Origin and genetic types of carbonatites

Abstract

The very high ore content of carbonatites determines the relevance of ascertaining the origin of these rocks. However, to date, this problem has not had a convincing solution. The obtained evidence of the hot heterogeneous accretion of the Earth allows us to explain all the features of their formation. With such accretion at the early stage of the Earths evolution, there was a layered global magmatic ocean. The accumulation of carbon dioxide during fractionation of its largest picrite layer led to the appearance of the most common residual ultrabasic carbonatites. Its very deep fractionation and the huge volume of this layer caused a substantial accumulation of rare and rare-earth elements in carbonatite residual melts. The expansion of the products of crystallization of the magmatic ocean by the spreading substance of the lower mantle superplumes during the formation of oceanic regions led to the absence of carbonatites in these regions and to their distribution mainly on ancient platforms. Fractionation of the basic layer of the magmatic ocean led to the emergence of the most ancient residual-basic carbonatites that formed the Seligdar apatite deposits on the Aldan shield. An example of residual-frictional carbonatites formed by fractionation of the products of frictional melting of differentiates of the magmatic ocean are the carbonatites of the Mesozoic Murunsky alkaline massif. In the areas of kimberlite magmatism, small intrusions of residual kimberlite carbonatites are widespread.