OVERVIEW OF THE IMPACT OF MINING ON THE ... - IIED pubs

The Limpopo basin encompasses an important ecological transition zone that marks the junction of four
separate bio-climatic regions. The area is considered to be very important in terms of the diversity of its fauna
and flora and also contains several important conservation areas. In addition, the Limpopo basin supports a
very large population, including some of the region’s poorest rural communities, as well as numerous urban
areas and farming communities and important forestry areas.
4.1.1 Geology, topography and soils
The Limpopo basin is located over the northern lobe of the Kalahari Craton, with the Limpopo River valley
marking the approximate position of the Limpopo Mobile Belt where considerable mineralization has taken
place. The Archaean Craton rocks comprise predominantly crystalline granitic and gneissic rocks, intruded by
various Greenstone belts as well as dolerite dykes and sills. Karoo System rocks overlie large areas of the
southern portion of the basin and these are also associated with younger sedimentary and crystalline rocks
consisting predominantly of sandstones, mudstones, conglomerates and shales. Recent sedimentary deposits
line most of the river valleys and provide important farming areas (Du Toit, 1960).
In the southern (South African) portion of the basin, the Bushveld Igneous Complex forms an extremely
important feature and contains a very large proportion of the region’s mineral wealth. The geological features
of this area consist mostly of basic mafic and ultramafic intrusive rocks, accompanied by extensive areas of
acidic and intermediate intrusive rocks. At the southern periphery of this area, large dolomite and limestone
formations occur, accompanied by extensive mineralization along their contact zones. Large areas of the
central portion of the Limpopo basin consist of various deposits of consolidated and unconsolidated sedimentary
rocks, with important belts of intrusive Greenstone rocks that are heavily mineralised. The north-south trending
rhyolites and lavas of the Lebombo Mountains mark the eastern border between South Africa and Mozambique.
Elsewhere, harder, silicified sandstones and cherts, as well as syenitic and granitic outcrops, form erosional
remnants that protrude above the generally undulating terrain (Du Toit, 1960).
In the western portion of the basin, large areas are covered with deep layers of sedimentary rocks comprising
sandstones, siltstones, mudstones and shales. The northern-western areas are also marked by extensive
intrusions of Greenstones and schists that contain significant gold, copper and nickel mineralization. Older
Karoo System rocks that contain important coal deposits also underlie these areas.
The northern and northeastern portions of the Limpopo basin located in Zimbabwe consist of large expanses of
undifferentiated gneisses and granites, with numerous mineralised Greenstone intrusions. The Great Dyke of
Zimbabwe intrudes into the northeastern corner of the Limpopo basin.
The eastern (Mozambique) portion of the Limpopo basin consists largely of unconsolidated and consolidated
sedimentary rocks with granitic intrusions exposed as erosional remnants in the landscape.
The topography of the Limpopo basin is extremely varied, ranging from sea level in Mozambique to over 2,400
metres in the mountainous region marking the transverse position of the northern extension of the Drakensberg
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