[en] A simple procedure for Pb separation from a range of geological materials was investigated and tested. The small quantity of reagents result in measured Pb contamination levels of less than 1.0 ng. The method provides maximum Pb yields which is advantageous for samples with low Pb concentrations. Stable emission and limited isotopic fractionation in the mass spectrometer are obtained by a technique of initial melting of the silica gel followed by analysing samples at a constant filament temperature of 1200 deg C. Three suites of low Mg felsites from the Loskop Dam sequence were investigated: An essentially unaltered, clinopyroxene-phyric rhyolite flow yielded well-defined Pb-Pb and Rb-Sr isochron ages of 2018 +58 -59 Ma and 1971 ± 22 Ma respectively - the oldest radiometric ages yet obtained for the Rooiberg Felsite; a slightly altered, black, porphyritic flow yielded Rb-Sr and Pb-Pb errorchron age estimates of 1933 ± 45 Ma and 1677 +236 -280 Ma respectively; a set of typical, oxidized, red felsites from the Selons River Formation scatter about the 1670 Ma Pb-Pb isochron. In addition, a suite of high Mg felsites from the Loskop Dam sequence yielded a poorly defined Pb-Pb isochron age of 1329 +643 -816 Ma and a set of rhyolite samples from the base of the Dullstroom Formation yielded a Pb-Pb isochron age of 2044 +129 -135 Ma. These results suggest that intrusion of the Bushveld Complex at 2050 Ma reset the Pb-Pb and Rb-Sr systems in the felsites, thus precluding determination of the true age of the Rooiberg. The Pb-Pb system in the partly altered, black, porphyritic lavas has been less resistant to low temperature resetting than the Rb-Sr system. Felsites that were altered and oxidized during an episode at ca. 1670 Ma appear to have undergone a U-leaching event. 16 figs., 19 tabs., 37 refs