Summary:
The deposits in the Red Dog district are classified as clastic dominated, although they also exhibit characteristics of carbonate replacement deposits.
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 Anarraaq 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 Anarraaq 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 Anarraaq 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.
Summary:
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.