Northern Star made eight discoveries over the past 12 months, increasing total resources by 44% to 8.9Moz and total reserves by 26% to 1.5Moz.

Importantly, the new resource estimate contains a 42% increase in the measured and indicated category, taking that total to 4.4Moz and underpinning growth in mine lives.

Much of the increased inventory is at the Jundee and Kalgoorlie operations, though Northern Star has also more than replaced the 622,000oz produced at Paulsens and Plutonic during the year.

Northern Star managing director Bill Beament said the results proved exploration as the most cost-effective way to grow assets value, with the additional resources to come at a cost of $19/oz.

“These figures more than justify our decision to invest $50 million in exploration over the past year,” he said.

“The simple fact is we would never be able to acquire resources and reserves at anywhere near that price.

“Growth through exploration unquestionably delivers shareholders superior returns.

“The economics of this strategy are even more attractive when it is remembered that each new ounce allows us to further leverage our existing infrastructure.”

At Jundee, where total resources increased by 59% to 1.35Moz, drilling has discovered high-grade mineralisation to 500m below the existing resources, with hits of 2.1m at 17.1 grams per tonne, 4.1m at 8.7gpt and 0.9m at 19.4gpt.

In light of these results, Northern Star will spend $17 million to build a 2.4km-long exploration drill drive to provide access for further testing of these structures.

At Kalgoorlie, total resources rose by 71% to 3Moz. The increase stemmed largely from a series of six stand-alone discoveries, including Kundana and Kanowna Belle, five of which are yet to be the subject of resource estimates.

Looking ahead, Northern Star expects to produce 535,000-570,000oz at an all-in sustaining cost of $1050-$1100/oz.

The slightly lower production forecast, which compares with the 581,000oz produced in the past financial year, reflects mine schedules designed to optimise asset base and sustain long-term production rates.

Beyond this year, scheduling is expected to change to reflect the start of production at the Central Tanami project and further additions from exploration.

Northern Star said it would spend another $35 million on exploration this financial year.