Potentiality of uranium mineralisation along NE-SW trending Sivarampuram-Nutanakalva fracture zone in basement granitoids of Cuddapah basin, Andhra Pradesh, India

Abstract The basement complex in the south of Cuddapah basin around Shivaramapuram-Nutankalva area comprises granite gneiss and patches of greenstone belts, which are traversed by fractures trending E-W, N-S, NE-SW and NW-SE directions. The fractures are often intruded by younger basic intrusive rocks. Several NE-SW trending fracture zones with uranium mineralization are observed in the study area. The Kamaguttapalle-Kammapalle fracture zone, another sympathetic fracture zone studied at around 16km NW of the above mentioned fracture zone, showed continuity of correlatable mineralization for over 200m along the strike and up to a vertical depth of 200m. Sivaramapuram –Nutanakalva area extends over a strike length of 15km with a plan width of 1 to 1.5km. The area exhibits structural complexity due to tectonic and metamorphic modifications. Regional schistosity and gneissosity trend vary from N-S to NNW-SSE directions. Hydrogeochemical exploration along Sivarampuram-Nutanakalva fracture zone has indicated anomalous concentration of uranium in water samples ranging from 100 to 19,434 ppb U (n=110). The NE-SW fracture zone has affected the Nagari quartzite of Cuddapah Supergroup suggesting post-Cuddapah reactivation. The radioactive anomalies of Sivarampuram in fractured basic dyke [0.13 and 0.19% U3O8 (β/γ; n=2)] and Katramuduku in fractured granite [0.014 to 0.135% U3O8 (β/γ); n=3] located along this fracture zone are significant. These surface anomalies vis-a-vis the hydro uranium anomalies along the NE-SW trending fracture make this zone a potential target for further exploration.