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Longer mine life, increased production
Mining the new Piaba underground and satellite open-pit deposits concurrent with the existing Piaba open pit will nearly double the Aurizona mine life and increase annual production.
<$1,200 per oz AISC
1,660 Koz @ 1.60 g/t gold
868 Koz @ 1.49 g/t gold
Mining and processing
Open-pit / underground / CIL plant
Estimated mine life
1. Based on the 2021 pre-feasibility study. See Cautionary Notes.
2. Based on costs outlined in the 2021 pre-feasibility study with rough adjustments for inflation. Costs will be updated in the 2023 feasibility study. See Cautionary Notes.
3. M&I Mineral Resources are exclusive of Mineral Reserves. See Operations / Reserves & Resources and Cautionary Notes.
In September 2021, Equinox Gold completed a pre-feasibility study outlining a planned expansion of the Aurizona mine. By mining the underground and satellite open-pit deposits concurrent with the existing Piaba open pit, the expansion would extend the Aurizona mine life to 11 years with average annual production of 137,000 ounces of gold per year and total life-of-mine production of 1.5 million ounces of gold. Peak production would average more than 160,000 ounces of gold annually for four years.
The Piaba gold deposit contains gold mineralization in a vein system that extends at least four km along strike with smaller, near-surface satellite deposits to the east and west of the main Piaba deposit. Drilling has shown that gold mineralization also extends below the ultimate Piaba open pit to depths greater than 1,000 m from surface.
The current operation consists of the Piaba open pit mine and a conventional crushing and grinding circuit with an 8,000 tonnes-per-day carbon-in-leach (CIL) plant. The expansion will incorporate ore from the existing Piaba open-pit deposit along with the new Piaba underground deposit and the new Tatajuba and Genipapo open-pit deposits. While the expanded mine will continue to use the existing CIL process plant and surface infrastructure, the existing electrical substation will need to be expanded and the mine will require additional tailings and waste rock storage. Mining and processing of underground ore concurrently with open-pit ore will increase the average feed grade to the CIL plant, increase annual gold production and extend the mine life. No flowsheet changes or plant modifications are expected to be required to treat ore from the future mining areas.
Equinox Gold is completing a feasibility study for the expansion with completion targeted for mid-2023. Permits have been received for three underground portal locations; underground development could start as early as Q4 2023.
- After-tax NPV5% of $314 million at $1,500/oz gold ($600 million at $1,800/oz gold)
- $464 million after-tax life-of-mine (LOM) cumulative net cash flow at $1,500/oz gold ($803 million at $1,800/oz gold)
- <$1,200/oz average AISC LOM
1.5 million oz LOM gold production at an average recovery of 90.5%
- More than 160,000 oz peak average annual gold production from 2026 to 2029
- 137,000 oz average annual gold production (LOM)
- $154 million underground mine initial capital costs, including $20 million contingency
- 11-year mine life with additional expansion potential from further exploration success
The pre-feasibility study contemplates a three-year capital development and construction timeline for the underground mine. Total initial capital costs during this period are estimated at $154 million. Leasing the mining fleet would reduce capital costs by $25 million. Sustaining capital for the life of mine is estimated at $383 million
The underground mine will be developed along a total strike length of 2.3 km beneath the Piaba open pit. Access to the underground mine will be via a ramp collared in fresh rock within the pit. The currently defined seven separate mining areas will be accessed by a 2 km main haulage decline with separate internal ramps. The first 800 m of the main haulage will be developed as a single heading to the location of the primary ventilation raise, which will also provide emergency egress. From that point onwards the ramp will be developed as a double ramp arrangement, with the second ramp used for ventilation purposes during production. All underground mine development is planned within fresh rock located on the hanging wall side of the mineralized body.
The proposed underground mining method is long-hole stoping due to good ground conditions and the steep dip of the deposit. The pre-feasibility study contemplates owner mining of stopes and underground development. Most of the stopes will include permanent rib pillars and be backfilled with rockfill sourced from the underground development and/or open pit waste. The requirement of cemented rockfill will be localized to higher-grade areas where mining recovery can be maximized by eliminating rib pillars and above sill pillars.
Open-pit mining is currently undertaken by a contractor using conventional drill and blast, load and haul methods.
The Piaba and Piaba East pits are currently in production and provide ore feed to the CIL process plant. Piaba East is a single-phase pit that is expected to be depleted by the end of 2024. Piaba pit will continue until 2032 to mine the remaining four phases of the design and also the crown pillar in the floor when underground mining is complete.
Additional open pit ore will be sourced from the Tatajuba deposit, located 4 km to the west of the Piaba pit, and from the Genipapo area, located 3 km to the east of the CIL plant.
Permitting and Timeline
The pre-feasibility study contemplates a three-year capital development and construction timeline for the new Piaba underground mine and a feasibility study is scheduled for completion in mid-2023. Permits have been received for three exploration decline portal locations within the Piaba pit, with the west end portal location available for development in fresh rock by Q4 2023.
Ore will be available early in the underground development phase, and Equinox Gold is reviewing additional opportunities to access higher-grade ore zones earlier in the underground mining schedule to enhance economics. First ore is released after approximately two years of development with steady state production achieved by Year 4. This production rate is maintained until mid-Year 7 and then reduces until underground mining is complete at the end of Year 10. The Crown Pillar between the Piaba open pit and underground will be recovered when underground mining is complete.