Antofagasta reported copper production in the fourth quarter of 2017 fell 1.3% to 177,800 tonnes compared to the previous quarter.
Higher production at Los Pelambres and the ramp-up of the Encuentro Oxides project offset lower production at Centinela Concentrates.
The slowdown in copper production in Q4 - versus the previous quarter - weighed on full year output.
Group copper production for the full year was 704,300 tonnes, in line with guidance but 0.7% lower than in 2016.
This was due to the impact of the expected lower grades at Los Pelambres and Centinela, which was offset by Encuentro Oxides coming into production in October and following the completion of the ramp-up at Antucoya in 2016.
Gold production was 40,500 ounces in Q4 2017, a 32.0% decrease on Q3 2017. For the full year production was 212,400 ounces, 21.6% lower than in 2016, reflecting lower grades and recoveries at Centinela.
Molybdenum production at Los Pelambres was 3,300 tonnes in Q4 2017. While output for the full year rose 47.9% on higher grades to 10,500 compared to the previous year.
Net cash costs were $1.36/lb in Q4 2017, a 15.3% increase compared with the previous quarter. This was primarily due to higher cash costs before by-products credits and the lower gold grade at Centinela and lower by-product revenue.
Group production in 2018 is expected to be in the range of 705,000 to 740,000 tonnes of copper, 190,000 to 210,000 ounces of gold and 11,500 to 12,500 tonnes of molybdenum.
Chief executive Ivan Arriagada said: 'Antofagasta had a strong year operationally. Copper production at 704,300 tonnes was in line with guidance and came in at a net cash cost of $1.25/lb.
'The new additions to our portfolio at Zaldivar, Antucoya and Encuentro Oxides now account for 25% of Group production, helping offset declines at our mature assets and providing Antofagasta with a platform for growth as copper prices recover,' Arriagada said.