Hydrothermal Ree Mineralization in the Amba Dongar Carbonatite Complex, Gujarat, India

We have studied two groups of overprinted (altered) carbonatites at Amba Dongar, India: weakly overprinted and strongly overprinted. The mineral association of quartz, florencite-(Ce), strontianite, barite and sparse bastnasite – parisite – synchysite typical of weakly overprinted carbonatites shows evidence of a high activity of OH−, (SO4)2−, Al and Si in the fluid. Later, the fluid was characterized by an increased activity of F−, (SO4)2−, REE and Si, reflected in the association of barite, fluorite, quartz and REE fluorcarbonates typical of strongly overprinted carbonatites. Hydrothermal minerals at the Amba Dongar were formed by re-equilibration and recrystallization of the primary minerals in the presence of OH−, (SO4)2−, F−, REE, Al and Si carried in solution by the hydrothermal fluid.