CGO is located in the Achaean Murchison Province, a granite-greenstone terrane in the northwest of the Yilgarn Craton. Greenstone belts trending north-northeast are separated by granite-gneiss domes, with smaller granite plutons also present within or on the margins of the belts.

Mineralisation at Big Bell is hosted in the shear zone (Mine Sequence) and is associated with the post-peak metamorphic retrograde assemblages. Stibnite, native antimony and trace arsenopyrite are disseminated through the K-feldspar-rich lode schist. These are intergrown with pyrite and pyrrhotite and chalcopyrite. Mineralisation outside the typical Big Bell host rocks (KPSH), for example 1,600N and Shocker, also display a very strong W-As-Sb geochemical halo.

Numerous gold deposits occur within the Cuddingwarra Project area, the majority of which are hosted within the central mafic-ultramafic ± felsic porphyry sequence. Within this broad framework, mineralisation is shown to be spatially controlled by competency contrasts across, and flexures along, layer-parallel D2 shear zones, and is maximised when transected by corridors of northeast striking D3 faults and fractures.

The Great Fingall Dolerite hosts the majority gold mineralisation within the portion of the greenstone belt proximal to Cue (The Day Dawn Project Area). Unit AGF3 is the most brittle of all the five units and this characteristic is responsible for its role as the most favourable lithological host to gold mineralisation in the Greenstone Belt.

The Big Bell Trend is mineralised a strike length of >3,900m, a lateral extent of up +50m and a depth of over 1,500m.

Great Fingall is mineralised a strike length of >500m, a lateral extent of >600m and a depth of over 800m.

Black Swan South is mineralised a strike length of >1,700m, a lateral extent of up +75m and a depth of over 300m.

CGO as a regional project covers the historic mining centres of Big Bell, Cuddingwarra, DayDawn, Tuckabianna and Pinnacles and includes two of Australia’s most prolific past producers in the Big Bell mine (2.6 million oz) and the Great Fingall mine (1.2 million oz).

Westgold’s strategy in this region has been heavily focussed on the re-start of the long-life Big Bell mine. After 3 years of de-watering, mine rehabilitation and refurbishment, ore has begun to flow from Big Bell.

Over FY20-21 this will build to steady state output and dominate ore feed for the Tuckabianna plant. Whilst Big Bell builds to full production, the Tuckabianna plant has been filled with various minor ore sources from small open pits at Day Dawn, low grade stockpiles and the small Comet underground mine at Pinnacles.

During FY2020, the majority of output has come mainly from smaller open pits and the small Comet underground which have served as stepping stones awaiting the ramp of the dominating Big Bell mine.

An emphasis on developing high grade ore sources which can offset a small volume of Big Bell production whilst materially improving the grade profile through the Tuckabianna mill. In particular there is a focus on high-grade quartz reef-hosted mineralisation in the Day Dawn region, which has hosted the significant past producers of Great Fingall and Golden Crown (head grades of 19.5g/t and 14g/t respectively). Great Fingall is expected to become Westgold’s latest underground mine adding to the regions overall gold output.

A focus on the Tuckabianna and Cuddingwarra mining centres which are dominated by more recent shallow open pit mining. These areas can support a renewed open pit mining phase and eventual underground extraction.

CGO has an existing conventional CIL processing plant.

The plant has a nameplate capacity of 1.4Mtpa though this can be varied between 1.2-1.6Mtpa pending rosters and material type.

Gold extraction is achieved using two staged crushing, ball milling with gravity concentration and Carbon in Leach.

A high portion of the Reserve mill feed have extensive data when processed at other plants in the past 2-3 decades. This long history of processing demonstrates the appropriateness of the process to the styles of mineralisation considered.

No deleterious elements are considered, as a long history of processing has shown this to be not a material concern.