From an economic and preliminary sustainability development analysis, it was concluded that an underground mining scenario with onsite flotation of gold-bearing sulphides followed by concentrate pressure oxidation (“POX”) was the preferred mining and processing route. The crushing, grinding and sulphide mineral flotation will be carried out at a mill site located close to the mine site. The sulfide concentrate will be filtered and trucked to the POX site for pre-treatment and gold and copper extraction. The POX plant will be located near Guayaquil, 300 kilometres from the mill site.

Processing

A flotation process followed by off-site pressure oxidation (“POX”) of the concentrate has been designed based on a 3,000 tonne per day ore production profile over an eight year mine life. 78% of the total planned ore to be milled and the resulting tailings will remain at the mine site. 58% will be used as underground paste backfill and the remaining 20% will be deposited on surface in the form of thickened tails in secured containment facilities.

The ore will be processed at two sites: a mill and a POX plant. To process the material, the ore is trucked from the mine and discharged into a fixed grizzly to break coarse blocks; the ore is then fed to a jaw crusher. The crushed ore will be stored in two 1,500 tonne silos. Ore is extracted by two apron feeders. A SAG mill was selected for primary grinding. SAG overflow is discharged to a screen, with the screen oversize reporting back to the SAG mill feed. The screen undersize is pumped to the secondary grinding circuit. A ball mill was selected for the secondary grinding unit. The ball mill is in closed circuit with cyclones to produce a final grind size of 80% minus 70 µm. Cyclone underflow reports to the ball mill. Cyclone overflow is fed to the flotation circuit at a 35 % solids density.

The flotation circuit consists of rougher and cleaner circuits designed to reduce tonnage to be transported to the POX site. The rougher flotation will be carried out using 7 tank cells in series with a retention time of 60 minutes to allow for optimum sulphide mineral recovery. The two step cleaning stage will be carried out using ten 5 m³ cells for the first cleaner and six 5 m³ cells for the second cleaner. The cleaner concentrate is pumped to a thickener. The thickener overflow is recycled as process water in the grinding circuit. A regrind circuit is required to achieve a final grind size of 80% minus 40 µm. Flotation tailings are sent to a paste backfill plant. Concentrate is trucked from the mill site to the POX plant. At the POX site, the makeup will be supplied in the form of fresh water from the river and reclaim water from the tailings pond. For the pressure oxidation circuit, an autoclave was selected to leach iron and copper sulphides and liberate gold and silver. The concentrate received at the POX site is re-pulped and fed to the autoclave. The solution is sent to copper cementation and the slurry from CCD underflow containing precious metals to CIL. From the CIL circuit, loaded carbon is pumped to the stripping circuit to extract gold. The pregnant solution is sent to a refinery unit equipped with electro-winning and smelting. This final step results in the production of bullions with high precious metals content.