Alkaline Rocks and Carbonatites of the World

Setup during HiTech AlkCarb: an online database of alkaline rock and carbonatite occurrences

Ol Esayeiti


Occurrence number: 
Longitude: 36.58, Latitude: -1.5

The Ol Esayeiti volcano is located southwest of the Ngong Hills and extends from the southwest corner of the Nairobi map sheet (No. 085-00-062) (Saggerson, 1991) into the Kajiado area to the south (No. 085-00-071) (Matheson, 1966). It comprises flows of phonolite, tephrite and trachyte which partly overlie the products of the Ngong volcano. A phonolite at the base of the succession contains phenocrysts of nepheline, up to 1.5 cm, anorthoclase, titanaugite and titanite set in a groundmass of alkali feldspar, oligoclase, aegirine-augite, aenigmatite and katophorite. The tephrites are typically feldspar-phyric, with oligoclase phenocrysts up to 1.5 cm; ‘barkevikite’ and titanaugite lie in a trachytic matrix of oligoclase, aegirine-augite, nepheline and magnetite.

6.7-?3.6 Ma (Baker et al., 1988).

BAKER, B.H., MITCHELL, J.G. and WILLIAMS, L.A.J. 1988. Stratigraphy, geochronology and volcano-tectonic evolution of the Kedong-Naivasha-Kinangop region, Gregory Rift valley, Kenya. Journal of the Geological Society of London, 145: 107-16.MATHESON, F.J. 1966. Geology of the Kajiado area. Report, Geological Survey of Kenya, 70: 1-51.SAGGERSON, E.P. 1991. Geology of the Nairobi area. Report, Geological Survey of Kenya, 98: 1-91.

Fig. 3_122 General map showing the distribution of volcanic rocks in south-central Kenya. The areas covered include the Narok and Mara River areas (No. 59), the Suswa area (No. 60), the Nairobi area (No. 62), and the Magadi area (No. 67). The volcanoes of Suswa (No. 61), Ngong (No. 63), Ol Esayeiti (No. 64), Olorgesailie (No. 68), Lenderut (No. 69) and Shombole (No. 70) are also indicated. (based on Geological Map of Kenya, 1:1,000,000, 1987).
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith