with feldspars and feldspathoids both in alkali syenites and in metasomatic fenites to be contained by residual carbonate. That is why carbonatites contained very low alkalies. The carbonatitic magma, after the melt separation, was intruded in Karroo sandstones, or earlier formed fenites. The bottom periphery of caldera, 0.5 km wide, is mostly built of feldspathic rocks (fenites), and little or no carbonatite. Under the name the fenites, several types of rocks are separated: fenised sandstones, syenite-fenite, syenite-fenite with nepheline, and feldspar breccias. The fenised sandstones and syenite-fenite form aureoles around carbonatites. The main characteristic for all fenites is metasomatic substitution and replacement of primary constituents by K-feldspar minerals. At the end of carbonatitic volcano activity, hydrothermal stage have led to the formation of exploitable mineral resources, both in carbonatites and fenites. See also Mozambique Monte Muambe References