Barro Alto

Goias, Brazil

Main commodities: Ni
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The Barro Alto lateritic nickel deposit is located in the State of Goias, Brazil, approximately 170 km north-west of Brasilia and 240 km north of Goiania (#location: 14° 37'34"S, 48° 42'28'W).

The deposit is located over the extreme north of the Barro Alto igneous-metamorphic complex which is found within a Mesoproterozoic eugeosynclinal sequence overlying a metamorphosed Palaeoproterozoic basement.

The Barro Alto Complex comprises an: i). Eastern Metagabbroic; ii). Ultrabasic; iii). Anorthositic; and iv). Western Metagabbroic Zone.

The tectonic evolution of the complex includes: i). an initial granulite facies, represented by pyroxene gneisses and ortho-amphilbolites enclosed within the basal complex; ii). a retrograde phase characterised by qreenschist and high amphibolite facies affecting both the complex and the enclosing metasediments, and iii). greenschist facies, observed in fault zones.

The lateritic nickel mineralisation is developed from serpentinised meta-peridotites of the Ultrabasic Zone and occurs as three main laterite/saprolite ore types occurring as a chain of six discrete areas developed along a broad fault zone. The deposit covers an area of 4.3 square km, over a strike length of 4.2 km and width of 1.25 km. The lateritic profile is generally <25 m thick, averaging 18 m. The laterites were developed from the Cretaceous to early Tertiary.

The typical profile comprises:
  2.5 m or more of barren ferruginous lateritic overburden
  ferruginous saprolite;
  argillaceous saprolite with 2.2 to 2.7% Ni oxide (the main ore zone);
  coarse saprolite cut by garnierite veins
  saprock and bedrock.

The principal nickeliferous minerals include, garnierite, gibbsite, goethite, hematite, limonite, maghemite and serpentine, with a gangue of chalcedony and quartz.

Before production commmenced, the deposit was reported to have contained a resource of 116.2 Mt @ 1.54% nickel, of which 62.4 Mt @ 1.66% nickel will be mined by conventional open pit methods and treated over a 26 year period.

At December 31st 2009 resources and reserves were (Anglo American Annual Report - resources are additional to reserves):
    Proved + probable reserves - 40.7 Mt @ 1.73% Ni
    Measured + indicated resources - 21.1 Mt @ 1.28% Ni
    Inferred resources - 60.5 Mt @ 1.45% Ni
    Total reserve + resource - 122.3 Mt @ 1.5% Ni.

The most recent source geological information used to prepare this summary was dated: 2006.    
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

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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