Keikamspoort

Keikamspoort is a composite carbonatite dyke which forms a ridge 2 km long and 300 m wide but no contacts are exposed (Verwoerd, 1993). The dyke consists of quartz-apatite beforsite, quartz-feldspar beforsite and lenses of biotite-rich beforsite. Uniformly fine-grained ankerite is the principal phase with calcite rare. Quartz, intergrown with apatite, forms veinlets and aggregates and there are quartz veins up to 1 cm thick. Apatite occurs as patches and segregations and, like K-feldspar crystals, is reddish because of much iron oxide. Needles, strings and aggregates of rutile are a characteristic accessory, pyrite is common, monazite produces lenticular aggregates up to 6 mm in length and minor magnetite, zircon, fluorite and possible strontianite have been identified (Verwoerd, 1993). There is also a little chalcopyrite, sphalerite and galena but pyrochlore has not been found although values of 460 and 355 ppm Nb have been determined. Assay results for Cu, Zn, Pb and Ag are in Verwoerd (1986). There is a narrow strip of syenite or fenite, in the form of a K-feldpar rock, adjacent to part of the carbonatite dyke and there is an outcrop of a similar rock 1 km to the northwest which is traversed by offshoots of the main carbonatite. A fresh sodalite-nepheline syenite, known as the Waterkop syenite, is exposed in a cutting along the Prieska-Copperton road, approximately 18 km from Keikamspoort, but the extent of the body is not known (Verwoerd, 1993).