The proposed gold processing facility for the MacLellan and Farley Lake projects is designed as a staged conventional crushing, grinding, gravity recovery, carbon-in-pulp (CIP) leaching, and cyanide destruction plant producing gold-silver doré.
Report context
The preliminary economic assessment for the MacLellan, Farley Lake, Burnt Timber, and Linkwood properties, Lynn Lake Gold Camp, Manitoba, was prepared for Carlisle Goldfields Ltd. The processing section (Recovery Methods) describes a proposed gold-silver processing facility designed to ultimately process a nominal 2.63 Mt/a or 7.50 kt/d of gold-silver mineralization. The mill is planned to be built in two stages: the first stage will process 1.31 Mt/a or 3.75 kt/d, with the remaining equipment installed after four years to reach full capacity. This facility is expected to produce an average of 145,092 troy oz/a of gold over the life of mine and 198,763 troy oz/a of silver during the years when MacLellan is operational. Recoveries are based on 93.7% gold recovery from Farley Lake and 89.3% gold recovery from MacLellan, with approximately 60% silver recovery possible from the MacLellan mineralization.
Processing route
Process flowsheet development
The process flowsheet was developed based on the results of test work conducted by SGS in Vancouver, British Columbia and by Witteck in Mississauga, Ontario. The selected process flowsheet will produce gold-silver doré as the final product.
Crushing circuit
The process uses a conventional crushing and grinding circuit with screens and cyclones for size control. ROM material will be trucked from the open pit mine and dumped directly into the jaw crusher feed hopper or stored on a stockpile for later processing. Two 86 cm by 112 cm jaw crushers will reduce ROM material from less than 400 mm to 135 mm; one crusher will be installed prior to mill start-up and the second during the second stage. Primary crushing will operate 17 h/d to process 238 t/h in the first capital stage and 475 t/h in the second stage. A grizzly screen with hydraulic rock breaker will handle oversized material.
Secondary crushing will reduce material to 32 mm using one standard head cone crusher measuring 1.5 m in diameter, operated in open circuit with screens. The tertiary crushing circuit will reduce material to 8 mm using one short head cone crusher measuring 2.4 m in diameter. The fine mineralized material bin will have a capacity of 13,300 t with a live bottom feeder.
Grinding circuit
Fine grinding will take place in a wet ball mill in closed circuit with cyclones. One ball mill measuring 4.4 m diameter by 9.7 m with 4,500 kW will be installed when the plant first begins production, and a second ball mill will be installed when the plant is expanded. Fresh material will be added at 166 t/h during the first years and 332 t/h at final capacity. Process water will maintain 70% solids in the ball mill. The ball mill product size is 80% passing 84 µm with a recirculating load of 300%.
Gravity gold recovery
Free or gravity gold is recovered separately by a centrifugal concentrator (KC-QS48, 48-inch diameter or equivalent). Gold thus recovered is subjected to intense cyanide leach followed by electrowinning. The centrifugal concentrator will operate intermittently on undersize material from a sieve-bend screen that ensures no +2 mm material enters the concentrators. Gold concentrate will be transferred to an intense leach tank (ConSep Acacia CS1000 or equivalent) once sufficient material has been collected, with each batch taking approximately one day to collect. The leach will take place at 50°C with approximately 1,000 g/L of cyanide and LeachAid added. Pregnant leach solution will be treated in a dedicated basketless EW cell.
Leaching and pre-aeration
Ground slurry advancing to leaching is first thickened in a conventional bridge thickener with steel wall measuring 35.6 m diameter to increase density to 40% solids. The design includes one thickener for both trains. Thickener underflow then advances to pre-aeration tanks.
Pre-aeration tanks will be sparged with air or oxygen. Six tanks measuring 17.2 m diameter by 17.2 m height will be installed, with three installed in each capital stage. Pre-aeration time is 24 h. Lead nitrate may be added at up to 300 g/t. The pH will be adjusted to between 8.0 and 11.0 with lime.
Leach tanks will be installed as two identical trains of seven tanks each, with tanks measuring 16.4 m diameter by 16.4 m height. Leach circuit retention time is 48 h. Sodium cyanide will be added at 1.0 to 1.5 g/L NaCN. The pH will be adjusted to 10.5 to 11 with lime. All leach tanks will be sparged; the first two leach tanks may need to be sparged with oxygen.
CIP adsorption circuit
Activated carbon will be used to remove gold from the slurry in the CIP circuit. The circuit will consist of one or two trains of six agitated tanks in series, with tanks measuring 8.3 m diameter by 8.3 m height. The CIP circuit will use Kemix pump cells arranged on the same level in a carousel pattern. Carbon will have a stage-wise residence time of 38 h, while pulp will continuously flow through the circuit with a residence time of 1 h in each stage. Approximately 25 g/L of granular activated carbon will be added to the sixth stage. The batch movement of carbon will be about 9.7 t, processed over 38 h.
Gold elution and electrowinning
Gold will be recovered from the loaded carbon using the AARL elution process. Up to 100% of loaded carbon may be subjected to an acid wash using hydrochloric acid to remove calcium scale and adsorbed base metals. Carbon will be soaked in approximately 3% sodium cyanide and up to 2% sodium hydroxide for about 30 min, then heated to approximately 110 to 120°C and 70 to 100 kPa and eluted with six to ten bed volumes of high-quality deionized water.
Gold will be removed from the pregnant eluate using basketless EW cells. The EW circuit will have four 4.25 m³ cells installed in two stages. Gold will be loosely deposited on the EW electrodes and pressure washed to form gold-rich sludge. This sludge will be dewatered in a filter press and dried, then mixed with fluxes and smelted in a 125 kW induction furnace to produce gold-silver doré.
Carbon regeneration
Some or all of the carbon may be regenerated in an electrically fired rotary kiln to remove organic poisons and reactivate the carbon. The kiln will process carbon at 750°C for 30 min. Reactivated carbon will be quenched and screened before being returned to the barren carbon storage tank.
Cyanide destruction
The barren CIP tailings will be pumped to cyanide detoxification tanks where cyanide will be treated using the INCO sulphur dioxide and air process. SMBS will be added to slurry in the presence of copper from copper sulphate. Test work indicates that 140 min will be required for this reaction. Slurries thus treated typically have less than 5 ppm CN WAD. One cyanide destruction tank measuring 11.5 m diameter by 11.5 m height will be installed in each stage.
Reagent handling and storage
Reagents will include lime (delivered on 40 t trucks, slaked on site), sodium hydroxide (delivered in totes), flocculant (bulk bags), sodium cyanide briquettes (boxes or drums), hydrochloric acid (totes), SMBS (bulk bags), copper sulphate (bulk bags), activated carbon (bulk bags), and lead nitrate (sacks).
Key reported parameters
| Criteria | Unit | Value |
|---|---|---|
| First Stage Overall Plant Feed | t/d | 3,750 |
| Second Stage Overall Plant Feed | t/d | 7,500 |
| Operation Rate | d/a | 350 |
| Primary Crushing Availability (Both Stages) | % | 70 |
| First Stage Secondary and Tertiary Crushing Availability | % | 47 |
| Second Stage Secondary and Tertiary Crushing Availability | % | 94 |
| Plant Remainder Availability (Both Stages) | % | 94 |
| Bond Ball Mill Work Index (design) | kWh/t | 12.4 |
| Bond Abrasion Index (design) | 0.158 | |
| Specific Gravity Plant Feed | g/cm³ | 2.7 |
| Mill Feed Size, 80% Passing | mm | 400 |
| Primary Crushing Product Size, 80% Passing | mm | 135 |
| Secondary Crushing Product Size, 80% Passing | mm | 32 |
| Tertiary Crushing Product Size, 80% Passing | mm | 8 |
| Ball Mill Product Size, 80% Passing | µm | 84 |
| Ball Mill Recirculating Load | % | 300 |
| Pre-aeration Time | h | 24 |
| Leach Circuit Retention Time | h | 48 |
| CIP Circuit Retention Time (pulp) | h | 6 |
| CIP Circuit Retention Time (carbon) | h | 228 |
| Carbon Retention Time (stage-wise) | h | 38 |
| Head Grade (design) Au | g/t | 2.30 |
| Head Grade (design, MacLellan only) Ag | g/t | 4.36 |
| Design Recovery Au | % | 90.7 |
| Design Recovery Ag | % | 60.1 |
Project website: https://www.canadianminingjournal.com/news/gold-resource-initial-burnt-timber-estimate-includes-780-500-oz/
Technical qualifications
The design criteria are based on test work conducted by SGS and Witteck. The process flowsheet was developed based on the results of that test work. Provision should be made to sparge the pre-aeration tank with air or oxygen depending on the results of additional test work. All leach tanks will be sparged with air, but future test work may indicate that the first two leach tanks should be sparged with oxygen. Lead nitrate addition of up to 300 g/t depends on the results of additional test work on a representative sample of mill feed. The silver value is only included in the process plan for material recovered from MacLellan because the mining plan does not account for silver in the Farley Lake mineralization. Recoveries of 93.7% gold from Farley Lake and 89.3% gold from MacLellan are stated; the overall design recovery of 90.7% is provided in the design criteria.
Source: Preliminary Economic Assessment for the MacLellan, Farley Lake, Burnt Timber, and Linkwood Properties, Lynn Lake Gold Camp, Manitoba, Carlisle Goldfields Ltd., Section 17.0 Recovery Methods.
Consolidated report summaries
The following former standalone pages about this operation were consolidated here on October 25, 2026. They are retained for source traceability; dates and figures reflect each report’s own effective date and may be superseded by the current information above.
Preliminary Economic Assessment — MacLellan, Farley Lake, Burnt Timber, and Linkwood Properties
Technical report details a proposed 3.5 Mt/a gold processing facility to treat mineralization from four deposits in the Lynn Lake Gold Camp, Manitoba.
Report context
The Preliminary Economic Assessment (PEA) for the MacLellan, Farley Lake, Burnt Timber, and Linkwood Properties was prepared for Carlisle Goldfields Ltd. The report covers a gold processing facility designed to process nominal 3.5 Mt/a or 10.64 kt/d of gold-silver mineralization from these four deposits. The facility would produce between 196,900 troy oz/a and 375,200 troy oz/a gold-silver doré. The processing route described is a proposed design, supported by test work conducted by SGS in Vancouver, BC, and by Witteck in Mississauga, ON. No historical operating data from these properties is presented in the report sections examined.
Processing route
Crushing and grinding
The proposed flowsheet begins with a covered ROM stockpile with a recovery trench and apron feeder. Material less than 400 mm is fed to a 127 cm by 152 cm primary jaw crusher operating at 458 t/h, reducing material to 180 mm passing. Primary crushing operates 24 h/d with dust collection systems at the crusher and conveyor transfer points.
Secondary crushing uses three 2.13 m diameter short-head cone crushers in closed circuit with a double deck vibrating screen. Oversize from the screen is returned to the cone crusher via a bucket elevator, while undersize at 16 mm passing advances to the fine mineralized material bin. The recirculating load to the cone crusher is 200% of the advancing flow. A fine ore bin with 13,300 t capacity uses a live bottom feeder with load-cell monitoring.
Tertiary grinding employs a wet ball mill, 6.7 m diameter by 9.5 m length, with 7,300 kW drive, in closed circuit with cyclones. Fresh feed is added at 458 t/h with process water to maintain 70% solids in the mill. The ball mill is equipped with a trunnion magnet to remove steel chips. Mill discharge is diluted to 40% solids and pumped to a cyclopack with cut-size of P80 84 µm. The recirculating load is approximately 300%.
Gravity gold recovery
Approximately 30% of cyclone underflow reports to a sieve-bend screen protecting two centrifugal concentrators (KC-QS48, 48-inch diameter or equivalent). Sieve-bend undersize advances to the gravity concentration circuit. Centrifugal concentrators operate continuously, producing a gold concentrate collected in a holding tank sized for approximately 3 t. Concentrator tails are returned to the ball mill.
Gold concentrate undergoes intense cyanide leaching in a ConSep Acacia CS2000 or equivalent system. The leach operates at 50°C with about 1,000 g/L cyanide and pH adjusted to approximately 11 using sodium hydroxide. LeachAid™ may be added. Leached gravity concentrate is returned to the ball mill to liberate any unexposed gold. Pregnant leach solution advances to a dedicated basketless electrowinning (EW) cell.
Leach thickening and pre-aeration
Cyclone overflow from ball milling reports to a 45.7 m diameter conventional thickener to increase density to 40% solids. Flocculent or lime may be added to improve settling. Thickener underflow advances to pre-aeration.
The pre-aeration circuit consists of seven tanks, each 16.5 m diameter by 16.5 m height, providing 24 hours residence time. Pre-aeration is conducted at relatively low pH (8.0 to 11.0) with lime addition. Up to 300 g/t lead nitrate may be added to form an insoluble lead hydroxide layer on pyrrhotite, reducing cyanide consumption. Air or oxygen sparging maintains high dissolved oxygen. During pre-aeration, an insoluble iron hydroxide layer forms on pyrrhotite, preventing its dissolution.
Carbon-in-pulp leach
Four stages of leaching follow pre-aeration, using 14 tanks each 16.5 m diameter by 16.5 m height, providing 48 hours leach residence time. Lime adjusts pH to 10.5 to 11, though the report notes that when processing feed high in arsenopyrite, operating pH should be reduced to prevent an insoluble arsenic oxide layer forming on gold particles. Sodium cyanide is added to the first leach tank at 1.0 to 1.5 g/L NaCN. Leach residue is expected to have approximately 1,500 mg/L CN T and 400 mg/L CN WAD. All leach tanks are sparged with air; the first two may require oxygen sparging based on additional test work. Tanks have feed standpipes to prevent short-circuiting, and flow between tanks is by gravity.
Carbon-in-pulp adsorption
The CIP adsorption circuit uses six tanks, each 11.6 m diameter by 11.6 m height, arranged in a carousel pattern using Kemix pump cells on the same level. The carousel arrangement keeps carbon in one tank, preventing back-mixing and reducing carbon breakage. Slurry flows continuously through the circuit with 1 hour residence time per stage. Carbon is removed from the circuit once every 38 hours. Barren carbon is added to the sixth stage once that tank is at least half-full of slurry, at approximately 25 g/L granular activated carbon. Slurry density may be adjusted between 35 to 50% solids.
When carbon in the first tank is fully loaded, that tank is taken offline and all carbon is pumped to the elution circuit. The offline tank is then refilled with slurry and barren carbon, returning to service as CIP 6. Slurry flow is redirected accordingly through the remaining tanks.
Elution and electrowinning
Gold is recovered from loaded carbon using the AARL elution process. Up to 100% of loaded carbon may undergo acid wash with hydrochloric acid (HCl) to remove calcium scale and adsorbed base metals. Gold is eluted in the elution column with a solution of sodium cyanide and sodium hydroxide made from high quality water at high temperature. Some or all carbon may be regenerated in an electric kiln.
Gold is removed from the pregnant eluate using basketless EW cells. Gold sludge is pressure washed from electrodes to cell bottoms, dewatered in a filter press, and dried. Dried sludge is mixed with fluxes and smelted in an induction furnace to produce gold-silver doré. Gold-rich sludge from the gravity circuit EW is combined with CIP EW sludge for filtration, drying, and smelting.
Cyanide destruction
Barren CIP tailings are pumped to the cyanide detoxification tank. Cyanide is treated using the INCO sulphur dioxide and air process. Sodium metabisulphite (SMBS) is added in the presence of copper from copper sulphate. Slurries thus treated are expected to have less than 5 ppm CN WAD. Treated slurry is pumped to the tailings storage facility.
Key reported parameters
| Parameter | Unit | Design Value | Basis |
|---|---|---|---|
| Overall plant feed | t/d | 10,640 | Plant design |
| Operation rate | d/a | 350 | Plant design |
| Primary crushing availability | % | 94 | Design estimate |
| Secondary crushing availability | % | 94 | Design estimate |
| Plant remainder availability | % | 94 | Design estimate |
| Bond ball mill work index (design) | kWh/t | 12.4 | Testwork |
| Bond abrasion index | , | 0.158 | Testwork |
| Specific gravity plant feed | g/mL | 2.7 | Assumed |
| Moisture content plant feed | % | 3 | Assumed |
| Mill feed size, 80% passing | mm | 400 | Design |
| Primary crushing product size, 80% passing | mm | 180 | Design |
| Secondary crushing product size, 80% passing | mm | 16 | Design |
| Secondary crushing recirculating load | % | 200 | Design |
| Ball mill product size, 80% passing | µm | 80 | Design |
| Ball mill recirculating load | % | 300 | Design |
| Preaeration time | h | 24 | Design |
| Leach circuit retention time | h | 48 | Design |
| CIP circuit retention time (pulp) | h | 6 | Design |
| CIP circuit retention time (carbon) | h | 38 | Design |
| Head grade (design), Au | g/t | 1.94 | Design basis |
| Head grade (design), Ag | g/t | TBD | Design basis |
| Design recovery, Au | % | 90.7 | Based on testwork |
| Design recovery, Ag | % | 60.1 | Based on testwork |
Project website: https://www.canadianminingjournal.com/news/gold-resource-initial-burnt-timber-estimate-includes-780-500-oz/
The design criteria listed are based on test work conducted by SGS and Witteck. The report states the facility will produce between 196,900 troy oz/a and 375,200 troy oz/a gold-silver doré based on 90% recovery of gold and 60% recovery of silver. Silver is only accounted for in the MacLellan deposit; higher production rates only occur when MacLellan is in production. Mineralogical investigations indicated the presence of silver in other mineralizations, but the mining plan does not show silver reporting to mill feed from those deposits.
Technical qualifications
This technical report presents a Preliminary Economic Assessment only. The processing flowsheet and all figures are based on testwork and design assumptions; they do not represent historical operating data from the MacLellan, Farley Lake, Burnt Timber, or Linkwood properties. The design criteria are derived from test work conducted by SGS and Witteck. Several operational parameters carry uncertainty: provision should be made to sparge the pre-aeration tank with air or oxygen depending on the results of additional test work; the first two leach tanks may need oxygen sparging based on future test work; and up to 300 g/t lead nitrate addition depends on results of additional test work on a representative sample of mill feed. The head grade for silver is listed as "TBD". The report contains a simplified process flow diagram (Figure 17.1) that is not reproduced in this article. No actual plant performance, production history, or operating cost data is presented.
Source: Preliminary Economic Assessment for the MacLellan, Farley Lake, Burnt Timber, and Linkwood Properties, Lynn Lake Gold Camp, Manitoba, Carlisle Goldfields Ltd., Section 17.0 Recovery Methods, pages 17-1 through 17-10.
