B2Gold said on Tuesday it had begun the phased closure of its Otjikoto gold mine in Namibia, once the country’s largest producer of the precious metal.

The mine, which began commercial production in March 2015, has reached the end of its open-pit gold resource, B2Gold said, adding it would gradually reduce its production until 2031, when it will cease operations completely.

Otjikoto’s production reached 161,614 ounces of gold last year, representing about 16% of B2Gold’s total output for 2022.

“B2Gold Namibia has commenced with the implementation of its Phased Mine Closure Plan at the Otjikoto mine. Phased downscaling of operations, in line with the closure plan, are only scheduled to commence during the first quarter of 2024,” a spokesperson told Reuters.

The last year of full open-pit mining production will be 2023, with output expected to be between 190,000 and 210,000 ounces of gold.

B2Gold noted it would continue to develop its underground mine at Otjikoto, which could extend the mine-life and replace some of the lost production from the open-pit operation.

The Canadian miner also has operations in Mali and the Philippines as well as exploration projects in Uzbekistan, Finland and Colombia.

It is also in the midst of acquiring Sabina Gold & Silver (TSX: BTO)(NYSE: BTG), a Canadian exploration and development company, which owns five high-grade gold projects in Nunavut. 

One of these projects, Back River, is expected to start producing gold in 2025 at an annual rate of 300,000 ounces for 15 years.