New geologic, fluid inclusion and stable isotope studies on the controversial Igarapé Bahia Cu-Au deposit, Carajás Province, Brazil

• Main Author: DREHER, Ana Maria
• Publication Date: 2008
• Other Authors: XAVIER, Roberto P., TAYLOR, Bruce E., MARTINI, Sérgio Luiz
• Format: Article
• Language: eng
• Source: Repositório Institucional de Geociências - RIGEO
• dARK ID: ark:/79692/0013000001cqf
• Download full: https://rigeo.sgb.gov.br/handle/doc/552
• topic: OURO; FERRO; CARAJÁS; BRASIL

The Igarapé Bahia Cu–Au deposit in the Carajás Province, Brazil, is hosted by steeply dipping metavolcano-sedimentary rocks of the Igarapé Bahia Group. This group consists of a low greenschist grade unit of the Archean (∼2,750 Ma) Itacaiúnas Supergroup, in which other important Cu–Au and iron ore deposits of the Carajás region are also hosted. The orebody at Igarapé Bahia is a fragmental rock unit situated between chloritized basalt, with associated hyaloclastite, banded iron formation (BIF), and chert in the footwall and mainly coarse- to fine-grained turbidites in the hanging wall. The fragmental rock unit is a nearly concordant, 2 km long and 30–250 m thick orebody made up of heterolithic, usually matrix-supported rocks composed mainly of coarse basalt, BIF, and chert clasts derived from the footwall unit. Mineralization is confined to the fine-grained matrix and comprises disseminated to massive chalcopyrite accompanied by magnetite, gold, U- and light rare earth element (LREE)-minerals, and minor other sulfides like bornite, molybdenite, cobaltite, digenite, and pyrite|Evaporite-derived fluids also exclude a significant participation of magmatic or mantle-derived fluids, reinforcing the role of nonmagmatic brines in the genesis of Igarapé Bahia. Considering this aspect and the geological features, the possibility that the deposit was generated by a hydrothermal submarine system whose elevated salinity was acquired by leaching of ancient evaporite beds should be evaluated