Mining of the Sabodala open pit is carried out by owner-operated conventional truck and shovel open pit mining.
The mine plan uses two cut-off grades for production assumptions. The higher cut-off grade is used to define material that can be treated economically in the plant at the time of production, whereas the material above the incremental cut-off grade will be mined and stockpiled and, depending on the economics of production at the time, will be treated at the end of the mine life.
The mining schedule is driven by balancing the truck hours required to deliver ore to the Run of Mine (“ROM”) pad and waste to the dumps annually in concert with the loading capacity. Ore in excess of process plant requirements is selectively stockpiled throughout the life of the operation.
To date, the ore treated by the Sabodala processing plant has been sourced from Sabodala, Masato, Gora, and Golouma.
The gold is recovered in the 89%-92% range with an average grind of 80% passing 75μm. There is potential for additional recovery and performance improvement with installation of a gravity circuit. The gold extraction process uses a conventional carbon-in-leach (“CIL”) flowsheet. The major equipment comprises of two stage crushing with a primary jaw and secondary cone crushing system. This is followed by one SAG mill transferred into a return pebble crusher, sizer by cyclone and two ball mills. During the leaching process, the gold leaches into solution in leach tanks when in contact with cyanide, then absorbs onto the carbon to liberate gold from the ore before being captured with the activated carbon. After elution and electrolysis, the gold is recovered by fusion and poured into doré bars.
The Sabodala processing plant was expanded in late 2012 to a design capacity of approximately 3.5 Mtpa (fresh ore) and 4.0 Mtpa with a mix of fresh and oxidized ore.
Mill Optimization Project
A mill optimization project was launched in mid-2015, which will add a second primary jaw crusher, screen and conveyor assembly to tie into our existing facility when it is completed in the fourth quarter of 2016.
Basic engineering for the mill optimization was completed in the first quarter of 2015 to finalize the design, layout, material quantities, procurement packages and an execution plan for construction.
Upon completion and ramp-up, the mill optimization is expected to increase throughput by up to 15% on an annualized basis for fresh ore; however, there may be potential to increase throughput further based on optimization of the grinding circuit once steady state has been achieved. In addition to higher production, unit processing costs are expected to decrease by approximately 5 percent. As of mid-2016, the project remains on schedule for completion in the third quarter 2016 with commissioning and full ramp up during the fourth quarter 2016.
For further details on the Company’s mineral processing activities, please refer to Chapters 13 of the Sabodala Technical Report.
The Sabodala mine generates its own power which is sourced from a 30 MW heavy fuel oil power station with an additional reserve of a 6 MW unit. The mine has ample water supply drawn from two dams with a combined capacity of approximately 11 million cubic metres, which can also be supplemented if required from water sourced via a pipeline from the Faleme River.