Officials confirmed that the operational life of Golden Sunlight, located 55km east of Butte in Jefferson County, has been winding down for some time; underground development has ceased there and management has limited mining only to existing areas.

While the mine's final mill run is currently scheduled for May, surface and underground exploration is ongoing at Golden Sunlight, with crews focusing on the southern extension of the Sunlight vein. Metallurgical test work and a structural geological model are also planned.

"Barrick will [also] be evaluating the potential to reprocess historic tailings, while conducting hydrological and geochemical studies to support ongoing water treatment and reclamation work as part of our commitment as responsible owners of the Golden Sunlight mine," the company said.

It will be reviewing its findings in the coming months, officials said, to determine its future plans for the mine.

Golden Sunlight, which sits at an elevation of 6,000ft (1,829m) in south-western Montana's Bull Mountain range, has been in operation since 1975. It produced 32,000oz of gold in 2018.