The Great Dyke or Dike is a linear geological feature that trends nearly north-south through the centre of Zimbabwe passing just to the west of the capital, Harare.
It consists of a band of short, narrow ridges and hills spanning for approximately 550 kilometres (340 mi).
The range is host to vast ore deposits, including gold, silver, chromium, platinum, nickel and asbestos.
The Great Dyke is unusual in that most ultramafic layered intrusions display near horizontal sill or sheet forms.
These mark the centres of the four sub-chambers within the Great Dyke magma system, namely (from north to south) Musengezi, Darwendale, Sebakwe and Wedza.
[3] Stratigraphically each sub-chamber is divided into a lower Ultramafic Sequence of dunites, harzburgites, olivine bronzitites and pyroxenites together with narrow layers of chromitite that constitute the bases of cyclic units and that are extensively mined along the Great Dyke, and an upper Mafic Sequence mainly consisting of a variety of plagioclase-rich rocks, such as norites, gabbronorites and olivine gabbros.
[4] Below the Ultramafic-Mafic sequences' contact, and in the uppermost pyroxenite (bronzitite and websterite) units are economic concentrations of nickel, copper, cobalt, gold, and platinum group metals (PGM).