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Western Mines on trail of Mt Keith-style nickel

Updated: Apr 30

The ultramafic complex at Western Mines’ Mulga Tank. Credit: File

Western Mines Group believes long nickel runs shown in assays from its first two holes to test shallow disseminated nickel under deep sands at its Mulga Tank project in Western Australia could have it hot on the trail of a potential Mt Keith-style deposit.

The company says reverse-circulation (RC) drilling in a 22-hole, 7035.5m program yielded one hole with a cumulative nickel run of 253m at 0.24 per cent nickel, while a second hole yielded 111m at 0.31 per cent nickel.

The first systematic drilling of the Mulga Tank ultramafic complex was designed to test the depth and consistency and lateral continuity of the shallow, uppermost zone of the disseminated nickel sulphide mineralisation that was observed in six of the company’s diamond holes.

Allowing for about a 320m average hole depth and 60m of sand cover, the drill pattern effectively swept a broad target volume of about 650 million cubic metres (more than 1.6 billion tonnes of rock) in the centre of the main body, much of which is demonstrably mineralised.

It continues the company’s remarkable journey of discovery at its flagship Mulga Tank nickel-copper-platinum group elements (PGE) project on the major ultramafic complex in the under-explored Minigwal Greenstone Belt, north-east of Kalgoorlie. And it also has it dreaming of proving up something similar to BHP’s renowned Mt Keith orebody that has a 224-million-tonne resource going at 0.53 per cent nickel.

The RC drilling program targeted a significant portion of the main body of the complex, covering an area of approximately 2.5km x 1km where we’d previously only drilled four diamond holes. This drilling dramatically increases the drillhole density in this ‘core’ area of the complex and will yield valuable data in exploring the lateral continuity of shallow disseminated mineralisation, and in systematically characterising the geology and geochemistry of the entire system. Western Mines Group managing director Dr Caedmon Marriott

The company says its results highlight broad zones where about 50 to 60 per cent of the samples from both holes show remarkably consistent nickel sulphide mineralisation coincident with highly-anomalous cobalt, copper and combined platinum and palladium (PGE) values of similar consistency within their respective ranges.

The first hole yielded three long intercepts from just below the ubiquitous sand cover, which ranges from 60m to 90m depth, all the way to 444m. The holes had all been planned with an initial target depth of about 300m in mind, but some were pushed further when interesting mineralisation was noted in drill chips.

The first hole offered up 162m at 0.2 per cent nickel, 123 parts per million cobalt, 81ppm copper, and 19 parts per billion PGE from 95m. It was followed up just 87m further down the hole with a run of 29m at 0.42 per cent nickel, 138ppm cobalt, 85ppm copper and 17ppb PGE from 344m.

The final intercept just 9m further downhole capped off the story with a good run of 62m at 0.25 per cent nickel, 136ppm cobalt, 61ppm copper and 53ppb PGE from 382m. The cumulative run calculates to a total of 253m at 0.24 per cent nickel, 128ppm cobalt, 76ppm copper and 27ppb PGE, with a sulphur-to-nickel ratio of 1.4.

The second hole produced a handy 29m at 0.24 per cent nickel, 141ppm cobalt, 103ppm copper and 23ppb PGE from 97m. Another 56m further down the hole, it offered up 19m at 0.28 per cent nickel, 112ppm copper, 9ppm copper and 30ppb PGE from 182m.

The third intercept began just 25m further down the hole, with 63m at 0.35 per cent nickel, 141ppm cobalt, 71ppm copper and 46ppb PGE from 226m. Interestingly, the last intercept included 23m at 0.44 per cent nickel, 154ppm cobalt, 118ppm copper and 70ppb PGE from 236m and a further 9m at 0.43 per cent nickel, 131ppm cobalt cobalt, 18ppm copper and 34ppm PGE from 272m.

The cumulative run calculates to 111m at 0.31 per cent nickel, 136ppm cobalt, 69ppm copper and 37ppb PGE, with a sulphur-to-nickel ratio of 0.7. It is interesting to note that both holes ran into mineralisation at 97m and 95m downhole depth, respectively.

Western Mines says its work on geochemical characterisation shows the host rock to be a high magnesium oxide adcumulate dunite, which in the first hole averages 48.3 per cent magnesium oxide and 0.16 per cent aluminium oxide, while the second hole runs 46.5 per cent and 0.2 per cent for the same oxides, respectively.

Management says the extensive intersections of adcumulate dunite within the complex, starting almost immediately under the sand cover, gives it the potential to discover one or more big-volume, low-grade type-two Mt-Keith-style disseminated nickel sulphide deposits within the Mulga Tank complex.

It says while broad intersections of visible disseminated nickel sulphide mineralisation can be easily observed in the diamond core drilling, it is typically more difficult to see in RC drill chips. But in this case, visual mineralisation was noted during geological logging of some of the RC holes.

The results from the first two holes show the concept of testing the uppermost zone of shallow mineralisation is working, with about 50 to 60 per cent of the samples showing a distinct geochemical signature of broad zones of mineralisation. Additionally, the first hole is in the south-western corner of the drill pattern, so it is not difficult to conclude that mineralisation is unlikely to be confined to the initial area drilled.

So, if this is just the entrée, then two serious main courses are still to follow when the rest of the RC results come in. And they could be a shallow and perhaps even open-pittable Mt Keith style of disseminated nickel mineralisation – or maybe a deeper Perseverance-style offering.

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