Introduction
Regional geological settings

The Bushveld Complex

The Bushveld Complex is an extremely large (66 000km²), two billion year-old layered igneous intrusion occurring in the northern part of South Africa. Rock types range in composition from ultramafic to felsic. The complex is not only unique in size, but also in the range and economic significance of its contained mineral wealth. In addition to the platinum group metals (PGMs) and associated base metals, vast quantities of chromite, vanadium and dimension stone are also produced.

The schematic diagram below shows the extent of the Bushveld Complex. The layered sequence, the Rustenburg Layered Suite, comprises five major subdivisions, ie the Marginal, Lower, Critical, Main and Upper zones. Two horizons within the Critical Zone, namely the Merensky Reef and the Upper Group 2 (UG2) Reef, host economically exploitable quantities of PGMs. These two horizons, along with other layers which can be traced for hundreds of kilometres around the complex, are the focus of Implats' operations. The PGMs – platinum, palladium, rhodium, ruthenium and iridium – as well as the associated gold, copper, nickel, cobalt, chromite and other minor metals and compounds, are mined and recovered concurrently.

IMPALA – MERENSKY Pyroxenite reef		IMPALA – MERENSKY Pegmatoid reef		IMPALA – MERENSKY		TAMBOTI – MERENSKY
Pyroxenite         Pegmatoid         Anorthosite/norite         Chromitite

IMPALA – MERENSKY
Pyroxenite reef

IMPALA – MERENSKY
Pegmatoid reef

IMPALA – MERENSKY

IMPALA – MERENSKY

 Pyroxenite      Pegmatoid      Anorthosite/norite      Chromitite

A detailed geological description of the various reef types is provided in the relevant operational sections. Examples of different Merensky Reef vertical grade profiles are shown on the previous page. It is clear that the grade distribution varies materially from area to area.

The UG2 Reef morphology and associated vertical grade distribution also differs significantly between regions (see below), specifically in terms of the width of the main platinum bearing chromitite layer and in the number of layers. In general the grade increases if the chromitite layer width becomes thinner.

Shaft sinking, Impala

IMPALA – UG2		AFPLATS – UG2		MARULA – UG2		TAMBOTI – UG2 (Normal)
Pyroxenite         Pegmatoid         Anorthosite/norite         Chromitite

IMPALA – UG2

AFPLATS – UG2

MARULA – UG2

TAMBOTI – UG2 (Normal)

 Pyroxenite      Pegmatoid      Anorthosite/norite      Chromitite