Sudan

Alkaline rocks are particularly abundant in the Sudan occurring typically as intrusions that are generally referred to in the literature as ring-complexes. Some of the ring-complexes listed in Vail (1978) are not alkaline, or only marginally so, but the majority include a greater or lesser proportion of peralkaline rocks, usually syenite or granite. A useful review of the geology and mineral deposits of the Sudan, including geological maps in colour at the scale of 1:2,000,000, is that of Vail (1978); he has also published a general account of the alkaline complexes (Vail, 1985). A full review of the geochronology will be found in Vail (1990) and Barth et al. (1983) outline the geochronology of the numerous intrusions concentrated in the Bayuda Desert. A 1:250,000 geological map of the area is that of Barth and Meinhold (1981). Vail and Duggua (1986 and 1991) have compiled bibliographies of geological papers on the Sudan between 1837 and 1985 and between 1986 and 1990.