The Rondonianas granites comprise over 30, usually circular, anorogenic intrusions emplaced in the Xingu complex of granulites, migmatites and gneisses. Most of the granites are biotite-bearing rapakivi types, but a number are peralkaline (see also Teotonio, 025-00-016). These are represented by aegirine and riebeckite granites, granophyres and syenites with dominantly potassic feldspars. The most significant accessory minerals are zircon and opaques with lesser sphene, fluorite and carbonate (Araujo et al. 1978).