Tanami Gold JV Locks in $38M Macmahon Deal to Unlock 400koz at Groundrush
Key Takeaways
- The Central Tanami Project Joint Venture (50% MGX, 50% Tanami Gold) has signed a $38 million contract with Macmahon Underground to construct the Groundrush underground decline, with portal works commencing September 2026.
- The 3.5km decline will reach approximately 350 metres depth over a 14-month construction period, providing underground drilling platforms for around 33,000 metres of resource definition drilling.
- The primary objective is converting 400,000+ ounces of Inferred Resources to the higher-confidence Indicated category — the geological standard required to support mine design and a credible development decision.
- The CTPJV's total Mineral Resource stands at 2.8 million ounces at 2.8 g/t Au (JORC 2012), with the Groundrush deposit alone accounting for 1.2 million ounces at 3.3 g/t Au.
- Resource conversion data from the decline drilling program feeds directly into the joint venture's targeted 2027 development decision for what management describes as a major new gold business in the Northern Territory.
MGX signs $38 million Macmahon decline agreement to unlock Groundrush gold
MGX Resources has secured a major underground development contract at its Northern Territory gold project. The Central Tanami Project Joint Venture (CTPJV) — owned 50% by MGX and 50% by Tanami Gold NL (ASX:TAM) — has signed a $38 million agreement with Macmahon Underground Pty Ltd, a subsidiary of Macmahon Holdings Limited (ASX:MAH), for construction of the Groundrush underground decline. On-surface works are already underway, with portal construction scheduled to commence in September 2026. This marks a key step toward the joint venture’s targeted development decision in 2027.
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Inside the Groundrush decline agreement
The contract with Macmahon is valued at approximately $38 million and covers portal and vent establishment plus the initial 3.5km of decline development to a depth of around 350 metres. The construction period is scheduled for 14 months.
The decline will provide underground drilling platforms to enable approximately 33,000 metres of resource definition (infill) drilling to a depth of around 650 metres. The objective is to convert over 400,000 ounces of Inferred Resources to the higher-confidence Indicated category — a requirement for mine design and development. Infill drilling is expected to commence towards the latter stages of the 14-month decline construction period.
| Parameter | Detail |
|---|---|
| Contract Value | ~$38 million |
| Contractor | Macmahon Underground Pty Ltd (ASX:MAH subsidiary) |
| Decline Length | 3.5km |
| Target Depth | ~350 metres |
| Construction Period | 14 months |
| Planned Drilling | ~33,000 metres |
| Target Conversion | 400,000+ oz Inferred → Indicated |
The bigger resource picture at Central Tanami
The CTPJV’s total Mineral Resource Estimate (JORC 2012) stands at 31.0 million tonnes at 2.8 g/t Au for 2.8 million ounces of contained gold. Within this, the Groundrush Gold Deposit accounts for 11.0 million tonnes at 3.3 g/t Au for 1.2 million ounces of contained gold.
This resource estimate was detailed in the company’s “Central Tanami Gold Project Mineral Resource Update” dated 11 November 2025. For you as an investor, this context matters: Groundrush represents the core asset within a multi-million-ounce resource base, and converting Inferred ounces to Indicated status de-risks the path to development by providing the geological confidence required for mine design.
Why resource conversion matters for investors
Under the JORC Code, mineral resources are classified by geological confidence. Inferred Resources represent mineralisation where data spacing and geological understanding are sufficient to estimate tonnage and grade, but not to support detailed mine planning. Indicated Resources carry higher confidence — closer drill spacing and better geological continuity — and are required for mine design and development decisions.
Building a decline provides underground access to drill systematically from platforms at depth, tightening the drill spacing and upgrading the geological confidence. Converting 400,000+ ounces from Inferred to Indicated is what supports a credible development decision in 2027. Without this conversion, the resource remains conceptual rather than mine-ready.
Other activity across the CTPJV site
Beyond the Groundrush decline, the joint venture is advancing several supporting workstreams:
- Jims Gold Deposit: Resource definition drilling recommenced in June 2026. Jims was previously mined approximately 25 years ago and offers potential as an expanded open-pit ore source to supplement Groundrush mineralisation. The current Mineral Resource Estimate for Jims totals 2.6 million tonnes at 2.7 g/t Au for 220,000 ounces of contained gold.
- Accommodation camp and utilities: Considerable repairs and improvements are underway to support upcoming activities.
- Infrastructure clean-up and repair: The site team is working to restore other infrastructure assets necessary for planned operations.
- Recruitment: Key site and project roles are being filled to support the development timeline.
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What comes next
Macmahon is scheduled to mobilise to site in September 2026 for commencement of in-pit portal construction activities. The 14-month decline build will provide access for underground drilling in the latter stages of the construction period. The resource conversion data will feed directly into the targeted 2027 development decision, building momentum toward what management describes as “establishing a major new gold business in the Northern Territory.”
Peter Kerr, MGX Chief Executive Officer
“The commencement of the Groundrush decline represents a key milestone in the CTPJV’s efforts to advance the project to a development decision and ultimate production.”
“We and our joint venture partner, Tanami Gold, look forward to sharing regular updates as we build momentum towards establishing a major new gold business in the Northern Territory.”
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