Sandkopsdrif (Zandkops Drift)

This carbonatite complex is about 1 km in diameter and gives rise to marked radiometric and aeromagnetic anomalies. Exposure is generally poor but less so in the west where drilling and prospecting pits have furthered exploration. The complex appears to be a pipe-like body in which the main component is a micaceous rock which is referred to as glimmerite by Moore and Verwoerd (1985). In places this rock has the structure of a breccia but elsewhere it has the pisolitic texture of a tuffisite; it contains much calcite and vermiculite after phlogopite and there are large rounded blocks of olivine melilitite. Pyrochlore was encountered in heavy mineral concentrates. A number of quartz sovite dykes, less than a metre thick, outcrop in the west and were encountered in a borehole. A lamprophyric dyke with 1 cm-diameter biotite phenocrysts, salite, titanite, ilmenite and apatite in a calcite matrix also occurs. Manganiferous and ferruginous gossans are present which contain a range of rare earth phosphates including churchite, goyazite and carbonate-apatite. Gneisses around the complex are intensively fenitized adjacent to the pipe with the development of secondary calcite, fibrous blue sodic amphibole and aegirine-augite. The fenitization extends for up to one kilometre from the contact. Geochemical anomalies for Zn, Nb and P occur. Some petrographic and mineralogical data on olivine melilitite are given by Boctor and Yoder (1986).