Geochemistry of the Sarnu-Dandali Carbonatites, District Barmer, Rajasthan, India

The Sarnu-Dandali carbonatites of Western Rajasthan are some of the few occurrences of a typical carbonatit-nephelinite magmatic association known from India. They occur as dykes and dykelets of sovitic-alvikite and ferrocarbonatite showing distinct variation in their chemistry. The sovitic-alvikites have high contents of BaO (up to 3.42%) and SrO (up to 1 %). Fractionation trend is marked by decreasing concentration of SrO from sovitic-alvikite (1.00%) to ferrocarbonatite (0.06%). Trace element contents reveal pronounced preference of Ce and other rare earth elements for sovitic-alvikites. Their oxygen and carbon isotope values are that of typical primary igneous carbonatites. The chemical and isotopic data reveal that the Sarnu-Dandali carbonatites are magmatic, fractionated and have originated from a mantle-derived nephelinitic magma.