The Bullabulling Project consists of 26 exploration licences, which cover a total area of 48.8 km2. The tenements are 100% owned by BelaraRox Pty Ltd. and are located 26 km west of Coolgardie in the Eastern Goldfields, Western Australia, around the Bullabulling gold mine (Figure 2 and Figure 8). Access to the ground is via two all-weather gravel tracks that lead north from the Great Eastern Highway 5 km east of the township of Bullabulling. Many of the tracks within the project area are haul roads developed during historical mining operations. In addition to being located next to a major highway, the project is also close to the Kalgoorlie-Perth Railway, the Goldfields Water Pipeline, and a regional powerline.
The tenements cover an area of low relief comprising undulating greenstone plains, with occasional low rises, capped with either laterite or outcropping weathered rocks. Colluvial flats generally slope southward. The project is within woodland-acacia thicket and woodland-mallee type vegetation. The ground contains little outcrop due to deep weathering. Ironstone pisolites and calcrete (nodular and massive) occur at the surface.
More than 3,000,000 Oz of gold (Au) have been produced from the Coolgardie Goldfield since 1892 from seven mining centres, including the Bullabulling Goldfield. The gold mineralisation is associated with an Archean orogenic gold mineral system, with the gold being concentrated in mafic and other iron- rich lithologies. The Bullabulling area has been the focus of considerable exploration efforts, especially in the 1990s and 2010s. Exploration programs have typically favoured soil sampling, RAB, air core, RC, and diamond drilling. Several hard-rock and lateritic gold deposits have been discovered and mined historically in the region, including the Bullabulling, Geko, First Find, and Endeavour gold mines. The BelaraRox tenements are relatively underexplored, with only soil sampling and limited RAB drilling conducted on part of the ground.
Figure 8. Domains of Eastern Goldfields Super Terrane (Swager, 1989).
3D Geological mapping and 2D and 3D mineral potential modelling using the weights of evidence spatial data modelling technique has been completed over the region. Mineral potential modelling is a technique used by geoscientists to objectively select exploration areas and identify targets for further exploration and development. Mineral potential maps generated by the modelling map areas with similar geological characteristics to known mineral deposits in the study area. The advantage of 3D mineral potential modelling compared to the usual 2D approach is that the 3D mineral potential modelling works with true 3D geometric relationships inherent to geological systems. This means any output targets will have a depth range associated with them, which is critical for exploration drill targeting and planning. Eleven of Bullabulling Project tenements have prospectivity modelling targets that have geological similarities to the known gold mineralisation at the Bullabulling and Geko gold mines. The most prospective target that extends to 400 m vertical depth is located in P15/5600, P15/5601 and P15/5602, which provides an immediate high priority target for drill testing (Figure 9). The 3D geology mapping has also mapped the prospective ultramafic lithologies that host the nickel mineralisation at the Nepean nickel mine in the eastern Bullabulling Project tenements.
Figure 9. Local geology surrounding the BelaraRox WA tenements. Red = basalt, green = dolerite, blue = felsic volcanics, orange = granite, pink = sediments, light green = ultramafics (Kenex Ltd, 2018b). Dots show locations of mineral occurrences (GSWA, 2018).
Geology And Mineralisation
The Bullabulling project area is located in the Bullabulling Goldfield, which is part of the Coolgardie Goldfield (Figure 8). The Coolgardie Goldfield covers approximately 900km2 from Mt Burgess in the north to the Londonderry Pegmatite in the south and is part of the Coolgardie Geological Domain of the Kalgoorlie Geological Terrane (Figure 8). The first discovery of gold in the Coolgardie Goldfield was in 1892, and it has since produced more than 3 million ounces of gold. More details of the regional geological setting is described in the Independent Geologist Report in Annexure A.
Archaean Orogenic gold deposits in the Bullabulling Goldfield occur in all lithologies, but with a spatial preference for mafic and iron rich lithologies (Figure 9). Gold mineralisation appears to be broadly synchronous with peak metamorphism, the main phase of granitoid emplacement and regional deformation. The most distinctive feature of the Bullabulling Goldfield compared to the greenstone sequences further to the east is the increase in regional metamorphic grade from greenschist facies in the east to mid to upper amphibolite facies in the west where the Bullabulling Project is located. Several different structural mineralisation styles are present, including gold in alteration halos along sheared ultramafic rock contacts, gold in gabbro-hosted quartz-vein sets, gold in fault-bounded quartz vein sets, and gold in laminated quartz reefs sited in brittle ductile shear zones.
Figure 10. Geological features interpreted from seismic data. Note anticlinal and dome-like features defined by the ultramafic amphibolite marker horizon in green mapped by the seismic associated with the main zones of gold mineralisation (in gold) and distinct discontinuity at depth that marks the top of the Bali Monzogranite (in purple) against which the folds terminate. The Bullabulling Monzogranite (in red) appears late and cuts the earlier structures and lithological contacts.
Mineralisation in the Bullabulling Project area is controlled by D1, D3, D4, and D5 structures (Partington et. al., 2017). Gold was deposited during D1-D4, with the geometry of the deposits being modified during D5 (Partington et. al., 2017). Gold is primarily hosted in D4 high strain zones, as well as adjacent D1 and D3 structures. The highest gold grades are associated with D5 high strain zones, particularly along the margin of the Bali Monzogranite, where D4 structures are locally steepened (Figure 9 and Figure 10). Gold mineralisation in the Bullabulling Goldfield is not confined to a major regional shear zone as previously interpreted, and that the distribution of gold mineralisation is more extensive than originally thought. Consequently, the prospectivity of the goldfield has been underestimated and exploration not effectively targeted (Partington et. al., 2017).
The ultramafic units are well defined reflectors in seismic data that can be traced from the contact of the Bali Monzogranite, where ultramafic amphibolite facies lithologies crop out with shallow dips, through to the Bullabulling Trend (Figure 10). The seismic maps a sequence of sub horizontal units that form a broad basin structure with several minor anticlines that taper out towards the Bali Monzogranite contact at depth. There is a clear spatial association between gold mineralisation with folds interpreted on the seismic sections, which have not been targeted to date by exploration (Figure 9 and figure 10). The largest gold resources along the Bullabulling Trend and at Gibraltar are spatially associated with the 100m scale folds. Additionally, folds tend to be located where the contact of the Bali Monzogranite steepens to more than 40o. The Bullabulling Project tenements that cover the contact of the Bali Monzogranite cover similar prospective structures that host mineralisation at the Bullabulling gold mine.
Figure 11. Historic soil sampling within the BelaraRox WA tenements coloured by gold assay.
More than 3,000 soil samples have been collected and 71 RAB holes have been drilled to sample the bed rock in the Bullabulling Project tenement area (Figure 11).
The RAB drilling is mostly shallow, with total depths of between 3 and 60 m, suggesting the depth potential has not been adequately tested when the 3D prospectivity targets are considered. A number of anomalous gold intersections in the RAB drilling have also not been followed up. The Bullabulling Project tenements are at an early stage of exploration, with only soil sampling and shallow RAB drilling having been conducted on the ground. There is therefore the potential for the discovery of gold and, or, nickel mineralisation at depth.