Integrated gravity-magnetic study for delineation of structural guided uranium mineralization zones at Kutni, Purulia, West Bengal

Abstract

The hydrothermally altered vein type uranium mineralization has been reported at different places along the South Purulia Shear Zone (SPSZ) towards 50 km north of the Singhbhum Shear Zone. An integrated close grid gravitymagnetic study over nearly one km2 area between Kutni and Dandudih villages within this shear zone has been performed to delineate the detail structural features, depth continuation, and associated uranium mineralization zones. The observed Bouguer and calculated residual gravity anomaly map depicts an ESE-WNW (on the east) to E-W (on west) trending low gravity zone on the extreme northern side of the area. The total field magnetic anomaly map also depicts the presence of high anomaly patches which is in accordance with the field observation of the exposed iron oxides (e.g. magnetite and goethite) over the same part of the study area. The 2D inverse modeling across the northern low residual gravity anomaly zones reveals steeply dipping low density structures with dip due north, south or vertical at places. The NS widths of these zones vary from 50-300 m with maximum probable depth extent of ~220 m. Previous researcher has also reported high radioactivity over the exposed quartz-magnetite-apatite bands on the northern part of the area. This band is exactly coinciding with the presently identified low gravity and high magnetic anomaly zones. These anomaly zones on the northern part of the study area are concluded to be hydrothermally altered uranium mineralization target zones. Thus, the results of this study will provide important guiding parameters for the future exploration programme over this region.