PETROLOGY, GEOCHEMISTRY AND STABLE-ISOTOPE STUDIES OF CARBONATE-RICH DYKE-LIKE BODIES, CHHAKTALAO AREA, MADHYA-PRADESH

Carbonate-rich racks occur as E-W trending dyke-like bodies in the Dec can 'basalts at Chhaktalao area in the lower Narmada valley and show a structurally controlled mode of emplacement. Modal composition shows calcite as the dominent mineral (similar to 90%). Ankerite, apatite, a ltered olivine, augite and opaques account for the remaining percentag e. Geochemically, these rocks show high CaO (>50%) with low SiO2, TiO2 , FeO and K2O. Trace element concentrations are low compared to aveng e carbonatites. Stable isotope studies show that delta(13)C (-1.74 par ts per thousand to -2.8 parts per thousand) and delta(18)O (+12.75 par ts per thousand to +13.35 parts per thousand) values do not compare wi th those of ''primary igneous carbonatites'' eventhough they fall with in the wide range of ''igneous carbonatites''. These rocks can be cons idered only as carbonate-rich rocks and not as true carbonatites.