The rainbow reefs of the Van den Heeversrust area, north-west of Odendaalsrus

Abstract

The geological succession in the northwestern portion of the Orange Free State Gold-fields, as disclosed by twenty-one bore-holes, is described. Special attention is paid to the Rainbow Reefs, occurring in the strata between the Lower Division of the Ventersdorp System and zone v.s.5. The reef at, or near, the base of zone VoSslC is correlated with the Ventersdorp Contact Reef on the Rand and the Orlmey Reef in the Klerksdorp area. Thin sections of the quartzite from all zones between V.S.lA and E.F.l were examined and microscopic differences were detected, which may be of diagnostic value for correlation purposes. A stratigraphical break at the base of zone v.s.1c is suggested and substantiated by the evidence obtained from a study of the zircon grains in zones V,S.lA to E.c.1.