The Kurmuk Gold Project proposes a conventional carbon-in-leach processing plant designed to treat 5 Mt/a of oxide ore and 4 Mt/a of fresh ore.
Report context
This report, dated 09 June 2023, presents the NI 43-101 Technical Report for the Kurmuk Gold Project in Ethiopia, prepared for Allied Gold Corp and Mondavi Ventures Ltd (to be renamed Allied Gold Corporation). The processing plant design was developed by Lycopodium using metallurgical testwork managed by Allied and Lycopodium. The proposed design is based on a robust metallurgical flowsheet using well-proven equipment, with equipment selection driven by suitability for duty, expected mine life, process performance, reliability, and ease of maintenance.
Processing route
Primary crushing and grinding
Ore is processed through primary crushing followed by crushed ore storage and reclaim. The grinding circuit uses a SAG/Ball Mill (SAB) combination with cyclone classification. An assessment by Orway Mineral Consultants indicated that a throughput of up to 5 Mt/a could be processed through the SAG/Ball circuit for oxide ores and 4 Mt/a for Ashashire fresh ores, with 7.5 MW drives on both mills. The milling rate ranges from 3.74 Mt/a for Ashashire pelite fresh to 5.26 Mt/a for Dish Mountain oxide ore. The target grind size is P80 75 µm.
Gravity concentration and cyanidation
The flowsheet includes gravity concentration with intensive cyanide leaching of concentrate and electrowinning. The leaching circuit comprises one leach reactor of 5,000 m³ and six CIL leaching tanks, each of 5,000 m³. Treating oxide ore at 5 Mt/a will result in reduced residence time in the CIL circuit, from 37 hours to 25 hours. The process plant includes an elution circuit with 14-tonne capacity, electrowinning, and gold smelting to produce gold doré.
Cyanide recovery and tailings management
Plant tailings are thickened for cyanide recovery using a 32 m diameter high-rate thickener, detoxified, and again thickened using a 32 m diameter high-rate thickener as a water conservation measure prior to disposal to a lined tailings storage facility located downstream of the process plant. The cyanide recovery thickener may be delayed as it is expected that the cyanide detoxification circuit will not need to be regularly operated to meet CN WAD 50 ppm in the decant pond.
Ancillary systems
An oxygen plant of 10 t/d capacity is included, along with air supply services. Reagent mixing, storage and distribution systems are provided, together with process, raw and potable water distribution. Duty-standby pumps have been included, including cyclone feed and tailings pumps.
Gold lock-up and inventory
Kurmuk has a high gravity gold content in the ores, leading to increased lock-up in the milling plant. With the gravity recovery circuit in place, total gold inventory is reduced to the equivalent of between 6 days and 10 days of production, varying depending upon head grade and carbon management. Lycopodium provided an estimate of gold inventory of 3,700 oz for inclusion into the financial model, representing six days of delayed production at 250 koz/a. This inventory is removed from the first production period and recovered at the end of the mine life.
Gold plant security
The gold plant, located close to an international border, will have three levels of security with appropriate fencing. A perimeter fence with gate house regulates entry to the administration building and plant warehouse. A double fence separated by about 10 m surrounds high security areas including crushing, milling, and leach circuits with the elution plant and associated facilities, with a clean-dirty change house for all workers entering the process plant area. The high-risk gold room is separately secured with additional access control, clean-dirty change house, motion sensors, closed-circuit television with monitoring, and security personnel.
Analytical laboratory
A proposal from an internationally recognized contractor for equipping the laboratory includes fire assay, wet chem, metallurgical laboratory, sample preparation and storage with an AAS room and a bullion room plus ablutions, lunchroom and offices. Approximately 8,000 mining and grade control samples will be analyzed per month, with 421 solids, 518 solutions and 113 carbon samples from the plant and 104 environmental samples. The equipping cost of $1.4 million has been incorporated into the capital schedule, with the building cost making a total of $2.7 million. The operating cost is estimated at $1.64 million per annum, based upon a budgetary proposal, with contractor staffing of 22 persons. The cost per sample is $14.23 each, incorporating 66% fixed charges. The laboratory building is to be supplied free by Allied to the contractor, while the facility will be equipped and operated by the contractor.
Product quality
The doré to be produced at Kurmuk is likely to contain between 90% and 95% gold with silver plus minor quantities of base metals. It is assumed that the doré will be shipped to Rand Refinery in South Africa, but this decision may be reviewed during future studies or project execution.
Key reported parameters
| Parameter | Value | Basis |
|---|---|---|
| Throughput | ||
| Oxide ore | 5 Mt/a | Design |
| Fresh ore | 4 Mt/a | Design |
| Head grade (overall project) | 1.53 g/t Au | Design |
| Gold recovery (overall project) | 92.0% | Design |
| Dish Mountain recovery | 93.9% | Design |
| Ashashire recovery | 90.3% | Design |
| Oxide/transition recovery (Ashashire) | 95.0% | Design |
| Grind size | P80 75 µm | Target |
| CIL residence time | ||
| Design | 37 hours | Design |
| At 5 Mt/a oxide | 25 hours | Calculated |
| Gold production (peak) | ~250,000 oz/a | Design |
| Gold production (average) | 200,000 oz/a | Design |
| Gold inventory (lock-up) | 3,700 oz | Estimate by Lycopodium |
| Power demand | ||
| Average | 21.4 MW | Design |
| Maximum | 28.9 MW | Design |
| Water demand | ||
| Fresh ore treatment | 1.71 Mm³/a | Design |
| Oxide ore treatment (peak) | 2.87 Mm³/a | Design |
| Dust suppression | 40 m³/h | Design |
| Leach reactor volume | 1 x 5,000 m³ | Design |
| CIL tank volume | 6 x 5,000 m³ | Design |
| Elution capacity | 14 tonnes | Design |
| Oxygen plant | 10 t/d | Design |
| Thickener diameter (cyanide recovery) | 32 m | Design |
| Thickener diameter (tailings) | 32 m | Design |
| Mill drives | 7.5 MW each | Design |
| Milling rate range | 3.74–5.26 Mt/a | Testwork by Orway Mineral Consultants |
| Cyanide detoxification target | CN WAD 50 ppm | Design criterion |
| Gold doré grade | 90%–95% gold | Expected |
Project website: https://alliedgold.com/our-portfolio/kurmuk-project/default.aspx
Technical qualifications
The process plant design is based on a proposed flowsheet using metallurgical testwork, with adequately detailed process flow diagrams, process design criteria and operational philosophy documentation prepared in support of the design. The cyanide recovery thickener may be delayed as it is expected that the cyanide detoxification circuit will not need to be regularly operated to meet CN WAD 50 ppm in the decant pond. Treating oxide ore at 5 Mt/a will result in reduced residence time in the CIL circuit, from 37 hours to 25 hours. The gold inventory estimate of 3,700 oz was provided by Lycopodium for inclusion into the financial model, representing six days of delayed production at 250 koz/a. The analytical laboratory proposal and cost estimates are based on budgetary proposals from an internationally recognized contractor. The power demand is estimated at an average of 21.4 MW with a maximum of 28.9 MW. Water demand estimates range from 1.71 Mm³/a for fresh ore to 2.87 Mm³/a for oxide ore treatment. Consumable consumption rates are based on metallurgical testwork and presented by ore type.
Source: NI 43-101 Technical Report for the Kurmuk Gold Project, Ethiopia, 09 June 2023, Sections 17, 17.1, 17.2, 17.3, 17.4, 17.5, 17.6.
