Rare earth element abundances in carbonatites and fenites of the Newania complex, Rajasthan, India

• Main Authors: S.G. Viladkar, P.B. Pawaskar
• Format: Article
• Language: English
• Published: Geological Society of Finland 1989-06-01
• Series: Bulletin of the Geological Society of Finland
• Subjects: Carbonatites; fenite; rare earths; Proterozoic; Newania; Rajasthan; India
• Online Access: http://www.geologinenseura.fi/bulletin/Volume61/sgs_bt_061_1_pages_113_122.pdf

The Newania carbonatite is intrusive into the Untala granite-gneiss of Precambrian age. An aureole of dominantly sodic fenites has been developed around the carbonatite. The primary dolomitic carbonatite magma has differentiated to ankeritic carbonatite and the latter has intruded, and in the process metasomatically replaced the former all along the intrusive contact. The rare earth element abundances show increases in total REE with LREE enrichment from coarse grained early dolomitic carbonatite to younger ankeritic carbonatite. However, the highest REE abundances are found in a dolomitic carbonatite rich in pyrochlore, zircon and Nb-silicate. Among the minerals in carbonatites the cumulate apatite shows the highest REE abundances while amphibole shows the lowest REE abundances. Magnetite and dolomite phenocryst show intermediate REE values. During fenitization of the Untala granite ‒ gneiss to syenitic fenites, REEs have been added to the country rock with LREEs > HREEs; and REEs behaved coherently during the process of fenitization.