The Meso-Proterozoic intracratonic basins are known for hosting medium to high grade, large tonnage, low cost unconformity-type uranium deposits in the world like-Athabasca Basin, Saskatchewan, Canada and the Pine Creek Geosyncline, Northern Territory, Australia. Similarly, there are fourteen Proterozoic basins in India, out of which, the unconformity-related uranium deposits are identified at Lambapur-Yellapur-Chitrial in the northern part of the Cuddapah basin. Based on the geological setting, age and fertile basement provenance, the other Proterozoic basins in India also hold promise for uranium mineralisation. In this context, the Chhattisgarh basin which is third largest Proterozoic basin in Central India occupying an area of 33,000 sq. km. with 2500m thick sediments, is identified as one of the major favourable targets for uranium mineralisation. It is located at the northern fringe of Bastar Craton in parts of Odisha and Chhattisgarh and comprises mostly siliciclastic sediments of Singhora, Chandrapur and Raipur Groups.
Uranium exploration carried out in the environs of Chhattisgarh basin mostly along the basin margins, have brought to light a number of uranium occurrences having sizeable dimensions hosted by both the basement rocks viz. Malaikhaman (0.026-0.11% U3O8), Makarumunda (0.013-3.3% U3O8), Damdama (0.026-0.43% U3O8) , Kashipali (0.010-0.96% U3O8), Karichhapar (0.011-0.40% U3O8) and the cover sediments viz. Juba-Banjhapali (0.010-0.078% U3O8), Govardhangiri-Bagia Nala (<0.010-0.80% U3O8), Chitakhol-Renkhol-Bokarda (<0.012-0.39% U3O8). The newly located uranium mineralisation in the sandstones of Rehatikhol Formation near Chhibra which is exposed intermittently over a strike length of 800m with grab samples (n=43) physically assayed 0.014 to 0.140% eU3O8, 0.010 to 0.120% U3O8 (β/γ) and <0.005% ThO2. Uraninite and pitchblende have been identified as uranium minerals. The favourable factors like geological, geochemical, geophysical, sedimentological, tectonic framework and presence of fertile granitic rocks (n=33, 5-26ppm U) in the provenance indicate its potentiality for uranium mineralisation. The exploration so far, has been mostly confined around shallow basin margins leaving deeper part unexplored. With the advancement of geophysical techniques like airborne magnetic, radiometric and electromagnetic surveys it would be possible to explore the deeper part of the basin. In addition, geochemical techniques such as hydro and litho-geochemical sampling could also be applied around suitable litho-structural settings, especially along the shear/fault zones trending NNE-SSW to NW-SE and their intersections with the ENE-WSW trending shear/fault zones.
The present paper deals with the potentiality of uranium mineralisation in the environs of Chhattisgarh basin with emphasis on recently located significant occurrence of uranium mineralisation near Chhibra in the Rehatikhol Formation of Singhora Group along the southeastern margin of Chhattisgarh basin.
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