TSX- and New York-listed gold producer Iamgold has announced positive results from a prefeasibility study (PFS) for its Essakane heap leach project, in Burkina Faso.

The results, which outline an economically viable project, justify the start of a feasibility study (FS) to further optimise the project development design, secure long lead equipment and improve project economics.

The PFS highlights include a 39% increase in probable reserves from 1.3-million ounces to 4.7-million ounces. Indicated resources increased from 800 000 oz to 5.1-million ounces, while inferred resources increased from 200 000 oz to 600 000 oz.

The PFS indicates a mine life of 8.5 years with mill throughput of 12-million tonnes a year and heap leach throughput of ten-million tonnes a year. This is an extension of three years to the mine life, compared with the 2016 technical report.

There is potential for a further mine life extension with the FS and the drilling of prospective satellite prospects near Essakane.

Further, the PFS reported a possible average yearly production increase of 16% to 480 000 oz, with peak yearly production exceeding 500 000 oz. The mine would be able to produce at all-in sustaining cost (AISC) of $946/oz.

The initial heap leach capital expenditure requirement is estimated at $155-million.

The infill drilling programme, conducted to upgrade targeted lower-grade inferred resources in support of the heap leach PFS, intersected higher grades than anticipated in several areas.

The impact of these results is still being assessed and may provide potential to outline additional zones of higher-grade mineralisation for processing at the existing carbon-in-leach (CIL) plant.

The drilling campaign is continuing and the results will be used to complete the delineation of both the lower-grade heap leach and higher-grade CIL mineralisation to optimise the development options as part of the recommended FS.

IAMGOLD CEO Steve Letwin commented that not only has the company been introduced to a new processing method that allows for economic incremental production, but also the company’s success at the drill bit has delivered a resource increase far greater than expected.

“While we knew that heap leaching had the potential to unlock additional reserves, we were positively surprised at, and benefited from, intercepting higher grades, which account for more than one-third of the 39% probable resources increase.

“Essakane is pursuing all avenues for enhancing the value of this already high-performing operation, including targeting additional resources from Essakane's large, prospective land package,” said Letwin.

Meanwhile, an initial resource estimate for the Gossey prospect is expected in the fourth quarter.

“With these positive results and the future work we have planned, we are targeting a mine life beyond 2030 and AISC below $900/oz."