Zimplats Holdings Limited is a subsidiary (87% shareholding) of Impala Platinum Holdings Limited (Implats). The remaining 13% is owned by independent shareholders. Zimbabwe Platinum Mines (Private) Limited is a majority owned operating subsidiary of Zimplats Holdings Limited.
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Summary:
The Great Dyke of Zimbabwe developed as a series of initially discrete magma chamber compartments, which coalesced as the chambers filled.
The Great Dyke has been sub-divided into five sub-chambers, namely the Wedza, Selukwe (Shurugwi), Sebakwe, Darwendale and Musengezi sub-chambers. The stratigraphic units in each sub-chamber are classified into the ultramafic (lower) and the mafic (upper) sequence. The ultramafic rocks are dominated from the base upwards by dunite, harzburgite and pyroxenite, while the mafic rocks consist mainly of gabbro and gabbronorite. Thin layers of chromitite occur at the bottom of cyclic units throughout the ultramafic sequences.
The PGM-bearing horizon is known as the Main Sulphide Zone (MSZ), which is part of the lower sequence and is located below the contact with the mafic sequence. The MSZ is located in the P1 pyroxenite, from 5m to about 50m below the ultramafic/mafic contact. The MSZ is a continuous layer, 2m to 10m thick, and forms an elongated basin. The zone strikes north-northeast, dips between 5° and 20° on the margins, and flattens towards the axis (centre) of the basin. Peak base metal and PGM values are offset vertically, with palladium peaking at the base, platinum in the centre and nickel towards the top.
Mining occurs in areas where the dip is less than 9°, referred to as the MSZ ‘Flats’, and areas with dips between 9° and 14°, which are referred to as the ‘MSZ Upper Ores I’ areas (UOR I). Currently no mining takes place in areas with a dip above 14°, which are referred to as the ‘MSZ Upper Ores II’ (UOR II).
Zimplats operation cuts obliquely across the 2m to 10m thick platinum-bearing MSZ orebody with an approximate north-northeast strike distance of 16km at Ngezi in the south, where the Mupani, Bimha, Mupfuti, Rukodzi and Ngwarati portals are located. Further to the north, at the Hartley Complex, the MSZ orebody extends over a 9km north-northeast strike distance. It is evident on the schematic that the MSZ orebody is a continuous layer within the Great Dyke. East-west striking fault structures form natural boundaries between the portal areas at Ngezi. The MSZ lithologies dip at between 5° and 20° near the margins and flatten towards the central part of the Great Dyke to form a flat-lying floor. The general mining infrastructure at Ngezi is located on the western side of the Great Dyke, where the orebody is accessed by portals.