MGX’s Groundrush Decline Locks in $38M Macmahon Deal to Unlock 400koz Gold
Key Takeaways
- The CTPJV has executed a $38 million contract with Macmahon Underground to construct a 3.5km decline at the Groundrush Gold Deposit, with portal construction commencing in September 2026.
- The decline will unlock approximately 33,000 metres of underground resource definition drilling, targeting conversion of over 400,000 ounces from Inferred to Indicated classification.
- Groundrush holds 1.2 million ounces of the CTPJV's total 2.8 million ounce resource at 3.3 g/t Au, making it the primary value driver for the joint venture.
- Infill drilling is expected to commence toward the end of the 14-month construction period, with the JV targeting a full development decision in 2027.
- Concurrent workstreams include resource definition drilling at the Jims Gold Deposit (recommenced June 2026), site infrastructure repairs, and recruitment of key operational roles.
Tanami Gold locks in $38m Macmahon deal to build Groundrush decline
The Central Tanami Project Joint Venture (CTPJV) has signed a $38 million agreement with Macmahon Underground Pty Ltd, a subsidiary of Macmahon Holdings (ASX:MAH), to construct the Groundrush underground decline in the Northern Territory. Tanami Gold (ASX:TAM) holds a 50% interest in the joint venture, with MGX Resources (ASX:MGX) holding the remaining 50%.
On-surface works are already underway, with portal construction scheduled to commence in September. The move marks a major milestone in the JV’s push toward a development decision in 2027, with the decline providing the infrastructure needed to unlock over 400,000 ounces of gold currently sitting in the Inferred category.
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Inside the $38 million Groundrush decline agreement
The agreement was executed between CTP JV Pty Ltd (the JV management entity) and Macmahon Underground Pty Ltd. Macmahon’s scope includes portal and ventilation establishment plus the initial decline development at the Groundrush Gold Deposit.
Key contract parameters:
- Contract value: ~$38 million
- Initial decline length: 3.5km
- Target depth: ~350 metres
- Construction period: 14 months
- Portal construction start: September 2026
Surface works are already well underway ahead of Macmahon’s mobilisation. Preparation of laydown areas and the re-establishment of in-pit ramp access to the decline portal location are in progress, ensuring the contractor can hit the ground running when construction begins next month.
Why the decline matters — unlocking 400,000 ounces
The decline is the platform for a major resource conversion programme. Once constructed, it will provide underground drilling platforms enabling approximately 33,000 metres of resource definition drilling.
Drilling will target the Groundrush Gold Deposit to a depth of approximately 650 metres. The core objective: convert over 400,000 ounces currently classified as Inferred into the higher-confidence Indicated category for mine design and development purposes. Infill drilling is expected to commence towards the end of the 14-month decline construction period.
Converting Inferred resources to Indicated is the critical step that de-risks a project toward a development decision. Inferred resources cannot be used in mine feasibility studies or economic models. Indicated resources can. For investors, this programme is what turns a theoretical resource into a mineable, developable deposit.
The resource base behind the project
The CTPJV holds a substantial resource base across its Northern Territory tenements. The current Mineral Resource Estimate provides scale context for the decline programme and the broader development pathway.
| Deposit | Tonnes (Mt) | Grade (g/t Au) | Contained Gold (Moz) |
|---|---|---|---|
| Total CTPJV MRE (JORC 2012) | 31.0 | 2.8 | 2.8 |
| Groundrush Gold Deposit | 11.0 | 3.3 | 1.2 |
| Jims Gold Deposit | 2.6 | 2.7 | 0.22 |
Figures per Tanami’s 11 November 2025 Mineral Resource Update. The Groundrush deposit accounts for 1.2 million ounces of the 2.8 million ounce total resource, making it the primary value driver for the joint venture.
Understanding an underground decline
A decline is a spiral or ramp tunnel that provides access from surface into the orebody. It serves two critical functions: during development, it provides drilling platforms that allow the JV to drill from underground (closer to the deep mineralisation) rather than relying solely on surface drilling. Once the mine is operational, it becomes the primary access route for mining equipment and ore haulage.
Building the decline now matters because:
- It enables resource definition drilling from underground platforms, improving drill accuracy and reducing hole lengths.
- It de-risks the project by proving access and ground conditions ahead of a full development decision.
- It turns a resource estimate on paper into physical infrastructure that demonstrates the orebody is accessible and mineable.
For investors, this is the infrastructure investment that bridges exploration to development.
Beyond Groundrush — other work advancing across the site
The joint venture is progressing work on multiple fronts, not just the decline. Concurrent site activities include:
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Resource definition drilling at the Jims Gold Deposit: Drilling recommenced in June 2026. Jims was previously mined 25 years ago and holds a current Mineral Resource Estimate of 2.6 million tonnes at 2.7 g/t Au for 220,000 ounces of contained gold. The deposit offers potential as an expanded open pit ore source to supplement Groundrush mineralisation.
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Repairs and improvements to site infrastructure: Considerable work is underway within the old accommodation camp and utilities areas adjacent to the central plant site location. The site team is also working to clean up and repair other infrastructure assets necessary to support planned upcoming activities.
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Recruitment of key site and project roles: The JV is building out its operational team ahead of the ramp-up in on-site activity.
These parallel workstreams demonstrate the project is advancing on multiple fronts, not just waiting on the decline to be built.
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A milestone on the road to a 2027 development decision
The commencement of the Groundrush decline marks the start of the substantive works programme de-risking the Central Tanami Project. The JV is targeting a development decision in 2027, with the decline and infill drilling programme forming the core of that pathway.
Brett Smith, Tanami Executive Director
“The commencement of the Groundrush decline represents a key milestone in the CTPJV’s efforts in advancing the project .Working with our JV Partner, MGX, both companies continue to progress the project and the establishment of a major new gold operation in the Northern Territory.”
The announcement was authorised for release by the Board on 31 August 2026. The 50/50 joint venture structure with MGX Resources remains unchanged, with both parties advancing the project toward production.
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