Geochemistry and petrology of granites, Dindi-Hajipur area, Nalgonda and Nagarkurnool districts, Telangana: Implication for Uranium mineralisation Venkateshwarlu M.*, Tiwari K.K., Bisht B.S., Jeyagopal A.V. Atomic Minerals Directorate for Exploration and Research, Hyderabad *E-mail: venkateshwarlu.amd@gov.in
Online published on 13 February, 2019. Abstract Archean – Paleoproterozoic granites forming the basement of Cuddapah sediments show anomalous uranium content (av. 2045ppm eU3O8) along the north-western margin of Cuddapah Basin, in Dindi-Hajipur area. In granites, though uranium mineralisation is largely disseminated in nature it is also restricted to a few ENE-WSW trending fractures, biotite patches and the selvage of quartzo-feldspathic injections. Geochemically, granites of Dindi-Hajipur area are acidic, fairly alumina rich (av. 14.49% Al2O3), potassic (av.5.20% K2O), low calcic (av. 0.98% CaO), metaluminous to peraluminous (A/CNK= 0.73 to 2.16) alkali-feldspar granite, typifying syn-collisional emplacement with an S and I-type affinity (ASI = 0.81 to 2.21), probably formed from a fractionated melt involving a crustal component. The differentiated (DI: av. 89.8) granites are characterised by elevated values of Rb, Ni, Zr and Pb, variable Th (22-207ppm) and U (10-738ppm) coupled with relatively low Sr and Ba. Predominance of Rb over Sr indicates high Rb/Sr ratio (av. 2.37) suggesting crustal inputs during magma generation. In grey-granite uraninite, U-Ti complex, U adsorbed on goethite and allanite are the identified radioactive phases. The occurrence of discrete uraninite and pyrite closely associated with uraninite indicates syngenetic (magmatic) origin. Magmatic and hydrothermal contributions are evidenced by the wide range of Th/U ratios (0.28–25.40) in this granite. Three uraniferous zones were delineated in Dindi-Hajipur area with the radiometric assay results (n=100) showing 0.009–0.010%eU3O8, 0.005–0.31%U3O8, 0.002–0.026ThO2, reflecting disequilibrium largely in favour of parent uranium (n=90) and less in favour of the daughters (n=7). The elevated uranium content in these granites opens a wide area for exploring granite hosted disseminated uranium mineralization in Hajipur-Dindi area. Top Keywords K-rich granites, S-type, Uraninite, Hajipur, Dindi, Telangana. Top |