The total resource is comprised of 34 deposits plus the stockpiles. The most significant underground deposits, in terms of contribution to the Ore Reserves, are located in the Main Fields and the Harlequin regions of the mining camp. The Main Fields region deposits can potentially be accessed from the Bullen Decline. The Harlequin Decline provides access to the Harlequin deposits.

Harlequin Region

The Harlequin mineralisation can be broadly grouped based on the host rock and mineralisation style.  Mineralisation is either associated with structures passing through granodiorites/porphyry/basalt contact, for example the HV6, HV5A, and Salamander Reefs, hosted within coarse-grained gabbroic host rocks, as is the case with the HV1 and HV1 East Reefs, or localised at the intersection of large NNE structures and shallow-dipping tensional veins (HV5F and HV5B).

The Redfin Reef is a cross-link tensional feature, with high grade mineralisation associated with the intrusive gabbroic dykes.  The Redfin, with its shallow undulating southerly plunge, has also been affected by latter east-west compression giving it its characteristic sigmoidal S-Type folding.  Strong biotite alteration and splitting of the main structures due to east-west compression occurring with the gabbroic dykes has seen an abundance of accessory minerals and ‘nuggety’ gold.

The Perch Reef mineralisation is mainly associated with moderate to strong north-south shearing passing through medium to coarse-grained gabbros.  Where the shear passes through a basalt lithology, low mineralisation occurs.  Movement on the shear has seen several mineralisation events, thus reef width in areas has been >3m.  Strong biotite alteration associated with shear foliation and gabbros has seen high grades and ‘nuggety’ gold.  

Typically the reef structures are more complex at Harlequin than those exploited at Main Fields, and are therefore more difficult to correlate between drilling. Gold grades are characterised by a high ‘nugget effect’ and are inhomogeneously distributed within the reefs with large barren or sub-grade regions common within reef.

Main Fields Region

The Main Fields region encompasses the Bullen, St Patricks, Norseman, Mararoa, O’Brien and Crown (Regent) deposits. St Patricks and Norseman are the most significant contributors of these deposits to the reserve base.

Gold mineralisation in the Main Fields region is typically hosted within narrow-vein quartz reefs. The Mararoa and Crown Reefs, that have historically hosted the bulk of the mineralisation, strike north-south and northeast-southwest respectively. The Norseman Reef is also hosted by a major north south striking structure, however, is less mineralised than Mararoa and Crown Reefs. All three reefs dip towards the east.

East-west striking structures or ‘cross-link’ structures have also been found to host quartz reefs and gold mineralisation. The Bullen Reef (including Bullen West) is hosted in a cross-link structure between the Crown and Mararoa Reefs and dips towards the south. The St Patricks Reef is hosted in a cross-link structure between the Mararoa and Norseman Reefs and dips towards the south. The O’Brien Reef is hosted in a north-south striking and east-dipping structure between the Crown and Mararoa Reefs.

Open Pit Resources

As at 30 June 2008, the Norseman open pit resources contributed 30 per cent of the total reserve inventories.

The total resource attributable to the surface deposits is 12 million tonnes at an average grade of 2.8g/t gold for 1.1 million ounces of gold. Resources are reported for the following deposits: Cobbler, North Royal, Lady Miller, Andronicus, Buldania Blackbutt, Buldania Teatree, Butterfly, Daisy, Daisy South, Gladstone, Golden Dragon, Kaipoi, Barker, Naracoorte, Chum, Sailfish, Slippers (Pipe), Sontaran and Thumb.

Other Underground Deposits

The Scotia, Ajax, Esperanto, Harlequin South and Railway deposits comprise the non Main Fields and Harlequin underground resource inventory. Of these, the Scotia deposit is considered the most important.

Scotia is located approximately 30 km south of the Norseman township and consists of irregular, east-dipping vein sets. The mineralised en-echelon veins are localised within a 30m shear zone with ore shoots plunging 20° towards the northeast.

The Scotia deposit was mined periodically by open cut and underground methods from the late 1980’s. The resource to mill reconciliation for the open pits was not good, principally due to the complexity of the ore zone geometry. Extreme short scale variability was noted in the ore zones with the strike length, thickness and attitude of the zones all highly variable.

Little detail is available on the approach and parameters used to construct the underground resource at Scotia, although a pseudo polygonal approach appears to have been implemented which, given the mineralisation style, is considered inappropriate at Scotia.