Subsurface Imaging by Modelling and Inversion of Geophysical Data to Delineate Targets for Uranium Exploration along Halbhavi-Madnal Tract, Bhima Basin, Karnataka, India

ABSTRACT The Bhima basin in Karnataka, India, has emerged as a key target for uranium exploration due to its structural complexity and potential for high-grade uranium deposits. The E-W trending KG Fault, characterised by intense fracturing and brecciation along the basin’s southern margin, hosts the structurally favourable locales for epigenetic, hydrothermal vein-type uranium mineralisation, associated with sulphides and carbonaceous matter as reductants. Extensive exploration by the Atomic Minerals Directorate for Exploration and Research (AMD) underscores its significance. Mapping the sympathetic fault zones and delineating the continuity of the KG fault zone is essential for planning subsurface exploration along the Halbhavi-Madnal tract, east of Kanchankayi and Hulkal village. This study employs an integrated geophysical approach, including magnetic and Induced Polarisation (IP)/ Resistivity surveys, for mapping and/or modelling key subsurface structures and potential mineralised zones, providing critical insights for optimising uranium exploration strategies along the Halbhavi-Madnal tract. The magnetic observations and 3D inverted low magnetic susceptibility confirm that the WNW-ESE trending Kurlagere-Gogi (KG) fault, along with its associated splays (FF’, F1F1’ and F4F4’), and the WNW-ESE trending fault (F5F5’) within the Bhima sediments, serve as primary conduits for uranium-bearing hydrothermal fluids. Induced Polarisation (IP)/Resistivity data identify key resistivity trends (LRT1 to LRT7). A spatial correlation between 3D inverted low magnetic susceptibility with the geospatial XZ planar surface of low resistivity trends identifies the KG fault (F3 - F3’) along with its associated splays (FF’ and F1F1’) as LRT1, LRT2, and LRT3, while the WNW-ESE trending fault (F5 - F5’) corresponds to LRT6. The insights of the spatial correlation study of low resistivity trends with high chargeability suggest the presence of disseminated sulphides, a favourable indicator for uranium deposits. The high-chargeability 3D wireframed zones (HChZ1 to HChZ4) of 5 mV/V-13.9 mV/V, along with the low resistivity and 3D inverted low magnetic susceptibility trends, highlight the potential zones for uranium mineralisation along the Halbhavi-Madnal tract. The findings enhance the structural understanding of the Halbhavi-Madnal tract, refining the geological model for uranium exploration. The insights gained from this research are crucial for prioritising drilling targets, as these insights highlight zones with high mineralisation potential.