Wilsons Hill Project
The company, via wholly owned subsidiary GBGM Wilsons Hill Ltd, is the holder of Mining Licence 4273 which covers the historic Wilsons Hill Goldfield, approximately 20 kilometres west of Bendigo. The title is currently under renewal.
History
The discovery of rich reefs in 1867 started a significant quartz reef mining period in Marong that lasted until the beginning of the First World War. At Wilsons Hill, gold was mined from the Duke of Edinburgh Reef and Wilsons Reef. The reported highest yield was 388 ounces from 63 tons of quartz from Wilsons claim on the Wilsons line.
Mining initially occurred as a series of open cuts up to 70 metres in length, trending north with the plunge of the field followed by various shafts as the mineralisation trended deeper. The Duke of Edinburgh was worked to the shallow depth of 60 metres with varying success. This reef was observed to be dipping to the west.
The 500 foot (167 metres) Whim Shaft is the deepest shaft sunk on the Wilsons Hill Reef, and was worked extensively to the north – it was also mined to the south, but yielded what was at the time a low yield of 15 g/t in this area. Approximately 34,000 ounces has been recorded as produced from Wilsons Hill.
Geology
The geology of the Wilsons Hill Goldfield is remarkably similar to that of the Bendigo goldfield with a regular turbiditic package folded into a series of rhythmic anticlines and synclines, controlled by a major west dipping fault zone, the Wilsons Hill Reef.
Mineralisation
The quartz reefs hosting the gold mineralisation appear to have a vertical repeat function of ~250 vertical metres which is similar to that observed at Bendigo which was mined to 1.4Km below surface. This repeat function was identified by WMC’s drilling in the 1980’s.
The quartz reefs appear to be quite continuous throughout the field with strike lengths of up to 600 metres observed. The gold mineralisation appears to be controlled by oblique structures intersecting the major reefs which have resulted in steep plunging but very high grade gold shoots of varying size.
Previous Exploration
Planet Resources Ltd completed 2,087 metres of costeaning during a programme in the 1970s and concluded that no significant near surface mineralisation was evident.
Western Mining Corporation (WMC) drilled a total of 6,043 metres consisting of 9 diamond (WHD1-9) and 44 RC (WHRC1-44) drill holes. Diamond drill hole WHD1 was drilled to test the principal folds of the goldfield. Several zones of quartz spurs with anomalous gold values were intersected. The best intersection to the west of the Albion Anticline returned 3.3 metres at 1.1 g/t gold.
Diamond drill hole WHD2 intersected an auriferous quartz reef structure about Grey’s Anticline 245 metres below the surface.
This was interpreted to be a ‘saddle’ reef by WMC. The intersection recorded 8 metres at 23.8 g/t gold and included 0.55 metres at 325 g/t gold. Wedging above and below failed to reproduce the results.
Grey’s Anticline was subsequently tested by diamond and percussion drilling over 1,600 metres of strike length with a number of anomalous gold intersections with sulphides present. The lack of grade intersections which disappointed WMC is not unexpected in a coarse gold environment and GBM believes the intersections are significant and require modelling, estimations and bulk sampling.
Figure 1 Greys Reef, looking north
Reef body in red, axial plane in purple.
- Note 1000 RL is ~250 metres below surface.
Extensive percussion drilling of the Wilsons Reef was undertaken after diamond drillhole WHD9 intersected shallow mineralisation with visible gold.
WMC reported anomalous gold values with occasional spikes which suggest the presence of coarse gold. WMC utilised 25g acid digest assay techniques at Wilsons Hill which, given the coarse gold environment and the sample size, would have underestimated the true grade. Limited fire assay checks were undertaken.
WMC abandoned the project in 1988 due to a lack of continuity in economic grades, as they interpreted it at that time.
Potential
In terms of underground targets today, the auriferous quartz veins mined from Wilsons Hill are considered to be shallow. GBM believes that considerable potential exists to find significant gold resources as extensions to the existing mined areas at the Wilsons Reef target as well as identifying reserves and resources in the new unworked repeat structure identified in the Grey’s Anticline. Additionally, potential repeats of this structure may exist at greater depth.
The Company is proposing a model that Wilsons Hill can contain at least 300,000 tonnes from two separate targets in the structures identified by WMC. Based on past mining at Wilsons Hill, a recovered grade range of between 7 to 10 g/t should be achievable.
Modelling of the WMC data has outlined a target that now requires close space resource drilling and bulk sampling.
GBM is now moving to gain the necessary approvals to undertake this work.
Additionally a further ground position has been obtained in the form of EL 4999 to allow shallow air core drilling to test the potential extension of the goldfield below the surrounding alluvial sediments.