Alkaline Rocks and Carbonatites of the World

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

Wonchi (Badda Rogghie)


Occurrence number: 
Longitude: 37.93, Latitude: 8.63

The Wonchi volcano is 50 km in diameter and rises to 3456 m. Little information has been traced but Gaeta and Mottana (1991) state that it is formed mostly of fine-grained pyroclastic deposits and is very complex with numerous calderas and satellite craters. The youngest caldera has walls consisting of fine-grained pyroclastic rocks containing scattered coarse-grained blocks of syenite. A sample of syenite investigated by Gaeta and Mottana (1991) consisted of albite phenocrysts in a groundmass of albite, microcline, aenigmatite, amphibole, zoned from sodian edenite to arfvedsonite, aegirine-augite zoned to aegirine, a little riebeckite and biotite and the very rare mineral wilkinsonite. Analyses of aenigmatite and wilkinsonite are given.

GAETA, M. and MOTTANA, A. 1991. Phase relations of aenigmatite minerals in a syenitic ejectum, Wonchi volcano, Ethiopia. Mineralogical Magazine, 55: 529-34.
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith