Capuia

This occurrence consists of numerous small hills and outcrops spread over an area of approximately 8x6 km, which are separated by recent sediments. Rock types include carbonatites, silicified feldspathic rocks, quartz fenites and breccias of basement granite. The carbonatites form two groups of small outcrops, which may be part of a ring, and are calcitic types with iron oxides and a little pyrite. No other petrographic details have been located. The silicified feldspathic rocks contain abundant iron oxides, form a discontinuous ring around the carbonatites and may be fenites, while within this ring are areas of feldspathic rock that are undoubtedly fenites. Lapido-Loureiro (1968), quoting Machado, refers to, and indicates on a map, areas of ‘'volcanic tuff' east and west of the centre, but no petrographic details are given. The breccias consist mainly of fragments of granite but in places these grade into a feldspathic carbonatite. Carbonatites towards the centre of the structure are associated with segregations of magnetite and, less commonly, of barite. High tenors of rare earth elements and Th have been found in these rocks.