West African Resources has released the results of a feasibility study for its 90%-owned Kiaka gold project in Burkina Faso, heralding a potential open-pit mining operation that can support a processing plant throughput of 8.4 Mt/y.
Kiaka is 140 km southeast of Ouagadougou, and 45 km south of the company’s existing Sanbrado gold mine.
The Kiaka mining study is based on conventional open-pit mining methods, with run of mine ore being directly fed to the crushing circuit. Mining operations will use a combination of 140 t (Cat 6015) and 230 t (Cat 6020) hydraulic excavators matched to 95 t dump trucks (Cat 777s).
Drill and blast will be required from near surface, with the parameters selected based on the relatively hard rock mass qualities and the required selectivity for mining of the ore. Given the broad mineralised zone, a portion of the blasting will be able to be undertaken on 10-m benches with more selective zones blasted on 5-m benches, the company noted. As such a combination of top hammer (Sandvik Panterra DP1500) and downhole hammer (Sandvik Leopard DI650) capable blast hole rigs will be employed.
To achieve the targeted processing rate, a total material movement averaging 21 Mt/y is required for the first seven years of the production schedule. With the pit staging deferring waste movement, this increases to an average of 35 Mt/y for the next six years of production before reducing to an average of 15 Mt/y for the remainder of the mine life.
The production profile is suited to an initial fleet of 2 x 230 t excavators and 1 x 140 t excavator matched to 95-t class trucks. The fleet will increase to 3 x 230-t excavators with 2 x 140-t excavators for the higher production requirement. Further work to investigate bulk mining scenarios and optimise fleet selection will be conducted, with further refinement of the drill and blast parameters also being undertaken in conjunction with fleet optimisation.
Kiaka’s free-milling gold ore is intended to be processed through a conventional single stage gyratory crushing and semi-autogenous ball mill crusher (SABC) milling circuit followed by carbon-in-leach (CIL) processing. Extensive metallurgical test work indicates Kiaka will deliver life of mine gold recoveries of 90% at a nominal 100-micron grind size.
Following review of the option studies the company selected the following major equipment:
- Primary gyratory crusher – a Metso Outotec Superior™ MKIII 54-75;
- SAG mill – 18 MW; and
- Ball mill – 9 MW
The crusher can achieve 8.4 Mt/y for the design blend at 65% availability. At a 70% loading, the throughput rate ranges from 9.2 Mt/y to 10.2 Mt/y on the design blend. The selected mills also have higher than typical design margin for the nameplate throughput rate with modelling conducted by OMC showing the selected comminution circuit is capable of a throughput of:
- 8.4 Mt/y (1,050 t/h) for 100% fresh ore feed when the 80th percentile ore characteristics are used;
- 9 Mt/y (1,125 t/h) for 100% fresh ore when modelled at the average (50th percentile) ore characteristics;
- 14 Mt/y (1,750 t/h) for 100% oxide ore feed; and
- 10 Mt/y (1,250 t/h) for a blended feed of 23% oxide and 77% fresh ore.
On a 100% basis, life of mine (18.5 years) production is scheduled to come in at 219,000 oz/y of gold.
West African Executive Chairman and CEO, Richard Hyde, said: “Kiaka will access power from the Burkina Faso grid predominantly supplied by low-carbon hydroelectric power from Ghana and the Ivory Coast with large Burkina Faso low-carbon solar projects planned to come online early in the mine life to supplement the grid.”
Hyde says WAF will investigate expanding Kiaka to plus-10 Mt/y through the addition of secondary crushing and debottlenecking the process circuit, as well as evaluating tenders for key major equipment received during the feasibility study, which had ranged widely in price and delivery lead times.
“There remains scope to reduce the capital expenditure and cost contingencies on this equipment, as well as shorten the lead times,” Hyde said. West African Resources is also looking at an owner-mining versus contractor (the current plan) study looking to lower mining costs and VAT working capital.