Alkaline Rocks and Carbonatites of the World

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Ketumbeine (Kitumbeine)


Occurrence number: 
Longitude: 36.22, Latitude: -2.88

This is a large, dome-shaped basalt volcano surmounted by a truncated cone and rising to over 3000 m. Apart from the dominant olivine basalts, which pass into basanites, the summit region is essentially trachytic. The trachytes are flow-banded lavas with sanidine microphenocrysts in a matrix of sanidine, aegirine-augite, opaque minerals and riebeckite. Phonolite also occurs. A few cones of scoria, agglomerate and tuff are present, particularly on the lower northern and southern flanks. There are four analyses of basalt and basanite, including trace element and Sr, Nd and Pb isotope data, in Paslick et al. (1995).

K-Ar ages of two olivine basalts from the southern slopes ranged from 1.54(0.10 to 1.87(0.08 Ma (Evans et al., 1971).
DAWSON, J.B. and PICKERING, R. 1964. Monduli. Geological Survey of Tanganyika, Quarter Degree Sheet, 54.EVANS, A.L., FAIRHEAD, J.D. and MITCHELL, J.G. 1971. Potassium-argon ages from the volcanic province of northern Tanzania. Nature, Physical Science, 229: 19-20.GUEST, N.J. and PICKERING, R. 1966b. Gelai and Ketumbeine. Mineral Resources Division, Tanzania, Quarter Degree Sheet, 40.PASLICK, C., HALLIDAY, A.N., JAMES, D. and DAWSON, J.B. 1995. Enrichment of the continental lithosphere by OIB melts: isotopic evidence from the volcanic province of northern Tanzania. Earth and Planetary Science Letters, 130: 109-26.
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