The Ahafo expansion, which was given government approval last year, was delivered on schedule and within budget for approximately US$186 million in development capital, the miner said.

The Ahafo mill expansion project, in turn, is expected to be completed in the second half of 2019.

Subika Underground is expected to add average annual gold production of between 150,000oz and 200,000oz per year for the first five years, and has an initial mine life of around 10 years.

Newmont CEO Gary Goldberg said: "In addition to increasing gold production and lowering costs at Ahafo, Subika Underground leverages the operation's existing infrastructure and experienced workforce to further extend mine life.

"The mine provides an underground platform to explore additional upside potential in adjacent ore bodies and also includes some of the latest fit-for-purpose technologies to enhance safety, productivity and efficiency."

According to Newmont, Subika Underground features semi-autonomous loading operations, proximity detection for vehicles, personnel tracking, and planned installation of ventilation-on-demand systems.