Introduction
The greenstones are economically important, hosting many gold, antimony, copper-zinc, iron, asbestos, talc, mercury, magnesite and gemstone deposits. Rocks found in this stratum are arenite, conglomerate, shale, lava, pyroclastic, lutaceous arenite and volcanic rocks. The Barberton Mountain Land is the most-significant gold-producing greenstone belt in South Africa. The main Groups included in this Supergroup are:
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Onverwacht Group of ultramafic to mafic volcanic rock,
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Fig Tree Group consisting of greywacke, shale, chert and dacitic volcanic rock
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Moodies group consisting of conglomerates, sandstone, siltstone and shale.
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Geohydrology
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Along the Limpopo River water is abundant due to lime deposits and and deep weathering. As much as 70 l/s can be pumped from a borehole. Water also abundant in “block” dolerite (highly fractured) towards Musina. More to the south, feldspates weathers to clay and therfore boreholes will have lower yields.
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Areas where there are many dykes will have good groundwater (e.g. Pietersburg's boreholes can produce up to 40 l/s).
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The granites of Johannesburg and Parys are low yielding due to very little weathering. However water is found along dykes or quartz veins.
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Source: http://www.cushmanfoundation.org
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