OceanaGold (TSX, NYSE: OGC) is studying a 50% expansion of its Waihi processing plant in New Zealand after drilling some of Wharekirauponga’s richest holes yet, including 6.3 metres grading 97.2 grams gold per tonne.
The producer is assessing an increase to 1.2 million tonnes a year from 800,000 tonnes that could allow its existing Martha underground mine and Wharekirauponga to operate concurrently after the latter starts producing in 2032. The proposal is to be evaluated in an updated Waihi District technical report due in January.
“These results confirm further continuity and up-dip extension of the southern high-grade zone which currently lies outside of reported reserves, therefore representing outstanding conversion and growth potential,” President and CEO Gerard Bond said in a release Thursday.
Bond’s comments follow OceanaGold’s announcement Wednesday that he plans to retire in April after five years as CEO. Executive search firm Spencer Stuart has been hired to consider internal and external replacements. Bond plans to remain as a special adviser for six months after stepping down.
OceanaGold’s upcoming technical report is expected to include new resources and reserves, an updated mine plan and an assessment of extending Martha beyond 2033. Scotiabank analyst Ovais Habib called it a key catalyst, saying the combination of more processing capacity and a longer Martha mine life could boost Waihi’s long-term production and value.
OceanaGold shares fell 2% to $38.66 Thursday morning in Toronto, giving the company a market value of $6.05 billion.
Reserve growth
The standout 6.3-metre intersection in hole WKP146C started at 481.5 metres downhole in the East Graben vein. Hole WKP150 cut 8.5 metres grading 41.5 grams gold from 399 metres, while WKP146A returned 9.6 metres at 18.5 grams from 401 metres in hanging-wall veins. The widths are estimated true widths.
A separate WKP146C intersection cut 6.6 metres grading 24 grams from 403.4 metres, including 1.2 metres at 107.7 grams. The latest 16 holes continue to extend the southern high-grade zone up-dip, with mineralization still open along strike and at depth, the company said.
OceanaGold expects the drilling to support upgrading a substantial part of the southern zone from inferred to indicated resources and an increase in reserves in its year-end estimate. Five rigs are now operating at Wharekirauponga, up from three when the company reported its previous drill results in April.
A December 2025 resource lists 2.63 million measured and indicated tonnes grading 17.3 grams gold per tonne for 1.46 million contained oz., and 2.9 million inferred tonnes grading 8.5 grams for 800,000 oz. gold.
Bigger Waihi
The planned expansion would go beyond the 800,000-tonne annual plant capacity included in OceanaGold’s 2024 prefeasibility study. That plan assumed Martha would remain the main ore source until 2033 before Wharekirauponga took over, with commercial production from the new mine beginning that year.
The earlier study outlined 1.6 million oz. of payable gold over a 15-year Waihi District mine life through 2038, including peak production of 253,000 oz. in 2035. It gave Wharekirauponga an initial reserve of 4.1 million tonnes grading 9.2 grams gold for 1.2 million oz.
Keeping Martha running longer while Wharekirauponga ramps up would change that sequence and make fuller use of the expanded plant.
“The ability to concurrently mine and process ore from Martha Underground and Wharekirauponga could support higher long-term production, improved infrastructure utilization, and enhanced value generation from the Waihi District portfolio,” Scotiabank’s Habib said.
Construction advances
Development of Waihi North is already underway. The decline, started in May, has advanced about 350 metres, while construction of the first ventilation shaft has begun. OceanaGold plans to add a second jumbo in the first half of next year to start developing the twin tunnel towards Wharekirauponga.
The water treatment plant began staged commissioning this month and early work on a new tailings storage facility is scheduled for the fourth quarter. Surface facilities at the Willows portal remain on track for completion by year-end.
Wharekirauponga lies about 10 km north of Waihi on New Zealand’s North Island. The 2024 plan calls for about 6.5 km of underground development to reach the deposit.
OceanaGold is also in the process of acquiring Australia’s Ausgold, whose Katanning project is expected to add another growth asset to the company’s portfolio. The transaction is targeted to close in December.
