Greatland Resources Ltd (AIM:GGP, OTC:GRLGF, FRA:G8G, ASX:GGP) has outlined a potentially significant southern extension to its West Dome Underground (WDU) system at Telfer, after a deep step-out drill hole at the Pinnacles prospect returned one of the strongest intercepts recorded from the project to date.
The company said a 1,858-metre diamond hole drilled from surface intersected 58.7 metres at 6.5 g/t gold and 0.1% copper from 1,754 metres, including 37 metres at 9.98 g/t gold and 0.14% copper, approximately 1.2 kilometres south of the current WDU mineral resource.
The result strengthens Greatland’s view that the key geological structures and stratigraphy hosting mineralisation at WDU continue further south beneath the West Dome area at the Telfer operation in Western Australia’s Paterson Province.
Pinnacles hole WRC15403A showing intercepts and Telfer shaft on interpreted geology with LLU in orange (200m+/- clip).
Managing director Shaun Day described the results as “among the best intercepts achieved from West Dome Underground drilling to date”.
“While the result is a single drill hole, it demonstrates the potential extension of West Dome Underground mineralisation to the south of our current resource,” he said.
The Pinnacles prospect sits around 1 kilometre south of the West Dome Open Pit and about 1.5 kilometres from Telfer’s existing underground crusher and hoist infrastructure, a factor Greatland said materially enhances the area’s development potential.
Pinnacles drilling location with respect to existing WDU resource and underground infrastructure - isometric view looking NNW.
Deep drilling confirms geological model
The drill hole, WRC14503A, was designed to test whether the geological structures and mineralised units recognised at WDU extended further south along the West Dome anticline hinge.
Greatland said the hole intersected the target stratigraphy within roughly 10 metres of the predicted position after drilling to around 1,750 metres downhole, reinforcing confidence in the company’s geological interpretation.
The high-grade interval is interpreted to correlate with the Lower Limey Unit (LLU), the same sulphide replacement horizon hosting much of the current WDU resource. Additional mineralisation was also encountered lower in the hole within a stockwork corridor interpreted as an extension of the WDU Western Stockwork Corridor.
West Dome Underground December 2025 Mineral Resource isometric view.
A further intercept of 34.1 metres at 1.1 g/t gold from 1,820 metres extended mineralisation deeper into the system, with weaker gold continuing to the end of hole at 1,858 metres.
Importantly, Greatland said the mineralisation remains open both north towards the existing WDU resource and south into entirely untested ground.
Core photos of top of mineralised section from 1,757.75m downhole to 1,782.2m showing the massive sulphide zone (red line) and the stockwork mineralisation in sediments (blue line). Core is laid out top to bottom then left to right.
Building on maiden WDU resource
The drilling update follows Greatland’s maiden WDU mineral resource estimate announced in March 2026, which outlined 8 million tonnes at 2.30 g/t gold and 0.44% copper for 600,000 ounces of gold and 35,000 tonnes of copper.
Telfer December 2025 Mineral Resource schematic, showing location of Pinnacles drill hole and closest historical intercepts.
WDU emerged as a priority exploration target during Greatland’s due diligence work ahead of its acquisition of Telfer, with the company accelerating drilling from underground positions throughout 2025 after taking ownership of the operation.
To December 2025, Greatland completed nearly 19,000 metres of drilling at WDU, confirming the continuation of key mineralised geological units already recognised in the historic Main Dome Underground system.
The broader Telfer-Havieron hub remains central to Greatland’s long-term growth strategy following its transition into mine ownership. Strong March quarterly results showed record cash generation as elevated gold prices boosted margins and strengthened the company’s balance sheet.
Existing infrastructure provides development advantage
Greatland highlighted the strategic advantage of Pinnacles’ proximity to Telfer’s existing underground infrastructure, including a crusher and hoist system capable of handling about 6 million tonnes per annum.
The infrastructure, originally developed for the Main Dome Underground operation, is currently operating well below installed capacity, with current mining rates around 1.2 million tonnes per annum (Mtpa).
The company said the existing shaft, pumping systems, ventilation network, power infrastructure and paste plant could all support future mining operations at WDU and potentially Pinnacles, reducing development intensity compared with a standalone underground project.
Follow-up drilling planned
Greatland is now planning at least three wedge holes from the existing drill hole to test mineralisation 50 to 100 metres along strike and down dip.
The company is also considering additional surface drilling between Pinnacles and the current WDU resource to assess continuity across the 1.2-kilometre gap and evaluate the potential for future resource growth further south.
The results continue to reinforce the scale potential emerging beneath the Telfer district, where Greatland controls both the operating Telfer mine and the adjacent Havieron gold-copper development project.