The 14 km long Whroo goldfield, located 130 km north of Melbourne, is one of the largest historic epizonal goldfields in Victoria and remains untested to depth. Alluvial gold mining commenced at Whroo during the initial gold boom of the 1850s and a settlement was quickly established. Significant alluvial workings are present throughout the field. Hard rock mining commenced in 1855.
Whroo at a glance
130 km north of Melbourne 12 km northwest of Nagambie
Earning up to 70%
Nagambie Resources Ltd
Number of holes drilled to date
EL 6158; EL 6212; EL 7205; EL 7209; EL 7237; EL 7238; RL 2019; ELA 7653
Select drill results (refer below for further details)
0.6 m @ 49.6 Au g/t from 324.9 m
0.5 m @ 16.2 g/t AuEq from 201.5 m
0.4 m @ 11.8 g/t AuEq from 262.4 m
0.2 m @ 16.6 g/t AuEq from 359.6 m
Whroo consists of the Balaclava Hill area which contains thirteen named reefs, while shallow workings extend the trend over 9 km to the White Hills mining area. Production at Whroo is estimated to have been 40,000 oz of gold at grades varying from 5 g/t gold to >700 g/t gold. At White Hills, 21 historic gold showings and mines occur within a larger alluvial gold field.
Location map of the exploration permits comprising the Whroo Project. WGS84 map projection
The largest producers at Whroo were the Balaclava Open Pit (23,600 oz gold), Albert Reef (1,170 oz gold) and Carrs Reef (913 oz gold). Balaclava Hill, Albert Reef and Stockyard Reef are associated with stibnite veins. At Balaclava Hill, a 137 m deep shaft and an open pit (80 x 40 m across and 30 m deep) were developed in 1855 and although the main stratigraphic and structural orientation was east-west, mineralisation was observed in both E-W, NNE and flat veins with average widths of 3.5 m. Outside of Balaclava, veins averaged 0.5 m width and ran multiple ounces. The Mary Reef was 2.1 m wide on average. The Peep-o’-Day Mine, a small antimony/gold mine had workings to 61 m depth. The Happy-go-Lucky Mine averaged 128 g/t gold. The vertical Albert Reef ranged from 0.03-3.7 m thickness and averaged over 94 g/t gold.
Since historic mining took place, modern exploration at Whroo has been relatively limited with few drill holes testing to below the level of oxidation, and a paucity of geophysical exploration. In the early 1970s ICI Australia and Newmont diamond drilled the only hole ever drilled (Whroo 1) at depth in the field and intersected 60 m @ 0.35 g/t gold from 133 m beneath the Balaclava open pit including 1.5 m @ 6.1 g/t gold from 108.0 m, 1.5 m @ 1.8 g/t gold from 149.5 m and 1.5 m @ 5.3 g/t gold from 179.5 m. Visible stibnite was recorded but antimony and arsenic were not assayed.
SXG has undertaken a detailed LiDAR survey at Whroo which extended the previously mapped Whroo historic mining field from 10 km strike to 14 km. GIS-based data analytics also identified 34,500 individual workings over 63 km² (~550 per km²) and classified the data as alluvial vs hard rock in character. A gradient array IP geophysical survey was conducted 8.5 km west of the Balaclava open pit at Doctors Gully over a 4 km² area.
WHROO LENGTH AND HISTORIC WORKINGS
Whroo project area showing significant alluvial and hard rock workings (34,500 individual workings identified). Doctor's Gully and Balaclava prospects with drill hole collars by TSX listed Mawson Gold Ltd prior to SXG's IPO in May 2022 are also shown.
Note the LiDAR data interpretations extended the mapped workings a further 4 km to the east.Three reconnaissance diamond drill holes for 330.5 m were also completed at Doctors Gully at the start of 2021, with the better results including 1.0 m @ 2.9 g/t gold from 45.3 m in MDDDG001, 3.8 m @ 0.7g/t gold from 71.7 m in MDDDG001 and 1.6 m @ 1.9 g/t gold from 24.7 m in MDDDG003. Details of the further results from these drill holes are set out below. Gold distribution suggests a high degree of mobility and re-concentration in the weathered zone.
In December 2021, two deep diamond holes were completed under the Balaclava open pit, which extracted 23,600 oz gold during the 1800s. The first drill hole, MDDBC001, drilled 120 m vertically below Whroo 1 and intersected the deepest and highest grades ever drilled on the Whroo project to date, intersecting a broad 200 m wide down hole zone of gold and antimony. It produced the best drill result on the field since hard rock mining commenced 167 years ago. Grades of up to 49.6g/t gold over 0.6 m from 324.9m and antimony grades including 0.2 m @ 16.5% antimony demonstrate the opportunity at the property. Drill hole MDDBC002 drilled 150 m west of MDDBC001 and intersected 0.7 m @ 5.0 g/t gold from 332.1 m.
Details of drill results received at the Whroo Project are set out in the Independent Geologist's Report dated 17 March 2022 and can be found here. A selection of key intersections from the drill holes at the Whroo Project are set out below:
Key intersections in the Whroo project reported using a 0.3 g/t AuEq cutoff over 2 m and including 5.0 g/t AuEq cut offs over 1 m.
Prior to these holes, the only test of gold mineralisation to depth (110 m vertically) along the entire Whroo goldfield was carried out by ICI Australia and Newmont in the early 1970’s when they intersected 63 m @ 0.35 g/t gold including 1.5 m @ 6.1 g/t gold and 1.5 m @5.3 g/t gold (Whroo 1).
Mandalay Resources’ Costerfield mine is the target model sought at the Whroo Project, where widths and grades observed in initial drilling are consistent with those observed from Costerfield, located 35 km south-west from the Whroo Project. The Costerfield mine corridor contains 2 Moz of gold equivalent, and in 2021 was one of the highest grade global underground mines and a top global producer of antimony. Mean drill hole true widths and grades at Costerfield are: Brunswick lode (0.7 m @ 9.0 g/t gold and 4.0% antimony), Youle lode (0.4 m @ 47.7 g/t gold and 11.4% antimony), Kendal Splay (0.3 m @ 92.8 g/t gold and 41.3% antimony) and Peacock lode (0.4 m @ 13.0 g/t gold and 6.0% antimony). The average vein width at Augusta is 0.3 m, while the Cuffley lode averaged 0.4 m. Average mined widths at Costerfield are 2.0 m.
WHROO – DIAMOND DRILL HOLES BENEATH THE BALACLAVA OPEN PIT
Cross section of drill hole MDDBC001 under the Balaclava open pit within the Whroo project. The logged margins of the pyritic sandstone unit are indicated (light yellow) and show the continuation below the original Whroo 1 drill hole completed in 1973 by Newmont/ICI.