Western Mines Group: digging deep at a pivotal moment

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) is at a pivotal time in the young minnow’s journey to identify an extensive working nickel sulphide mineral system in Western Australia.

The company has always adopted a ‘ballsy’ go big and dig deep approach with exploration at its flagship Mulga Tank Project.

Complementing that mindset is a willingness to adopt modern technology to better understand Mulga Tank – a major ultramafic complex found on the under-explored Minigwal Greenstone Belt.

Managing Director Dr Caedmon Marriott tells Mining.com.au that one hole in particular epitomises Western Mines’ “real balls exploration” approach and has led to a figurative fork in the road for the company.

Hole MTD027 intersected 1,500m thickness of high MgO meso-adcumulate dunite ultramafic containing disseminated magmatic sulphides (trace to 2%) that in a number of places coalesced into interstitial blebs (3-5% sulphide).

As drilling goes for a junior, Marriott says this is deep.

“We don’t shy away from being brave. We’ve now drilled 3 deep holes at Mulga Tank – the 2 co-funded EIS holes 23 and 26, and then our own, which just evolved into a deep hole and wasn’t initially planned to be drilled to 1,600m.

This is incredibly punchy. That is real balls exploration. It’s incredibly expensive for a little company like us but it just goes to show how exciting and potentially massive this thing is.”

Critical juncture

Marriott says it also presents a number of opportunities.

“We’re at a fork in the road in terms of what’s before us. We’ve now demonstrated extensive disseminated mineralisation within the complex, Mt Keith-style nickel mineralisation, so as I alluded to the market before, with an RC rig we can very quickly and easily drill down 300 (metres) in the top section and we can start to prove up a shallow disseminated resource in the top couple of hundred metres of this body.

If we can demonstrate that it’s laterally continuous over something like 2 kilometres by a kilometre by 100 metres thick, that’s still millions and millions of tonnes of contained nickel. It’d be huge, so one avenue of our future exploration becomes that and looking to test the shallow top section with RC. We’ll be doing that over the next month or two.

But we’re really beginning to believe this is a hybrid system, more similar to Perseverance, with both a disseminated cloud and basal massive sulphides. On the other fork in our exploration strategy we will continue looking for this massive sulphide component.”

Sands of time

Marriott notes there’s a few intricacies with this. One element is that historical attempts at aircore and RC drilling were often unable to overcome the issue of sand cover, as the rigs would get bogged. This is in large part why the area is underexplored.

Western Mines is using a multipurpose rig to drill and case pre-collars through the sand. The holes are spread over a 2,000m x 1,000m area across the centre of the main body of the complex, at about 500m x 300m spacing, and will attempt to drill to 300m target depth.

Broad intervals of shallow disseminated nickel sulphide mineralisation, within the top 250 vertical metres, have been seen across previous diamond drillholes MTD012-MTD022-MTD023-MTD026 some 2.3km apart. More recently visible sulphide mineralisation was seen in hole MTD027 about 1.5km further east.

However, the MD says it’s the depth of the complex that has caught Western Mines’ attention. In order to really understand the magnitude of the Mulga Tank Ultramafic Complex, Marriott knows he and the team must think big in terms of the approach to this critical juncture.

Having spoken to various industry stalwarts about new techniques around, including Mike Jones from Impact Minerals (ASX:IPT), Marriott engaged Expert Geophysics to undertake the firm’s pioneering MobileMT geophysical survey across the entire Mulga Tank Ultramafic Complex.

The aim is simple – further unlocking the 3D architecture and targeting accumulations of massive nickel sulphide.

Marriott says this is just another step in the company’s systematic and forward-thinking exploration strategy. Combined with its existing 3D datasets, such as magnetics, gravity, and the extensive geological information gained from recent deep EIS holes, the deep resistivity and conductivity mapping provided by the MobileMT system is unlocking further insight into the complex.

This progressive technology is capable of deep 3D geoelectrical mapping of resistivity and conductivity down to >1km, which the MD hopes may be well suited to directly detecting deep massive sulphide targets at the project.

Deeper insights

Given the depth the company has been drilling, the MD says it makes sense to utilise technology that lends itself to penetrating deeper into the ground.

“I just love the size of this thing, right. There’s these 1,500 metre holes we’ve drilled through it, with significant mineralisation all the way down them.

We’ve been able to fly the whole belt with MobileMT pretty quickly and cheaply to quite a high resolution. Our previous surface EM was probably only good down to 300, maybe 500 metres at best. Whereas magnetotellurics can go down to 1,000 or 1,500 metres, depending on your conditions.

“I just love the size of this thing, right. There’s these 1,500 metre holes we’ve drilled through it, with significant mineralisation all the way down them

We’re using the MobileMT to map the resistivity of the rocks. We expect the dunite body, the intrusive body that we’re targeting, to naturally be very resistive, and the footwall around it, the basalts and shales. to be less resistive and more conductive. The inverse of resistive is conductive. So, it’ll map the architecture quite well of our project, but then we hope to see more conductive anomalies, within an overall resistive dunite body, that could be potential sulphide targets.”

MobileMT is the latest innovation in airborne electromagnetic technology and the most advanced generation of Airborne Natural Source Audio Frequency Magnetotelluric (AFMAG) technologies. It utilises naturally occurring electromagnetic fields in the 25Hz to 20,000Hz frequency range and is essentially a high-resolution deep resistivity and conductivity mapping tool capable of delivering 3D geoelectrical information down to >1km depth – this should effectively target the entire Mulga Tank Complex and basal contact, based on the company’s geological model.

The MD adds: “It’s magnetotellurics, which is using the Earth’s natural electromagnetic frequencies. A lot of these other EM technologies, like downhole EM, airborne or surface based Moving Loop EM or fixed loop EM – you have an electromagnetic source which pumps a current into the ground and then you have the receivers that then measure that.

Whereas magnetotellurics uses the Earth’s natural fields, there’s no pumping source. The Earth is constantly being charged by lightning and various other processes. Essentially, it’s mapping resistivity, how resistive the rocks are, and it’s supposed to be able to do it down to about a kilometre or over a kilometre. So much deeper than EM.”

Transitional period

The recent deep hole MTD027 was located on the eastern side of the Mulga Tank Complex in an area that has had no previous drilling. The hole was designed to test a coincident gravity and magnetic high and minor MLEM anomaly.

Numerous intersections of high-tenor massive nickel sulphide immiscible globules and remobilised massive nickel sulphide veinlets were observed frequently down the length of the hole (confirmed by spot pXRF readings up to 37% Ni).

These frequent observations of remobilised sulphide veinlets, with examples of high-grade material filling rock fractures, opens up the eastern margin area in the search for accumulations of massive nickel sulphide.

Together with EIS holes MTD023 and MTD026, hole MTD027 demonstrates an extensive magmatic nickel sulphide mineral system within the complex, which Marriott says has now been shown across the entire 4.5km wide main body.

Assay results for MTD026 show cumulative disseminated nickel sulphide mineralisation of 840m @ 0.28% Ni, 140ppm Co, 103ppm Cu, 24ppb Pt+Pd with S:Ni 1.6. MTD026 intersected a cumulative 1,400m thickness of high MgO adcumulate dunite ultramafic containing disseminated magmatic sulphides (trace to 2%) that in a number of places coalesced into interstitial blebs (3-5% sulphide) and even approaching net textured (5-10% sulphide) over a cumulative 950m.

Multiple intersections of high-tenor remobilised massive nickel sulphide blebs and veinlets were also observed down the length of the hole.

“We can’t stress enough the importance of the sulphide mineralisation

Marriott adds: “We can’t stress enough the importance of the sulphide mineralisation. Although we’re not getting the grades seen at Mt Keith, to get 840m of it is pretty nuts, really. It’s just huge, potentially an order of magnitude larger. Whereas Mt Keith has 0.35-0.4% material with no sulphides in, here we’re seeing visible disseminated blebs at anything over 0.25% generally if it’s visible it’s recoverable.

And then we’ve gone on and drilled hole 27, we thought that was going to be a relatively shallower hole into the edge of this bowl that we model the intrusion as, and that ended up going very deep as well. In essence, we’re seeing really good results and strong evidence for a hybrid system with basal massive sulphide – so we’re very committed to always getting to the bottom of this thing.

If you’re drilling 1,500 metre holes and seeing 900 metres of mineralisation, which is then confirmed by assays, and it’s all nickel sulphide, it’s pretty incredible, really. So, I think that’s indicative of how brave and frontier it is.

So where do we go from here, then? I guess that’s what we’re in, not a state of transition, but that’s what we’re still getting our heads around, in a sense. How best to target both the shallow disseminated material and deeper massive sulphides in parallel.”

Western Mines Group is an exploration company driven by the goal to create significant investment returns through exploration and discovery of high-value gold and nickel sulphide deposits across a portfolio of highly prospective projects located on major mineral belts of Western Australia.

The company has been continuously drilling at Mulga Tank since November 2022.

Earlier this month, Powder X-Ray Diffraction (XRD) analysis performed on a series of reconnaissance samples taken from drill core identified the mineral brucite (Mg(OH)2) as well as hydrotalcite group minerals.

These minerals have been implicated in the passive sequestration of atmospheric CO2 in mine tailings at several locations worldwide and in particular, tailings from the giant dunite-hosted Mt Keith nickel deposit in Western Australia.

The MD explains that with the XRD, although only a small group of samples were analysed as part of this first pass study, the results clearly demonstrate the mineralogy of Mulga Tank Ultramafic Complex contains critical components which could partially or entirely mitigate the output of atmospheric CO2 generated in future mining activities.

“These super deep holes have really unlocked things for us but we’ve barely scratched the surface

Moreover, he says the presence of brucite and hydrotalcite group minerals may result in any tailings generated via a conventional crush, grind and flotation processing route being amenable to relatively rapid sequestration of atmospheric carbon via carbon mineralisation processes thereby significantly enhancing the “green” credentials of the project by producing net-zero carbon nickel, along with the possibility of a carbon credit by-product revenue stream.

Marriott says while there have been exciting exploration results to date demonstrating an extensive nickel sulphide mineral system within the Mulga Tank Ultramafic Complex, a transitional period awaits the company.

“These super deep holes have really unlocked things for us but we’ve barely scratched the surface. We’re increasingly confident we’ve discovered a huge nickel sulphide mineral system at Mulga Tank. There’s significant Mt Keith-style disseminated mineralisation but more than likely we believe this is a hybrid system more similar to Perseverance, with both a disseminated cloud and a basal massive sulphide component – finding that portion is where this project gets really exciting.”

Write to Adam Orlando at Mining.com.au

Images: Western Mines Group
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Written By Adam Orlando
Mining.com.au Editor-in-Chief Adam Orlando has more than 20 years’ experience in the media having held senior roles at various publications, including as Asia-Pacific Sector Head (Mining) at global newswire Acuris (formerly Mergermarket). Orlando has worked in newsrooms around the world including Hong Kong, Singapore, London, and Sydney.