Red Dog is comprised of a number of sedimentary hosted exhalative lead-zinc sulphide deposits hosted in Mississippian-age to Pennsylvanian-age sedimentary rocks. The orebodies are lens-shaped and occur within structurally controlled (thrust faults) plates, are relatively flat-lying and are hosted by marine clastic rocks (shales, siltstones, turbidites) and lesser chert and carbonate rocks. Barite rock is common in and above the sulphide units. Silicification is the dominant alteration type. The sulphide mineralization consists of semi-massive to massive sphalerite, pyrite, marcasite and galena. Common textures within the sulphide zone include massive, fragmental, veined and, rarely, sedimentary layering. The Red Dog plate consists of strata of the Lisburne and Etivluk Groups as well as the Okpikruak Formation. The plate is detached in incompetent shales of the Kuna Formation (part of the Lisburne Group) and structurally overlies the Wolverine Creek plate and underlies the Key Creek plate. The general mineralization zonation within the mine deposits (Qanaiyaq, Main, Aqqaluk, and Paalaaq) consists of: • Barite, commonly the uppermost mineralized unit consisting of disseminated to massive and laminated fine grained pyrite, sphalerite, galena mineralization increasing downward; • Silica rock, generally underlying barite, is variably mineralized similar to the barite, and represented by secondary crystalline quartz replacing barite and carbonate; • Massive sulphide, forming the high-grade intervals and consisting of reddish-brown sphalerite, galena, pyrite mineralization with grades varying from 20 to 50% Zn, and high Ag content; • Sulphide vein and breccia zone, formed by typically symmetric bands of tan sphalerite, red–brown sphalerite, galena and pyrite, commonly present at the base of the deposit. Brecciation caused by dissolution of barite and carbonate, and cross-cutting breccias are common, and may represent multiple phases of sulphide deposition. Sulphide-bearing barite occurs as two distinct textural types: white to grey, fine-grained (10–50 µm) equigranular grains intergrown with sulphides, and white, coarse-grained (up to 3 cm) crystals with interstitial sulphides. In the Aqqaluk and Paalaaq deposits, base-metal and iron sulphides locally occur as crude interlayers with the barite. Sulphide-poor barite is found at the top of each deposit near or on the contact between the Ikalukrok unit and the Siksikpuk Formation. Sulphide-poor barite is white to light grey, fine-grained, and commonly well bedded. Massive sulphide is a term used at the Red Dog Mine for material that contains greater than 40 wt% sulphide minerals (sphalerite, galena). Most of the Main, Aqqaluk and Qanaiyaq mineralization is massive and unbedded, consisting of abundant sulphide grains and aggregates disseminated in a baritic, silica, or sulphidic matrix. Fragmental textures also are present in massive sulphide mineralization. Banded sulphides in shale are rare, but have been reported from Aqqaluk and Paalaaq. Sulphide veins are present in all of the deposits, although they are most abundant and consistently developed at Aqqaluk, where they are found mainly at the base and periphery, and less commonly in the centre of the deposit. At Aqqaluk, the veins typically cut rocks of the Ikalukrok unit and all mineral facies except the sulphide-poor barite. The veins are steeply dipping, trend north–northeast, and vary in width from 1 mm to 1 m. Vein density can be so intense as to constitute bulk ore-grade zones. Vein-style mineralization at Qanaiyaq is uncommon and its distribution at Paalaaq is poorly documented. The Main deposit has been mined out. It extended 1,600 m in a northwest direction, with a width varying from 150 m to 975 m and up to 135 m thick. To the north and northeast, the Main deposit merges with the Aqqaluk deposit, as the Main and Aqqaluk deposits are actually a single deposit separated for convenience along a line defined by the Red Dog and Shelly creeks. The Aqqaluk deposit is defined as any mineralization that is potentially mineable by open pit methods that lies north of the roughly east–west line made by Shelly Creek and Red Dog Creek, downstream of the Shelly Creek intersection. Any Paalaaq (sub-lower plate) mineralization mined in an open pit would also be considered to be part of the Aqqaluk deposit. Lower-plate mineralization forms the largest component (70% to 80%) of the Aqqaluk Mineral Reserves and Mineral Resources. The dimensions of the mineralization at the Aqqaluk deposit are 700 m east–west, 600 m north–south and up to 150 m thick. Thicknesses of the veined unit vary from 3 m to 30 m, whereas the sulphide and the silicic exhalites vary from 3 m to 80 m in thickness. The barite cap ranges from 1 m to 80 m thick. The Paalaaq deposit is an arcuate-shaped mineralized zone lying to the north of the Aqqaluk deposit. The deposit is approximately 1,200 m long in a north–south direction, is 100 m to 200 m wide from east to west and up to 60 m thick. The Paalaaq deposit is contained within a thrust sheet below the Aqqaluk deposit, referred to as the sub-lower plate. The mineralization is open to the north, pinches out to the east and is partially structurally terminated on its western extension. The Qanaiyaq deposit (known historically as the Hilltop deposit) lies approximately 600 m to the south of the Main deposit. It is contained in a flat-lying segment of the Red Dog plate that is 850 m long by 600 m wide, which has been thrust over a thick sucession of the Okpikruak Formation within the Wolverine Creek plate. The segment of Red Dog plate forms the crest of a hill, thus the limits of mineralization are well defined. Ore grade mineralization occurs in a zone that is approximately 450 m long by 300 m wide with an average thickness of 45 m. The A?arraaq deposit is situated 6.2 km northwest of Paalaaq. It is an elongate lens-shaped massive sulphide body hosted within black, carbonaceous, siliceous shale at an average depth of 650 m). It occurs near the base of a large northeast-vergent thrust sheet in a sequence of black shale, chert and calcareous turbidite of the Ikalukrok unit. A massive barite body straddles the contact between Ikalukrok unit and the overlying Etivlik Group chert and shale, and is separated from the deposit by ~90 m. Unlike the Main, Aqqaluk, Paalaaq and Qanaiyaq deposits, the massive barite at A?arraaq is not mineralized. The mineralized zone is contained within a larger lens of silicified and pyritic shale that is 1,200 m long, 700 m wide and 140 m thick. The Aktigiruq deposit is situated directly to the north of the A?arraaq deposit and roughly 12 km to the northwest of the Red Dog Mine. Aktigiruq is the most aerially extensive of the known Red Dog district deposits, and has a mineralized footprint of approximately 2,500 m by 1,300 m. The deposit dips to the southwest, and the thickest section of mineralization is roughly 850 m deep; mineralization occurs from about 400 to 1,000 m depth. The Su deposit is located 22 km northwest of the Red Dog Mine and is interpreted to be situated on the same north–south trending package of Red Dog plate stratigraphy (Su subplate) that overlies the Wolverine Creek plate to the east, and underlies higher structural plates, including the IP Creek plate and the Kelly River Allochthon to the west.

Ore is currently mined from the Aqqaluk and Qanaiyaq pits. All future ore production is also expected to be mined from these pits. The mining method employed is conventional open pit drill-and-blast and truck-and-shovel technology.

The larger of the two, the Aqqaluk pit, is approximately 945 m (3,100 ft) along its widest axis, east–west, and an average of 701 m (2,300 ft) in the perpendicular, north–south. The smaller of the two, the Qanaiyaq pit, is located 1.4 km (4,700 ft) south of the Aqqaluk pit and is approximately 732 m (2,400 ft) along its widest axis, northwest–southeast, and an average of 457 m (1,500 ft) in the perpendicular, northeast–southwest.

Both pits are mined on single 7.6 m (25 ft) benches and are accessed via two-lane haul roads. The haul roads are designed with a running width of 22.9 m (75 ft) and include 3.7 m (12 ft) safety berms and 1.8 m (6 ft) ditches; the total design width is 28.3 m (93 ft). Long-term haul roads are designed to a maximum grade of 10%, and short-term haul roads are designed to a maximum grade of 12%.

The Aqqaluk pit is generally dry, but seeps occur in fracture zones. Pumping rates from the Aqqaluk pit vary from up to 75.7 l/s (1,200 gpm) in spring and summer, down to less than 6.3 l/s (100 gpm) in winter. The Qanaiyaq pit is generally dry. Wet conditions can become problematic in both pits during spring freshet after winters with deep snow pack if temperatures increase too quickly. This leads to rapid snow melt causing water to report to the lowest bench of the pits at a rate greater than the peak pumping capacity. These extreme freshets are mitigated by storing the excess water on the lowest bench and adjusting the mining plan to excavate higher benches for the few days required for the pumping system to catch up and remove the water.

Three of the four phases in the Aqqaluk pit remain to be mined and mining of the first of the two phases in the Qanaiyaq pit started in 2016. The Qanaiyaq pit is planned to operate until 2027 and the Aqqaluk pit until 2031. The final year will also treat the low-grade ore stockpile. The waste to mill feed strip ratio over the life of the Aqqaluk pit is 0.87:1. The waste to mill feed strip ratio over the life of the Qanaiyaq pit is 2.18:1. Waste rock from the Aqqaluk and Qanaiyaq pits will be used to completely backfill the mined-out Main and Qanaiyaq pits.

The mineral processing facilities employ conventional grinding and sulphide flotation methods to produce zinc and lead concentrates.

The Red Dog flow sheet uses three stages of grinding and froth flotation technology to recover sphalerite and galena to the zinc and lead concentrates respectively. Following crushing and grinding, slurry reports to a pre-flotation circuit to remove elemental sulphur and naturally occurring organic material. The pre-flotation section consists of both a rougher and a cleaner stage. The rougher stage consists of mechanical cells while the cleaner circuit is a Jameson cell. The Jameson cell is used to minimize the loss via entrainment of both fine lead and zinc particles to the pre flotation concentrate using dilution. The lead flotation circuit consists of a rougher circuit in closed circuit with cleaner columns. Xanthate is used as sulphide collector and cyanide is used as the main pyrite depressant. Tower mills are used for regrind to provide additional mineral liberation. Typical lead recovery to the lead concentrate varies between 55-65% depending on ore type. The final lead concentrate is thickened and filtered. The lead flotation tailings reports to the zinc circuit. Copper sulfate is used to activate sphalerite while xanthate is used as the sulphide collector. The zinc flotation circuit consists of a rougher circuit followed by three stages of cleaning and a retreat circuit. The zinc rougher concentrate is reground by one M5000 IsaMill for additional liberation. The tailings from the zinc cleaner circuit is further reground in another M5000 IsaMill before feeding a three stage zinc retreat circuit. The zinc retreat final concentrate is combined with the zinc cleaner concentrate to make up the final zinc concentrate. The zinc concentrate is then thickened and filtered.

Concentrate is stored on site then hauled by truck to the port site facility on the Chukchi Sea. The concentrates are stored at the port and then shipped to the contracted smelting facilities during the shipping season between early July and early October.

Construction progressed on the US$135 million mill upgrade project, called VIP2, with planned startup on schedule for the first quarter of 2020. The project started construction in late 2017, and is expected to increase average mill throughput by about 15% over the remaining mine life, helping to offset lower grades and harder ore.

The VIP2 project envisages that the main modifications to the grinding circuit will be to allow the SAG1 and SAG2 mills to draw the same amount of power as the SAG3 mill, and the addition of one M15000 IsaMill as a quaternary mill. The flotation circuit will be augmented with six OK-16 lead scavenger cells and one Jameson cell as a zinc 1st rougher concentrate cleaner.

Construction on the mill upgrade project, called VIP2, was completed in 2020.

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