New drilling results have enabled Western Mines Group to make a significant geological breakthrough at its flagship Mulga Tank nickel project in WA’s Eastern Goldfields. The results include those for a diamond tail drilled to extend and deepen an earlier reverse circulation (RC) drillhole, and for two other RC holes.
Together with other holes in the western margin of the main body of the Mulga Tank Complex, their geochemical signatures confirm that a significant chunk of the basal sequence has been uplifted closer to surface from its original deeper position within the complex.
Combined with the previous RC drill samples, the assay results for the diamond drill hole reveal 442m of cumulative nickel sulphide mineralisation assaying 0.26 per cent nickel, 129 parts per million (ppm) cobalt, 78ppm copper, and 27 parts per billion (ppb) combined platinum and palladium.
Most notably, however, the diamond tail also revealed the existence of higher-grade sulphide mineralisation at greater depth within the basal zone, comprising 74m at 0.32 per cent nickel, 142ppm cobalt, 115ppm copper, and 31ppb combined platinum and palladium from 762m. The interval also included 23m going 0.42 per cent nickel, 144ppm cobalt, 74ppm copper, and 44ppb combined platinum and palladium from 812m depth.
Five other RC drillholes yielded broad zones of nickel sulphide mineralisation, with higher nickel, sulphur and relevant geochemical indices known as chalcophiles, along with barren zones that show relatively familiar geochemical stratigraphy of the basal complex. Those five holes delivered cumulative intercepts between 171m and 98m with nickel in the range of 0.3 per cent and 0.21 per cent, respectively.
Intriguingly, the five holes were designed to test new areas of the complex and a hypothesis that the southwestern part of the main body could be the most uplifted portion of the complex. That extended to the idea that enriched basal horizons could be intersected close to the surface, albeit still beneath the ubiquitous sand cover across the complex.
The company says the latest work will greatly aid in modelling the architecture of the vast Mulga Tank nickel-rich dunite complex and validates its theory that the southwestern part of the main intrusive body defined to date represents the most uplifted portion. The development is a crucial step forward in the company’s hunt for high-grade massive nickel sulphides, as it provides a clearer roadmap for future drilling by homing in on the most prospective and possibly shallower part of the higher-grade system.
The Mulga Tank project is centred on a large mafic-ultramafic intrusive complex in the Minigwal Greenstone Belt, 190km northeast of Kalgoorlie, which the company believes is analogous to other well-known major nickel sulphide-hosting intrusions in WA.
The initial and current mineral resource estimate for Western Mines’ Mulga Tank project stands at a jaw-dropping 1,97 billion tonnes at 0.27 per cent nickel, containing over 5.3 million tonnes of nickel.
The indicated resource component of that resource is 565Mt averaging 0.28 per cent nickel, 134ppm cobalt, 104ppm copper and 18ppb combined platinum and palladium.
The key to unlocking these types of deposits often lies in identifying the “basal contact” – the floor of the intrusion where heavy nickel-copper-platinum group element sulphides are most likely to have settled and accumulated as magma cooled.
By confirming the western margin of the complex has been uplifted from its original position, Western Mines has effectively brought part of the highly prospective basal contact target significantly closer to surface, making it easier and cheaper to drill, potentially delivering substantial cost savings in any future mine development.
Collectively, the results from holes MTRC001 and MTRC083 to MTRC087 look to validate the idea that the southwestern part of the main body represents the most uplifted portion of the Complex. They were designed to follow up-dip from holes MTD028 and MTRC011 and investigate whether enriched basal horizons could be intersected nearer surface.
This new geological understanding allows Western Mines to move from just proving the existence of a working nickel sulphide system to actually homing in on part of its high-grade heart. The company can now refine its targeting strategy and focus its exploration for high-grade massive sulphides on shallower areas with the highest probability of success.
The long-term demand outlook for high-quality nickel sulphide discoveries remains robust, driven by the global energy transition and the resulting seemingly insatiable need for battery metals. New discoveries in tier-one mining jurisdictions such as Western Australia are particularly sought after.
The hunt for a major mineral deposit is often a geological detective story, and Western Mines appears to have just uncovered another vital clue, in which a shallower higher-grade zone could have important implications for the timing of elements of a future mine plan.
With a refined geological model in hand and a high-priority, higher-grade basal target zone now clearly identified along the western margin, the company looks well-placed to zero in on what it hopes will be a company-making discovery.
Is your ASX-listed company doing something interesting? Contact: matt.birney@wanews.com.au
Get the latest news from thewest.com.au in your inbox.
Sign up for our emails