TSX-listed Fortuna Mining has announced positive results from the feasibility study for its Diamba Sud gold project, in Senegal, confirming an economically robust openpit conventional carbon-in-leach (CIL) gold mine and advancing one of Fortuna’s key growth opportunities.

The feasibility study indicates an after-tax net present value of $1-billion, an internal rate of return of 60% and a one-year payback at $3 500/oz of gold.

The study also indicates a strong first four years, with average gold production of 158 000 oz/y, as well as a 9.4-year life-of-mine (LoM) with average gold production of 116 000 oz/y.

Moreover, the study also shows a low-cost profile for the project, with an average all-in-sustaining cost of $1 056/oz over the first four years and $1 332/oz over the LoM.

Additionally, Fortuna says it continues advancing camp construction, office facilities and a new site access road.

A letter of intent has been executed with African Power Services as the power station engineering, procurement and construction contractor to secure the heavy-fuel oil (HFO) and light-fuel oil (LFO) generators.

The company says front-end engineering design (FEED) is being completed to support early procurement of critical path equipment, including the semiautogenous grinding mill, to reduce project schedule risk.

“Diamba Sud is a standout growth project with high returns, fast payback and is expected to be our lowest-cost mine. Together with our Séguéla mine expansion, Diamba Sud supports our plan to grow our annual gold production rate by approximately 60% to more than 500 000 oz in 2028,” says Fortuna president and CEO Jorge Ganoza.

“With the recent receipt of the environmental decree from the Senegalese government and the feasibility study complete, we are ready to move Diamba Sud toward a final investment decision (FID) upon completion of the mining permit process,” he adds.

Fortuna notes that the 2026 Diamba Sud feasibility study supersedes the preliminary economic assessment (PEA) dated October 15, 2025, and reflects a more advanced, higher-confidence project with stronger production, a longer mine life, improved technical definition and reduced execution risk.

Key optimisations to the project include a higher production profile where gold production increases from 106 000 oz/y in the PEA to 116 000 oz/y in the feasibility study, including average production of 158 000 oz/y over the first four years compared with 147 000 oz/y over the first three years in the PEA.

Additionally, the company notes that the project life increases from 8.1 years in the PEA to 9.4 years in the feasibility study, supporting an extended production and cash flow profile.

Fortuna says material growth in the indicated mineral resource category supports conversion to probable mineral reserves, establishing a stronger foundation for the feasibility study mine plan.

Moreover, average feed grade increases from 1.63 g/t gold in the PEA to 1.75 g/t gold in the feasibility study, while metallurgical recoveries increased from 90% in the PEA to 91% in the feasibility study.

Fortuna says the feasibility study advances the project to a level of accuracy considered consistent with an Association for the Advancement of Cost Engineering (AACE) Class 3 estimate, typically corresponding to an accuracy range of about -10% to +15%.

The company says it is embarking on the further advancement of early works to enable a rapid construction ramp-up following FID, to secure long-lead equipment and to protect the project’s critical-path.

Meanwhile, Fortuna notes that the initial mineral reserve estimate (MRE) for Diamba Sud represents a major milestone and provides the foundation for a long-life, low-cost openpit operation with strong production and cash flow potential.

The probable mineral reserves total 20.5-million tonnes averaging 1.75 g/t gold, containing 1.15-million ounces of gold. Importantly, the company says, Diamba Sud remains open for further growth.

The feasibility study mine plan is based on the current mineral reserve, while additional opportunities remain to convert mineral resources into mineral reserves and to expand the resource base through continued drilling.

The company says this provides Fortuna with a clear pathway to potentially extend mine life, enhance future production and increase the overall value of the project.

The company says the MRE is supported by feasibility study level technical work, including metallurgical, geotechnical, hydrogeological, environmental, mine planning, processing, infrastructure and cost studies.

Since 2023, Fortuna says it has invested meaningfully in mineral exploration at Diamba Sud, with the growth reflected in the maiden MRE. The company says this work has increased both the scale and confidence of the resource base and supports the feasibility study mine plan.

The project retains further upside, particularly at Southern Arc, where recent drilling indicates the potential to extend mineralisation.

Fortuna says ongoing drilling is expected to test open extensions, improve geological confidence in areas currently classified as inferred resources and identify additional mineralisation beyond the current feasibility study mine plan.

The company says this work provides a clear pathway to further expand and upgrade the resource base, with the potential to support future mine life extensions and additional value creation.

MINING, PROCESSING

Further, Fortuna notes the feasibility study outlines a conventional openpit gold mining operation feeding a central processing facility over a 9.4-year project life.

The mine plan incorporates the Area A, Area D, Karakara, Kassassoko, Moungoudi, Southern Arc, and Western Splay deposits, with mining sequenced to support a consistent production profile over the LoM.

The pit optimisation shells used to constrain the mineral reserve were generated using a gold price of $2 900/oz and a revenue factor of one. Optimisation parameters included government royalties, refining, mining, processing and general and administrative costs to support realistic pit designs and economic assumptions.

Mining will use conventional openpit methods, including drilling and blasting for both oxide and fresh ore, followed by truck-and-shovel mining operations.

Ore from the openpits will be processed through a conventional CIL plant designed to produce gold doré, incorporating crushing, milling, gravity recovery, CIL processing, carbon elution and gold recovery.

The process plant is designed to treat the ore at an average annual processing rate of about 2.26-million tonnes, producing 1.05-million ounces of gold at an LoM metallurgical recovery of 91%.

Meanwhile, the feasibility study also incorporates a fully geomembrane-lined tailings storage facility (TSF) designed in accordance with industry best practices and the Global Industry Standard on Tailings Management.

Fortuna says the tailings management system will include a tailings pipeline and a water return pipeline housed within a geomembrane-lined trench, together with associated tailings pumps.

The TSF will be developed as a side-valley facility formed by robust, multi-zoned earth-fill embankments and constructed using the downstream methodology. It is designed to accommodate 20.5-million tonnes over the LoM.

The company says water management has been designed to maximise recycling and minimise environmental impacts on surrounding communities.

A water storage dam will serve as the main collection and storage facility for clean, raw and process water. Raw water will be supplied by pipeline from the water harvesting dam and supplemented by pit dewatering activities.

Process water from the TSF will be recycled back to the process plant, with site operations designed as a closed-circuit system to maximise water reuse.

Power will be supplied through an integrated hybrid power solution comprising HFO, solar PV and battery energy storage system components. The company says the HFO power generation component has been agreed with African Power Services with solar integration targeted during the first year of operations.

CAPITAL COSTS SUMMARY

Fortuna says the feasibility study estimates total initial capital required to develop Diamba Sud at $397.5-million, including $72.1-million in pre-production costs and $33.7-million in contingency.

Sustaining capital is estimated at $64-million over the 9.4-year LoM, with closure costs estimated at an additional $14.5-million.

Pre-production mining capital includes all mining activities required prior to commissioning of the processing facility. This includes the mining of 3.6-million tonnes of waste and 315 000 t of ore to establish an ore stockpile ahead of processing operations, as well as contractor mobilisation and setup costs.

The processing plant capital estimate is based on a facility with a nameplate fresh ore throughput of two-million tonnes a year, designed to accommodate up to 2.5-million tonnes a year with an oxide blend. The company says the capital cost estimate assumes an engineering, procurement, construction and management implementation approach.

NEXT STEPS

Fortuna says it has approved an early works budget of $73-million to derisk Diamba Sud’s development schedule and advance site readiness alongside permitting and preparation for an FID.

The company notes that early works are progressing, including the site access road and camp expansion, while tenders for key infrastructure packages, including the TSF, are also advancing.

The company adds that FEED and other detailed design studies are well advanced in support of project execution planning. This work is focused on long-lead items and critical-path activities, allowing selected orders to be placed as early as the third quarter of 2026.

The power plant HFO and LFO generators have already been secured, with site delivery expected mid-2027. Of the approved $73-million early works budget, Fortuna says about $18-million has been spent to date.

With the feasibility study now complete, Fortuna says it is well positioned to advance Diamba Sud toward an FID, subject to the receipt of the required permitting approvals.

The company says the tender process for the processing plant contract is under evaluation, with a notice of award expected later this month.

Fortuna explains that a positive FID would position Diamba Sud to begin full construction in the fourth quarter of this year, following the wet season, with first gold pour targeted before the end of the second quarter of 2028.

Beyond the feasibility study base case, the company says Diamba Sud retains meaningful upside through continued exploration, resource conversion, and project optimisation.

Ongoing drilling is expected to test extensions to known deposits, upgrade inferred mineral resources and evaluate opportunities to convert additional resources into mineral reserves.

Further optimisation opportunities may also be assessed through detailed engineering, mine sequencing, procurement, and operating cost refinement as the project advances toward an FID and construction.