Western Mines Group (ASX: WMG) says it is now well on its way to confirming a hybrid nickel system with high-grade massive sulphide potential at its Mulga Tank complex near Lake Minigwal in WA’s Eastern Goldfields region.
The bold claim comes after the company nailed high-grade nickel results from three new reverse-circulation (RC) drillholes put in to test the limits of the Mulga Tank core. The three holes yielded cumulative nickel intercepts ranging between 174m and 193m thick and assaying between 0.28 per cent and 0.33 per cent nickel, with one hole delivering the project’s best intersection – a continuous 193m going 0.33 per cent nickel, 152 parts per million cobalt, 310ppm copper and 25ppb platinum group elements (PGE) from 107m and ending in mineralisation.
Management says the hit is its best to date at the project.
Among other intercepts in the highlight hole are zones of 4m at 1.14 per cent nickel, 501ppm cobalt, 803ppm copper and 0.14g/t PGE from 224m and another 5m at 0.61 per cent nickel, 258ppm cobalt, 0.49 per cent copper and 32ppb PGE from 229m. The hole ended with a flourish in a final run of 5m at 1.92 per cent nickel, 711ppm cobalt, 0.21 per cent copper and 0.18g/t PGE from 283m.
All three holes ended in mineralisation and all exhibit broad zones of nickel sulphide mineralisation featuring elevated nickel and sulphur coinciding with anomalous copper and PGEs.
The team is excited by these results, with MTRC046 showing the best high-grade intersection at the projec, to date. It’s further validation of the extensive Mulga Tank nickel sulphide mineral system and the potential the Complex could hold. The more we drill the more we’ve become increasingly convinced of the hybrid nature of the system and potential to host higher-grade massive sulphide.
Western Mines Group Managing Director Dr Caedmon Marriott
The company had proposed 23 holes for the current program. Four holes were centred around a single drillhole of interest in the high-grade core of the deposit, while a further three were designed to infill and/or extend the far south-eastern corner of the grid.
Results have already been received for the four-hole bracketing of the hole of interest in the centre of the grid. The results are the first to be returned from the northernmost east-to-west fence of five proposed extensional holes at 200m spacings designed to test the southern limits of the high-grade zone.
Assays are awaited for the remaining two holes at the eastern end of the same line, for the entire fence of a further seven holes 200m south of the current line and for the three satellite holes off the south-east corner of the grid. The four remaining holes for the program have been assigned to regional scout drilling off to the north-west of the complex.
The consistency of analyses in results from across the seven recent holes is remarkable.
Together, Western Mines’ past two sets of results reflect continuity of the high-grade core for a further 100m south of two previously-drilled holes to the north. Those two holes bored out 198m of rock at 0.28 per cent nickel and 145ppm cobalt from 108m in one hole and 199m at 0.31 per cent nickel and 139ppm cobalt from 119m in the other.
The line of three holes carries mineralisation beyond the envelope of the company’s JORC resource target modelling that was constrained by the original phase-one drilling pattern. All three holes show broad intersections of disseminated nickel sulphide mineralisation with high sulphur and chalcophile signatures that point to a bigger nickel system than the company envisaged previously.
Management says it is beginning to clearly define a hybrid style of nickel deposit at Mulga Tank where two styles of nickel mineralisation exist.
The first and shallowest style comprises an upper disseminated zone of nickel mineralisation lying just beneath the original natural surface – before it was buried under 60m to 90m of recent transported sands – and extending to depths of about 200m.
The second variety of mineralisation comprises an extensive deeper nickel sulphide system that has been steadily expanding with every phase of drilling.
The latest results reinforce Mulga Tank’s status as not just a type 2 disseminated sulphide system, but that it is more likely to represent a “Perseverance-style” hybrid type 1/2 system with a high-grade massive sulphide component.
BHP’s Perseverance nickel ore deposit near the WA town of Leinster occupies a regionally-extensive ultramafic unit near the eastern margin of the Agnew-Wiluna segment of the regional Norseman-Wiluna Greenstone Belt. The Perseverance orebody lies at the stratigraphic base of the ultramafic complex and is composed of high-grade massive and heavily disseminated sulphides within an extensive sheet of weak sulphides.
Several holes across all three of Western Mines’ RC programs have returned higher-grade assay results between 1 per cent and 4.5 per cent nickel. Such zones have typically been logged as “matrix to semi-massive sulphide” in drill chips, which the company says highlights the high tenor of the sulphide system.
The latest results reinforce its growing view that, in addition to Mulga Tank’s disseminated style, all the necessary geological processes are working to produce high-grade, high-tenor massive sulphide material.
Management will now be waiting with bated breath for results from its next line of holes in the extreme south of the grid to prove another 150m to 200m of southward extension of nickel mineralisation – especially high-grade sulphides. The company says it will try to get a preview of that possibility by following up the latest highlight result with a downhole electromagnetic (DHEM) survey to see what signatures lie near the hole, before undertaking more RC and diamond drilling in that area.
A large, low-grade, open-pittable deposit is being defined within the Mulga Tank complex by Western Mines’ various phases of drilling and within the disseminated mineralisation, several high-grade nickel pods are beginning to emerge as the drilling density is increased.
It is a WA geological story that is starting to truly take shape.
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