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SolGold outlines new copper-gold-silver block cave mine plan at Alpala

SolGold has laid out plans to develop a mine at its majority-owned Alpala copper-gold-silver deposit, in northern Ecuador, that will use block cave mining methods applied over several caves designed on two vertically extensive lifts.

The preliminary economic assessment on Alpala estimated a pre-production capital expenditure of $2.4-2.8 billion for a mine that could produce 150,000 t/y of copper, 245,000 oz/y of gold and 913,000 oz/y of silver in concentrate over the life of mine.

The PEA stated a post-tax net present value (8% discount) of $4.1-4.5 billion based on an average $3.30/lb ($7,275/t) copper price, $1,300/oz gold price and $16/oz silver price depending on a 40-60 Mt/y throughput rate.

As part of the PEA, four mine production cases were pre-selected and assessed. This included a 40 Mt/y option over a 66-year mine life, a 50 Mt/y blueprint with a staged ramp up and a 57-year life, a 50 Mt/y fast ramp-up plan with 55-year life and a 60 Mt/y route with 49-year life.

Unit C1 operating costs over the life of the mine were estimated at $0.90/lb copper after gold and silver credits using the 50 Mt/y, fast ramp-up plan.

Resources scheduled in the PEA block cave designs accounted for 2.4 Bt at 0.54% CuEq ROM grade.

SolGold said the prefeasibility study is expected to be completed in December 2019 with a definitive feasibility study scheduled for completion at the end of 2020.

SolGold CEO, Nick Mather, said: “The unusually low operating costs modelled are due to the relatively soft, fractured nature of the ore, resulting in enhanced caveability, a high degree of fragmentation in the cave and ease of crushing and millability, combined with low hydroelectric (consumption and unit) costs. The overall scale efficiencies also assist in the delivery of modelled low operating costs.”

Metallurgical work at Alpala, which is ongoing, indicates gold contents in the pyrite concentrate will require additional investigation to identify an efficient recovery strategy, SolGold said.

Additional metallurgical work is expected to identify solutions for recovery of gold and copper in the pyrite concentrate along with a sulphuric acid product.

Over the period to the end of 2019 when SolGold aims to complete the prefeasibility study, activities will focus on exploration, a new mineral resource, metallurgy and process design, investigation of further tailing disposal options and incorporation of further geotechnical and hydrogeological data into the PFS basis, SolGold said.

SolGold will also commence permitting and fiscal discussions with the Ecuador Government and financial discussions with third party financiers for SolGold’s share of the project costs following completion of the FS.