Minas Gerais, Brazil

Main commodities: Au
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The Raposos orogenic gold deposit is located within the Morro Velho cluster of mines in the north-eastern section of the Quadrilatero Ferrifero district, some 12 km south-east of Belo Horizonte, Minas Gerais, Brazil (#Location: 19° 58' 8"S, 43° 48' 48"W).

The geology of the Quadrilátero Ferrífero is dominated by Archaean and Proterozoic volcano-sedimentary sequences and Precambrian granitic complexes. The oldest rocks in the district are an Archaean gneiss-migmatite complex which is overlain by the late Archaean Rio das Velhas Supergroup.

This supergroup is sub-divided into the basal Quebra Osso Group, succession of komatiitic ultramafic and mafic rocks with BIF intercalations, overlain by the Nova Lima Group, a middle sequence of schists and phyllites that contain lenses of dolomitic and calcic white marble and by thin beds of iron formation, and finally the upper Maquine Group of quartzites, conglomerates and phyllites. These are discordantly overlain by the Palaeoproterozoic Minas Supergroup quartzites, schists, phyllites, meta-conglomerates, carbonates and iron formations that produce the major iron deposits of the district.

The Raposos gold deposit is hosted by itabirites / banded iron-formation (BIF) of the Archaean Rio das Velhas greenstone belt. The hanging wall rocks to the itabirites are hydrothermally-altered ultramafic schists, while metamafic rocks and their hydrothermal schistose products form the footwall.

Three ductile to brittle deformational events (D1, D2 and D3) are defined by planar and linear structures at the Raposos deposit, while a fourth group of structures comprise spaced cleavages that are considered to be a brittle phase of D3.

The Raposos orebodies comprise sulphide-bearing D1-related shear zones within itabirites, with associated quartz veins, and are the result of sulphidation of magnetite and/or siderite. Pyrrhotite is the principal sulphide mineral, followed by lesser arsenopyrite and pyrite.

See also the Morro Velho Operation record.

The most recent source geological information used to prepare this summary was dated: 2007.    
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.

Mina Raposos

  References & Additional Information
   Selected References:
Junqueira P A, Lobato L M, Ladeira E A and Simoes E J M,  2007 - Structural control and hydrothermal alteration at the BIF-hosted Raposos lode-gold deposit, Quadrilatero Ferrifero, Brazil: in    Ore Geology Reviews   v32 pp 629-650
Junqueira P A, Lobato L M, Ladeira E A Simoes E J M,  2007 - Structural control and hydrothermal alteration at the BIF-hosted Raposos lode-gold deposit, Quadrilatero Ferrífero, Brazil: in    Ore Geology Reviews   v.32 pp. 629–650
Lobato L M, Ribeiro-Rodrigues, L C and Reis Vieira, F W,.  2001 - Brazils premier gold province. Part II: Geology and genesis of gold deposits in the Archean Rio das Velhas greenstone belt, Quadrilatero Ferrifero: in    Mineralium Deposita   v.36 pp. 249-277
Tolbert G E,  1964 - Geology of the Raposos gold mine, Minas Gerais, Brazil : in    Econ. Geol.   v.59 pp. 775-798

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 takes no responsibility what-so-ever for inaccurate or out of date data, information or interpretations.

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