Geophysical Signatures of a +5.4Moz gold deposit, NE Bankan, Guinea, West Africa.

A suite of geophysical techniques were completed over the +5.4Moz NE Bankan (NEB) gold deposit in Guinea, W Africa. Petrophysics on core indicate a correlation of low magnetic susceptibility and high chargeability with increasing gold grade. Gradient Array IP (GAIP), Pole Dipole IP (PDP IP), ground gravity, ground and airborne magnetics and radiometrics were collected. IP surveys were most effective in mapping high chargeability and resistivity responses, related to sulphide and silica alteration, respectively, associated with the gold mineralised rock volume. Extending the deposit footprint, 3D modelling of chargeability and resistivity shells indicate considerable depth (+400m) and along strike (+500m) continuity of the mineralised system. Gravity data help map intrusive bodies and structural contacts. NEB is associated with a low order ~1-2mgal density feature, an interpreted mafic body, slightly off set from the deposit. A NE-SW trending gravity gradient, sub-parallel to the plunge of the high-grade core of the deposit, indicates a cross-fault control on localisation of high-grade gold. At the regional scale, both gravity and aeromagnetics show a major N-S trending structural corridor crosscut by NE-SW faults that appear to facilitate gold mineralisation.