Gatsuurt Mining & Milling
Mining of the Central Zone and the Main Zone will occur during two distinct phases. The initial phase involves the mining of those ores amenable to CIP processing including all the oxide ore and a portion of the transitional ore. Any ore not amenable to CIP processing would be stockpiled when mined. The mining program is planned with a 7.5 cubic metre shovel and a fleet of 50-tonne trucks to move the waste and ore. As Gatsuurt is approximately 60 kilometres (by road) from Boroo, the ores will be recovered from the Gatsuurt stockpiles and hauled to Boroo using road haul truck vehicles with 40-tonne haulage capacity. The mine is planned to operate 24 hours per day and seven days per week at a rate sufficient to ensure average processing of 4,800 tonnes of ore per day.
The second phase of mining is the pit development to expose and mine those ores not amenable to CIP processing but amenable to BIOX® processing. The mining rate and haulage rate will operate to support the average 4,800 tonnes per day milling rate at the modified Boroo processing facility.
Once project approvals have been received, the Gatsuurt CIP ores will be processed at the Boroo CIP facility. Approximately 24 months before the scheduled completion of mining and processing of the Gatsuurt CIP ores, construction will begin on the BIOX® plant, and associated infrastructure, in preparation of processing the Gatsuurt BIOX® ore.
The processing of the Gatsuurt BIOX® ores at Boroo will require modifications and additions to the Boroo facility. As the BIOX® ores from Gatsuurt require a finer grind, the instantaneous feed rate will be 5,200 tonnes per day (an average feed rate of 4,800 dry tonnes per day for 365 days per year) at a grind of 80% passing 75 microns. Following the grinding circuit, a flotation circuit composed of a rougher and scavenger circuit will be added to recover the sulphides and produce a concentrate with approximately 12% sulphide-sulphur and 7% of the original mass. The flotation concentrate will then report to the BIOX® circuit. Following oxidation of the sulphides and neutralization of the slurry, the oxidized slurry will then be leached with cyanide for 24 hours and the gold will be recovered on carbon in a new Kemix carousel CIP circuit. The slurry reports to the cyanide destruction circuit initially and then to the tailings management facility. Flotation tailings will report to a separate tailings management facility that will permit the recycling of process water to the mill facility.
An overall gold recovery of 76% (including gravity recovery) is projected for the oxide and non-refractory transition through the existing Boroo mill facility, and 87% total recovery (including gravity recovery) is projected for the refractory ores by the BIOX® treatment process.
With respect to the modifications to the Boroo mill, an engineering firm will be engaged to provide detail engineering, procurement and construction management services. Capital investments for phase 2 work are conditional on the receipt of the necessary permits and commissions for the BIOX® facility.