Alkaline Rocks and Carbonatites of the World

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Occurrence number: 
Longitude: 15.32, Latitude: -21.97

Eureka consists of several curving carbonatite dykes with a maximum thickness of 7 m (Dunai et al., 1989). They intrude feldspathic quartzites which are fenitized for up to 20 m and intensely fenitized along the contacts with the production of 20 cm thick orthoclasite zones. Verwoerd (1967) describes the occurrence as a monazite deposit in which the monazite forms aggregates of platy crystals up to 13 cm across with a chemistry more akin to that of carbonatite monazite than pegmatite monazite. The carbonate rock consists of 30% dolomite, 5% calcite and 5 % of magnetite, graphite and pseudomorphs of serpentine-like minerals, secondary carbonates and goethite. Analyes of four carbonatite samples by Dunai et al. (1989) indicated 24,550 to 30,580 ppm Sr and 87Sr/86 values of 0.70286-0.70318.

A separated sample of monazite dated by the Pb method gave 500(20 Ma (Burger et al., 1965).
BURGER A.J., KNORRING, O.VON and CLIFFORD, T.N. 1965. Mineralogical and radiometric studies of monazite and sphene occurrences in the Namib Desert, South-West Africa. Mineralogical Magazine, 35: 519-28.DUNAI, T., STOESSEL, G.F.U. and ZIEGLER, U.R.F. 1989. Note: a Sr isotope study of the Eureka carbonatite, Damaraland, Namibia. Communications of the Geological Survey of Namibia, 5: 89-90.VERWOERD, W.J. 1967. The carbonatites of South Africa and South West Africa. Handbook, Geological Survey of South Africa, 6: 1-452.
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