FireFly Metals (ASX:FFM) completed the preliminary economic assessment for the restart of production at the Green Bay Ming Mine copper-gold project in Canada, according to a Tuesday Australian bourse filing.

The assessment considered two production scenarios, a 1.8 million tonnes-per-annum (tpa) base case and a larger 4.6 million tpa alternative. The base case scenario resulted in an after-tax net present value of around AU$2.2 billion and an internal rate of return of 42% over an initial around 32-year mine life. This showed annual projected average production of 50,000 tonnes of copper-equivalent metal over a 14-year period at steady state after ramp-up to peak at 60,000 tonnes of copper-equivalent metal per annum.

The alternative scenario resulted in an after-tax net present value of around AU$3 billion and internal rate of return of 40% over an initial around 22-year mine life, with annual projected average production of around 90,000 tonnes copper-equivalent metal over 11 years at steady state.

The project is now underpinned by a revised independent mineral resource estimate of 60.2 million tonnes at 2.4% grade of copper-equivalent in the measured and indicated resource categories and a further 23.5 million tonnes at 2.5% grade of copper-equivalent of inferred mineral resources.