Barton Gold Begins Mine-Siting Drill at Tunkillia as PFS Nears

Barton Gold has crossed the line that separates an explorer from a developer. Infrastructure sterilisation drilling is now underway at the Tunkillia Gold Project in South Australia, which means the company is no longer only defining what sits in the ground; it is deciding where to build the mine on top of it.

That shift has arrived alongside two other milestones in a single month. The Environmental Scoping Report was approved on 7 September 2026, and a fresh set of assay results, with grades reaching up to 36.9 g/t Au, landed on 16 September 2026. Three de-risking events have compressed into one reporting window, against a project of real scale: 1.6 Moz Au, an A$1.4 bn net present value and a 73% internal rate of return from the May 2025 scoping study, with a Pre-Feasibility Study (PFS) targeting Q1 2027.

What follows below matters if you are weighing whether to act before or after that PFS. This piece sets out what Barton has just confirmed, what remains unresolved, and what the Q1 2027 study will need to show for the headline economics to hold.

What infrastructure sterilisation drilling actually means for Tunkillia’s development clock

Sterilisation drilling sounds like a technical footnote. It is closer to a starting gun.

The work involves drilling beneath the proposed footprints of major infrastructure to confirm that nothing economically valuable sits underneath. At Tunkillia, that means testing the ground where three things will eventually go:

• Waste rock dumps
• The tailings storage facility (the engineered structure that holds processing residue)
• The processing plant itself

– The point is to avoid building permanent infrastructure over gold you would later want to mine. Barton formally announced the commencement of this program on 19 August 2026.

Here is why the timing carries weight. You only drill to sterilise specific sites once layout options have been narrowed to specific locations. That narrowing is the tell. It means the project has moved past the question of whether Tunkillia holds enough gold and into the question of where to put the mine.

The resource work that preceded this was substantial. Combined Phase 1 and Phase 2 drilling reached 520 holes and 57,653 metres before the sterilisation phase began. A broader campaign of 60,000 m of reverse-circulation drilling and 3,000 m of diamond drilling is now running in parallel, feeding the PFS being led by GR Engineering Services toward its Q1 2027 target.

For an investor tracking Tunkillia on the development curve, that parallel activity is the signal. Site-layout decisions and study work are advancing together, which is what a credible PFS timeline looks like from the outside.

Why the Environmental Scoping Report approval matters alongside the drilling

The Environmental Scoping Report is an early formal step in South Australia’s assessment process, not a final tick. It sets the terms for the more detailed environmental work that comes later.

Mining permit sequencing in South Australia follows a structured pipeline where each approval stage sets the evidentiary requirements for the next, which is why the Environmental Scoping Report approval functions as a gating milestone rather than a standalone tick.

The connection to the drilling is direct. The infrastructure siting data that sterilisation holes generate will feed straight into the later, more rigorous environmental impact documentation. In other words, the drilling and the permitting are not separate tracks; the first supplies evidence the second will require.

New high-grade zones confirmed: what the latest assay results add to the resource picture

Two assay releases in three weeks tell a story of escalating confirmation.

The first came on 31 August 2026. Barton reported an intercept of 6 m at 6.61 g/t Au from 70 m, including a standout 1 m at 32.4 g/t Au from 73 m. Strong, shallow, and within the areas already earmarked for early mining.

The second, on 16 September 2026, went further. It confirmed a new high-grade zone in the shallow, central portion of the existing starter-pit outlines, with individual samples reaching 36.9 g/t Au.

That location is the part worth pausing on. The zone sits above mineralisation already built into the current model, which means it was not anticipated in the resource estimate as it stands today.

Managing Director Alex Scanlon has characterised the Phase 2 results as delivering unexpected upside in certain zones.

Infill drilling continues to “surprise to the upside,” confirming a new high-grade zone within the shallow, central portion of the existing high-value starter-pit outlines.

Here is what the two releases look like side by side.

The current Tunkillia mineral resource estimate stands at 1.6 Moz Au and 3.1 Moz Ag under JORC 2012, dated March 2025, up roughly 120,000 oz of gold from the prior figure. Phase 2 alone comprised around 39,000 m across 311 holes, all aimed at the shallow starter-pit areas.

The JORC 2012 resource reporting standards establish the classification framework that governs how Tunkillia’s 1.6 Moz Au estimate is categorised into Inferred, Indicated, and Measured confidence levels, with independent competent person sign-off required before any ASX disclosure.

No updated resource estimate has been published since March 2025. That makes the next estimate a live catalyst, and it is why these September assays matter to you as a directional read. A high-grade zone confirmed above the modelled starter pits suggests the starter-pit economics in the scoping study may be conservative. The starter pits are the earliest cash-generating piece of the plan, so any upward revision to their grade profile has an outsized effect on early payback.

Scoping study economics in context: what the A$1.4 bn NPV assumes and what could change it

The headline numbers are the reason Tunkillia draws attention. The May 2025 Optimised Scoping Study modelled a 5 Mtpa open-pit operation producing around 120,000 oz of gold a year, and the core metrics read strongly:

• Net present value: A$1.4 bn (pre-tax, 7.5% discount rate)
• Internal rate of return: 73%
• Capital payback: approximately 0.8 years
• Life-of-mine revenue: A$4.8 bn
• Life-of-mine operating cash flow: A$2.7 bn

– The near-term engine is the pair of starter pits, S1 and S2. Together they are modelled to produce 365,000 oz of gold and 923,000 oz of silver over an initial 27-month window, generating roughly A$1.7 bn in operating free cash. That is the fast-payback story in one line.

Now the assumption behind it. The study modelled revenue at A$5,000/oz gold and optimised the pit at A$3,500/oz. As of 19 September 2026, the live Australian spot price sat at A$6,133.62/oz, per the Melbourne Gold Company. That is more than A$1,100/oz above the study’s revenue assumption, which is supportive, though it is not a price you can bank across a multi-decade mine life.

Australian gold price dynamics, including the currency effect that amplifies AUD-denominated returns when the US dollar strengthens, are a structural tailwind that scoping studies priced at A$5,000/oz may materially understate at current spot levels.

Just how much that assumption matters is captured by Edison Investment Research.

Edison found that raising the gold-price assumption to A$5,000/oz increased the pre-tax project NPV7.5 by 176.6% and pushed the IRR above 73%.

That is the leverage embedded in the project. It cuts both ways: a materially lower long-term gold price would compress the same figures just as sharply.

Edison’s own risk-adjusted number is the more sober benchmark. After applying discounts for stage of development, sovereign risk and commerciality, it derived a post-tax NPV of approximately A$895.9 m, or about A$4.09 per share. An October 2025 Edison note suggested Tunkillia alone could support around A$1.44 per Barton share, reinforcing its status as the company’s primary value driver.

The read for you is this. With spot running well above the study assumption, the headline NPV probably understates the economics at today’s prices, but the gap between a scoping study and a funded mine is exactly where cost inflation, capital-market conditions and permitting timelines do their work. TradingView commentary from 16 September 2026 made the same point: an MRE upgrade and a PFS showing improved economics are what would turn Tunkillia into a stronger near-term share-price catalyst.

Risks that sit between the scoping study and a producing mine

Treat the A$1.4 bn figure as a directional indicator for a scoping-stage project, not a number that survives unchanged to first gold. The distance between the two is where the risk lives.

Start with the study-to-reality gap. Scoping-study economics routinely shift through PFS and Definitive Feasibility Study (DFS) work as geotechnical, metallurgical and cost-inflation realities get incorporated. Industry precedent shows IRRs and payback periods tend to compress as contingency and more conservative assumptions are applied. Edison’s move from an unadjusted A$1.4 bn to a risk-adjusted A$895.9 m is that discipline made explicit.

Scoping study revisions at comparable ASX gold projects show how production-target upgrades and grade improvements can materially shift IRR and NPV figures between study iterations, a pattern relevant to reading Tunkillia’s Phase 2 assay results as directional signals ahead of the PFS.

The gap between scoping-study and PFS numbers is a documented feature of mine development: feasibility study economics routinely tighten as geotechnical, metallurgical and cost-inflation inputs replace the broader assumptions that underpin early-stage modelling.

The permitting pipeline is honest work still ahead. The Environmental Scoping Report is an early milestone, and the sequence that follows carries schedule uncertainty. The main steps still to clear:

1. Updated mineral resource estimate
2. PFS publication, targeted for Q1 2027
3. Full environmental impact assessment
4. Mining lease application, expected after the PFS
5. Capital raise
6. Construction decision

– For context on pace, Australian gold projects typically take four to seven years from first scoping-study economics to first production, even with strong numbers and a clear permitting path. Tunkillia’s timeline should be read in years and capital-raising events, not quarters.

One analyst data point circulating from an Investing.com item carried a speculative buy classification and an implied target of around A$2.05/share against a then-prevailing price near A$1.08. Treat that as illustrative of analyst sentiment rather than verified guidance; it should not anchor a view on its own.

Funding and cost escalation as the twin variables to watch

The funding question is specific to a junior developer at pre-PFS stage. There is no binding offtake, no construction finance in place, and a development cost base that has not yet been audited to DFS standard. Executing a 5 Mtpa open-pit operation requires substantial capital that Barton has yet to raise.

Cost escalation is the second variable. Inflation across Australian mining services, processing equipment, energy and labour has been a documented feature of the sector, and scoping-study capital estimates are subject to revision. Both variables sit outside the drill results, and both will shape the final economics.

What the Q1 2027 PFS needs to confirm for Tunkillia to move to the next tier

The PFS is the document that decides whether the scoping-study economics survive contact with harder engineering assumptions. It is the threshold Tunkillia must clear to be judged a fundable project rather than a compelling development story.

To do that, the study, led by GR Engineering Services, needs to pull several inputs together:

1. Phase 2 drilling results
2. Sterilisation drilling findings
3. An updated mineral resource estimate, ideally lifting ounces into Measured and Indicated categories
4. Geotechnical data
5. Metallurgical test work
6. Updated capital and operating cost estimates

– The prospective milestone sequence that follows sets your expectations for timing.

Knowing what the PFS must contain changes how you will read it when it lands. If it validates the Optimised Scoping Study economics with more rigorous inputs, it is a genuine de-risking event and the trigger for a mining lease application. If it revises the numbers down or flags further work, it is a study that keeps the project in the queue rather than moving it forward.

What investors are watching before the PFS lands

Barton has confirmed a great deal in a short window; the near-term calendar is what will resolve the remaining uncertainty. Four events sit on the watchlist between now and the PFS:

• Remaining Phase 2 assay results
• The updated mineral resource estimate (no confirmed date)
• Sterilisation drilling outcomes feeding into PFS mine design
• The Q1 2027 PFS publication itself

– The convergence of sterilisation drilling, high-grade assay confirmation and Environmental Scoping Report approval in a single month tells you Barton is executing across several workstreams at once. That is the behaviour you would expect from a team serious about a Q1 2027 deadline.

The macro backdrop helps. At above A$6,100/oz, current Australian gold prices sit well above the study’s A$5,000/oz revenue assumption. But the development clock is driven by study and permitting milestones, not the gold price. Tunkillia is Barton’s primary value driver, anchoring 1.6 Moz Au of a 2.2 Moz Au and 3.1 Moz Ag portfolio, and the PFS is the next real de-risking gate. The post-PFS step, a mining lease application, is where the funded-mine question genuinely begins.

This article is for informational purposes only and should not be considered financial advice. Investors should conduct their own research and consult with financial professionals before making investment decisions. Past performance does not guarantee future results. Financial projections and forward-looking statements are speculative and subject to market conditions, commodity-price movements, permitting outcomes, and various risk factors.