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Mpumalanga, South Africa
Main commodities: Ni Cu Co PGE PGM Au

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The Nkomati Ni-Cu-Co-PGE deposit is located within the Uitkomst Complex, an 8x1 km and up to 650 m thick, NW-SE trending, flat lying, poorly layered, sill like, 2025 Ma mafic body of harzburgite, gabbro, pyroxenite and gabbro-norite. Nkomati is approximately 325 km east of Rustenburg. The deposit is also some 75 km to the east of the south-eastern lobe of the main 2050 Ma Bushveld Complex, with which it is believed to be genetically associated. It plunges at around 4 degrees to the NW and cuts basement rocks of the Transvaal Supergroup, including quartzite, shales (in part graphitic), the Malmani Dolomite and Archaean granitoids.

The Uitkomst Complex comprises: i). a basal 6-30 m thick gabbro (possibly an earlier sill), overlain by ii). a sulphide bearing lower harzburgite (50-90 m) containing sedimentary xenoliths, iii). chromitiferous harzburgite (±60 m), iv). main harzburgite (±300 m), v). upper pyroxenite (60 m) and vi). upper gabbro-norite (±250 m). Drilling and field relations suggest the complex was initially emplaced discordantly at the base of the Transvaal Supergroup bounded by two NW-SE trending fracture systems.

The Uitkomst complex contains three disseminated, sulphide mineralised zones hosted by the basal gabbro and lower harzburgite, namely the Basal Mineralised Zone (BMZ), Main Mineralised Zone (MMZ) and the Chromititic Pyroxenite Mineralised Zone (PCMZ) for a resource in 2005 of 139 Mt @ 0.49% Ni, 0.19% Cu, 0.02% Co and 1.04 g/t PGE+Au.

Massive sulphide mineralisation is found in the immediate footwall of the Complex, within the Transvaal sediments and the Archaean granite gneiss. The orebody consists of three lenses separated by mafic/ultramafic intrusions and is accessed by means of two vertical shafts and a decline. The initially exploited orebody, the MSB, had an initial reserve of 2.86 Mt @ 2.04% Ni, 1.13% Cu, 0.10% Co, 1.65 g/t Pt, 4.18 g/t Pd, 0.16 g/t Rh, 0.18 g/t Au. The current (2005) resource of the MSB is 13.2 Mt @ 2.98% Ni, 0.97% Cu, 0.17% Co, 5.62 g/t PGE+Au.

The Combined Mineral Reserves for the current mine and expansion project (Dec 2004) including the MSB and MMZ zones was: 51.7 Mt @ 0.52% Ni, 0.2% Cu, 0.03% Co, 1.15 g/t PGE+Au.

In addition, the Uitkomst Complex hosts massive to semi-massive chromitite mineralisation within the chromitiferous harzburgite.

The Nkomati mine is a joint venture between African Rainbow Mines (50%) and LionOre (50%).

The most recent source geological information used to prepare this decription was dated: 2005.    
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:
de Waal S A and Armstrong R A,  2000 - The age of the Marble Hall diorite, its relationship to the Uitkomst Complex, and evidence for a new magma type associated with the Bushveld igneous event : in    S. Afr. J. Geol.   v103 pp 128-140
de Waal S A and Gauert C D K,  1997 - The Basal Gabbro Unit and the identity of the parental magma of the Uitkomst Complex, Badplaas, South Africa: in    S. Afr. J. Geol.   v100 pp 349-361
de Waal S A, Gauert C D K  1997 - The Basal Gabbro Unit and the Identity of the Parental Magma of the Uitkomst Complex, Badplaas, South Africa: in    J. of African Earth Sciences   v100, no.4 pp 349-361
Gauert C D K, de Waal S A, Wallmach T  1995 - Geology of the Ultrabasic to Basic Uitkomst Complex, Eastern Transvaal, South Africa: An Overview: in    J. of African Earth Sciences   v21, no.4 pp 553-570
Hammerbeck E C I, Schurmann L W  1998 - Nickel: in Wilson M G C, Anhaeusser C R, (eds),  The Mineral Resources of South Africa Council for Geoscience, Pretoria    pp 471-482
Kenyon A K, Attridge R L, Coetzee G L  1986 - The Uitkomst Nickel-Copper Deposit, Eastern Transvaal: in Anhaeusser C R, Maske S, (eds),  Mineral Deposits of Southern Africa Geol. Soc. of South Africa, Johannesburg   v2 pp 1009-1017
Maier W D, Gomwe T, Barnes S.-J. , Li C, Theart H,  2004 - Platinum Group Elements in the Uitkomst Complex, South Africa: in    Econ. Geol.   v99 pp 499-516
Maier, W.D, Prevec, .A., Scoates, J.S., Wall, C.J., Barnes, S.-J. and Gomwe, T.,  2018 - The Uitkomst intrusion and Nkomati Ni-Cu-Cr-PGE deposit, South Africa: trace element geochemistry, Nd isotopes and high-precision geochronology: in    Mineralium Deposita   v.53, pp. 67-88.
Theart H F J and de Nooy C D,  2001 - The Platinum Group Minerals in two parts of the Massive Sulphide Body of the Uitkomst Complex, Mpumalanga, South Africa: in    S. Afr. J. Geol.   v104 pp 287-300
Trubac, J., Ackerman, L., Gauert, C., Durisova, J. and Hrstka, T.,  2018 - Platinum-Group Elements and Gold in Base Metal Sulfides, Platinum-Group Minerals, and Re-Os Isotope Compositions of the Uitkomst Complex, South Africa: in    Econ. Geol.   v.113, pp. 439-461
Yudovskaya, M., Naldrett, A., Woolfe, J., Costin, G. and Kinnaird, J.,  2015 - Reverse compositional zoning in the uitkomst chromitites as an indication of crystallization in a magmatic conduit: in    J. of Petrology   v.56, pp. 2373-2394.

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, its employees and servants:   i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and   ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.

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