Turquoise Hill Resources Ltd.'s attributable net income in the fourth quarter of 2018 rose 97.7% year over year to US$101.0 million, from US$51.1 million in the year-ago period, according to a March 14 release.

Revenues for the quarter stood at US$346.2 million, up 37.5% from US$251.7 million in the prior-year period, due to higher gold revenue, driven by a substantial jump in gold production, partially offset by a decline in copper revenue.

Total operating cash costs for the company's Oyu Tolgoi mine in Mongolia came in at US$242.4 million, up from US$217.7 million a year ago, owing to higher freight and royalty costs.

All-in sustaining costs in the period were US$2.01/lb of copper produced, falling from US$2.05/lb produced a year earlier on stronger gold sales as well as higher head grades and recoveries.

Capital expenditures on a cash basis totaled US$371.8 million, rising 12.5% from US$330.4 million a year earlier, with the majority of the amount attributed to the underground expansion project at Oyu Tolgoi.

For the full year of 2018, the company's attributable net income surged 126.9% to US$411.2 million from US$181.2 million, reflecting the increase in gold revenue and lower unit costs of production.

Revenues, meanwhile, came in at US$1.18 billion, up 25.6% from US$939.8 million a year earlier. Capex totaled US$1.30 billion, up from US$917.5 million recorded in 2017.

As previously reported, Oyu Tolgoi is expected to produce 125,000 to 155,000 tonnes of copper and 180,000 to 220,000 ounces of gold in concentrates in 2019.

Turquoise Hill also recently flagged a delay in sustainable first production for the underground expansion at the mine as a result of potential mine design changes and a delay in construction work.