Barrick's shrinking production profile could see output fall by 1.5m ounces within two years. World no 2 Newmont Mining forecasts 14% growth next year.
Plutonic is the highest-cost of Northern Star's five mines, producing around 79,000 ounces last financial year at an all-in sustaining cost of $1550 an ounce.
The permit marks another key step in the process of moving towards development of the 1.45 million carat diamond resource in the West African country, said the company.