Copper-in-concentrate production by Mongolian miner Oyu Tolgoi in the fourth quarter of 2017 surged 22.8% from Q3 to 45,300 mt, thanks to operational records set for open-pit mining and concentrator throughput, as well as higher grades and improved mill availability, parent company Turquoise Hill said in its annual report Friday.

The open-pit mine in Q4 extracted 28.929 million mt of ore, up from 27.466 million mt in Q3, its data showed. Oyu Tolgoi also produced 35,000 oz of gold-in-concentrate in Q4, down 12.9% from Q3, and 285,000 oz of silver-in-concentrate, down 19.2% from the previous quarter.

For full-year 2017, Oyu Tolgoi produced 157,400 mt of copper-in-concentrate, down from 201,300 mt in 2016.

Its 2017 gold-in-concentrate output was 114,000 oz, down from 300,000 oz in 2016, while silver-in-concentrate output fell to 974,000 oz from 1.42 million over the same period.

Oyu Tolgoi sold 149,300 mt of copper-in-concentrate in 2017, down from 188,900 mt in 2016. Sales of gold-in-concentrate fell to 111,000 oz in 2017, from 347,000 oz the previous year, while silver-in-concentrate sales fell to 860,000 oz, from 1.28 million oz over the same period.

In Q4, the miner sold 35,700 mt of copper-in-concentrate, down 3.3% from Q3, 27,000 oz of gold-in-concentrate, down 6.9% from the previous quarter, and 205,000 oz of silver-in-concentrate, down 10.5% from Q3.

For 2018, Oyu Tolgoi is targeting production of 125,000-155,000 mt of copper and 240,000-280,000 oz of gold in concentrates.

Located in the South Gobi region, Oyu Tolgoi is expected to be the world’s third-largest copper mine at peak production in 2025. Copper output is expected to rise by more than 340% between 2018 and 2025 when the Hugo North underground block-cave mine Lift 1 reaches peak production, it said.

Average output from 2025 to 2030 is expected at over 550,000 mt/year of copper.

Meanwhile, Turquoise Hill expects any force majeure-related sales impact to be made up over the next few quarters.

Oyu Tolgoi posted a revenue of USD 939.8 million in 2017, down from USD1.20 billion in 2016 on lower sales volumes partially offset by higher copper prices.