IAMGOLD's January 2025 technical report on the Westwood Complex in Québec, effective September 30, 2024, describes the Doyon plant refurbished in 2013 to 1.0 Mt/a, with paste backfill and tailings deposition in the mined-out Doyon pit.
The Technical Report on the Westwood Complex, Québec, Canada, prepared by IAMGOLD Corporation and consultants with an effective date of September 30, 2024 and dated January 2025, covers the Westwood underground mine, the Grand Duc open pit and the Doyon process plant. The plant was first built in the 1970s and last refurbished in 2013 to raise throughput to 1.0 Mt/a, with upgrades to grinding, cyanidation, carbon stripping and tailings cyanide destruction and a new paste backfill plant. It treats ore by conventional cyanidation to produce gold-silver doré.
Critical Data
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Report effective date | September 30, 2024 | Not applicable | Report dated January 2025, IAMGOLD Corporation |
| Plant capacity after 2013 refurbishment | 1.0 | Mt/a | Doyon plant |
| Nominal processing rate | 3,106 | t/d | Basis for leach retention times |
| Primary crusher | 1.07 x 1.22 | m | Single-stage jaw crusher |
| Ore bins | 2,800 | dmt each | Fed by belt conveyor |
| SAG mill | 2,700 | HP | Closed circuit with primary hydrocyclones |
| Ball mill | 1,000 | HP | Closed circuit with secondary hydrocyclones |
| Target grind | 85% passing 75 | µm | Not applicable |
| Total leach retention | 40.5 | h | At the nominal rate |
| Paste backfill rate | 70 nominal, 144.6 maximum | t/h | Two paste circuits |
| Process plant power | About 35 to 36 | kWh/t | Hydro-Québec supply |
| Process water | About 1.1 | Mm³/a | Based on 2022 to mid-2024 use |
Overview
Since 2013 the Doyon plant has run both continuously and in batch mode, depending on ore availability. It currently operates around the clock, but the report says parts of the current mine plan have less ore, and the plant will then run in batch mode, for example selected weeks in a month or three to four days a week. The plant has also toll-treated custom material from other operations, and the report notes that its flexible flowsheet keeps this an option outside the life-of-mine plan.
The flowsheet is single-stage primary crushing, two-stage SAG and ball mill grinding, a gravity circuit, pre-leach, carbon-in-leach (CIL) and carbon-in-pulp (CIP), followed by gold recovery and carbon handling. Leach residue goes to SO2/air cyanide destruction, part of the detoxified slurry feeds the paste backfill plant, and the rest goes to the mined-out Doyon open pit.
Key Process Stages
Ore handling and crushing. Ore hoisted from the Westwood shaft is trucked 2.5 km to the crusher house. A front-end loader feeds a grizzly feeder ahead of the 1.07 m by 1.22 m jaw crusher, and a belt conveyor carries crushed ore to the plant's bins of 2,800 dmt each.
Grinding and gravity. A 2,700 HP SAG mill runs in closed circuit with primary hydrocyclones, whose overflow feeds a 1,000 HP ball mill in closed circuit with secondary hydrocyclones. Part of the secondary cyclone underflow goes to a gravity circuit of a Sweco screen, a 30 inch Knelson concentrator and a shaking table. Gravity tails return to grinding, and the gravity concentrate goes to the refinery. The target grind is 85% passing 75 µm.
Leaching and adsorption. At 3,106 t/d the leach and adsorption train gives 40.5 hours of retention: primary leach tanks 4.9 hours, CIL tanks 6.9 hours, secondary leach tanks 16.2 hours and CIP tanks 12.6 hours.
Cyanide destruction. Leach residue is split between two parallel SO2/air reactors. Liquid oxygen, delivered by truck and vaporized, is normally used in detoxification, with process air as a backup. A buffer tank holding 14 hours of backfill plant feed keeps detoxified slurry available if the process plant stops.
Paste backfill. Two 2 km pipelines link the process and backfill plants, one carrying tailings and the other returning filtrate. They drain by gravity in case of a break or power failure. Two paste circuits allow two stopes to be filled at once with different recipes. The plant was designed for 144.6 t/h, and the required nominal rate is 70 t/h.
Gold recovery. Loaded carbon is acid washed and stripped in high-pressure Zadra reactors with a hot, low-concentration sodium cyanide and caustic solution. Two parallel electrowinning cells produce a sludge that is filtered, dried and smelted into doré. Carbon is regenerated in a kiln before returning to the CIL and CIP tanks.
Tailings. Tailings not used for backfill are pumped to the mined-out Doyon open pit.
Additional Interesting Data and Summary
The main reagents are grinding media (38 mm balls for the ball mill and 133 mm for the SAG mill), quicklime, cyanide, oxygen, caustic soda, sulphur dioxide, and slag and cement for paste backfill. Two compressors supply plant and instrument air, and two more supply process air for oxidation in the leach tanks. Power comes from Hydro-Québec over a 120 kV line, and a generator provides emergency power for lights and fire pumps.
The plant uses about 1.1 Mm³ of process water a year, mostly reclaimed from the tailings facility and the Doyon water management system, with the Bousquet River available when needed and used for fresh and gland seal water. An average of 4.0 to 4.5 Mm³ of water from the whole Westwood property is treated each year at a high-density sludge plant before release.
In summary, the 2024 report presents Doyon as a refurbished 1.0 Mt/a gravity and CIL-CIP mill whose main operating feature for the coming years is flexibility: batch operation when ore is short, toll milling as an option, and tailings split between paste backfill and the Doyon pit.
Key Processes
- Single-stage jaw crushing
- SAG and ball milling to 85% passing 75 µm
- Gravity concentration (Knelson concentrator and shaking table)
- Pre-leach, CIL and CIP
- Acid wash, Zadra stripping, electrowinning and smelting to doré
- Kiln carbon regeneration
- SO2/air cyanide destruction
- Paste backfill and in-pit tailings deposition
Source: Technical Report on the Westwood Complex, Québec, Canada, IAMGOLD Corporation, effective date September 30, 2024 (January 2025).
Technical report and processing history
The following archived source profiles have been consolidated here to preserve the project’s processing history and study context.
Mineral Processing Circuit of Westwood Mine
The Westwood Mine processing circuit is a comprehensive gold recovery system utilizing cyanidation with carbon adsorption, built upon a refurbished Doyon Mill facility. The circuit was significantly upgraded between 2011-2013 to optimize gold recovery from Westwood ore.
Processing Flow and Equipment:
1. Ore Handling:
– Underground ore is transported 2.5km by truck to the mill
– Single-stage jaw crusher (1.07m x 1.22m) with grizzly feeder
– Belt conveyor system to mill bins (2,800 dmt capacity each)
2. Grinding Circuit:
– 2,700 HP SAG mill in closed circuit with primary hydrocyclones
– 1,000 HP ball mill with secondary hydrocyclones
– Target grind size: 80% passing 53 microns (270 mesh)
3. Gravity Recovery:
– Secondary cyclone underflow feeds gravity circuit
– Equipment includes Sweco screen, 30″ Knelson concentrator, shaking table
– Gravity concentrate sent directly to refinery
– Tailings return to grinding circuit
4. Leaching and Adsorption:
– 55 hours total retention time at 3,106 tpd nominal rate
– Circuit breakdown:
• Primary leach tanks: 4.7 hours
• CIL tanks: 6.6 hours
• Secondary leach tanks: 31.3 hours
• CIP tanks: 12.1 hours
5. Gold Recovery:
– Acid wash vessel and high-pressure Zadra stripping reactors
– Two parallel electrowinning cells
– Gold sludge filtered, dried, and smelted into doré bars
– Carbon regeneration kiln for reactivation
– Carbon attrition system for fresh carbon preparation
6. Tailings Management:
– SO2/Air cyanide destruction process
– Two parallel detox reactors
– Split between paste backfill plant and Doyon open pit disposal
– Buffer tank with 14 hours capacity for backfill feed continuity
7. Paste Backfill System:
– Two 2km pipelines (feed and return)
– Designed for 144.6 tph maximum (operating at 70 tph)
– Two circuits for simultaneous stope filling
– Water recovery system to mill
Key Operational Parameters:
– Annual throughput: 1,100,000 tpy (after optimization)
– Mill availability: 96%
– Operating weeks/year: 52
– Design capacity: 2,425 tpd
Reagent Consumption (annual):
– Cyanide: 945,000 kg
– Quick lime: 5,640,000 kg (combined mill and environmental)
– SO2: 1,118,000 kg
– Slag/cement: 8,273,000 kg (backfill)
– Grinding media: 1,805,000 kg
Innovations and Notable Features:
– Refurbishment of 1970s Doyon Mill with modern equipment
– Optimized throughput increased capacity from 850,000 to 1,100,000 tpy
– Dual-purpose tailings management (backfill and pit disposal)
– Sophisticated paste backfill system with water recovery
– Comprehensive cyanide destruction circuit
Technical Challenges and Solutions:
1. Zinc Recovery Consideration:
– Initial assessments showed potential for zinc recovery
– Subsequent studies deemed uneconomical
– Solution: Process high-grade zinc ore through cyanidation only
2. Tailings Management:
– Existing Doyon tailings facilities nearing capacity
– Solution: Utilize Doyon open pit (11.3 MCUM capacity)
– Environmental criteria met for pit disposal
3. Throughput Optimization:
– Original design capacity of 850,000 tpy
– Solution: Circuit upgrades increased to 1,100,000 tpy
4. Power Management:
– Mill represents 8% of total milling cost
– Solution: Adequate contract with Hydro-Quebec (30,000 kW max)
Water Management:
– Primary source: Tailings management facility and Doyon system
– Secondary source: Bousquet River
– Annual treatment: 4.0-4.5 MCUM in HDS plant
– Water recycling from backfill plant to mill
The processing circuit demonstrates a well-integrated system combining modern gold recovery techniques with efficient tailings management and backfill production, all while maintaining environmental compliance through comprehensive cyanide destruction and water treatment systems.
Technical Report on the Westwood Complex
Technical Report on the Westwood Complex
| Company | IAMGOLD |
| Date | 2025 |
| Region | Quebec, Canada |
| Commodities | Gold, Silver |
| Mine Type | Underground |
| Throughput | 3,106 tpd |
| Mine Life | LOM |
| Status | Operating |
Executive Summary
This technical report details the recovery methods and operational status of the Westwood Complex in Quebec, Canada, operated by IAMGOLD. The process plant, originally constructed in the 1970s, underwent a significant refurbishment in 2013 to increase throughput to 1.0 Mt/a. Upgrades were implemented across the grinding, cyanidation, strip, and tailings cyanide destruction circuits, alongside the construction of a new paste backfill plant to meet operational needs. The facility is designed to operate continuously 24/7, though batch mode operations are planned for periods of reduced ore availability.
The plant treats underground ore via a conventional cyanidation process. Run-of-mine ore is crushed in a single-stage jaw crusher and ground using a two-stage semi-autogenous grinding (SAG) mill and ball mill circuit. The flowsheet includes a gravity separation circuit, pre-leach, carbon in leach (CIL), and carbon in pulp (CIP) circuits to produce gold/silver doré. The targeted grind size is 85% passing 75 µm, with a nominal processing rate of 3,106 t/d.
Environmental and waste management are integral to the operation, featuring a SO2/air cyanide destruction process for tailings and a paste backfill plant that utilizes tailings to fill stopes. Two parallel lines connect the process and backfill plants, allowing for simultaneous filling of two stopes with different recipes. Water management involves reclaiming water from the tailings storage facility and the Doyon reclamation system, with fresh water sourced from the Bousquet River. The plant consumes approximately 35–36 kWh/t of power annually.
Reports
Concepts
Website: https://www.iamgold.com/English/operations/westwood/default.aspx
Report Date: 2025
Region: Quebec, Canada
Project Status: Operating
Commodity: Gold, Silver
Throughput: 3,106 tpd
Mine Life: LOM
Mine Type: Underground
Ore type:
Westwood Mine — 2020 Technical Report
Westwood Mine — 2020 Technical Report
| Company | IAMGOLD |
| Mine | Westwood Mine |
| Date | 2020 |
| Region | Quebec, Canada |
| Commodities | Gold, Zinc, Copper |
Executive Summary
The NI 43-101 Technical Report for the Westwood Mine outlines the recovery methods and processing facilities designed by IAMGOLD. The processing plant utilizes the existing Doyon Mill, which was refurbished between 2011 and 2013 to accommodate Westwood ore. The design criteria support an annual production of 850,000 tonnes, with a throughput capacity optimized to 1,100,000 tonnes per year. The facility focuses on gold recovery through cyanidation, with provisions for paste backfill and tailings management.
The mill process includes crushing, grinding, gravity separation, and leaching circuits. Underground ore is hoisted and crushed via a single-stage jaw crusher before grinding in a semi-autogenous (SAG) mill and ball mill. Gravity recovery is achieved using Knelson concentrators and shaking tables. The leaching circuit employs a combination of Carbon-in-Leach (CIL) and Carbon-in-Pulp (CIP) tanks, followed by cyanide destruction using the SO2/Air process.
Although a copper-zinc flotation circuit was initially considered for higher-grade zinc ore lenses, it was deemed not economical in the 2018 revision. Consequently, the current operating plan processes zinc ore via cyanidation only, without zinc credits. The tailings are managed through a paste backfill plant for underground support, with excess tailings pumped to the Doyon open pit.
Reports
Website: https://www.iamgold.com/English/operations/westwood/default.aspx
Report Date: 2020
Region: Quebec, Canada
Project Status:
Commodity: Gold, Zinc, Copper
Throughput:
Mine Life:
Mine Type:
Ore type:
Westwood Project — 2013 Technical Report
Westwood Project — 2013 Technical Report
| Company | IAMGOLD Corporation |
| Date | 2013 |
| Region | Quebec, Canada |
| Commodities | Gold |
| Mine Type | Underground |
| Throughput | 2,425 tpd |
| Annual Production | 850,000 tonnes/year |
| Status | Development |
Executive Summary
The Westwood Project NI-43-101 Technical Report outlines the recovery methods for the Westwood gold project, utilizing the refurbished Doyon Mill. Preliminary assessments indicated potential for zinc recovery, but subsequent drilling failed to validate resources sufficient for flotation capital expenditure. Consequently, the operating plan focuses on gold recovery via cyanidation, with the mill design retaining the potential for future zinc development if resources are identified. The mill refurbishment completed in early 2013 includes gold cyanidation and tailings desulphurization circuits.
The design criteria are based on a mine production plan, the existent Doyon Mill, metallurgical testwork from 2007-2009, and IAMGOLD operational experience. The nominal annual production is set at 850,000 tonnes per year, with an initial phase of 600,000 tpy. The daily mine throughput is the main design constraint, targeting 2,425 tonnes per day at 96% mill availability. All underground ore is hauled to the mill for crushing, grinding, and processing on site.
Processing involves a SAG mill and ball mill circuit followed by gravity separation for free gold recovery. The leaching circuit utilizes cyanidation with carbon absorption and stripping. Tailings management includes a cyanide destruction plant (SO2-AIR detox) and a paste backfill plant moved closer to the shaft to reduce pumping costs. Desulphurization flotation is implemented to treat tailings for environmental rehabilitation of the Doyon tailings ponds.
Website: https://www.iamgold.com/English/operations/westwood/default.aspx
Report Date: 2013
Region: Quebec, Canada
Project Status: Development
Commodity: Gold
Throughput: 2,425 tpd
Mine Life:
Mine Type: Underground
Ore type:
Westwood Mine: Gold Processing Circuit Upgrades
Overview
The Westwood Mine processing facility is a refurbished version of the original Doyon Mill from the 1970s, upgraded between 2011-2013 to efficiently process Westwood ore. The plant features modernized grinding, leaching, adsorption, and stripping circuits, with enhanced cyanide destruction capacity and a new paste backfill plant to support underground operations.
Key Process Stages
- Ore Handling: Underground ore is trucked 2.5km to the crusher house, processed through a single-stage jaw crusher (1.07 x 1.22 m) with grizzly feeder
- Grinding: 2,700 HP SAG mill in closed circuit with hydrocyclones, feeding a 1,000 HP ball mill. Target grind size: 80% passing 53 microns
- Gravity Separation: Sweco screen, 30″ Knelson concentrator, and shaking table recover gravity gold concentrate
- Leaching: 55-hour total retention time across primary leach (4.7h), CIL (6.6h), secondary leach (31.3h), and CIP (12.1h) tanks
- Cyanide Destruction: SO2/Air process with parallel detox reactors and 14-hour buffer capacity for backfill operations
- Paste Backfill: Dual-circuit system with 2km pipelines, designed for 144.6 tph capacity (operating at 70 tph)
- Gold Recovery: Zadra stripping reactors, two electrowinning cells, and carbon regeneration kiln producing doré bars
- Tailings: Disposal in Doyon open pit with partial usage for paste backfill
Critical Data
| Parameter | Value |
|---|---|
| Annual Throughput | 1,100,000 tonnes |
| Mill Availability | 96% |
| Daily Processing Rate | 3,106 tpd |
| Power Consumption | 8% of milling costs |
| Water Treatment | 4.0-4.5 MCUM annually |
Key Reagent Consumption (Annual)
| Material | Quantity (kg) |
|---|---|
| Grinding Media | 1,805,000 |
| Quick Lime (Total) | 5,640,000 |
| Cyanide | 945,000 |
| SO2 | 1,118,000 |
| Slag/Cement | 8,273,000 |
IAMGOLD Westwood Complex: Gold Processing Circuit & Key Operations
- Processing Circuit: ROM ore undergoes single-stage crushing, followed by SAG/ball mill grinding (target: 85% passing 75 µm), gravity separation, and cyanide leaching (CIL/CIP).
- Gold Recovery: Zadra stripping reactors and electrowinning cells produce doré bars; carbon is regenerated and reused.
- Throughput: Nominal rate of 3,106 t/d (40.5-hour leach retention time).
- Tailings Management: SO₂/air cyanide destruction; tailings are either used for paste backfill (70 t/h capacity) or pumped to the Doyon open pit.
- Energy & Water: 35–36 kWh/t power consumption; 1.1 Mm³ annual process water demand, primarily sourced from reclaimed TSF water.
- Key Upgrades: 2013 refurbishment included grinding, cyanidation, and paste backfill plant additions.
Source: IAMGOLD Corporation
