Age determinations of the Zoetlief Group - a Ventersdorp Supergroup correlate

A minimum age limit of 2700 Ma is given for the Zoetlief Group by its field relationships with the Bothaville and Allanridge Formations of the Ventersdorp Supergroup. Attempts at dating the Zoetlief Group using various whole rock techniques - Rb-Sr, Pb-Pb and Sm-Nd - have thus far failed to produce an acceptable crystallisation age of the Zoetlief volcanics. Further Sm-Nd work could conceivably change this picture. Dating by means of the zircon evaporation technique has similarly resulted in ages lower than the 2700 Ma age limit. Single zircon studies by chemical separation or ion microprobe would be of value. Nevertheless, the isotopic data show striking resemblances to the age patterns that have been obtained for the lavas of the Ventersdorp Supergroup and provide strong support for correlating these successions. Thus there appears to be a good case for correlating the quartz porphyry of the Kareefontein Formation with the Maquassie Quartz Porphyry of the Platberg Group. The differences in the degree of deformation between the Zoetlief and Ventersdorp may merely reflect varying local tectonic conditions and need not present an obstacle to this correlation. 2 figs., 1 tab., 19 refs