Alkaline Rocks and Carbonatites of the World

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

Simien Mountains (Semien, Ras Dashan)


Occurrence number: 
Longitude: 38.25, Latitude: 13.17

Simien is a large volcanic cone rising from an extensive area of low angle lavas to a maximum height of 4543 m. It is essentially basaltic but there are comenditic dykes, which may be spherulitic, and larger rhyolitic intrusions. Mohr (1967a) reproduces two analyses of peralkaline rhyolites from Comucci (1950), which the author has not seen, and they apparently contain sanidine and quartz phenocrysts in a spherulitic and micro-felsitic groundmass in which aegirine-augite microlites are prominent. Fuller accounts have not been located.


COMUCCI, P. 1950. Le vulcaniti del Lago Tana (Africa Orientale). Accademia Nazionale Lincei, Rome. 209 pp.MOHR, P.A. 1967a. Review of the geology of the Simien Mountains. Bulletin of the Geophysical Observatory, Haile Sellassie I University, Addis Ababa, 10: 79-93.

Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith