Alkaline Rocks and Carbonatites of the World

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Occurrence number: 
Longitude: 9.33, Latitude: 10.4

This rather small occurrence consists of an approximately circular, 3 km-diameter biotite granite, an earlier concentric arfvedsonite granite along its southern margin, and an overlapping system of cone sheets and radial dykes. The arfvedsonite granite consists of perthite and a little albite, quartz, prisms of amphibole, minor biotite, abundant astrophyllite and accessory fluorite and zircon. Apart from mica the biotite granite also contains a little hornblende and fluorite is a widespread accessory. The system of cone sheets and dykes extends all around the intrusion and comprises a perthite-quartz porphyry with minute prisms and films of a blue sodic amphibole in the matrix.

BUCHANAN, M.S., MACLEOD, W.N., TURNER, D.C., BERRIDGE, N.G. and BLACK, R. 1971. The geology of the Jos Plateau. Volume 2, Younger granite complexes. Bulletin, Geological Survey of Nigeria, 32: 1-159.
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