Fenelon Gold Project — 2023 Technical Report

This technical report presents a proposed process plant design for the Fenelon Gold Project based on laboratory-scale test work and benchmarked data.

Report context

The NI 43-101 Technical Report for the Detour-Fenelon Gold Trend Property and Preliminary Economic Assessment of the Fenelon Gold Project, Quebec, Canada, is dated August 2023. The report describes a proposed processing route for material from the Project, with design criteria derived from testwork performed mainly at the SGS Lakefield laboratory.

Processing route

Summary and basis

The proposed flowsheet was established based on laboratory-scale test work performed mainly at the SGS Lakefield laboratory. Several process route options were reviewed in initial stages of the study. Based on analysis, a gravity circuit followed by conventional leach and carbon-in-pulp process route was selected as most suitable for the deposit and project economics. The unit operations selected are all typical for gold recovery, and the proposed flowsheet uses standard processes and technologies.

Proposed flowsheet overview

The proposed process plant consists of primary crushing, followed by a grinding circuit comprising a semi-autogenous ball mill (SAG) in closed circuit with a pebble crusher and ball mill in closed circuit with cyclones (SABC circuit). A gravity circuit, followed by intensive leaching, recovers coarse gold from cyclone underflow, while cyclone overflow is treated in a carbon-in-leach (CIL) circuit. Gold and silver are recovered in an adsorption-desorption-recovery (ADR) circuit, electrowinning (EW) cells and gold room produce doré.

The plant also includes a reagent preparation area and process and industrial water circuits. Following the process plant, a SO₂/Air cyanide detoxification circuit and then a tailing flotation circuit are proposed. The tailing flotation would produce a sulphide concentrate tailing and a tailing with no sulphide. The sulphide concentrate tailing would mainly produce paste backfill to send underground and/or dry for tailings storage. The no sulphide tailing would send to dry tailings storage and/or to produce paste backfill to send underground.

Mineralized material stockpile

Mineralized material would be hauled from the mine and conveyed to a covered stockpile providing approximately 7,000 tonnes of live storage. The mill feed stockpile is equipped with two apron feeders to regulate feed at 317 tonnes per hour into the SAG mill.

Grinding circuit and gravity circuit

The proposed grinding circuit is an SABC circuit comprising a single variable speed SAG mill and a single fixed speed ball mill. The SAG mill would operate in closed circuit with a pebble crusher, followed by a ball mill operated in closed circuit with cyclones. The product particle size exiting the grinding circuit cyclone overflow would contain 80% passing 75 µm material.

A SAG mill size of Ø8.5 m x 3.8 m (Ø28’ x 12.5’) effective grinding length was selected with a total installed power of 5,400 kW. The SAG mill would be fitted with discharge grates and a trommel screen. SAG mill trommel oversize would be conveyed to a 200 kW pebble crusher, and undersize discharges into a common pump box with the ball mill discharge feeding the cyclone cluster.

A ball mill, Ø5.5 m x 7.9 m (Ø18’ x 26’) EGL, fitted with a trommel screen, was selected for secondary grinding with total installed power of 5,400 kW. The ball mill would operate in closed circuit with a cluster of cyclones producing an average product P80 of 75 μm.

Underflow from the cyclone cluster would be split into three streams by the cyclone underflow launder, with approximately 50% of the underflow constituting feed to the gravity circuit (25% to each concentrator). The gravity circuit would consist of two gravity screens and two variable-speed centrifugal concentrators. Concentrate from the gravity concentrators would feed the Intensive Leach Reactor (ILR) circuit. The ILR pregnant solution would be pumped to the pregnant tank and electrowinning cell dedicated to the gravimetric circuit in the gold room.

Pre-Leach thickening and carbon-in-leach

Prior to leaching, ground slurry from cyclone overflow would pass through a trash screen before feeding the pre-leach thickener feed box. Based on equivalent material, a Ø30 m thickener was selected. Underflow from the pre-leach thickener at 45% (w/w) solids would be pumped to the CIL circuit feed distribution box.

Slurry would gravitate to the first pre-leach tank. Lime and oxygen would be added to the pre-leach tank to oxidize pyrrhotite mainly. The pre-leach tank and CIL circuit tanks would consist of a bank of seven agitated tanks, each 15 m in diameter, mechanically agitated and operating in series. Lime would be added to maintain pH of approximately 11, and sodium cyanide would be added in CIL tanks along with process oxygen sparged through the tank bottoms. Slurry travels through the CIL circuit via inter-stage pumping screens, while gold-loaded carbon is pumped counter-current to slurry flow.

Adsorption, desorption and recovery circuit

The gold recovery circuits are based on processing 5 tpd of loaded carbon with a high-pressure Zadra process. Loaded carbon from CIL circuits is transferred into an acid wash vessel. A batch of 3% (w/w) hydrochloric acid cold solution is prepared. The acid wash sequence involves injection of dilute acid solution, followed by soaking for one hour, then rinse cycles.

Carbon elution (stripping) is initiated when a barren strip solution of 1% NaOH and 0.5% NaCN circulates through the elution column at a flow rate of two bed volumes per hour for 8 hours at elevated temperature and pressure. Final heating of barren solution uses a heat exchanger where strip solution contacts hot water from propane-powered boilers to reach nominal strip solution temperature of 135°C. A pressure control valve maintains the column at nominal pressure of 650 kPa.

After stripping, carbon is transferred to a dewatering screen and then to a carbon regeneration kiln operating at nominal temperature of 700–800°C. Two EW cells recover gold and silver from pregnant strip solution. A separate dedicated EW cell treats the ILR pregnant solution. Each EW cell is equipped with a rectifier and fitted with stainless steel anodes and stainless steel basketless cathodes.

CIL tailings thickener and cyanide destruction

Slurry from the CIL circuit flows to a carbon safety screen, then to a 30 m diameter CIL tails thickener. Overflow from the tails thickener gravitates to the process water tank to recover free cyanide. Tails thickener underflow at 65% solids is pumped to cyanide destruction tanks.

Cyanide destruction uses the SO₂/Air process in two tanks providing retention time of 2 hours. Sodium meta-bisulphite solution is added as SO₂ source, and oxygen is injected by spargers.

Tailings flotation circuit

The proposed tailings flotation circuit consists of one conditioning tank, five rougher tank cells and two thickeners (one for flotation concentrate and one for flotation tails). Flotation would be able to produce a high sulphide tailings concentrate and a low sulphide tailing. DF-208 and Xanthate (PAX) collectors and MIBC frother are added as reagents.

Key reported parameters

Technical qualifications

The report explicitly states that the values presented in the design criteria (Table 17.1) were derived from testwork data, benchmarked values, GMS’s database or based on Wallbridge’s requirements. The process flowsheet was established based on laboratory-scale test work performed mainly at the SGS Lakefield laboratory; no pilot plant or operating plant data from the Project itself are presented. Grinding media consumption was estimated using benchmarking data for similar projects and adjusted using power calculations. Mill liner replacement schedules were based on vendor recommendations and GMS’s database. The report presents a proposed design only; no historical operating data for this Project are included, and no testwork results beyond laboratory scale are reported.

Source: NI 43-101 Technical Report for the Detour-Fenelon Gold Trend Property and Preliminary Economic Assessment of the Fenelon Gold Project, Quebec, Canada – August 2023.