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Pietersburg Group

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Pietersburg Group

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The Pietersburg Greenstone Belt occurs near the northern margin of the “low-grade” granite-greenstone terrain of the Kaapvaal Craton. To the north lies the “high-grade” granite-greenstone terrain which constitutes the Southern Marginal Zone of the Limpopo Belt. The original relationship between the two terrains has been overprinted by the effects of the Limpopo Orogeny and are therefore not known. The rocks can be subdivided into two sequences. The first comprises a sequence of massive to pillowed metabasalts, metagabbros and metaperidotites, as well as BIF, fine-grained mafic tuffs and sediments. The sequence was subjected to extensive hydrothermal metamorphism at low pressures and variable temperatures in the greenschist to amphibolite facies. The second sequence, known as the Uitkyk Formation, comprises a sequence of terrestrial clastics, which overlie the first sequence with a profound unconformity. Sedimentology indicates that the Uitkyk Formation formed in a prograding alluvial fan or braided alluvial plain. The Uitkyk sediments were deformed and infiltrated by fluids that precipitated quartz-tourmaline (±gold) and siderite soon after deposition.

Source: The geology and tectonic evolution of the Pietersburg Greenstone Belt, South Africa by M de Witt et al (1991)