The Wilsons Hill project covers the historic Wilsons Hill Goldfield, approximately 20 kilometres west of Bendigo.
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.
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. Total historic mine production of the Wilsons Hill Field recovered in excess of 34,000 ounces of gold.
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.
WMC located 5 main parallel structures trending 340o that are spaced 50 - 100 m apart. The Albion structure was considered the central structure that was flanked to the east by the Grays anticline and to the west by the Wilson anticline.
Saddle reef mineralisation was reported to occur within each structure with an east dipping fault occurring to the east of Gray’s anticline. A west dipping fault reef occurs to the west of Wilson anticline. The 500 foot (152.4 metres) Whim Shaft is the deepest shaft sunk on the Wilson Hill Reef.
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 interpreted structure is shown below.
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. RC drilling returned significant intercepts including 6m @ 2.63g/t Au, 5m @ 2.02 g/t Au and 14m @ 1.73 g/t Au.
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.