A study of Late Palaeozoic Witteberg Group rocks (Cape Supergroup) near Kirkwood, Eastern Cape was carried out to determine the viability of extracting silica for solar cell production. Mineralogical, geochemical and structural analyses of selected outcrops of quartz-arenites showed that source rocks in the study area do not possess the appropriate chemical attributes to warrant extraction of silica. Despite this finding the study presents valuable information on strata composition and structural data which are compared and interpreted with known regional structural patterns of the Cape Fold Belt in the Eastern Cape.
Samples from the Witpoort Formation were analyzed using petrographic light microscopy, scanning electron microscopy and X-ray fluorescent spectroscopy. Analyses indicate that samples are composed almost entirely of quartz, with accessory biotite, muscovite, sericite, baryte, apatite, rutile and monazite. Haematite occurs most frequently along fractures, and is more prevalent in the Rooirand Member than the Perdepoort Member, giving the former a reddish brown colour on outcrop. The presence of chemical impurities is thought to be partly controlled by the original depositional environment, namely, near-shore and beach environments.
Strata in the study area display a range of fold styles, mostly showing northward vergence. Low angle thrust faults dip south and some thrusts dip north. In general, the orientation of fore-thrusts and folds in the study area indicate a northward-directed compression event during the Late Palaeozoic. This pattern conforms to the structural development in other parts of the Cape Fold Belt in the Eastern Cape. South-dipping normal faults and strike-slip faults post-date thrust faulting, and formed during the breakup of Gondwana, during the Mesozoic, transecting all other structures in the study area.