The project area lies adjacent to the South Australian border west of Broken Hill in New South Wales.
This area is known to have significant Cobalt mineralisation with large resources defined at the Mutooroo and Thackaringa deposits (Figure 2).
The Thackaringa deposits are now controlled by planned IPO, Cobalt Blue Holdings Limited, bringing a strong focus on Cobalt development in this region.
Broken Hill, New South Wales
Within the Ophara Project there is an advanced prospect, the Great Goulburn prospect, which is the focus of the Company’s initial exploration efforts. This prospect has similarities to the adjacent Cobalt occurrences however it is unique in having low-copper and high-gold mineralisation associated with the Cobalt.
Apart from this prospect there is very limited exploration completed for Cobalt, which is a result of the largely soil and sand covered plains here which hindered early prospectors, and also more recent explorers being focussed on Broken Hill style Zinc-Lead mineralisation, or copper mineralisation.
Due to extensive soil cover in the area, there has been little effective exploration work until PlatSearch and Inco Limited completed exploration in 2001 to 2004. 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, however very little follow-up work has been completed since this time.
Great Goulburn Prospect
The most advanced prospect and the focus of the Company’s planned activities is the historic Great Goulburn prospect where two small shafts were excavated back in the 1890’s.
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 1000 ppm 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
|31.6m to 41.4m, 9.8 metres @ 0.145% Co; 694 ppm Cu, 0.307g/t Au|
|47.4m to 50.4m, 3.0 metres @ 0.153% Co; 247 ppm Cu, 0.359g/t Au|
The Platsearch/Inco work clearly showed that the quartz-magnetite host rock extended much further than the outcropping areas with Calcrete gold in particular (and Copper) indicating a synformal fold of the unit and about 1.5 km strike (Figure 3). It remains uncertain how far the unit extends to the north-east under transported cover where calcrete sampling may have been ineffective.
In 2002 PlatSearch/Inco completed three RC drill holes with variable results. This work was important in refining the geometry of the quartz-magnetite unit which until then had uncertain sub-surface geometry. Holes GG1 and GG3 are both interpreted to have been drilled underneath the ‘keel’ of a synformal shaped quartz-magnetite unit.
Figure 4 shows the location of this drilling on geochemical and geophysical anomaly location at Great Goulburn.
Hole GG2 intersected the quartz-magnetite unit at 48 to 56 metres and returned an average grade of 0.266 g/t Au, and 0.103% Co.
In 2008 PlatSearch brought Minotaur Operations Pty Ltd in as a farm-in partner and operator. Minotaur completed one RC hole at Great Goulburn targeting a modelled deeper magnetic body below Anglo DDH OT1.
Drillhole 08RCHT02 intersected quartz-feldpsar-biotite-muscovite gneiss with varying amounts of sillimanite-chlorite from 0 to 51 metres. An 18 metres thick zone of quartz-magnetite-pyrite rock was intersected from 51 to 69 metres. This unit is interpreted as the main mineralised horizon and contains anomalous Au, Ag, Cu, Co, Mo and S (Table 1). The anomalous results extend above and below the quartz-magnetite rock i.e. from 48 to 76 metres. Results are comparable to previous drilling by Australian Anglo-American.
The quartz-magnetite unit recorded high magnetic susceptibility values with the highest reading of 407 x10-3 SI units at 53 – 54 metres. Cu, Co, Au and magnetic susceptibility are displayed in Figure 5 relative to downhole lithology.
Significant results include 8m @ 0.16% Co, 0.091% Cu, 0.38 g/t Au and 0.95 g/t Ag or 16m @ 0.12% Co, 0.075% Cu, 0.3 g/t Au and 0.88 g/t Ag.
Future Exploration Activities
The Company has reviewed data and conducted field reconnaissance of cobalt-gold mineralisation at Great Goulburn and has designed an exploration program to test for extensions to this known mineralisation.
The prospect area has limited outcrop, which mostly coincides with the known mineralisation that occurs as gossans on two small hills. The Cobalt-Gold mineralisation is known from previous drilling to be closely associated with magnetite and pyrite at depth.
A small historical ground magnetic survey highlighted the known mineralised area through definition of subsurface magnetic anomalies. Regional aeromagnetic surveys indicate that there are elevated magnetic areas along strike from the Great Goulburn mineralised area. These elevated magnetic areas are under thin soil cover and warrant more detailed magnetic surveying to outline potential new mineralised areas.
In addition, soil sampling and rock chip sampling defined mineralisation around this outcropping area and field inspection in November suggested that the area along strike is likely to suit conventional soil sampling over large parts.