Khumani (Bruce, King, Mokaning)
Northern Cape, South Africa
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The Khumani iron ore mine is located just to the SW of the township of Kathu in the Northern Cape province of South Africa (#Location: 27° 51' 10"S, 23° 1' 4"E).
The 10 mtpa mine (Assmang Limited) was formerly known as the Bruce, King and Mokaning ("BKM") Project, which refers to the farms on which the iron ore resources are located. The iron ore deposits are located adjacent to Kumba Iron Ore's Sishen mine, and approximately 60 km north of Assmang's Beeshoek mine.
As at Sishen, the deposits are hosted within a sequence of Palaeoproterozoic sediments of the Transvaal Supergroup and lie on a limb of the Maremane anticline.
For detail on the setting and stratigraphy, see the separate Sishen record.
The ore at Khumani is situated along the contact between the Gamagara formation and the underlying Manganore iron formation in the northern part of the regional domal structure. Two ore types are present:
i). laminated hematitic ore of the Manganore iron formation, similar to that at Sishen, and
ii). conglomerate ore of the Doornfontein Conglomerate member at the base of the Gamagara formation.
The distribution of the Manganore iron formation is restricted, only being preserved in pockets above the Wolhaarkop Breccia below the Gamagara unconformity. This ore has been enriched with the high grade iron margin crosscutting primary bedding, although most sedimentary features of the original finely banded iron formation are preserved. The Khumani deposits are characterised by large stratiform bodies and prominent hanging wall outcrops. The down-dip portions of the iron formation are well developed, although in outcrop, the deposits are thin and isolated.
The basal Doornfontein Conglomerate is best developed where it overlies the Manganore iron formation. The conglomerate is lenticular and persistently developed along strike. It comprises stacked, upward fining conglomerate-gritstone-shale sedimentary cycles. The lowest conglomerates and gritstones tend to be rich in sub-rounded to rounded hematite ore pebbles and granules and are the basis of the main orebodies in this unit. The proportion of iron oxide pebbles decreases upwards, so that the upper conglomerates usually contain poorly sorted, angular to rounded chert and banded iron formation pebbles.
Hematite is the dominant ore mineral, although limonite and specularite are also present. The K2O content of the ore appears to be directly related to the abundance of muscovite and illite, while the Al2O3 is the result of kaolinite and muscovite in the ore. The ore is depleted in Na and P, with the latter occurring as trace apatite.
Ore is present in two main areas, at Bruce and King, which are approximately 10 km apart. The Bruce orebodies are to be mined from three main and four or five satellite pits, some of which abut the eastern Sishen boundary. The larger Bruce pits will cover areas of from 2000 to 750 m x 750 to 500 m in area with final depths of 95 to 170 m. The King orebody will be mined as part of the expansion to a 16 mtpa rate in two pits, the larger of which will cover an area of 3000x1000 m, exploiting near surface ore to the west, and following it down dip to ultimate depths of 230 m.
Iron ore is mined from a series of open pits and hauled to the primary and secondary crushers, from where, it is transferred by conveyor to stockpiles ahead of the beneficiation plant. The run-of-mine ore will be stockpiled on blending beds in two categories, 'on grade' and 'off grade'. On-grade material will then be washed and screened to produce the final products incorporating tertiary crushing of the oversize material from the screening plant. Off-grade material will also be washed and screened and the oversized material crushed in the tertiary crushers and, thereafter, beneficiated through jigs to remove contaminants. Products will be stockpiled ahead of transport via the 860 km Sishen-Saldanha railway line to the port of Saldanha Bay on South Africa's West Coast from which the iron ore is being exported. Three products are being produced, lumpy, DR lump and fines, with respective grades of 66, 65.5 and 65% Fe.
Total proven + probable reserves as at June 30, 2007, were:
444.7 Mt @ 64.7% Fe, 0.14% Mn, 0.25% K2O, 1.77% Al2O3, 0.04% P and 3.8% SiO2.
Total measured + indicated + inferred resources at the same date, were:
685.5 Mt @ 64.6% Fe.
Ore reserve and mineral resources in 2014 (ARM Resources) were:
Measured + indicated resources - 709.0 Mt @ 64.26% Fe;
Proved + probable reserves - 512.9 Mt @ 64.46% Fe;
The most recent source geological information used to prepare this summary was dated: 2010.
This description is a summary from published sources, the chief of which are listed below.
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