Geochemistry of Precambrian Carbonatite Complexes of India: Present Status of, and Gaps in our Knowledge

Carbonatites of Precambrian age occur at Newania and Mundwara in Rajasthan, Sevathur and Hogenakal in Tamil Nadu, Kunavaram in Andhra Pradesh, and KolJegal in Karnataka. The Newania carbonatite is 959±24 m.y. old (K-Ar age of an alkali amphibole), and the Sevathur carbonatite is 720±30 m.y. old (K-Ar age of a biotite). Although comprehensive geochemical studies involving major, minor, and trace elements and carbon, oxygen and strontium isotopes have been undertaken on the 37.5±2.5 m.y. old Eocene carbonatite complex at Amba Dongar, Gujarat, geochemical studies on the Precambrian carbonatites of India have been confined only to routine determinations of selected elements like Sr, Ba, Y, Ce, La, Nb, Zr, Th, Mn, Ti, F and P to demonstrate their carbonatitic affinites. Except for two K-Ar ages, and for some limited trace element data, no attempts have been made to elucidate the chronologie and petrogenetic evolution of these Precambrian carbonatites by the application of Rb-Sr, K-Ar, and U-Pb geochronometry, critical element ratios, stable and radiogenic isotope abundances, and geothermometry. Basic researches aimed at formulating geochemical criteria for locating commercially exploitable economic Precambrian carbonatite complexes are yet to be initiated in India.