M.V. Subramanyam

KADAPA: Kadapa basin constitutes 27 per cent of uranium resources of India and economic viability of the deposits make the basin a “uranium province”, K. Umamaheswar, Additional Director (R&D), Atomic Minerals Directorate for Exploration and Research, Hyderabad, said on Friday.

Exploration began as early as in the late fifties and sixties for vein-type uranium mineralisation in basement granoids and subsequently the focus shifted to QPC type mineralisation at the base, Prof. Umamaheswar said in his presentation at the valedictory session of the two-day national seminar on ‘Geodynamics and mineral resources of proterozoic basins of India,' at Yogi Vemana University, Kadapa.

In his address with special emphasis on Kadapa basin, he said exploration input gained momentum with the discovery of dolostone-hosted uranium mineralisation in Vempalle formation.

Proterozoic basins

Fourteen proterozoic basins identified in the country are the primary targets for hosting unconformity type uranium deposits, he said. They were taken up for exploration considering the favourability factors like basinal topography, lithological set-up added with large sediment thickness, fault structures, alteration features and intrusive felsic bodies into the basement rocks.

Uranium found recently at Lambapur-Peddagattu, Chitrial, Koppunuru (0.065 to 0.085 % U308), Thummalapalle (0.050 % U3O8) near Pulivendula in Kadapa basin (0.18 % U3O8), Gogi in Bhima basin (0.18 % U3O8) and Deshmur (0.070 % U3O8) in Kaladgi basin have indicated the possibility of identifying similar type of uranium mineralisation in other proterozoic basins of the country, Prof. Umamaheswar noted.

Exploration strategy

Exploration strategy in Kadapa basin evolved with time and uranium mineralisation is located at different stratigraphic levels and economical viability of these deposits make Kadapa basin into a “Uranium province”, he remarked.

Vempalle dolostone-hosted syngenetic stratabound uranium mineralisation is located in Thummalapalle area in Kadapa district in the southwest part of Kadapa basin.

In the northern part, unconformity-associated uranium mineralisation is identified at the base of Srisailam and Banaganapalle formations in the Lambapur-Peddagattu-Chitrial areas in Nalgonda district and in Koppunuru area in Guntur district.

Vein-type of uranium mineralisation has also been found in the Gulcheru formation in the south-western part of the basin.

Shallow deposits

The exploration strategy adopted so far has targeted shallow deposits up to 100 m. depth mainly involving ground radiometric, gamma ray logging of boreholes and hydrogeochemical techniques besides petromineralogical and geochemical characterisation of basement and cover sediments, the AMD Additional Director said.

Favourable geological criteria suggest that mid-proterozoic Kadapa basin is expected to contribute large uranium deposits in Srisailam and Palnad sub-basins.