Alkaline Rocks and Carbonatites of the World

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Guraka Hill


Occurrence number: 
Longitude: 8.9, Latitude: 10.7

Guraka Hill rises to over 200 m and is almost circular in plan with a diameter of about 1 km. It consists of two types of syenite but contacts between them have not been located. The outer syenite is variable in texture and composition being drusy and pegmatitic over wide areas. Phenocrysts of perthite are up to a centimetre in length and the mafic minerals, which are generally gathered into clots, are aegirine - aegirine-augite, aenigmatite, amphibole, usually as rims around pyroxene, and biotite. An inner syenite is finer grained and contains fayalite, which is usually altered, aegirine-augite, amphibole and aenigmatite. Chemical analyses and modes of the two types are given by Jacobson and MacLeod (1977).

JACOBSON, R.R.E. and MACLEOD, W.N. 1977. Geology of the Liruei, Banke and adjacent younger granite ring-complexes. Bulletin, Geological Survey of Nigeria, 33: 1-117.
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