A Reappraisal of an Archaean Carbonatite of Nellore Schist Belt, South India

Field observations, trace element and isotopic results are reported for rocks classified as carbonatites from Vinjamur area in the Nellore schist belt. These carbonate rocks occur either inter-bedded with metasedimentary quartzites and pelites or in association with calc-alkaline rather than alkaline volcanic rocks. No fenitised contacts are seen. Their Nb and REE contents are too low for carbonatites. Samples free from baryte veins have less than 150 ppm of Sr with an isotopic ratio greater than 0.7100 δ¹³C_PDB range from -1.58 to - 0.56 ‰ and δ¹⁸O_SMOW from +14.00 to +16‰ , All these features, individually and collectively, show that the carbonate rocks of Vinjamur are most probably sedimentary and not igneous in origin.