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Doug Bright
Viking Mines’ detailed phase one gravity and magnetic surveys at its Linka tungsten project in Nevada have confirmed anomalies over known tungsten-rich zones. The geophysics also identified multiple new priority targets, including some hidden structures beneath younger volcanic cover.
From a gravity perspective, Viking’s logic is simple. At Linka, the principal tungsten mineral, scheelite, is hosted in dense, coarse-grained metamorphic skarn-type rocks.
Skarn formations typically form by the chemical alteration of limestone or dolomite, typically by high-temperature hydrothermal fluids from magma intrusions.
Tungsten is one of the densest known elements, boasting a specific gravity (SG) of 19.3 – the same hefty weight as gold. While Linka’s main tungsten ore mineral, scheelite, is lighter with an SG of 6.1, it still packs plenty of punch when concentrated in skarn rocks.
‘Coupled with high tungsten prices of US$1,850/mtu of APT, we are advancing the project rapidly.’
Viking Mines managing director and chief executive officer Julian Woodcock
Those mineralised zones may often exceed an SG of 3.5, creating a sharp density contrast with surrounding rocks which lights up in gravity surveys.
Early indications suggest this simple exploration method is working, with Viking saying its phase one gravity data have revealed coincident anomalies across known mineralisation at the company’s adjacent Linka Main and Conquest prospects.
Adding to the project’s credentials, geophysics has also outlined multiple distinct gravity highs across the wider area, providing a virtual hit list of new priority targets crying out for mapping and sampling.
Viking’s magnetic surveying has mapped key geological boundaries and contrasts, with exposed limestones appearing magnetically quiet while volcanic rocks produce a noisier response, helping to pinpoint critical rock contacts.
Viking Mines managing director and chief executive officer Julian Woodcock said: “The preliminary data has indicated that we can see both the geological contacts where mineralisation occurs, and potential direct priority targets where we see gravity high anomalies. The occurrence of gravity highs coincident with areas of known mineralisation at Linka Main and Conquest demonstrates that the technique can resolve areas of increased density.”
Notably, a big magnetic high defined on the western side of the survey grid is showing all the hallmarks of a regional-scale intrusive body, possibly a quartz monzonite, associated with the tungsten-mineralised system.
Viking is now targeting zones where the intrusive body abuts rocks with a lower magnetic signature like limestones, as prime ‘contact-style’ mineralisation targets.
Further encouragement has come from Viking’s identification of notable northeast-trending structures slicing across the interpreted intrusion, suggesting that detailed magnetic surveys can also map potentially important geological pathways beneath the younger volcanic cover.
By combining its gravity and magnetic datasets, the company believes it can follow the mineralised corridor for about 820 metres to a point where it sub-crops between Linka and Conquest and for a further interpreted 800 metres beneath the southwest volcanic blanket.
Viking’s phase one geophysical program included 2.2 square kilometres of ground magnetics and 0.5 square kilometres of detailed gravity surveying.
The company has already moved to expand the magnetic program, which will run for a further 2.8 square kilometres to the west to help map the full size of the buried intrusion.
Meanwhile, the gravity grid will also be extended to cover another 0.35 square kilometres to the southwest across volcanic cover in search of underlying mineralised zones of higher density.
Once phase two surveying is complete, Viking plans to get boots back on the ground to map and conduct rock-chip sampling to validate the new targets.
It has also flagged a trial gradient array-induced polarisation (GAIP) survey over the northernmost Conquest mineralised zone to assess whether this fast, cost-effective exploration tool can provide another layer of target definition.
The latest encouraging geophysical results follow Viking’s recent update on initial metallurgical tests, where simple gravity separation produced an impressive 22.9 per cent tungsten trioxide concentrate from a calculated 1.4 per cent tungsten trioxide feed, a beneficiation ratio of 16:1.
The coarse grind successfully delivered a rougher recovery of 63.7 per cent – a punchy early result Viking believes could translate into a relatively simple processing pathway with further optimisation.
Putting it all together, Viking is starting to build a tidy end-to-end Linka story, with higher-confidence targeting emerging from modern geophysics, backed by early processing encouragement.
If phase two geophysics continues to highlight hotspots under cover, the company should be able to refine its shortlist of targets to follow up as it pushes towards the next round of on-ground work.
Is your ASX-listed company doing something interesting? Contact: mattbirney@bullsnbears.com.au
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