Alkaline Rocks and Carbonatites of the World

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Occurrence number: 
Longitude: 34.98, Latitude: -17.6

In a north-south line extending over 250 km from Sena southwards more than 40 plugs of phonolite and nephelinite occur. The only descriptions traced are those of Teale and Smith (1923), which are based on only a few samples. The phonolites are aphanitic rocks with abundant microphenocrysts of nepheline, a few of aegirine, aegirine-augite or a sodic amphibole, and rare ones of anorthoclase. An olivine nephelinite described by Teale and Smith (1923) was collected on Baramwana Hill, close to Sena, and is a porphyritic rock with phenocrysts of olivine in a groundmass of augite, nepheline, a little biotite and abundant magnetite and perovskite.

They cut the middle Cretaceous Sena sandstone.
TEALE, E.O. and SMITH, W.C. 1923. Nepheline-bearing lavas and intrusive rocks from south of the Zambezi River, with a note on an outcrop of Karroo lavas in the Buzi Valley, Portuguese East Africa. Geological Magazine, 60: 226-37.
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith