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Western Mines closes in on massive sulphides system

Updated: Apr 30

Western Mines Mulga Tank drill core showing nickel sulphides. Credit: File

Western Mines Group believes it is getting closer to proving up a “Perseverance-style” massive sulphides system at its Mulga Tank project in Western Australia’s Eastern Goldfields region after coring 950m of nickel-rich ultramafic rocks.

The company says disseminated nickel mineralisation was intercepted in seven separate zones in a diamond drillhole from 134m to more than 1014m. It is showing elevated nickel and sulphur in combination with copper and combined platinum group elements (PGE), with a cumulative 466m assaying an average of 0.35 per cent nickel, 139 parts per million cobalt, 63ppm copper and 43 parts per billion PGE.

The seven selected intervals comprise 16m at 0.31 per cent nickel from 134m, 30m at 0.3 per cent from 158m, 20m at 0.27 per cent from 219m, 24m at 0.27 per cent from 282m, 120m at 0.32 per cent from 410m, 116m at 0.27 per cent from 630m and 140m at 0.49 per cent from 874m. The deepest interval includes 82m at 0.55 per cent nickel from 886m.

Management believes the evidence uncovered at Mulga Tank to date suggests the potential for something similar to BHP-Billiton’s Perseverance Mine in Leinster – a komatiite-related copper-nickel sulfide deposit regarded as one of the biggest in the world with reserves of 45 million tonnes of ore grading 2.05 per cent nickel.

The latest hole (MTD028) was drilled to a depth of 1107.5m and was terminated after penetrating 67.2m of the expected footwall suite of black shale, basalt and silicified shales from 1040.3m.

Management says geochemistry shows the nickeliferous host rock, encountered from immediately under sand cover, to be almost all high-temperature adcumulate to extremely adcumulate-textured dunite, with aluminium oxide generally less than 0.5 per cent and magnesium oxide greater than 40 per cent.

The company believes Mulga Tank could also possibly mirror Mt Keith’s large-volume, low-grade disseminated nickel sulphide deposit. Mt Keith has one of the world’s biggest low-grade, large-tonnage disseminated nickel sulphide deposits hosted by olivine cumulate in ultramafic volcanic rocks.

We continue to see better results from Mulga Tank. Those from MTD028 show the broadest and highest-grade assays of disseminated sulphide mineralisation yet seen at the project. High tenor remobilised massive sulphide veinlets were seen throughout this zone as well as in surrounding holes, further confirming the basal contact of the intrusion is prospective for massive sulphides and our belief this is likely a hybrid Type 1/2 mineral system more akin to Perseverance, with both disseminated and massive components. Western Mines managing director Dr Caedmon Marriott

The company says the upper shallow disseminated zone immediately beneath sand cover is increasingly the focus of studies into the potential for the open-pit mining of a near-surface resource to a vertical depth of between about 200m and 280m. An ongoing RC program is testing the lateral continuity of the shallow mineralisation on an open grid pattern across the complex.

Western Mines says geological logging is validated by assays and confirm extensive zones of mineralisation, with significant evidence for “live” magmatic sulphide chemical processes. The long intercepts of deeper mineralisation, usually more than 100m, are now being viewed as potentially “cloud-style” hybrid sulphide mineralisation typical of a style that surrounds the Perseverance deposits.

Alternatively, the company suggests higher grades within the deep broad zone could be amenable to bulk underground mining.

MTD028 is the seventh diamond drillhole put into the project and infills a zone between two previous holes to test the western margins of the complex and a previously-defined western geophysical electromagnetic (EM) conductor anomaly. The company says all observations were along predicted lines, with disseminated sulphides occurring in four distinct zones in similar fashion to the previous holes.

It says that while its previous deep diamond hole, about 2km closer to the eastern margin – and the deepest part of the dunitic intrusive – produced the best results, the latest hole was on a par.

Management explains that when all four deep holes are viewed together, they highlight the extent of nickel sulphide mineralisation in the Mulga Tank complex. It appears to be contained within a zone, as interpreted from aeromagnetics and increasingly proven by drilling, measuring about 4.4km east-west by about 3.2km north-south.

Western Mines recently revealed it was awarded $220,000 in its second round of West Australian Government’s exploration initiative support (EIS) for a third deep diamond hole, which has yet to be drilled. The award will co-fund the drilling of a hole to at least 1500m depth to test the deepest part of the Mulga Tank ultramafic complex.

And it is plain to see that the project is growing in stature with every drillhole put into it.

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