Following the merger announced at the end of November 2021 of Capstone Mining (TSX: CS) and Chilean miner Mantos Copper, Capstone has filed 43-101 compliant reports for the two new mines in its portfolio – Mantos Blancos in the Antofagasta region and Mantoverde in the Atacama region.
Both mines are open pit copper producers formerly belonging to Mantos. Mantos Blancos produces 40,000 to 50,000 tonnes of copper in concentrates and cathodes annually. Mantoverde has a capacity of 60,000 tonnes of copper cathodes annually. Plans are in place to expand both operations.
At Mantos Blancos, sulphide ores are floated, and oxide ores are leached. Proven and probable reserves of sulphide ore total 122.6 million tonnes grading 0.69% copper and 5.66 g/t gold, containing 854,000 tonnes of copper and 22,307 oz. of gold. Proven and probable reserves suitable for dump leaching total 6.7 million tonnes grading 0.18% copper, containing 12,000 tonnes of copper.
To expand production at Mantos Blancos, a debottlenecking plan has been created. The project will raise daily throughput to 20,000 tonnes from 11,000 tonnes. In 2024, annual production will grow to 55,000 tones of copper at an all-in sustaining cost of $1.97 per payable pound. The estimated capital cost of $249 million is fully financed.
After debottlenecking, Mantos Blancos will undergo a phase two expansion using existing equipment and the dump leach to boost out put to over 80,000 tonnes annually by 2025.
The Mantoverde mine, which is 30% owned by Mitsubishi Materials Corp., produces copper by flotation of both sulphide and oxide ores and by heap and dump leaching oxide and mixed ores.
Proven and probable reserves of sulphide and mixed sulphide ores suitable for flotation total 235.7 million tonnes grading 0.6% copper and 0.11 g/t gold, containing 1.4 million tonnes of copper and 807,000 oz. of gold. Proven and probable reserves of leachable oxide ore total 255.6 million tonnes grading 0.24% copper, containing 617,000 tonnes of copper.
Expansion at Mantoverde includes building a new sulphide concentrator that will treat 236 million tonnes of ore over the 21 year life of the mine. The expanded plant will have an annual output of 122,000 tonnes copper in 2024 at an all-in sustaining cost of $1.64 per payable pound. Gold production will rise to 31,000 oz. per year. Again, the expansion is fully financed, thanks to the $846.6 million package arranged a year ago by Mantos.
When the merger of Capstone and Mantos closes, the expectation is that the combined company will operate under the name of Capstone Copper.
(This article first appeared in the Canadian Mining Journal)