This is the first in a 2-part feature series.
This article is a sponsored feature from Mining.com.au partner Western Mines Group Ltd. It is not financial advice. Talk to a registered financial expert before making investment decisions.
Western Mines Group (ASX:WMG) may be a junior exploration company but the nickel-focused Perth-based miner is “chasing a really big prize”.
The company is driven by the goal to discover ‘high-value’ gold and nickel sulphide deposits across a portfolio of ‘highly prospective’ projects located on major mineral belts of Western Australia.
What differentiates Western Mines from other nickel exploration plays is the major komatiite-hosted nickel system the company has within its portfolio.
While komatiite-hosted nickel deposits are fairly well known in Western Australia, generally most other nickel sulphide deposits are mafic intrusion-related such as Nova Bollinger in the Fraser Range, and famous camps around the world like Norilsk or Jinchuan.
Managing Director Dr Caedmon Marriott explains that the ultimate prize the company is after sits within the underexplored Minigwal Greenstone Belt, where Western Mines has strategically assembled a 395km-square landholding.
Its flagship project and primary focus is the Mulga Tank Ni-Cu-PGE Project – a major dunite ultramafic complex where previous work shows significant evidence for a working sulphide mineral system and is considered ‘highly prospective’ for Ni-Cu-PGE mineralisation.
Marriott notes that ‘world-class’ examples of komatiite-hosted nickel deposits include Kambalda (35 million tonnes @ 3.1% Ni), Perseverance (50Mt @ 2.3% Ni), and Mt Keith (643.7Mt @ 0.58% Ni).
Similarities to world-class komatiite-hosted nickel deposits
The reason Mulga Tank is considered the main prize is the abundance of similarities it shares with nearby world-class examples of komatiite-hosted nickel deposits such as Perseverance and Mt Keith in particular.
The MD says they are actually nearly identical.
“It’s the same rock type. We haven’t yet found massive sulphide like Perseverance but the disseminated nickel sulphide we’ve seen we know for a fact looks exactly like Mt Keith – as our Technical Director Dr Ben Grguric worked there and wrote a lot of the scientific papers on it. As he says, ‘Any of our drill core could be core from Mt Keith, it looks just the same, including the disseminated sulphide mineralisation’.”
Grguric, who spent his early career with WMC Resources and mining behemoth BHP (ASX:BHP), and in particular at BHP’s Mt Keith nickel operation, was gobsmacked when reviewing some of Western Mines’ recent drill core.
Assessing the core, Grguric declared: “Strewth, that looks like Mt Keith ore zone right there. Damn, there’s a lot of sulphides in this.”
Grguric has extensive experience in mineral exploration and scientific research, with direct involvement in a number of gold and nickel discoveries over the past 30 years. He is considered a leading expert on WA nickel sulphide exploration with more than 50 peer-reviewed scientific papers.
“… that looks like Mt Keith ore zone right there. Damn, there’s a lot of sulphides in this”
Marriott says bringing Grguric on board has been a coup for the company given his intimate knowledge of Mt Keith and the incredible parallels they hope Mulga Tank has with the renowned project.
“At Mulga Tank the similarities that we’re seeing with the rocks that host Mt Keith is really quite incredible.”
Low-grade disseminated sulphide ore is mined from the Mt Keith nickel mine, which is a large open-pit operation. The ore is processed through large concentrators and dryers as part of BHP’s mine-to-market integrated nickel business Nickel West.
Mt Keith was brought into production by Western Mining Corporation (WMC) in 1995 and was taken over by BHP which became owner and operator in 2005. In August 2021, BHP announced it would expand production by 40% at the nickel mine, with a new semi-autogenous grinding (SAG) mill, flotation technology, and two new Liebherr excavators. The company said at the time that the operation would be expanding to 15 million tonnes per annum (Mtpa).
While Western Mines has been somewhat frustrated by the sand cover in the region, it is the reason why the Minigwal Greenstone Belt has never really been explored, despite BHP first looking there in the 1980s.
The sand cover means typical early stage geotechnical techniques such as geological mapping, rock chip sampling, and finding gossans, cannot be undertaken. It can also be an impediment to drilling, which led to Western Mines having to go straight to diamond drilling.
The MD notes: “Many cheaper first pass drilling techniques such as RAB or aircore have failed in the sand cover but we’re able to handle it with our diamond technique. Having to go straight to diamond in a way is actually good as that gives us a lot of good geological information.”
Minigwal Belt first identified by BHP in 1980s
The aforementioned Minigwal Belt and Mulga Tank dunite were first identified by BHP in the 1980s yet are still underexplored due to the sand cover.
Marriott says the prospectivity of this overlooked portion of the eastern Yilgarn Craton is particularly exciting. And while BHP would likely now focus on near-mine developments, Western Mines has demonstrated through greenfield exploration that komatiite rocks in the area are mineralised.
“Yes, it was first discovered by a large regional airmag survey over the eastern Yilgarn and they were actually looking for Olympic Dam IOCG style deposits. Nowadays I’d suggest BHP mostly only invests in near-mine brownfield exploration and not so much on greenfield.
“So, we think a new, overlooked, underexplored belt like Minigwal is very exciting given we’ve demonstrated the komatiite rocks here are mineralised”
They’re (BHP) spending tens of millions of dollars if not hundreds of millions exploring around Mt Keith on quite a well explored/looked at belt. So, we think a new, overlooked, underexplored belt like Minigwal is very exciting given we’ve demonstrated the komatiite rocks here are mineralised.”
Marriott adds that even as recently as 2001-02, there had only been a few holes drilled in the region that went beneath the sand cover. By the time that Western Mines acquired the project back in 2019-20, there were only about 11 or 12 holes beneath the sand in a very large area.
“The area has been known about but because of the sand cover it hasn’t really been tested.”
That is, until now.
Western Mines is keeping an eye on the prize and will spend much of 2023 drilling to investigate just how similar Mulga Tank is to Mt Keith.
Keeping an eye on the prize
A phase two diamond drilling program at the Mulga Tank Ni-Cu-PGE Project is now underway where the company plans to drill a minimum 6 holes for 4,000-5,000m to test follow-up targets.
The phase two drilling program is expected to last until the end of March-early April 2023. Each hole will vary in time taken to drill dependent on depth but the company intends to update shareholders on significant news flow as the program progresses.
The targets and drillholes selected are based on a combination of geophysical modelling of recent DownHole Electromagnetic (DHEM) results and previous Moving Loop Electromagnetic (MLEM) results along with geological interpretation of the complex and geochemical vectoring work.
As part of the drill program, the deep EIS holes (EIS1 and EIS2) will be the first holes to truly test the centre of the Mulga Tank dunite and will be the deepest ever drilled at the project. The aim is to capture and characterise a complete cross-section of the intrusion. EIS1 will test the base of the W Conductor and the centre of the complex, while EIS2 will test a significant gravity high at the base of the intrusion, that may represent the feeder system for the whole complex.
The MD notes: “We like to be very transparent and communicate to shareholders and after the end of each hole or batch of similar holes we try to put out updates on what we’ve seen in the hole and drill core.
So far, we’ve been deliberately testing a range of different targets and different areas of the Mulga Tank Ultramafic Complex. We have drilled 11 holes to date and have seen visible nickel sulphide in 7 of them – despite the fact they’ve been scattered all over the place – there’s evidence for a working nickel mineral system over a very large area and there could be multiple deposits.
“So far, we’ve been deliberately testing a range of different targets and different areas of the Mulga Tank Ultramafic Complex”
We think this is a great result and indication of prospectivity. Large areas remain untested and it is only now in phase two that we’re starting to follow-up and narrow down the search on certain targets.
We haven’t found massive sulphide yet but we have found evidence for close proximity in quite a few holes with remobilised sulphides seen.
The disseminated sulphide we have seen, we have shown to be nearly predominantly pentlandite (i.e. nickel sulphide) rather than barren iron sulphide (pyrite, pyrrhotite) (for example hole MTD020). This really shows potential for Mt Keith-style mineralisation.”
Technical Director Grguric has helped complete some very interesting thin section work, which confirms abundant pentlandite throughout the system, both as disseminated interstitial blebs in hole MTD020 and in remobilised veins.
Marriott says the company is now growing in confidence when talking about an extensive working nickel sulphide mineral system throughout the Mulga Tank Ultramafic Complex.
Further technical work, including mineralogical section analysis, has been completed on drill core from the first program. This work confirms the abundance of ‘high-tenor’ disseminated pentlandite (up to 38% Ni recorded by Scanning Electron Microscope (SEM)) in samples from hole MTD020, with minimal pyrrhotite and pyrite observed.
The MD adds that this supports the near identical nickel assay results by 4 acid versus aqua regia digest suggesting a high percentage of nickel in sulphide form versus silicate nickel. This has very positive implications for the potential of an extensive working mineral system for type 2 Mt Keith-style disseminated nickel sulphide mineralisation.
In part 2 of this feature series, Marriott details that Mulga Tank is emerging as the new nickel frontier in Western Australia.
He outlines that having the company’s flagship project in an overlooked portion of the eastern Yilgarn Craton is an attractive mining and investment proposition for a myriad of reasons. However, Marriott explains the company is keeping an eye on the prize, which is looking for nickel sulphide and more specifically komatiite rock/systems.
Western Mines is edging closer to claiming that prize at Mulga Tank.
Write to Adam Orlando at Mining.com.au
Images: Western Mines Group Ltd
