Corumba, Urucum

Mato Grosso do Sul, Brazil

Main commodities: Fe
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The Corumba - Urucum district is located in western Mato Grosso do Sul, Brazil, along the border with Bolivia. It hosts extensive manganese rich ironstones of late Neoproterozoic age. The district is some 170 km in length, the greater part of which is in Bolivia. An approximately 30 km strike length of mineralisation is found in Brazil, where the iron formation reaches a thickness of up to 300 m. Resources are stated as being as much as 36 Gt at an average grade of 54% Fe, embracing higher grade enriched zones containing 890 Mt @ 63% Fe.

The host Jacadigo Group is preserved in a series of 8 tabular mountains that rise up to 1000 m out of the swampy lowlands of the Pantanal. Basement is represented by gneisses and amphibolites, with lesser schists and quartzites, cut by 889 to 1200 Ma granitoids. These are unconformably overlain by the Neoproterozoic Jacadigo Group, which comprises a lower 200 m thick Urucum Formation composed of conglomerate and siltstone, followed by mainly black shale and siltstone, passing up into mainly sandstones. All of these rocks have been cemented by carbonates.

The Urucum Formation is followed by the 300 m thick Santa Cruz Formation. The base of this unit is marked by dropstones and the change from carbonate cement to manganese and iron oxides in the host cross bedded sandstone of the 80 m thick lower member. This member carries a basal 0 to 7 m thick manganese rich horizon (Mn1) with concretionary/nodular, detritus-rich and layered massive ores. The upper member is almost exclusively composed of chemical sediments. It commences with a widespread band of layered massive ore that is 0 to 3.5 m thick (Mn2). This is followed by a 70 to 270 m thick monotonous sequence of hematite-jaspilite which covers an area of 120 sq. km. A third 0-2.35 m thick manganese horizon (Mn3) is intercalated with the hematite-jaspilite 40 to 45 m above Mn2, while a fourth such band, Mn4 which is 0-1.4 m thick, is found a further 45 m higher. Mn3 and Mn4 are again layered massive manganese oxide beds. Erratic dropstone from 0.05 to 1 m across are found sporadically throughout the chemical sediments. The exposed Jacadigo Group in the Urucum district is surrounded by the unconformably overlying limestones and dolomites of the late Neoproterozoic Corumbá Group.

The fresh jaspilitic ores of the lower Santa Cruz Formation average 50% Fe, while the supergene enriched sections carry up to 67% Fe.

The higher grade, enriched ores occur in two forms, namely:

i). canga - Fe-hydroxide-cemented breccias of hematite-jaspilite - occurs as a sub-recent weathering crust in places, and
ii). 'colluvial' ore in the form of weathered 0.01 to 10 m blocks of hematite-jaspilite which form debris cones and fans on the flanks of the tabular mountains.

The un-enriched hematite-jaspilites are predominantly composed of micro-crystalline hematite and crypto-crystalline red jasper forming alternating bands on a micro- and macro-scopic scale. In finely laminated ores, spherical and concentric aggregates of hematite and jasper are preserved.

Rio Tinto operates the Corumbá iron ore mine through it's 100% owned subsidiary Mineraçao Corumbaense Reunida, with the output being transported by barge down the major Paraguay River to Argentina. Vale, who also exploits iron and manganese from its nearby Urucum mine, purchased the iron operations from Rio Tinto in 2009.

The most recent source geological information used to prepare this summary was dated: 2002.    
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:
Gutzmer, J., Chisonga, B.C., Beukes, N.J. and Mukhopadhyay, J., C.A.,  2008 - The geochemistry of banded iron formation-hosted high-grade hematite-martite iron ores: in Hagemann S, Rosiere C, Gutzmer J and Beukes N J, (eds.), 2008 Banded Iron Formation-Related High-Grade Iron Ore, Reviews in Economic Geology   v.15 pp. 157-183
Klein C, and Ladeira E A,  2004 - Geochemistry and Mineralogy of Neoproterozoic Banded Iron-Formations and Some Selected, Siliceous Manganese Formations from the Urucum District, Mato Grosso do Sul, Brazil: in    Econ. Geol.   v99 pp 1233-1244
Urban H, Stribrny B, Lippolt H J  1992 - Iron and Manganese Deposits of the Urucum District, Mato Grosso do Sul, Brazil: in    Econ. Geol.   v87 pp 1375-1392

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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