A preliminary economic assessment of the Nabanga Project, effective September 30, 2019, evaluates the potential viability of a combined open pit and underground mining operation processing 360,000 tonnes per year of mineralized material.
Report context
This technical report constitutes a Preliminary Economic Assessment (PEA) for the Nabanga Project, prepared in conformance with NI 43-101 and Form 43-101F1. The report is effective as of September 30, 2019, and supports a SEMAFO press release of the same date. The Property was acquired by SEMAFO from Orbis Gold Limited in 2014–2015. The PEA evaluates only the fresh (sulphide) portion of the Nabanga deposit, with mineral resources estimated as of December 31, 2018. The project is located approximately 250 km south-east of Ouagadougou, Burkina Faso, accessible via Route Nationale RN04 and RN18, followed by an unsealed dirt road that crosses the Kompienga River.
Processing route
Run-of-Mine feed and crushing
The Nabanga concentrator is designed to process a nominal 360,000 tonnes of Run-of-Mine (ROM) mineralized material per year. ROM mineralized material will be crushed by a jaw crusher and transported to a stockpile by conveyor.
Grinding circuit
Crushed material is reclaimed from the stockpile by an apron feeder to a semiautogenous grinding (SAG) mill. The SAG mill discharge is screened; screen oversize is returned to the SAG mill. SAG screen undersize is pumped to a ball mill circuit operating in closed circuit with cyclones.
Flotation and concentrate leaching
Cyclone overflow flows to the flotation circuit. Flotation concentrate will be ground to 25 micron and processed in an intensive leach reactor.
Tailings leaching
Flotation tailings will be processed in a conventional carbon-in-leach (CIL) circuit, followed by carbon elution, electro-winning and refining.
Overall recovery
The estimated combined gold recovery is 92%.
Power supply
Power demand was determined to be 5.8 MW based on estimated connected loads, running loads and running power for process operation. The power plant consists of five generators using light fuel oil (LFO), with four in operation and one in stand-by, maintenance or repair.
Site infrastructure
In addition to the concentrator building, the site will include administration and mine offices, an accommodation camp and cafeteria, a warehouse, a metallurgical laboratory, and a security gate. A new access road of about 11 km will be developed from the RN18 to the Nabanga Process Site, starting approximately 80 km south of Fada-N’Gourma.
Key reported parameters
| Parameter | Unit | Value | Basis |
|---|---|---|---|
| Mill feed capacity | tonnes per year | 360,000 | Proposed design |
| Life of mine | years | 9 | Proposed mine plan |
| Total gold produced over LOM | ounces | 571,000 | Proposed schedule using 92% recovery |
| Mill recovery | % | 92 | Proposed design estimate |
| Inferred mineral resource tonnage | Mt | 3.4 | Estimate as of Dec. 31, 2018 |
| Inferred resource grade | g/t Au | 7.7 | Estimate as of Dec. 31, 2018 |
| Inferred contained gold | x1,000 oz | 840 | Estimate as of Dec. 31, 2018 |
| Open-pit extractable mineralized material | Kt | 616 | Proposed mine plan |
| Underground extractable mineralized material | Mt | 2.364 | Proposed mine plan |
| Bond work index material characterization | , | Very hard, medium abrasive | Testwork by ALS Ammtec (two tests) |
| Cyanidation characteristics | , | Refractory; high cyanide concentration required | Testwork by ALS Ammtec |
| Initial capital cost (pre-production) | ‘000 USD | 83,697 | Class 4 estimate (±35% accuracy) |
| Sustaining capital cost | ‘000 USD | 55,910 | Proposed estimate |
| Total operating cost per ounce | $/oz | 662 | Proposed estimate |
| Total all-in sustaining cost per ounce | $/oz | 760 | Proposed estimate |
| Base case gold price assumption | $/oz | 1,300 | Historical data-based assumption |
| Pre-tax NPV at 5% discount rate | M USD | 146.7 | DCF analysis (Q3-2019 projections) |
| After-tax NPV at 5% discount rate | M USD | 99.8 | DCF analysis (Q3-2019 projections) |
| Pre-tax IRR | % | 31.4 | DCF analysis |
| After-tax IRR | % | 22.6 | DCF analysis |
| Pre-tax payback period | years | 3.5 | DCF analysis |
| After-tax payback period | years | 4.4 | DCF analysis |
Project website: https://www.newswire.ca/news-releases/semafo-positive-pea-results-for-nabanga-832494618.html
Technical qualifications
This Preliminary Economic Assessment is based on a Class 4 capital cost estimate as per AACE Recommended Practice 47R-11, with a target accuracy of ±35%. The report states that although some individual elements of the capital cost may not achieve the target level of accuracy, the overall estimate falls within the parameters of the intended accuracy. Mineral resources are stated using an average density, constrained in a preliminary optimized pit, and estimated exclusively for the fresh (sulphide) portion of the deposit. The PEA notes that no mineral reserves have been estimated. The report recommends proceeding to the next level of feasibility study and identifies several trade-off studies needed, including: grinding using one large mill or two smaller ones; intensive cyanide leaching of flotation concentrate; carbon-in-leach versus carbon-in-pulp; post-leach thickener versus no thickening; and large bulk reagent tanks versus totes. Additional physical characterization test work, flotation concentrate characterization, and leach and adsorption variability testing are recommended.
Source: SEMAFO, NI 43-101 Technical Report, Preliminary Economic Assessment – Nabanga Project, November 2019, Sections 1.6–1.16, 2.1, 2.3.
