Alkaline Rocks and Carbonatites of the World

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Oas And Lofdal


Occurrence number: 
Longitude: 14.75, Latitude: -20.35

Within the Welwitschia Inlier of basement rocks occurs the approximately 10x5 km Oas hornblende quartz syenite intrusion. About 1 km north of Oas, according to a map in Hoffman et al. (1996), are two small bodies (approximately 1.5x1.5 km) that comprise the Lofdal nepheline syenite, of which no details are given. Also north of Ofdal and covering an area of some 13x8 km are numerous east-west-trending felsic and carbonatite dykes. The carbonatites carry abundant fluorite in places and up to 180 ppm Th and 260 ppm W; up to 460 ppm Nb has been recorded in the nepheline syenite (Verwoerd, 1993).

U-Pb dating of zircons from the Oas quartz syenite gave 756(2 Ma (Hoffman et al., 1996).
HOFFMAN, P.F., HAWKINS, D.P., ISACHSEN, C.E. and BOWRING, S.A. 1996. Precise U-Pb zircon ages for early Damaran magmatism in the Summas Mountains and Welwitschia Inlier, northern Damara belt, Namibia. Communications of the Geological Survey of Namibia, 11: 47-52.VERWOERD, W.J. 1993. Update on carbonatites of South Africa and Namibia. South African Journal of Geology, 96: 75-96.
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