Olmoti And Elanairobi (Embagai)

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Occurrence number:

163-00-008

Country:

Tanzania

Location:

Longitude: 35.72, Latitude: -2.87

Carbonatite:

The extinct volcanoes of Olmoti and Elanairobi rise well above 3000 m and their products, not as yet mapped in detail, merge and cover an extensive area being truncated by major rift faults and overlain by later volcanics from Kerimasi (No. 163-00-007). The circular crater of Olmoti is nearly 4 km in diameter and underlain by lake deposits. An even larger structure, the Embagai caldera, surmounts Elanairobi and contains a crater lake. The dominant rock type is basalt, frequently with olivine, but occasional flows of trachyte, phonolite, notably on the summit ridge of Olmoti, and nephelinite occur and are exposed in the wall of the rift valley. Tuffs and agglomerates are also widely distributed.

Age:

Four K-Ar ages quoted by Foster et al. (1997) for Olmoti rocks ranged from 1.65±0.03 to 1.07±0.05 Ma and four Elanairobi rocks gave 0.5±0.4 to about 0.6 Ma.

References:

FOSTER, A., EBINGER, C., MBEDE, E. and REX, D. 1997. Tectonic development of the northern Tanzanian sector of the East African rift system. Journal of the Geological Society of London, 154: 689-700.GUEST, N.J., JAMES, T.C., PICKERING, R. and DAWSON, J.B. 1961. Angata Salei. Geological Survey of Tanganyika, Quarter Degree Sheet, 39.PICKERING, R. 1965. Ngorongoro. Geological Survey of Tanzania, Quarter Degree Sheet, 53.

Map:

Fig. 3_295 Distribution of volcanic rocks in northern Tanzania (based on map of J.B. Dawson). and Fig. 3_300 Olmoti and Elanairobi, Lemagrut, Oldeani, Sadiman and Ngorongoro (after Pickering, 1964 and 1965).

Location:

All locations > Africa > Tanzania

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