Western Mines Group has kicked off the new year with a 17-hole reverse-circulation (RC) drilling program at its Mulga Tank project in Western Australia’s Eastern Goldfields to better resolve a high-grade core in a shallow nickel zone identified last year.
The program will build on epic results from last year that not only established the basic shape of the main dunite body at the company’s nickel project, but also found the massive disseminated nickel zone.
The team has been back on site for the last 10 days. They have completed clearing the drill pads and have drilled the majority of the ~60m pre-collars for the RC program - this RC drilling should start in the next day or so. Western Mines Group managing director Dr Caedmon Marriott
Previous work earlier last year largely comprised several diamond drill holes to probe the depths, lateral extents and footwall characteristics of the Mulga Tank dunite ultramafic body near Lake Minigwal, north-east of Kalgoorlie, which successfully identified good grade nickel sulphides in deeper holes.
A drilling progressed, it became apparent that significant disseminated nickel was showing up in the uppermost sections of the diamond holes, with remarkable lateral persistence and depth uniformity that was crying out to be tested with a dedicated program.
The mineralisation was found not far below the original natural surface that is now buried under 60m to 90m of running sands, requiring novel rotary mud-drilling methods to case off the sands until a RC hammer drill bit could be brought to bear on the disseminated nickel zone lying beneath.
Once proven successful, the new RC program developed into a 22-hole program on a 500m-by-300m grid pattern to establish the thickness, consistency and lateral extent of the new zone. The campaign had a phenomenal hit rate, with just one single hole falling short in expectations.
Just as the program was reaching its half-way point, it became apparent that the new shallow disseminated zone being fleshed out featured a distinct high-grade core that also warranted closer evaluation.
Last year’s RC drilling ended on a high note with nickel intercepts of 2m at 1.05 per cent in one hole and 1m at 1.19 per cent in another. Respective cumulative nickel intercepts from the two holes include impressive runs through the near surface disseminated nickel zone of 168m at 0.29 per cent nickel and 159m at 0.29 per cent nickel, with both holes ending in mineralisation.
The total analysis for the first hole shows 2m at 1.05 per cent nickel, 394 parts per million cobalt, 583ppm copper and 27 parts per billion platinum group elements (PGE) from 196m, including 1m at 1.58 per cent nickel, 574ppm cobalt, 708ppm copper and 39ppb PGE from 197m.
The second hole featured 1m at 1.19 per cent nickel, 424ppm cobalt, 234ppm copper and 21ppb PGE from 277m and 1m at 0.96 per cent nickel, 368ppm cobalt, 68ppm copper and 41ppb PGE from 289m.
A third hole also produced impressive runs of nickel grades consistent with results from 19 of the company’s 20 holes to date, with a cumulative run of 91m at 0.24 per cent nickel, including two continuous intercepts of 24m at 0.28 per cent and 39m at 0.24 per cent.
The disseminated zone starts almost immediately beneath the sand cover and extends from as shallow as about 100m and as deep as about 320m. It appears to be laterally continuous and looks likely to extend well beyond the limits of the current RC drill pattern.
The new program is designed to infill gaps from the previous RC campaign to assist with the final modelling of the disseminated zone – and especially its high-grade component, which will in turn determine the direction and focus of immediate future RC and diamond drilling.
Following the 17-hole program, a new deep diamond hole will be drilled under the provisions of the company’s third Exploration Incentive Scheme (EIS) award, valued at $220,000. Further extensional RC drilling is planned, the scope of which will depend on how far the disseminated zone extends in both east-west and north-south directions.
The EIS hole will be designed to identify a sulphide-enriched keel in the deepest part of the complex, based on the company’s previous deep core drilling, and will also test a coincident MobileMT anomaly about 1160m below the surface and near the basal contact.
With all but one batch of assays left to receive last year, the company undertook a first pass review of all drillhole results from the project. It included mapping out the size and scale of the geochemical anomalies identified that could define a significant, shallow mineralised target within the main dunite body of the Mulga Tank ultramafic complex.
The study concluded with two models derived from a low-value (greater than 0.15 per cent nickel) and a higher-value (greater than 0.2 per cent nickel) cut-off zone that when combined, indicate some 647 million cubic metres of mineralised disseminate may be present.
The volume is constrained by depths limits of about 100m below surface to eliminate oxidised material and extends to the maximum depth of RC drilling.
The significance of that is enormous, as it implies potential for open-pitting of some of the resource with relatively straightforward free-dig pre-strip of the overlying sands, excavation of the additional oxidised zone and further excavation of less oxidised/fresh disseminated material for at least some of the remaining depth, subject to pit optimisation.
Western Mines says further modelling and drill targeting work is ongoing, with additional targets and drillholes expected to soon be announced. It remains on track to establish an initial JORC exploration target estimate for the shallow mineralised zone within the main dunite body of the Mulga Tank complex.
Mulga Tank has never failed to positively surprise and the next phase of drilling seems unlikely to disappoint as the company continues to de-risk its potentially globally significant, large-scale, open-pittable nickel sulphide deposit.
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