Alkaline Rocks and Carbonatites of the World

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Wachacha

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Occurrence number: 
054-00-031
Country: 
Ethiopia
Location: 
Longitude: 38.65, Latitude: 8.87

Wachacha is a well preserved volcanic dome of some 100 km2 centred about 20 km west-southwest of Addis Ababa. The volcano consists of trachytic flows, tuffs, breccias and possible plugs. The trachytes are probably peralkaline. Carbonate veins and dykes in the summit area were, in the absence of thin sections (P.A. Mohr, pers. comm., 1995), thought to be carbonatites. However, M.S. Garson (pers. comm., 1990) says that they are not carbonatites.

Age: 
Four K-Ar determinations on sanidine phenocrysts from a flow at the summit gave an average age of 4.5(0.1 Ma (Miller and Mohr, 1966).
References: 
M.S. Garson, pers. comm., 1990.MILLER, J.A. and MOHR, P.A. 1966. Age of the Wachacha trachyte-carbonatite volcanic centre. Bulletin of the Geophysical Observatory, Haile Sellassie I University, Addis Ababa, 9: 1-5.P.A. Mohr, pers. comm., 1995.
Location: 
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith