TORONTO (miningweekly.com) – Canadian copper producer Capstone Mining has extended the mine life of its largest mine, the Pinto Valley operation in Arizona, more than doubling the mine life to 23 years and increasing throughput by 8% without any major capital investment.

The TSX-listed miner on Monday released the results of an updated prefeasibility study (PV3) on the Pinto Valley operation, outlining a more-or-less similar mine plan as previously envisaged, but with increased throughput rates and adding 13 years to the mine life, which will end in 2039.

“The mine plan calls for relatively higher grade in 2016 and 2017 with low sustaining capital requirements, resulting in a C1 cost, including capitalised stripping, ranging from $1.90/lb to $2.00/lb of copper and all-in costs (AIC) ranging from $2.10/lb to $2.20/lb of copper in those years," stated president and CEO Darren Pylot.

"The grade profile allows us to weather the current copper price environment and the mine plan gives us significant flexibility, with the next major decision point being to advance the first PV3 pushback in 2020. Our focus will continue to be on process improvements, with significant leverage to the upside when copper prices improve,” he continued.

Key outcomes of the study included a revised mineral statement that comprised an increase in proven and probable reserves to 473.8-million tonnes grading 0.31% copper, which could support yearly output of copper in concentrate at 122.8-million pounds of copper and 1.9-million pounds of molybdenum.

Mill output would rise to 20.4-million tonnes a year in 2017, from 19.8-million tonnes in 2016, through improvements in maintenance and operational practices.

The company advised that extending the mine life to 2039 from 2026 would require: revisions of two significant permits, including the aquifer protection permit, issued by the Arizona Department of Environmental Quality to expand an existing tailings facility and permit a new mine waste-rock storage facility; an amendment to the plan of operations, issued by the US Forest Service and related to expanding the tailings storage facility; mine expansion; and outstanding permit renewals.

Capstone also announced on Monday that it expected Pinto Valley to produce 63 000 t of copper this year, at AIC of $2/lb to $2.10/lb.

In 2016, Capstone expected to produce 108 000 t of copper from its Pinto Valley, Cozamin and Minto mines. Consolidated output from 2017 to 2020 was expected to average between 70 000 t/y and 85 000 t/y of copper.

Copper miners had been under pressure as the price of the red metal dropped significantly in recent months, trading on Monday below $2/lb.