- JORC modelling using cost effective legacy data for the Broken Hill project is focused on several areas within the tenure that exhibit significant high-grade Zn-Co mineralisation;
- This is CCZ’s secondary focus area and a JORC compliant zinc Inferred Resource is likely to be generated relatively soon;
- Legacy core samples are currently being assayed for cobalt; and
- Incremental exploration upside in the mix as the initial desktop review uncovered numerous Co (max 0.12%), Cu (max 12%) and Zn (max 17.7%) anomalous zones in the tenure neighbourhood.
The Broken Hill Project Group includes two tenements.
Broken Hill Project, New South Wales
Exploration Rationale: Unexpected high-grade Zn-Co mineralization discovered
CCZ’s Broken Hill Project is circa 20km west-southwest of Broken Hill and 10km northeast of Alloy Resources Ophara Project in the Broken Hill Region, NSW. Notably, large Cu-Au-Co deposits have been identified to the south by Broken Hill Prospecting. However, desktop work done by CCZ’s geologists have discovered several areas that exhibit signficant high-grade zinc-cobalt mineralisation. More importantly, there is ample legacy data to model two JORC compliant Inferred Resources for zinc relatively quickly, which saves materially on drilling costs.
Interestingly, the Broken Hill Project occurs in an area which is known to have significant cobalt mineralisation in the southern Curnamona Craton, with large resources defined at the Pyrite Hill and Thackaringa deposits – this was the prime reason for acquiring the tenements. These prospects have similarities to both these cobalt occurrences. However, it is unique in having low-copper and high-gold mineralisation associated with the cobalt surface gossans.
Past explorers were targeting more Broken Hill style base metal mineralisation or Cloncurry style iron formation hosted copper-gold. As cobalt was not a focus they have left some other cobalt gossans, similar to Great Goulburn and Pyrite Hill, for further follow up.
Whilst all three have a strong association with pyrite mineralisation, the majority of the regional mineralisation appears to be more of a replacement style deposit associated with a quartz-magnetite stratigraphic unit.
The host rocks are several thick (8-27m) units of a quartz-magnetite rock within the Radian Gneiss of the Proterzoic Willyama Group. The footwall at various deposits has been described as a quartz-feldspar-biotite-muscovite gneiss with varying amounts of sillimanite and chlorite. The mineralised zones are quartz-magnetite-pyrite rocks which contain anomalous Au, Ag, Cu, Co, Mo and S. Anomalous results often extend above and below the quartz-magnetite rock.
Extensive historical surface rock-chip sampling the region confirms mineralisation with maximum values of 1.2% cobalt and 2.4 g/t gold, hosted in a quartz-magnetite rock unit.
Due to extensive soil cover in the area, there was little effective exploration work until PlatSearch (now Variscan Mines Ltd; ASX – VAR) and Inco Limited completed exploration in 2001-04 over areas that partly covered the project area. Preliminary reconnaissance gossan sampling carried out in 2002 resulted in 14 base and precious metal prospects being defined for further work. Further follow-up sampling plus compilation of old auger/RAB data from earlier explorers by PlatSearch in 2003 defined a total of 20 prospects, several within the prospect. However, very little follow-up work has been completed since this time.
Alloy Resources (ASX: ALY) recently reported that one of its more advanced areas and, focus of planned activities, is the historical Great Goulburn prospect where two small shafts were excavated back in the 1890s. Prospectors were attracted to an outcropping gossanous quartz-hematite rock unit which had some associated gold mineralisation.
Modern testing of the prospect occurred in 1981 when Australian Anglo American completed two short diamond drill holes DDH OT1 and DDH OT2. Using a 1,000ppm Co cut-off, the following grades were returned;
- DDH OT1: -45 degrees towards 215 degrees
- 40.7m to 64.0m, 23.3 metres @ 0.138% Co; 581 ppm Cu, 0.393g/t Au
- DDH OT2: -85 degrees towards 162 degrees
- 47.4m to 50.4m, 3.0 metres @ 0.153% Co; 247 ppm Cu, 0.359g/t Au
- 31.6m to 41.4m, 9.8 metres @ 0.145% Co; 694 ppm Cu, 0.307g/t Au
Cobalt Blue (ASX: COB), which has farm-in arrangements for the Thackaringa cobalt deposits is close to CCZ’s Broken Hill Project. According to its listing prospectus, the global Mineral Resource inventory is 35.7Mt at 1.85 pounds per tonne cobalt (grade: 841ppm).