Gravity-Magnetic Studies for Uranium Exploration Over Manbazar-Kutni Area of South Purulia Shear Zone (SPSZ), West Bengal, India Using Hydro-Uranium Anomalies as Guidance: Correlation between gravity-magnetic and hydro-uranium anomalies for prospecting of uranium mineralization

Abstract

Both tectonic belt, the South Purulia Shear Zone (SPSZ) and the Singhbhum Shear Zone (SSZ) within the Singhbhum craton of East Indian Shield, has been identified with similar geometrical shape and mineralization. The mineralization of these regions is mainly structural guided and hydrothermally generated. An integrated gravity-magnetic study has been conducted around Manbazar-Kutni area across SPSZ to decipher the subsurface configurations, presence of faults/fractures. These structural features may form favourable condition for mineralization. The first degree trend surface separated residual gravity as well as the Bouguer gravity and magnetic anomaly maps depicted the ESE-WNW trending SPSZ on the SW part of the area. The observed negative gravity and moderately high magnetic anomalies around Dighi, Chepua villages are also characterized by medium to high hydro- uranium anomaly from earlier hydro-uranium anomaly studies. Therefore, the negative gravity and moderate positive magnetic anomaly zones are concluded to be hydrothermally altered brecciated zone and the possible uranium mineralized zone. The interpreted faults /lineaments from the gravity-magnetic anomaly maps show good correlation with the exposed one and with the hydro-uranium anomalous zones. Further, the 2D gravity model across the shear zone depicts three low density altered zones (most likely sheared granite and mineralization zone) over the granitic basement along SW-NE profile from Kutni to Chepua village under a thin cover of granitic schist of CGGC. Since surface signature of nuclear radiation has not been observed, uranium mineralized zone could be at a large depth within these altered zones. Thus, the study demonstrates the effectiveness of gravity-magnetic methods in delineating subsurface configuration and to identify the altered zones/faults/lineaments which will act as favourable factors for structural guided radioactive mineralization in conjunction with other know mineralization indication.