Stable carbon and oxygen isotope studies on carbonatites from Sung valley, Meghalaya and Ambadongar and Siriwasan, Gujarat

Stable isotope variations in carbonatites are generally due to (a) differences in the isotopic composition of source magmas (b) fractionation processes during the evolution of a carbonatite magma (reflected generally by correlated variations in {delta}{sup 13}C and {delta}{sup 18} O) and (c) post magmatic alteration (which may have little effect on C isotope composition but can introduce major changes in the O isotopic ratio). Stable isotope studies of carbonatites are useful in identifying crustal contamination effects that are generally masked in Sr and Nd isotopic ratios. Therefore, combined radiogenic and stable isotope studies are useful in characterising mantle sources and understanding various processes involved in the generation and evolution of carbonatite magmas.