Economic importance of some carbonatites in India and the relation of Amba Dongar carbonatite complex to plateau basalts

Abstract

The igneous apatite deposits which are of considerable importance in the fertiliser industry, are associated with three inter-related types of intrusive rocks, namely, carbonatites, nepheline syenites and alkaline ultrabasic rocks. The economic significance of the four carbonatite alkalic complexes is indicated, and the feasibility of utilising the Amba Dongar carbonatite complex for multipurpose chemical industry is discussed. Attention is drawn to the genetic relation of carbonatite alkalic complexes to the alkaline and ultrabasic rocks. In the context of Amba Dongar carbonatite, the differentiation trends in the tholeiitic basalts (involving the earlier separation of pyroxenes), and the relation of the carbonatites, nephelinites and phonolites are delineated with the help of differentiation diagrams and chemical data.