THE PROBLEM OF CARBONATITES AND CARBONATITE COMPLEXES

By analysis of publisked and authors data the conclusion was made that primary chemical composition of carbonatites was predo minautly alkali-carbonate similar to ones of carbonatites and tuffs of Oldoinyo Lengai volcano (with high content of Na2CO3, K2CO3, CaCO3 and subordinately MgCO3, FeCO3). Such carbonatite melts reacted on country rocks (more often granitoids) and caused a fenitization of them while residual components СаСО3, MgCO3 and FeCO3 crystallizel as well known types of carbonatites (calcitic, dolomitic, ankeritic). Intrusive carbonatite complexes consist of such ultrabasic and alkaline racks as olivinites (rarely dunites), jacupiragitespyroxenites, melilitites, ijolites-melteigites, nepheline and alkaline syenites, phoscorites and carbonatites wich can be present in different combination (completely alone or two types of mentioned rocks). Silicate alkaline melts (of melilitite, melanephelinite types) related to carbonatite magmas were normatively and modally unsaturated with SiO2 and feldsparless. Basalt melts are not able to generate carbonatites. Carbonatites different from visually similar calciphyres and marbles by geochemical peculiarities and ore potential.