Gold
mineralisation at the Macraes Gold Project is hosted in the Hyde-Macraes shear
zone and can be traced for ~30 km along strike, although economic resources are
confined to a seven kilometre section in the vicinity of the Macraes township. The shear zone, which
typically dips at a low angle (~20) to the NE, is bounded by an upper hanging
wall shear and a lower footwall fault. Mineralisation occurs along the
hangingwall of the shear zone as well as in low angle concordant shears and
stockworks. Ore types include graphitic cataclasites with
variable amounts of quartz veining, 'lode schists' and quartz-vein stockworks.
Mine geology and grade control activities are designed to ensure accurate
definition of ore and waste as well as the accurate prediction of ore grade.
Grade control involves an integrated process of blast hole sampling, geological
mapping and geostatistical modelling. Geological mapping is carried out post
blasting by means of excavating trenches across are zones defined by assay data.
Conditional Simulation is used to model raw assay data to define ore-waste
contacts and estimate ore block grade, although, geologically defined contacts
have precedence. Low angle ore zones impart a wedge shaped geometry to many ore
blocks. These ore blocks are bounded by contacts that can be selectively mined
to, thereby reducing misallocation of ore and minimising grade
dilution.