Morro do Ouro, Brasilia, Rio Paracatu

Minas Gerais, Brazil

Main commodities: Au
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The Morro do Ouro gold deposit at the Brasilia Mine of Rio Paracatu Mineracao S.A. in Minas Gerais is located some 240 km SSE of Brasilia and 500 km NNW of Belo Horizonte.

It is hosted by Neo-Proterozoic sediments of the Brasilia Fold Belt on the western margin of the São Francisco Craton within the Central Brazil Shield. These 850-1000 Ma sediments were deformed between 680-650 Ma.

The mineralisation is hosted by carbonaceous phyllites of the Paracatu Formations which comprises a thick succession of such graphitic phyllites with interbedded layers and lenses of impure quartz sandstones which are generally quartzitic. These have been thrust over carbonates of the Vazante Formation that belong to the same stratigraphic package.

The Morro do Ouro gold deposit is localised within a structure that is a subsidiary of a larger thrust. The extensive flat lying orebody lies within the horizontal segment of a monoclinal thrust that is characterised by a strong mylonitic foliation within the host graphitic phyllites. In detail the better gold is found along the hinge zones of isoclinal folds and along S-C surfaces which were transformed into dilatant sites during progressive shearing. The same progressive shearing produced intense boudinage of quartz veining introduced in preceding episodes of the same deformational event.

In the oxide zone gold occurs as free metal in the quartz boudins, accompanied by sulphides and minor carbonate and after decomposed sulphides in the enclosing phyllite, concentrated in pressure shadows produced by the presence of the boudins. The initial viability of the deposit was determined by the flat lying attitude of the ore zone which forms a low hill with no overburden, enhanced by the deep oxidation of the ore. The oxidation has released gold from the sulphides and carbonates to be free milling, while it has also decomposed the rock so no crushing or blasting is required in the oxide zone.

In the primary zone gold is distributed in the lattice or in micro-fractures within iron and arsenic sulphides, and in association with carbonates.

The operation is one of the lowest grade profitable mines in the world. In 1999 some 17.47 Mt of ore were mined at an average grade of 0.45 g/t Au. The gold recovery was 73%, for 5.7 t (0.185 Moz) of gold at a cash cost of $US 176 per oz.
    Reserves and resources in 1999 stood at 124 Mt @ 0.41 g/t Au.

Published Ore Reserves and Mineral Resources at December 31, 2006 (Kinross Gold Corp.) were:
    Proved + Probable reserves1262 Mt @ 0.4 g/t Au for 505 t of contained gold.
    Measured + indicated resources were 67.5 Mt @ 0.33 g/t Au for 22 t of gold.
Production in 2006 amounted to 17.637 Mt of ore @ 0.38 g/t Au, for 5.42 t of Au produced (ie. 81% recovery of the 6.7 t contained gold).

Published Ore Reserves and Mineral Resources at December 31, 2015 (Kinross Gold Corp. Annual Reserves and Resources Report, 2016) were:
    Proved + Probable reserves - 687.990 Mt @ 0.40 g/t Au for 300 t Au;
    Measured + Indicated resources - 315.508 Mt @ 0.30 g/t Au for 102 t Au; (exclusive of reserves)
    Inferred resources - 10.515 Mt @ 0.40 g/t Au for 4.5 t Au

The mine has been in production since 1988. In 2000, Rio Paracatu Mineracao was controlled by RTDM, the Brazilian subsidiary of the operator Rio Tinto (51%) with the balance held by TVX Normandy. From December 2004, the operating company was wholly owned by Kinross Gold Corporation.

The most recent source geological information used to prepare this summary 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.

  References & Additional Information
   Selected References:
Freitas-Silva F H, Dardenne M A, Jost H  1991 - Lithostructural control of the Morro do Ouro, Paracatu, Minas Gerais, gold deposit: in Ladeira E A (Ed.),  Brazil Gold 91 Balkema, Rotterdam    pp 681-683
Hitzman M W  1997 - Sediment-hosted Zn-Pb and Au deposits in the Proterozoic Paracatu Vazante fold belt, Minas Gerais, Brazil: in    http://www.dregs.org/absa997.html    1p
Zini A, Forlim R, Andreazza P, de Souza A   - The Morro do Ouro gold deposit, Paracatu, Minas Gerais: in   Gold and Zinc-Lead Deposits of Paracatu and Vazante xiii IGES - II CGBq (excxursions)    pp 133-139

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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