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Igarape Bahia
Para, Brazil
Main commodities: Au Cu

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The Igarapé Bahia Au-Cu-(REE-U) deposit is located in the Carajás Mineral Province of Para State Brazil, ~60 km west of the Carajás township (or Nucleo Urbano) and ~40 km south of the Salobo deposit.
(#Location: 6° 1' 57"S, 50° 33' 59"W.

Igarapé Bahia is hosted by the Igarapé Bahia Group, considered to be a lower greenschist facies metamorphosed unit of the Archaean (ca. 2.75 Ga) metavolcano-sedimentary Itacaiúnas Supergroup which comprises two lithological and stratigraphic domains: a lower metavolcanic unit composed of metavolcanic rocks and acid to intermediate volcanoclastics; and an upper clastic-chemical metasedimentary unit and volcanoclastic rocks. The Igarapé Bahia orebodies represents a 100 to 150 m thick gossan-laterite zone from which significant amounts of gold (>60 t) were mined until 2003. Where not outcropping, the primary mineralisation is obscured by a 250 m thick unconformable siliciclastic unit referred as the Aguas Claras Formation.

The copper-gold mineralisation at the Igarapé Bahia deposit is hosted by a hydrothermally altered breccia at the contact between the footwall mafic volcanics, with associated BIF and hyaloclastite, and a dominantly coarse to fine-grained metasedimentary sequence in the hanging wall. The breccia unit is exposed at or near the surface as a semicircular annulus, with a form similar to a ring complex with a diameter of approximately 1.5 km. The mineralised breccia unit occurs as a 2 km long by 30 to 250 m thick series of fault dislocated bodies on the southern, northeastern and northwestern sections of this structure, dipping steeply outwards at ~75°, and is nearly concordant with the metavolcanic-sedimentary wallrocks.

The economically extracted ore at Igarapé Bahia is largely developed as a supergene gossan-laterite enrichment within the 150 to 200 m thick oxide profile. Three orebodies have been mined at this contact, forming a semi-circular trace at the surface namely, Acampamento - dipping at around 75° to the north-east, Furo Trinta to the south-east, and Acampamento Norte to the north-west, forming an outward dipping domal structure in three dimensions.

The oxide zone is characterised by supergene enrichment and hematite, goethite, gibbsite and quartz. This is underlain by a transition zone that may be up to 50 m thick with enriched supergene malachite, cuprite, native copper and goethite and minor amounts of digenite and chalcocite responsible for high grade Cu and Au. This zone is in turn underlain by primary Cu-Au mineralisation, represented by hydrothermal breccias containing chalcopyrite, bornite, carbonate, magnetite and minor molybdenite and pyrite.

Strong hydrothermal alteration of the host sequence produced intense chloritisation, Fe-metasomatism, Cu-sulphidation (chalcopyrite and bornite), carbonatisation, silicification, tourmalinisation and biotitisation in the primary zone.

Gold-copper mineralisation is localised at the commonly brecciated contact between the metavolcanics and the meta-volcaniclastics-metasediments and comprises, magnetite/siderite heterolithic breccias and hydrothermally altered metavolcanics. These rocks are enriched in REE (monazite, allanite, xenotime, bastnäsite and parisite), Mo (molybdenite), U (uraninite), F (fluorite), Cl (ferropyrosmalite) and P (apatite).

The deposit was mined by CVRD/Vale between 1991 and 2002 at a production rate of up to 10 t Au per annum for a total production of 97 t of recovered gold. The remaining reserve in 1998 was quoted as 29 Mt @ 2 g/t Au (Tazava and Oleira, 2000). Reserves in 1999 were quoted by Tallarico et al. (2000) as 18.5 Mt @ 1.97 g/t Au

The most recent source geological information used to prepare this decription was dated: 2001.    
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd.   Unauthorised copying, reproduction, storage or dissemination prohibited.

Igarape Bahia

  References & Additional Information
   Selected References:
Dreher A M, Xavier R P , Taylor B E and Martini S L,  2008 - New geologic, fluid inclusion and stable isotope studies on the controversial Igarape Bahia Cu-Au deposit, Carajas Province, Brazil : in    Mineralium Deposita   v43 pp 161-184
Huang, X.-W. and Beaudoin, G.,  2019 - Textures and Chemical Compositions of Magnetite from Iron Oxide Copper-Gold (IOCG) and Kiruna-Type Iron Oxide-Apatite (IOA) Deposits and Their Implications for Ore Genesis and Magnetite Classification Schemes: in    Econ. Geol.   v.114, pp. 953-979.
Melo, G.H.C. de, Monteiro, L.V.S., Xavier, R.P., Moreto, C.P.N. and Santiago, E.,  2019 - Tracing Fluid Sources for the Salobo and Igarape Bahia Deposits: Implications for the Genesis of the Iron Oxide Copper-Gold Deposits in the Carajas Province, Brazil: in    Econ. Geol.   v.114, pp. 697-718.
Pollard, P.J., Taylor, R.G., Peters, L., Matos, F., Freitas, C., Saboia, L. and Huhn, S.,  2019 - 40Ar-39Ar dating of Archean iron oxide Cu-Au and Paleoproterozoic granite-related Cu-Au deposits in the Carajas Mineral Province, Brazil: implications for genetic models: in    Mineralium Deposita   v.54, pp. 329-346.
Tallarico F H B, Figueiredo B R, Groves D I, Kositcin N, McNaughton N J, Fletcher I R and Rego J L  2005 - Geology and SHRIMP U-Pb Geochronology of the Igarape Bahia Deposit,Carajas Copper-Gold Belt, Brazil: An Archean (2.57 Ga) Example of Iron-Oxide Cu-Au-(U-REE) Mineralization: in    Econ. Geol.   v100 pp 7-28
Tallarico, F.H.B., Oliveira, C.G. and Figueiredo, B.R.,  2000 - The Igarape Bahia Cu-Au mineralization, Carajas Province: in    Revista Brasileira de Geociencias,   v.30, pp. 230-233.
Tazava E, de Oliveira C G  2000 - Igarape Bahia Au-Cu-(REE-U) deposit, Carajas Mineral Province, Northern Brazil: in Porter T M (Ed), 2000 Hydrothermal Iron Oxide Copper-Gold & Related Deposits: A Global Perspective PGC Publishing, Adelaide   v1 pp. 203-212
Weisheng Zang, Fyfe W  1993 - A three-stage genetic model for the Igarape Bahia lateritic gold deposit, Carajas, Brazil: in    Econ. Geol.   v88 pp 1768-1779
Williams, P. J., Kendrick, M.A. and Xavier, R.P.,  2010 - Sources of Ore Fluid Components in IOCG Deposits: in Porter T M, (Ed), 2010 Hydrothermal Iron Oxide Copper-Gold and Related Deposits: A Global Perspective PGC Publishing, Adelaide   v.3, pp. 107-116.
Xavier R P, Monteiro L V S, Souza Filho C R, Torresi I, Carvalho E R, Dreher A M, Wiedenbeck M, Trumbull R B, Pestilho A L S and Moreto C P N,  2010 - The Iron Oxide Copper-Gold Deposits of the Carajas Mineral Province, Brazil: an Updated and Critical Review: in Porter T M, (Ed),  2010 Hydrothermal Iron Oxide Copper-Gold and Related Deposits: A Global Perspective PGC Publishing, Adelaide   v.3 pp. 285-306
Xavier, R.P., Monteiro, L.V.S., Moreto, C.P.N., Pestilho, A.L.S., de Melho, G.H.C., Delinardo da Silva, M.A., Aires, B., Ribeiro, C. and Freitas e Silva, F.H.,  2012 - The Iron Oxide Copper-Gold Systems of the Carajás Mineral Province, Brazil: in    Society of Economic Geologists,   Special Publication 16, Chapter 17, pp. 433-454.
Zang W, Fyfe W S  1993 - A three-stage genetic model for the Igarape Bahia Lateritic Gold deposit, Carajas, Brazil: in    Econ. Geol.   v 88 pp 1768 - 1779

Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge.   It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published.   While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo, its employees and servants:   i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and   ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.

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