In a market update yesterday, Oceana's chief executive Mick Wilkes announced the estimated mineral resource of the new Martha Underground Project, where there has so far been a total 30,777m of test drilling.
Oceana reported an increased total estimated indicated resource, up by 136% to 331,000oz of gold.
Mr Wilkes said recent exploration results had highlighted continued high-grade gold intersections at Waihi, just south of the Coromandel peninsula.
"Over the past two years, we've made prudent investments in extensively drilling out the mineralised structures beneath the Martha open pit," he said.
Success with the latest underground operation has prompted Oceana to speculate a 10-year life of mine extension could be in the offing.
Mr Wilkes said in that period Oceana had reported "dozens of significant drill intercepts" and a the growing resource had now culminated into the estimated 331,000oz.
"We'll continue to invest in our extensive drill programme from the two underground drill drives and have allocated a budget of over $US11million for 2019 to go with the $US8million planned spend for our newly discovered WKP prospect," he said.
At WKP, which is about 14.5km from Waihi, Oceana had reported an estimated initial resource of 234,000oz of gold in the estimated, indicated category.
Oceana Gold received its resource consent in February, and no parties filed appeals against it. Part of the proposed underground operation will be beneath Waihi township, which has been mined successfully in the past.
Mr Wilkes said the focus of drilling with six underground rigs and two surface rigs was balanced between growing the estimated gold resource and gaining data to support feasibility studies and mine planning.
Over the next 12 to 18 months Oceana would continue its exploration programme along the two underground drill drives to discover further resources.
Mr Wilkes said the Waihi vein system was extensive and the primary structures such as the Martha, Empire, Edward and Royal veins were "in-part well defined".
However, there were additional veins which were also returning high-grade gold intersections, he said.
