Local Achaean rocks of the Zimbabwe Craton, largely

Local Geology

The Selukwe
Subchamber is about 90km long, and 7km wide (Figures 2 to 4. The shape of the
Selukwe Subchamber has to some extent been controlled by the proximity of the
Selukwe greenstone belt, in that it has been deflected and constricted in

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Overall though,
the broad structure of the Selukwe Subchamber is similar to that of the other
subchambers with an upper mafic sequence (280m thick) overlying an ultramafic
sequence (exposed thickness of 1600m). In transverse section the subchamber is
synclinal in shape, with essentially the same lithological succession being
exposed on both sides of the longitudinal axis. Asymmetry in the layering
pattern close to the walls is attributed to the physical shape of the chamber
walls and the contrasting nature of the wall rocks, which are greenstones on
the west, and granite on the east. A number of prominent transverse, steeply
dipping faults interrupt the overall continuity of the Selukwe Subchamber and
these, combined with the change in shallow plunge direction (from north to
south for the northern zone and in the opposite direction for the southern
zone), result in a repetition of the lower gabbronorite on the longitudinal
axis. This has implications for major ground challenges which has been
experienced at the Mine.Regional Geology

The Great Dyke is a layered mafic and ultramafic intrusion that cut across the
dominantly Achaean rocks of the Zimbabwe Craton,
largely composed of granites and greenstones. The Zimbabwe Craton is bounded by
the Zambezi metamorphic belt to the north, the Mozambique belt to the east, and
the Limpopo belt to the south. The Great Dyke, aligned approximately NNE, is
about 550km long and between 4km and 11km wide. Parallel to it are a number of
gabbro and quartz gabbro satellite dykes. The Great Dyke is longitudinally
subdivided into a series of narrow contiguous layered chambers and sub chambers
(Figure 4). The two main chambers have been recognized with further
subdivisions totalling five subchambers on the basis of structure, style of
layering, and continuity of layers. The North Chamber is subdivided into
the Musengezi, Darwendale and Sebakwe subchambers, and the South Chamber into
the Selukwe and Wedza subchambers. Unki
Mining Company is located within the Selukwe Subchamber of the South Chamber of
the Great Dyke in Zimbabwe