Integrated geophysical study of the Subika Gold Deposit in the Sefwi Belt, Ghana

Geophysical datasets, namely, electrical resistivity, induced polarization, magnetic susceptibility were measured and aeromagnetic interpreted on the Subika concession of Newmont Ghana Gold Limited in order to delineate and model the zone of gold mineralization. The electrical resistivity and induced polarization results delineated the gold mineralized zone as a narrow discrete resistor (>4900 ohm m) and high chargeability (>7.2 ms) zone with a strike length of about 2 km. A strip log plots of 12 diamond drilled core samples showed the zone of mineralization with high alteration and low magnetic susceptibility. Analysis of laboratory magnetic susceptibility measured on selected samples from the pit and selected core samples from the mineralized zones showed a negative correlation between the magnetic susceptibility and gold grades with a correlation coefficient of -0.2 and -0.74, respectively. Similarly, magnetic depth slice produced from the 3D model of the aeromagnetic data depicts the zone of gold mineralization with a low magnetic signature. The zone mineralization was also observed to be striking in the north-east direction. Mineralogical analyses of rock samples revealed alteration processes such as carbonization, sericitization, silicification, chloritization and sulphidation resulting from hydrothermal alteration which accounted for the low magnetic and the magnetic susceptibility signatures of the mineralization zones. The strong resistivity and chargeability response of the mineralized zones are therefore attributed to the silicification and sulphidation alteration, respectively. The results show the effectiveness of applying integrated geophysical, petrophysical as well as mineralogical study in revealing gold mineralization potential of the Subika deposit and the Sefwi belt as a whole.