Regional stream sediment geochemical survey of South Africa

Abstract

During 1973 the Geological Survey of South Africa embarked on a regional geochemical stream sediment sampling programme which will eventually cover then entire 1.2 million km 2 of the country. Samples are collected at an average density of 1/km 2 and where possible from first order streams. To date, 190000 samples, representing 16% of the area of South Africa, have been collected and analysed for 23 elements by XRF. In addition, a limited number of analyses for uranium by delayed neutron activation have been done. The high sampling density along with the fact that 12000 to 15000 samples are collected annually will result in a prolonged duration to complete the programme, probably several decades. Those parts of South Africa having a higher probability for discovering mineralisation were therefore sampled first. Two such parts include the Karoo uranium province and the predominantly Cu-Pb-Zn metallogenic province in the northwestern Cape. Sampling is at present being carried out over the Transvaal Bushveld metallogenic province. Orientation geochemical surveys are carried out before regional sampling is conducted in any particular area. The object is to establish optimum size fractions, pathfinder elements etc. The results of some of these orientation studies are discussed. To date virtually no ground follow-up work has been carried out by the Geological Survey, but this is expected to change in the future. The geochemical results have merely been released on Open File in the form of geochemical maps which should assist private exploration companies. The geochemical results should also contribute toward IGCP Project 259.