Alkaline Rocks and Carbonatites of the World

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Occurrence number: 
Longitude: -4.15, Latitude: 16.48

A concentration of small dykes extends in an east-west zone for about 20 km some 15 km south of Lac Faguibine. Nearly 40 dykes were located by Monod and Palausi (1961) and they are characterised by their small size, not exceeding 40 cm in width. The rocks are glassy with phenocrysts of augite, magnetite, nepheline, which may comprise as much as 70% of the phenocrysts and larger crystals of which may be partly altered to cancrinite. Corroded crystals of quartz and calcite are certainly derived from country rock sediments. There are a number of problematical features posed by these rocks.

MONOD, T. and PALAUSI, G. 1961. Sur des manifestations fissurales de laves à néphéline au sud de lac Faguibine (Mali). Bulletin de l'Institute Français d'Afrique Noire, Dakar, 23A: 251-82.
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