The Caribou deposit is a volcanic hosted massive sulphide deposit (VMS) typical of the The Bathurst Mining Camp (BMC).

The Caribou deposit consists of the following units from the base upward:
(1) dark gray to black carbonaceous shale, pale gray phyllite, graywacke, and chloritic schist interbedded with hydrothermally altered pale green felsic volcanic rocks (footwall of the deposit);
(2) stringer sulfides cutting hydrothermally altered sedimentary and felsic volcanic rocks; (3) massive sulfides comprising a vent complex and bedded sulfides;
(4) chloritic schist at the contact between massivesulfides and overlying felsic volcanic rocks; and
(5) interbedded felsic volcanic and sedimentary rocks.

Mineralization within the Caribou deposit is composed of seven lenses that are zoned mineralogically and chemically from a copper-rich vent-proximal facies (vent complex) near the bottom and western part of each lens, to a lead-zinc-rich vent-distal facies (bedded sulphides) near the top and eastern part of each lens. Although it is impossible to rule out one large sulphide lens that was dismembered during deformation, the common clustering of modern and ancient deposits in vent fields is consistent with multiple vent sites at Caribou.

The vent complex consists predominantly of pyrite + pyrrhotite + chalcopyrite + magnetite, whereas the bedded sulphides are composed of pyrite + sphalerite + galena + arsenopyrite + tetrahedrite. The massive sulphides are zoned such that copper, bismuth, cobalt, europium/europium*, and copper/ (copper + lead+ zinc) decrease, and zinc, lead, silver, tin, indium, arsenic, antimony, molybdenum, cadmium, mercury, and gallium increase, from the vent complex to the bedded sulphide facies. Compared to bedded sulphides, sphalerite, galena, and pyrite in the vent complex are also iron-, silver-, and arsenic-rich, respectively.

The western sulphide lenses at Caribou are underlain by a sulphide stringer zone that is composed mostly of pyrite + quartz + siderite impregnations and veins with iron chlorite selvages cutting hydrothermally altered felsic volcanic and sedimentary rocks. Because the rocks are highly strained, the sulfide stringer zone appears strata bound and individual sulphide veins occurs sub-parallel to bedding.

The massive sulphides consist of seven en échelon lenses, numbered 10 to 80 around the Caribou fold. The zones consist of 90% sulphides, mainly pyrite, sphalerite, galena and chalcopyrite. The main gangue minerals are magnetite, siderite, stilpnomelane, quartz and chlorite. Lenses 10, 20, 30, 70, and 80 occur on the north limb of the Caribou fold while lenses 40 and 60 are mostly on the eastern limb of the fold.

The Caribou Mine has been previously developed and mined by different owners, employing a variety of mining methods. On November 2, 2012, Trevali gained control of Caribou through the acquisition of Maple Minerals Corporation. Trevali commenced underground mining in 2015 and commercial production was declared for the Caribou Mine and processing plant effective July 1, 2016.

Modified Avoca is the main mining method, supplemented by uphole retreat for partial sill pillar recovery. Modified Avoca stopes employ unconsolidated waste rock and surface stockpiled waste rock as backfill. Crown pillar recovery is not currently considered in the mine plan due to a lack of geotechnical information. 45-tonne capacity underground haul trucks transport the mined material through the underground ramp system and out of the mine through the conveyor portal, where surface stockpile pads, crusher and the process plant is located. On February 1, 2017, the Company announced, that as part of the planned transition from contract mining to an owner-operated model, the Company would procure a new underground mining fleet. The Company subsequently committed to an investment of approximately C$20 million to supply and maintain a full fleet of Sandvik supported mining equipment for the Caribou Mine. The fleet of equipment started arriving at site in May 2017. Increased operating efficiencies were seen in the new underground haul trucks and scoop trams of 23% and 4.3%, respectively. In addition, mine dilution has decreased to 8.4 % from 18.2% in the first half of 2017 due to the new cable bolter performance and efficiency.

The process plant at Caribou is a conventional milling and sulphide flotation plant with a 3,000 tonne per day nameplate capacity. The process plant includes crushing, screening, grinding, regrinding, and zinc, and lead flotation and filtering circuits to produce zinc, and lead concentrates. Concentrate production is stockpiled onsite prior to shipping and sale to Glencore. The zinc concentrate is transported by rail to Valleyfield, Quebec for further processing while the lead concentrate is further processed at Glencore’s nearby Belledune smelting complex.