Anitapolis is a partially zoned intrusion of 5 km2, the emplacement of which produced a system of radial and concentric fractures in the surrounding Precambrian granites. The granites were fenitized with development of sodic pyroxene and amphibole, particularly along fractures, and pass inwards from quartz-bearing to quartz-free syenites. The intrusive complex consists of ijolites, biotite pyroxenite, nepheline syenite and carbonatite. The ijolites are variable in composition, passing into urtites. Intimately associated with the pyroxenites, which contain 52-62% pyroxene and 30-44% biotite, are glimmerites. Carbonatite forms a discrete area in the north of the complex, but is also present as dykes and veins: it is sovite with phlogopite, magnetite, apatite, amphibole and serpentinized olivine. An analysis of the carbonatite is given by Carraro et al. (1967, p. 16).