This report summarizes the feasibility study for reopening the Goldex mine to exploit the M and E zones at a proposed rate of 5,100 tonnes per day.
Report context
The Goldex mine began commercial production in August 2008 on the GEZ zone and operated until production was suspended indefinitely on October 19, 2011, to allow for investigations into water inflow and ground stability issues. On that date, the remaining reserves at Goldex, containing 1.4 million ounces of gold, were reclassified as mineral resources. On October 14, 2012, Agnico-Eagle staff completed a feasibility study for the exploitation of the M and E zones at the Goldex mine. These are the Goldex mine’s first mineral reserves since the mineral reclassification in October 2011, and they are based on the results of the feasibility study and the current Life of Mine. On July 25, Agnico-Eagle’s Board of Directors approved the development of the M and E zones at the Goldex mine, based on preliminary results of the feasibility study.
Processing route
Historical plant description and performance
The Goldex processing plant was commissioned in April 2008 and went into commercial production in August 2008. An expansion project in 2010 increased the throughput rate of the processing plant from 6,900 to 8,000 tonnes per day, with peaks of up to 9,500 tonnes per day utilizing secondary crushing. The plant closed in October 2011 when the mining was suspended, and it has been on care and maintenance since then. The existing Goldex processing plant flowsheet includes crushing and ore handling, grinding and gravity, flotation, concentrate thickening and handling, cyanidation and CIP, a tailings system, and a paste backfill plant.
Proposed processing design
The current feasibility study proposes that the plant reopens in 2013 and operates at a rate of 5,100 tonnes per day, with the addition of a paste backfill plant to return some of the tailings to fill mined-out stopes as part of the mining plan. The proposed operating schedule is 24 hours per day, seven days per week at 95% plant availability.
Most of the gold at Goldex occurs as free particles recoverable by gravity concentration. The balance of the gold occurs as finer particles associated with pyrite. The processing methods chosen to recover the gold take advantage of its coarse native character and its association with pyrite.
The broken ore is crushed underground by a jaw crusher and then hoisted to surface. The processing facilities on surface include secondary crushing, grinding, a gravity circuit to recover coarse free gold, sulphide flotation, a flotation concentrate-handling facility, and a gold room to smelt the gravity concentrate into doré bars, the final product. The thickened flotation concentrate is transported in slurry-handling trucks 40 km to the LaRonde processing facility where it is fed to a dedicated Goldex leach extraction circuit. The extracted gold joins the LaRonde carbon-in-pulp circuit for gold recovery.
The Goldex processing facility includes flotation tails disposal at two existing tailings ponds: one located at Manitou (24 km east of the Goldex complex), and a nearby auxiliary pond (4 km south of the complex).
Metallurgical testwork history
The report describes historical pilot plant metallurgical testwork and more recent metallurgical tests. A bulk sample from the GEZ yielded metallurgical results presented in Table 13.1. Table 13.2 summarizes gravity recoverable gold (GRG) data for the GEZ, E, M and D zones. Table 13.3 summarizes flotation recovery data for the GEZ, E, M and D zones.
Metallurgical design parameters
Gravity recovery models for M and E zones were developed. Flotation recovery models for M and E zones are presented in Figure 13.2. Cyanidation of flotation concentrate recovery models for M and E zones were developed. Carbon adsorption recovery models for M and E zones were developed. Global gold recovery models for M and E zones are presented in Figure 13.3, comparing Goldex alone with a combination of Goldex and LaRonde circuits.
Processing risks
The report identifies processing risks including reducing fines gold losses at flotation from overgrinding, and mass pull extraction and gold-pyrite recovery as a function of pH control. Recommendations include further investigation of particle size distribution to improve gold recovery in the flotation circuit, and testing the effect on gold recovery of paste backfill ratio levels higher than 20% in the millfeed.
Key reported parameters
| Parameter | Value | Basis |
|---|---|---|
| Proposed throughput rate | 5,100 tonnes per day | Design for feasibility study |
| Historical throughput rate (after 2010 expansion) | 8,000 tonnes per day, with peaks up to 9,500 tonnes per day | Actual historical operating data |
| Proposed plant availability | 95% | Design assumption |
| Expected metallurgical gold recovery | 93% | Established by metallurgical testwork |
| Proposed operating schedule | 24 hours per day, seven days per week | Design assumption |
| General processing plant design criteria | 5,100 tonnes per day operation | Reference in Table 17.3 |
| Distance to LaRonde processing facility | 40 km | Design parameter for concentrate transport |
| Distance to Manitou tailings pond | 24 km east of Goldex complex | Existing tailings disposal location |
| Distance to auxiliary tailings pond | 4 km south of Goldex complex | Existing tailings disposal location |
Project website: https://www.agnicoeagle.com/English/operations-and-projects/global-operations-and-development-projects/goldex-complex/default.aspx
Technical qualifications
The Goldex mine began commercial production in August 2008 on the GEZ zone and continued to operate until production was suspended indefinitely on October 19, 2011, to allow for investigations into water inflow and ground stability issues. On that date, the remaining reserves at Goldex, containing 1.4 million ounces of gold, were reclassified as mineral resources. The operations in the GEZ remain suspended indefinitely. The feasibility study was finalized in October 2012 for bringing the M and E zones into production at an average rate of 5,100 tonnes per day.
The mineral reserves presented in this report are based on the indicated resources in the M and E zones as of December 31, 2011. The design parameters for the primary stopes include 10% dilution and 95% mine recovery for both zones. The parameters for the secondary stopes include 20% dilution and 85% mine recovery. The metals prices and currency exchange rate assumptions used to establish the reserves were based on three-year trailing averages for the period ending May 1, 2012, of US$1,342 per ounce gold, and an exchange rate of C$1.03 per US$1.00. The operating costs of C$41.09 are based on the most recent documented costs in the Abitibi region.
Specific recommendations to further reduce project risk include detailed definition drilling for the E Zone, continued drilling of other satellite zones, particularly the D Zone, continued ground water modelling, assessment of stope stand-up time for both mining zones, continued installation of the upgraded underground ground-monitoring system, further investigation of particle size distribution to improve gold recovery in the flotation circuit, and testing the effect on gold recovery of paste backfill ratio levels higher than 20% in the millfeed.
Source: Technical Report on Production of the M and E Zones at Goldex Mine, October 14, 2012, Items 1, 2, 13, 17.
