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

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 hydrouranium
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.