Kolomela mine is operated by the Anglo-American group company Kumba Iron Ore through its subsidiary Sishen Iron Ore Company (SIOC).
SIOC is 76.3% owned by Kumba Iron Ore (KIO). Exxaro Resources Limited owns 20.6% of the remaining shares, and the SIOC Community Development Trust owns 3.1%.
KIO is 69.7% owned by Anglo American. Industrial Development Corporation owns 12.9% of the shares, with the remaining shares owned by minority shareholders. Kolomela Mine itself is 100% owned by SIOC.
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Summary:
The Kolomela ore deposit is located on the southern ends, of the iron ore belt in the Northern Cape, South Africa.
The Kolomela mine orebodies comprise hard, high-grade, conglomeratic and laminated haematite orebodies. The ores have been preserved as three separate orebodies within basinal and graben structures up to 2km long, 400m wide and 300m deep.
The only BIF present at Welgevonden appears to be that of the Kuruman Iron Formation, with the Griquatown Iron Formation having been removed by erosion. The main structural characteristic in the west of the Welgevonden area is the Wolhaarkop Dome, an overturned anticline replicating the larger Maremane Dome, which occurs in the east of the deposit.The ore bodies are intensely folded and faulted, and are preserved within erosional remnants that are not as continuous, but are of similar structural types to those encountered at Sishen.
Two tectono-stratigraphic settings for the ore bodies have been defined by Alchin and Botha: a palaeosinkhole-hosted setting applicable to the Ploegfontein, Leeuwfontein and Klipbankfontein ore bodies; and a synclinal basin setting applicable to the Welgevonden and Kapstevel ore bodies. Marginal deformational effects, thought to be related to the ~2.2 Ga Kheis event, occur towards the west of the deposit and decrease rapidly to the east. The scattered nature of the ore bodies at Welgevonden could be due to the removal of upper lithologies by erosion and/or due to smaller, less connected underlying palaeosinkhole, pseudo-graben and synclinal structures. The Sishen South deposit is also much smaller than the main ore body at Sishen and early exploration estimates put its mineable ore reserves at approximately 25% of those at Sishen.
Iron ore at Kolomela is associated with the chemical and clastic sediments of the Proterozoic Transvaal Supergroup. These sediments define the western margin of the Kaapvaal Craton in the Northern Cape province. The stratigraphy has been deformed by thrusting from the west and has undergone extensive karstification. The thrusting has produced a series of open, north-south plunging anticlines, synclines and grabens and karstification has been responsible for the development of deep sinkholes. The iron ore at Kolomela has been preserved from erosion within these geological structures. These structures are therefore important exploration targets.
The Transvaal Supergroup lithologies were deposited on a basement of Archaean granite gneisses and greenstones, and/or lavas of the Ventersdorp Supergroup. In the Sishen-Postmasburg region, the oldest rocks of the Transvaal Supergroup form a carbonate platform sequence (dolomites with minor limestone, chert and shale) known as the Campbell Rand Subgroup. The upper part of the Transvaal Supergroup comprises a BIF unit, the Asbestos Hills Subgroup, which has been conformably deposited on the carbonates. In places, the upper portion of the BIF has been supergene-enriched to Fe = 60%. The iron ore/BIF zone is referred to as the Kuruman Formation. The ores found within this formation comprise the bulk of the higher-grade iron ores in the region.
Four distinct high-grade iron ore types have been described at Kolomela in the various separate iron ore deposits:
• High-grade (Fe-rich) laminated ore, which constitutes the main ore type and comprises alternating micro bands of high-lustre haematite with equally thin, porous bands of lower-lustre haematite and specularite. The primary lamination of the precursor BIF is still preserved, suggesting supergene enrichment (in situ replacement) of silica by iron.
• High-grade (Fe-rich) clastic-textured ore, comprising alternating haematite and specularite layers, thicker than those of the laminated ore and characterised by distorted, wavy bedding and occurs as lenses and massive units.
• High-grade (Fe-rich) collapse breccia-type ore, comprising angular fragments of laminated and clastic-textured ore in chaotic arrangement. The fragments are cemented by fine-grained specularite and haematite. The brecciation is probably as a result of karstification of the underlying dolomites, i.e. the collapse breccia ore is the product of sudden, brittle collapse of laminated and clastic-textured ores into underlying solution cavities and is preserved in deep sinkhole structures.
• High-grade (Fe-rich) conglomeratic ore, comprising poorly sorted, rounded to sub-rounded haematite pebbles and clasts in a ferruginised matrix representing, which usually occurs very localised and is considered to represent ferruginised Gamagara conglomerates.
• In addition, material defined in the geological models with an in situ 50% = Fe < 61%, comprising ferruginised BIF, conglomerates and collapse breccia material, is termed medium-grade ore.