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Western Platinum Section - Marikana (Karee, Middelkraal), Pandora - Bushveld Complex

Gauteng, South Africa

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The Western Platinum or Marikana group of PGE mines, which includes Karee, Middelkraal, Westerns, Easterns and Marikana open-pit distributed over a strike length of ~27 km. These mines are located in the Northwest Province of South Africa, ~20 km to the east of Rustenberg on the southern margin of the Western Lobe of the 2050 Ma Rustenburg Layered Suite of the Bushveld complex in northern South Africa.

The Pandora PGE mines are located in the Brits District, contiguous with, and immediately to the east of the the Marikan group over a strike length of approximately 12 km.

The Marikana group of mines exploit both the Merensky and the UG2 Reefs over a strike length of ~27 km. Both the Merensky and the UG2 reefs sub-outcrop below a thin layer of black soil throughout most the strike length, although most of the near surface ore has been removed by open pit mining. The strata and reefs strike ~east-west and generally dip at between 8°N in the west, preogressively increasing to 13°N in the far east (Lonmin, 2012).

The UG2 Reef occurs 130 to 210 m below the Merensky Reef, with the intervening rocks between the two reefs gradually increasing from west to east. At the Marikana Operations, the UG2 Reef normally comprises a narrow tabular chromitite layer, which varies between 1.0 and 1.4 m in thickness. Localised internal waste comprising pyroxenite or anorthosite can occur within the reef. In the west, the Leader Chromitite layer separates from the main UG2 Chromitite creating a zone of "split reef" (Lonmin, 2012).

The Merensky Reef varies across the Marikana area, and has been subdivided into several facies (or reef sub-types) based on the occurrence of distinct lithological units within the reef. Two major types, pegmatoidal and non-pegmatoidal faciesare recognised, which have been separated further into a total of seven different facies based on the occurrence of thin chromitite layers in the order of several mms thick. Grade and thickness characteristics are controlled by the facies. In general, the facies change from ESE to WNW, with lower grade nonpegmatoidal types occur to the east and the higher grade pegmatoidal types in the western and deeper areas (Lonmin, 2012).

The Pandora operations cover the Merensky Pyroxenite and the UG2 Chromitite Layer over a strike length of ~12 km, where the mineralised layers sub-outcrop below a thin layer of black soil along 5 km of strike length, that is contiguous to the Marikana mining operations. Most of the near outcrop UG2 Reef has been removed by open pit mining. The layering of the complex strikes ENE and dips ~13° to the north. At Pandora, the UG2 Reef normally comprises a massive chromitite layer, which varies in thickness over the property but is generally between 1.0 and 1.5 m thick. Localised areas of internal waste can occur (Lonmin, 2012).

The Merensky Reef at Pandora is a thick low grade non-pegmatoidal type and no Mineral Resources have yet been defined for the Pandora JV as continuity of potentially economic mineralisation in this variably mineralised unit has not yet been established. The UG2 Reef is mined from underground via Lonmin’s Marikana E3 Incline shaft access (Lonmin, 2012).

For more details of the occurrence, geology and mineralogy of these reefs, see the Rustenberg Section record.

For an outline of the setting, geology and distribution of mineralisation within the Bushveld Complex, see the separate Bushveld Complex record.

Reserves on the Merensky Reef of the Western Platinum section in 1986 (Farquhar 1986) totalled: 161 Mt @ 5.67 g/t PGE, 0.16% Ni, 0.10% Cu.

The ore reserves and mineral resources at the Marikana Mines at 31 December, 2011 (Lonmin, 2012) were:
    Merensky Reef,
        Proved + Probable Reserve - 96.71 Mt @ 4.06 g/t 4E (Pt+Pd+Rh+Au);
        Measured + Indicated + Inferred Resource - 71.3 Mt @ 6.21 g/t 4E (Pt+Pd+Rh+Au),
    UG2,
        Proved + Probable Reserve - 232.44 Mt @ 4.06 g/t 4E (Pt+Pd+Rh+Au);
        Measured + Indicated + Inferred Resource - 92.1 Mt @ 5.75 g/t 4E (Pt+Pd+Rh+Au).
    Combined Merensky Reef + UG2,
        Measured + Indicated + Inferred Resource - 893.54 Mt @ 4.83 g/t 4E (Pt+Pd+Rh+Au).


The ore reserves and mineral resources at the Pandora Mines at 31 December, 2011 (Lonmin, 2012) were:
    Merensky Reef,
        No resources or reserves,
    UG2,
        Proved + Probable Reserve - 18.13 Mt @ 4.02 g/t 4E (Pt+Pd+Rh+Au);
        Measured + Indicated + Inferred Resource - 189.96 Mt @ 4.65 g/t 4E (Pt+Pd+Rh+Au).


For detail consult the reference(s) listed below.

The most recent source geological information used to prepare this summary was dated: 2011.     Record last updated: 14/11/2012
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
 References to this deposit in the PGC Literature Collection:
Carr H W, Kruger F J,. Groves D I, Cawthorn R G  1999 - The petrogenesis of Merensky Reef potholes at the Western Platinum Mine, Bushveld Complex: Sr-isotopic evidence for synmagmatic deformation: in    Mineralium Deposita   v34 pp 335-347
Farquhar J  1986 - The Western Platinum Mine: in Anhaeusser C R, Maske S, (Eds.), 1986 Mineral Deposits of South Africa Geol. Soc. South Africa, Johannesburg   v2 pp 1135-1142
Junge M, Oberthur T and Melcher F,  2014 - Cryptic Variation of Chromite Chemistry, Platinum Group Element and Platinum Group Mineral Distribution in the UG-2 Chromitite: An Example from the Karee Mine, Western Bushveld Complex, South Africa : in    Econ. Geol.   v.109 pp. 795-810


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