Carbonate-hosted Indian U-deposits − Tummalapalle in the Cuddapah Basin and Gogi-Kanchanakayi in the Bhima Basin: Attributes for their Genetically Divergent U-mineralisation

Amongst the 15 types of U-deposits worldwide in divergent host-rocks, carbonate rocks generally are amongst the least U-bearing in the Earth’s crust. In India, two carbonate-hosted U-deposits were hitherto established by the AMD − around Tummalapalle in the Cuddapah basin and Gogi-Kanchanakayi (G-K) in the Bhima basin, with the former having the largest resources but low-grade (U3O8: >0.222 Mte, ~0.045%) and the latter with the highest grade but low-tonnage (U3O8: ~0.18%, 6,461 te) amongst the Indian U-deposits. Their attributes, drawn from the field and laboratory studies, viz., physiographic and geomorphic province, host-rock of U-mineralisation, stratigraphic setting, nature and extent of mineralisation, grade and tonnage, structural aspects, petro-/minera-graphy, petro-/ore-mineral-/isotopic-geochemistry, depositional environment, controls of mineralisation, source and type, mineral processing, and possible generation of critical minerals, are presented. From these, the factors responsible for their genetically divergent U-mineralisation, viz., strata-bound, syn-/dia-genetic, phosphatic dolostone-hosted U-deposit at Tummalapalle (and contiguous areas) and structurally-controlled, epigenetic, hydrothermal vein-type, brecciated non-phosphatic limestone-hosted   G-K U-deposit are discussed. Based on these, the following guidelines in the prospecting for U in a carbonate region are suggested: after establishing a fertile source for U, phosphatic carbonate rock appears potential for syn-/dia-genetic U-mineralisation, whereas non-phosphatic carbonate rock involved in major structural disturbances is potential for epigenetic U-mineralisation, with reductants of organic matter and sulphides in both cases will enhance the quantity of primary U-minerals and, hence, U-grade.