Yamana Gold's 2021 feasibility study update for the Wasamac gold project near Rouyn-Noranda, Québec, crushes ore underground and grinds it to P80 60 µm ahead of a thickened leach-CIP circuit and Zadra elution.
The Wasamac Project N.I. 43-101 Technical Report on the Wasamac Feasibility Study Update, Québec, Canada, was prepared by Ausenco Engineering Canada and others for Yamana Gold Inc., with an effective date of July 16, 2021. Several flowsheets were weighed against the testwork and economic modelling, and the selected unit operations are all typical for gold processing. The plant is designed for 7,500 t/d (2.7 Mt a year) against a nominal mining rate of 7,000 t/d. The extra capacity allows for future increases in mining rate and eases ramp-up.
Critical Data
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Report effective date | July 16, 2021 | Not applicable | Ausenco for Yamana Gold Inc. |
| Design throughput | 7,500 t/d (2.7 Mt/a) | Not applicable | Nominal 7,000 t/d |
| Availability | Crushing 70, plant 92, tailings filtration 82.5 | % | 6,132 crushing hours a year |
| Primary crusher | Jaw, 1,150 x 760 mm, underground | Not applicable | Vibrating grizzly feeder at 417 t/h |
| SAG mill | 7.6 m x 4.0 m EGL, 4.1 MW with VSD | Not applicable | Trommel and 132 kW pebble crusher |
| Ball mill | 6.1 m x 8.8 m EGL, 6.0 MW | Not applicable | Closed with hydrocyclones |
| Grind size | P80 60 | µm | SAG feed F80 99 mm |
| Pre-leach thickener | 22 m high-rate | Not applicable | Underflow at 50% solids to leach |
| Leach and CIP | 3 leach + 7 CIP tanks, 33 h | Not applicable | Dissolved oxygen 20 mg/L, pH 10.5 to 11 |
| Reagents | NaCN 0.6, hydrated lime 1.0 | kg/t | Design criteria |
| Elution | Pressure Zadra, 7 t column at 140°C | Not applicable | Propane-fired strip heater |
| Cyanide destruction | SO2/O2 with SMBS, about 70 min | Not applicable | CN WAD from 150 to below 10 mg/L |
| Tailings filtration | Two plate-and-frame filters, 10 to 12% moisture | Not applicable | 412 t/h to drystack |
Overview
The plant crushes ore in an underground jaw crusher and conveys it to a covered surface stockpile. A SAG mill with pebble crusher and a ball mill closed with cyclones grind the ore. After trash screening and pre-leach thickening, the slurry goes to leach and carbon-in-pulp (CIP) adsorption. Loaded carbon is acid washed and stripped by pressure Zadra elution, followed by electrowinning and smelting to doré. Tailings go through SO2/O2 cyanide destruction and thickening, then either to a paste plant for underground backfill or to a filter plant that feeds a drystack. Excess water is treated before discharge to the James Bay basin.
Key Process Stages
Crushing and stockpiling. Haul trucks tip directly into a run-of-mine bin with a static grizzly and a fixed rockbreaker. A vibrating grizzly feeder feeds the jaw crusher at 417 t/h. Crushed ore is conveyed from the underground crushing pocket to a covered stockpile with about 8,000 t of live storage. Two variable-speed apron feeders reclaim at 317 t/h to the SAG feed conveyor, where pebble lime is added at a constant rate.
Grinding. SAG mill discharge passes a trommel. Oversize pebbles are crushed and returned to the mill, and the undersize goes to the cyclone feed pumpbox. The ball mill is fed by cyclone underflow, and its trommel oversize goes to a scats bunker. Cyclone overflow at 33% solids passes a trash screen to the 22 m pre-leach thickener with flocculant. Thickener overflow is recycled as process water.
Leach and CIP. Three leach tanks and seven CIP tanks give 33 hours of residence at 50% solids. Oxygen is sparged to hold 20 mg/L dissolved oxygen, hydrated lime sets pH at 10.5 to 11, and cyanide is added to the first leach tank. Carbon is advanced counter-current, and recessed impeller pumps move slurry and carbon between tanks and to the loaded carbon screen.
Cyanide destruction. CIP tails at 49% solids pass a carbon safety screen to a single detox tank. About 70 minutes of SO2/O2 treatment with oxygen, lime, copper sulphate and sodium metabisulphite reduces weak-acid-dissociable cyanide from a maximum of 150 mg/L to below 10 mg/L.
Tailings thickening, paste and filtration. Detoxified tails are thickened in a 22 m high-rate thickener. The underflow is pumped to the paste plant for underground backfill or to the tailings filtration plant. There, a stock tank with 2.5 hours of residence feeds two plate-and-frame pressure filters. The cake, at 10 to 12% moisture, is discharged at 412 t/h to a stockpile and trucked to the drystack. When the filter plant is down, tailings go to the paste plant.
Acid wash, elution and gold room. Loaded carbon soaks in weak hydrochloric acid in a 7 t column, and the spent acid goes to cyanide destruction. A high-cyanide caustic solution then strips the carbon at 140°C in a pressure Zadra column. The cooled pregnant solution flows through electrowinning cells and back to the column. Sludge is smelted to doré.
Additional Interesting Data and Summary
The plant was deliberately sized above the 7,000 t/d mining rate to allow for future increases and an easier ramp-up. Filtrate and wash water from the filter presses go to a clarifier, and excess water returns to the process water tank.
In summary, the 2021 Wasamac feasibility update is a conventional SAG-ball and leach-CIP gold plant at 7,500 t/d. It has an underground primary crusher, a pre-leach thickener, Zadra elution, and tailings split between paste backfill and filtered drystack.
Key Processes
- Underground jaw crushing and covered stockpile
- SAG milling with pebble crushing and ball milling to P80 60 µm
- Pre-leach thickening
- Leach and carbon-in-pulp adsorption with oxygen sparging
- Acid wash, pressure Zadra elution, electrowinning and smelting to doré
- SO2/O2 cyanide destruction
- Tailings thickening, paste backfill and pressure filtration to drystack
Source: Wasamac Project N.I. 43-101 Technical Report on the Wasamac Feasibility Study Update, Québec, Canada, prepared by Ausenco Engineering Canada Inc. and others for Yamana Gold Inc., effective date July 16, 2021.
Earlier report summaries
Earlier versions of this profile, based on older technical reports, are retained below for source traceability. Dates and figures reflect each report’s own effective date and are superseded by the current information above.
Wasamac Project – Feasibility Study
This feasibility study assesses the proposed development of the Wasamac deposit as an underground gold mine and processing plant in Rouyn-Noranda, Quebec.
Report context
The NI 43-101 Technical Report for the Wasamac Project, a feasibility study prepared for Monarques Gold Corporation, has an effective date of December 1, 2018 and a signature date of December 3, 2018. The project is an advanced stage gold exploration project located 15 km west of Rouyn-Noranda in the Abitibi gold mining camp of Quebec, Canada. The study incorporates advanced mining designs integrating Rail-Veyor technologies and a paste backfill system, and investigates processing options, tailings and water management facilities. All monetary units in the feasibility study are in Canadian dollars based on fourth quarter 2018 dollars.
Processing route
Process plant design
The proposed carbon-in-pulp (CIP) process plant is designed to have a capacity of 6,900 tpd. The process plant is located some 2 km from the mine site, with neutral dry-stacked tailings disposal located some 5 km further to minimize the project footprint locally. The simplified process flow diagram is provided in the original report as Figure 17-1.
Crushing and grinding
Ore is transported from the underground mine to surface via the Rail-Veyor system to a discharge bin and crusher feed conveyor. The crushing building processes ore, which is then conveyed to a crushed ore stockpile and mill feed conveyor. Grinding is performed in the grinding area of the process plant.
Gold recovery
The process flowsheet includes a CIP circuit, an elution circuit, and a carbon regeneration area. The gold room handles final gold recovery. A reagent tank and park supplies process reagents. The proposed gold recovery method involves cyanidation within the CIP circuit. Average gold metallurgical recovery is 88.2% over the life of mine.
Metallurgical testwork
Metallurgical testwork was conducted on samples from the Main Zone and Zones 1, 2, and 3. Testwork sample maps for each zone are provided in the original report as Figures 13-1 through 13-4. The testwork included comminution testing measuring Axb (resistance to impact breakage) for each zone, with frequency curves presented in Figures 13-5 through 13-8 of the original report. Gravity Recoverable Gold (GRG) testing, Bond work index (BWi) testing, and leach variability testing were conducted on samples designated with Z_X_-GRIND-_Y_ and Z_X_-VAR-_Y_ naming conventions.
Tailings management
Tailings are processed through press filters in the tailings filtration area to produce filtered tailings for dry stack deposition. The tailings management facility uses a dry stack deposition plan with progressive reclamation sequencing. Tailings production operates in two modes: paste production mode and tailings production mode, as illustrated in flux diagrams (Figures 18-26 and 18-27 of the original report). The tailings storage facility designed capacity accommodates the years of production and produced tailings volumes as shown in Figure 18-15 of the original report.
Water management
The site water management design includes a concentrator retention basin and a TSF retention basin with specified design volumes. Sub-watersheds of the concentrator area and TSF area in undeveloped conditions were analyzed (Figures 18-24 and 18-25 of the original report). The water treatment plant design includes capital and operating costs.
Backfill system
A paste backfill plant is proposed to supply backfill to the underground mine. The paste backfill and slurry tailings distribution systems were designed with associated capital and operating costs.
Key reported parameters
| Parameter | Value | Basis |
|---|---|---|
| Process plant capacity | 6,900 tpd | Design |
| Mine production rate | 6,000 tpd | Design |
| Life of mine ore processed | 21.5 Mt | Design |
| Average diluted feed grade | 2.56 g/t Au | Design |
| Average gold recovery | 88.2% | Design (supported by testwork) |
| LOM payable gold production | 1,556,800 oz | Design |
| Peak annual gold production | 195,600 oz | Design |
| Average annual payable gold | ~142,000 oz | Design |
| Historical ore treated (1965-1971) | ~1.9 Mt | Historical operating data |
| Historical grade (Main Zone surface pillar, Karpoff 1986) | 740,000 t at 3.39 g/t Au | Historical estimate |
| Historical grade (Main Zone, Karpoff 1986) | 814,000 t at 5.83 g/t Au | Historical estimate |
| Historical grade (Zone 1, Karpoff 1986) | 88,000 t at 5.14 g/t Au | Historical estimate |
| Historical grade (Zone 2, Karpoff 1986) | 25,000 t at 5.79 g/t Au | Historical estimate |
| Historical grade (Zone MacWin, Karpoff 1986) | 92,000 t at 4.94 g/t Au | Historical estimate |
| Comminution test parameters | Axb frequency curves per zone | Testwork |
Project website: https://iaac-aeic.gc.ca/050/evaluations/exploration?projDocs=80879&culture=en-CA
Project website: https://wasamac-eng.agnicoeagle.com/project-description-2
Technical qualifications
The processing sections of this report are based on metallurgical testwork and process plant design completed for the feasibility study. The report notes that the qualified person responsible for chapters 13 (metallurgical testwork) and 17 (process plant) did not personally visit the property. The process plant design is presented at a feasibility study level of accuracy and is supported by laboratory testwork on samples from the Main Zone and Zones 1, 2, and 3. The report specifies that operating costs for the process were developed at a feasibility study level. Capital costs include contingency of $31.2 million and indirect costs of $52.4 million. The report does not provide actual plant operating data as the project is not in production.
Source: NI 43-101 Technical Report, Wasamac Project – Feasibility Study, Monarques Gold Corporation, effective December 1, 2018, signature date December 3, 2018. Relevant sections: 1 (Summary), 13 (Mineral Processing and Metallurgical Testing), 17 (Process Plant), 18 (Infrastructure).
