Full-year guidance was increased to 39,000-41,000 tonnes copper from the previous 37,000-40,000t after Riotinto produced a record 11,055t of copper in the September quarter, up 3.5% year-on-year.
The period was also the second straight quarter where output exceeded 10,000t, bringing the year-to-date production to 30,942t.
Atalaya's mining unit outdid itself as well, sending 2.8 million tonnes of ore for processing, a 16.7% year-on-year increase.
The average grade was 0.5% copper, down from 0.58% in the September 2017 quarter, while copper recovery jumped to 88.4% from 85.95% a year ago.
Riotinto had 2,725t in on-site inventory at the end of September.
Atalaya is planning to increase production in 2019 and had made additional mining equipment available on site in preparation.
It said its 15Mt per annum expansion project was on schedule, with progress at 65% at the end of September.
The expansion is scheduled for mechanical completion at the end of the June 2019 quarter.
Atalaya shares were up 1.67% Wednesday to £2.46 (US$3.24).
