The most northerly of the alkaline complexes of Air, Adrar Bous has an elliptical form of 20x12 km. It comprises three units (Husch and Moreau, 1982), a western arc, of high relief, mainly of adamellites and monzonites; an extensive area in the south, east and west of low relief, consisting predominantly of gabbroic rocks with subsidiary amounts of more mafic and anorthositic rocks, within which are outcrops of metamorphosed basement shales and conglomeratyes which may be xenoliths or possibly septa between intrusions. A third unit forms interior and northern zones of peralkaline granite, monzonite and micromonzonite which is topographically high. The basic rocks display a weak layering which dips inwards with more olivine-rich rocks towards the base of the series. The micromonzonite includes varieties containing hastingsite and biotite which form dykes cutting the basic rocks. This was followed by emplacement of granites with sodic amphiboles followed by an aegirine granite that was partly obliterated by intrusion of a later sodic amphibole granite (Black et al., 1967). Mineral data on the basic rocks are given by Husch and Moreau (1982) who also include three whole rock analyses for this series.