Uranium Mineralization in Singhbhum Shear Zone, Bihar II. Occurrence of 'Brannerite'

Composite grain-aggregates of titanium and uranium oxide phases resemble, both in texture and composition, those described as 'brannerite' grains occurring in quartz-pebble conglomerate-type uranium deposits such as those of Witwatersrand in South Africa and Blind River in Canada. The grain-aggregates contain variable amounts of quartz, rutile, anatase, uraninite, brannerite (s.s), pyrite, galena and hematite. Intimate inter-growths of uranium-rich and titanium-rich phases are observed. 'Brannerite' grains are secondary in origin, both detrital and metamorphic ilmenite being the antecedent mineral. They have been formed by the action of uranium-bearing solutions on ilmenite under conditions which favoured (i) alteration of ilmenite to titania by removal of iron (ii) simultaneous precipitation of uranium from solutions as uraninite and (iii) adsorption of uranium by titania. This can take place under both reducing and oxidizing conditions.