characterized by metasomatism leading to REE enrichment, which is especially significant for LREE (e.g., Tallarico et al, 2000;Grainger et al, 2008;Xavier et al, 2012). Pronounced LREE enrichment is in fact a distinctive characteristic of IOCG-type deposits worldwide (Groves et al, 2010).…”

Múltiplos estágios de alteração hidrotermal do depósito de óxido de ferro-cobre-ouro Furnas, Província Carajás: evolução paragenética e química mineral.

“…Para os depósitos da Província de Carajás, a presença de minerais ricos Cl e elevadas salinidades para os fluidos hidrotermais são atribuídas à influência de componentes magmáticos na evolução do sistema hidrotermal e gênese dos depósitos (Igarapé Bahia, Tallarico et al, 2000;Tallarico, 2003;Salobo, Lindenmayer & Teixeira, 1999;Gameleira, Lindenmayer et al, 2002).…”