Newmont president and CEO Tom Palmer said the expansion would further improve costs and extend the life of the mine.

"Building on the success of the first expansion completed in 2017, Tanami Expansion 2 will provide a platform to further explore the area's prolific mineral endowment and potentially extend the operation's mine life beyond 2040," he said.

"The Tanami district and Australia as a whole continue to offer significant value generating opportunities for our shareholders."

The expansion includes construction of a 1,460m shaft, additional capacity in the processing plant, and supporting infrastructure to enable profitable recovery of ore at depth to 2,140m below surface.

The shaft construction is already well underway.

The expansion will allow Newmont to access to the Auron deposit, discovered in 2008 below the Callie orebody, and the Federation and Liberator discoveries.

Deutsche Bank expects the project to add 100,000 ounces of gold per annum of production between 2023 and 2027.

While the company did not provide capital cost and schedule estimates, previous estimates were for capex of US$700-750 million and a construction time of 2-3 years.

Newmont will provide more information in December with the release of its long-term outlook.

Tanami has been in production since 1986, and has produced over 10 million ounces of gold.

The mine produced a record 505,000oz of gold last year to be Australia's fourth-largest gold operation.

Tanami is forecast to produce 500,000oz of gold this year at all-in sustaining costs of $705 an ounce.