An Integrated Geophysical Approach to Unveil Alteration Zones and Geologic Structures for Sulphide–Uranium Mineralization in Singhbhum Shear Zone, India

Abstract

Singhbhum Shear Zone (SSZ) also referred as Copper Belt Thrust (CBT), located at the southern margin of North Singhbhum Fold Belt (NSFB) is well-known for highly mineralized copper, uranium and other sulphide minerals deposits. In order to the identify favourable structures that could host the sulphide–uranium mineralization in Gurulpada area of SSZ, an integrated geophysical study was conducted using magnetic, self-potential (SP), electrical resistivity tomography (ERT) and induced polarization (IP) surveys. The present study identifies pronounced magnetic anomalies in the central part due to presence of magnetite mineral along the shear planes of quartz-chlorite-schist (±sericite) and basic dykes, exhibiting an ENE–WSW orientation, which follows the geological strike and the trend of the shear zone within the area. Low magnetic intensity in the southern part of area suggests demagnetization caused by hydrothermal alteration, indicate mineralized zones. SP anomaly map has identified six zones exhibiting negative anomalies. Tilt derivative (TDR) and Euler deconvolution (ED) technique were applied on magnetic and SP data to depict geological structures that control mineralization and its depth. Magnetic and SP anomalies along the profile are plotted with a 2D inverted resistivity and chargeability section for comparative analysis. The inverted resistivity and chargeability model, illustrated as 2D cross sectional view and a 3D fence diagram, has delineated several anomalous zones at varying depths. The high magnetic anomaly, corroborated with negative SP values, is associated with low resistivity and high chargeability zones, indicating the disseminated sulphide ore bodies with quartz and magnetite mineral along the shear planes. Conversely, positive SP, high chargeability and high resistivity zones signify disseminated sulphide deposits that infilled quartz veins and intense silicification in the fractured zones. The 3D pseudo iso-surface chargeability models indicate high chargeability values (M ≥ 15 mV/V) oriented in an ENE–WSW direction. The integration of geophysical (magnetic, SP, ERT and IP) anomalies and geological (bedrock and trench sampling) data, in conjunction with borehole analysis, confirms the presence of sulphide–uranium mineralization in the study area. The present study reaffirms the presence of ENE–WSW trending ductile-brittle intense shear and hydrothermal alteration zones, which are key indicators of sulphide–uranium mineralization in the study area. The findings revealed that the mineralization accommodated within the quartz-chlorite-schist (±sericite) of the Chaibasa Formation of the Singhbhum Group, appearing as dissemination and fracture filling in association with quartz and magnetite in certain locations. Thus, these integrated geophysical studies are essential for understanding and delineating the complex structural and mineralogical framework of the SSZ. They provide a foundation for further exploration and exploitation of economically significant mineral deposits in this highly mineralized region.