Fenitized Sandstones in Amba Dongar Carbonatites, Gujarat, India

Potash fenitization of sandstones of Amba Dongar carbonatite-complex was described earlier by Deans et al. in 1972. The present work mainly deals with newly found soda-fenites in carbonatites, rich in aegirine-augite, aegirine, albite and orthoclase. The chemistry of potash fenites and soda fenites (new analyses) reveals two trends in Amba Dongar fenites; (i) 'normal fenitization' in which both soda and potash have been added and (ii) predominantly potash fenitization leading to the development of potash fenites. The fenitlzing solutions were supplied by the carbonatite magmas (both sovite and ankeritic carbonatite).