Alkaline Rocks and Carbonatites of the World

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Affara Dara

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Occurrence number: 
054-00-017
Country: 
Ethiopia
Location: 
Longitude: 40.8, Latitude: 12.6

The Affara Dara peralkaline granite is exposed over 35x25 km but to the west is partially covered by younger basalts that emanated from the Alayta and Boina eruptive centres. In the south highly altered basalts, thought to be of Tertiary age, are intruded; the metamorphic aureole is less than 50 m wide. The most abundant rock type is a coarse-grained riebeckite granite but syenites also occur. Near the margins a finer grain size prevails. Small dykes of peralkaline granite aplite and biotite-bearing pegmatites are found near the periphery, the latter also occurring in the altered basaltic country rocks.

Age: 
A K-Ar determination on granite gave 25(0.9 Ma (Barberi et al., 1972a).
References: 
BARBERI, F., BORSI, S., FERRARA, G., MARINELLI, G., SANTACROCE, R., TAZIEFF, H. and VARET, J. 1972a. Evolution of the Danakil Depression (Afar, Ethiopia) in light of radiometric age determinations. Journal of Geology, 80: 720-9. BARBERI, F., CHEDEVILLE, E., FAURE, H., GIGLIA, G., MARINELLI, G., SANTACROCE, R., TAZIEFF, H. and VARET, J. 1973b. Geology of Northern Afar (Ethiopia) (with a geological map, scale 1:500,000). Revue de Geographie Physique et de Geologie Dynamique, Paris, 15: 443-89.
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