The Application of Geophysics Over the Mount York Gold Deposit, Western Australia

A resource of about 1 Mt of gold at 2.7 g/t has been delineated at Mount York, 120 km south-southeast of Port Hedland in the Pilbara Region of Western Australia. The deposit is contained within a banded iron-formation.

In order to supplement ongoing geological investigations to define the resource, a geophysical programme was undertaken to assist mapping and also delineate primary sulphide zones which could have associated gold mineralisation. Aeromagnetic, spectral induced polarisation, surface and downhole electromagnetic surveys, and downhole density logging were undertaken.

The magnetic data clearly outlined the lateral extent of the banded iron-formation but were unable to delineate subtle structure which was thought to control primary mineralisation. Induced polarisation and electromagnetic surveying provided numerous targets in both the primary and oxidised zones. Drill testing of these primary-zone targets intersected sulphide mineralisation but, unfortunately, no gold mineralisation of economic width and grade. Downhole density logging of the secondary oxide zone allowed the density of the mineralisation to be better defined and hence provided a sound base for resource calculations.