The Rainy River deposit is an auriferous VMS system (Pelletier 2016) with a primary syn-volcanic source and possibly a secondary syn-tectonic mineralization event.

At Rainy River, gold and silver are the dominant metals and the base metal (Cu-Pb-Zn) sulphides, although good indicators of the presence of gold, represent less than 10%, by volume, of the host rock. This is in contrast with other VMS systems that generally contain large amounts of base metals. However, there are exceptions, i.e., gold-rich VMS deposits that often contain modest amounts of base metals relative to gold (Mercier-Langevin et al. 2015 and references therein).

The Rainy River deposit occurs within a sequence of felsic to intermediate, calc-alkaline metavolcanic rocks which is bounded to both the north and south by a lower mafic volcanic sequence. This mafic sequence is intruded by the trondhjemitic Sabaskong batholith to the north. Felsic to intermediate rocks are intruded to the east of the deposit by the Black Hawk monzonitic stock. In the deposit area all rock units strike approximately east-west and dip to the south, subparallel to the main foliation recognized in the area.

The Rainy River deposit comprises eight distinct zones of gold and silver mineralization. The bulk of the gold mineralization at Rainy River is contained in sulphide and quartz-sulphide stringers and veins hosted by felsic quartz-phyric rocks.

ODM/17 Zone
The ODM/17 Zone is a seri ........

Mining at Rainy River currently uses open pit methods. It will transition into a combined open pit and underground (OP+UG) operation. Underground development commenced at Intrepid in 2021.

The open pit mine is a conventional truck and shovel mining operation, with a fleet of 220t payload haul trucks combined with diesel-powered hydraulic excavators and large front-end loaders (FELs) as primary loading units. The open pit operates at an annualized peak mining rate of 153,000 tpd of ore, and the waste has an overall strip ratio of 2.32:1 (waste:ore).

Haulage ramps were designed nominally at 33 m width and a maximum ± 10% grade, except for the bottom few benches where widths were permitted to be reduced to one-way traffic of 20 m and ± 12% grade.

The plan for the Main Zones underground operation is to access the various ore zones from two portals. The IntrepidDeposit will be accessed from one portal, with a decline started in 2021 (still under development as part of an orebody investigation project).

The underground operations will be accessed via declines and follow a mechanized longitudinal long-hole open stoping technique to mine the underground Mineral Reserves. Underground ore production rates will be variable but will reach the planned maximum of approximately 5,500 tpd in 2026.

The Rainy River mine will thus entail a continuation of the existing OP operation, plus two UG operations using mining methods optimized to th ........

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The Rainy River processing plant has two main mineral processing buildings:
- Primary Crushing Building; and
- Main Process Plant.

The process flowsheet consists of the following unit processes:
• Gyratory crusher.
• Coarse ore stockpile, discharged through draw pockets by apron feeders.
• SAG mill feed conveyor.
• SAG mill.
• Pebble crusher.
• Ball mill.
• Gravity concentration of cyclone feed slurry.
• Intensive cyanide leaching of the gravity concentrate using an Acacia reactor.
• Pre-leach thickener.
• Cyanide leaching.
• CIP circuit.
• Cyanide destruction using the sulphur dioxide-air process.
• Carbon stripping using the Zadra process.
• Electrowinning of the eluent and gravity concentrate leach solution.
• Casting of gold and silver doré bars (doré) in an induction furnace.

Gravity concentration
Three ports of the cyclone feed distribution header are piped directly to ........