Iamgold has reported results from a feasibility study that supports a modest increase in throughput at the carbon-in-leach (CIL) processing plant at its Essakane open-pit gold mine in northeast Burkina Faso. When CIL processing comes to an end in 2026, operations will continue through 2031 based on heap leach processing of lower-grade ore. Plant optimization work to increase CIL throughput from 10.8 million metric tons per year (mt/y) to 11.7 million mt/y would require capital investment of just $9 million.
Commissioning of the expansion is planned for the third quarter of 2020. Following the expansion, gold production through 2026 would average 433,000 ounces per year (oz/y), with a peak year of 530,000 oz/y.
Diluted grade of feed material to the CIL plant would average 1.24 grams/mt gold. Lower-grade material would be stockpiled and held for heap leach processing.
Heap leaching would begin following the end of CIL process plant operations. Use of the existing primary gyratory and secondary cone crushing circuits during heap leaching would reduce the capital intensity of the heap leach scenario, which has an optimized annual throughput rate of 8.5 million mt/y. Annual gold production from heap leaching is forecast at 73,000 oz/y. The average processed grade for heap leaching is forecast at 0.40 g/mt.
Capital expenditures to develop the heap leaching operation are estimated at $115 million. The development scenario envisages installation of tertiary crushing using a high-pressure grinding role unit, material handling conveyors, and a carbon-in-column adsorption plant. Loaded carbon would be transported to the existing plant facilities for stripping and refining.
Additional major infrastructure would include the leach pads, solution distribution and collection systems, and solution ponds. Existing camp capacity and power generation exceed the capacity that will be required during heap leach operations, and thus a reduction in manpower and general and administration costs will be realized during heap leach operations vs. current CIL operations.
The Essakane property currently hosts 4.876 million oz of gold in indicated resources at a grade of 0.98 g/mt gold. Proven and probable reserves stand at 3.985 million oz grading 0.96 g/mt gold.
Life-of-mine direct cash costs of production are estimated at $778/oz, and all-in sustaining costs are estimated at $949/oz.
As construction of the heap leach facility is not required until 2025, Iamgold retains the option of re-evaluating the economics of that construction project at that point in time. Given that the CIL process generates higher recovery and would not require additional capital investment, there may be a case where the existing stockpiled ore planned for the heap leach process might generate superior economics by processing through the existing CIL circuit, especially in scenarios with higher gold prices than have been used for the current feasibility study.