Alkaline Rocks and Carbonatites of the World

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Alkaline rocks are concentrated in two areas in Nigeria; the Jos Plateau of central and northern Nigeria and the Benue Valley in the southeast and along the border with Cameroon. The Jos Plateau suite consists of a remarkable series of essentially granitic intrusions, which are known as the Younger Granites and also as the Nigerian Anorogenic ring complexes, with less extensive extrusive rocks. Many of the granite complexes form spectacular ring structures, some formed of numerous intrusions. Non-alkaline rocks are more voluminous than alkaline ones amongst the Younger Granites but most occurrences include a greater or lesser proportion of peralkaline granite and/or syenite, with extrusive peralkaline rocks also present in some centres. A preliminary review of the province was given by Jacobson et al. (1958) with much fuller accounts of most of the individual complexes by MacLeod et al. (1971) and Buchanan et al. (1971). Further detailed accounts of nine of the complexes are in Bennett et al. (1984) and Turner (1976) also reviews the province. The province as a whole is clearly depicted on a geological map at a scale of 1:500,000 compiled by Kinnaird (1981), while a map of the northern part of the province only, at a scale of 1:250,000, has been compiled by Turner (1979). Reviews of the geology and mineralization are given by Bowden et al. (1984), Bowden and Kinnaird (1984), and Pastor and Turaki (1985) while Hossain and Turaki (1983) have compiled a bibliography of the province and the associated tin mineralization.
The volcanic rocks of the Benue Valley consist of a number of lava plateau together with several concentrations of plugs and other minor intrusions. Little detailed work has been done on these rocks and although a proportion of the plugs are known to be alkaline information on the lavas is sparse. Wright (1976) reviewed the data available at that time.



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