Canada

Caribou Mine

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Overview

Mine TypeUnderground
Commodities
  • Zinc
  • Lead
  • Silver
  • Gold
Mining Method
  • Avoca
  • Longitudinal retreat
Backfill type
  • Undefined backfill
Production Start2016
ShapshotThe Caribou operations consist of an underground mine with significant underground development, a fully permitted mill, and a sulphide flotation recovery plant.

On Aug. 19, 2022, following review of its operations at the Caribou Mine in New Brunswick, the Company has suspended operations due to operational and financial challenges. The mine was put on a care and maintenance program. No timeline for a potential restart of operations has been defined.

On Aug. 19, 2022, Trevali Mining Corporation announces that the Company had received an Initial Order for creditor protection from the British Columbia Supreme Court under the Companies' Creditors Arrangement Act (the "CCAA").

In Jan. 26, 2023, Trevali Mining Corporation announced that, in accordance with an order of the Supreme Court of British Columbia, the Court appointed FTI Consulting Canada Inc. as receiver, without security, of all the assets, undertakings and property of Trevali Mining (New Brunswick) Ltd.

Owners

SourceSource
CompanyInterestOwnership
Trevali Mining Corp. 100 % Indirect
The Caribou property is owned 100% by Trevali and is held in the name of Trevali Mining (New Brunswick) Ltd.

Trevali and its subsidiary Trevali Mining (New Brunswick) Ltd. ("Trevali NB") were granted CCAA protection on August 19, 2022.

Effective from January 24, 2023, FTI Consulting Canada inc. (FTI) was appointed as Receiver of all the assets, undertakings and property of Trevali NB, including all proceeds thereof, other than any real property, mineral claims, mining leases or real property leases owned or held by Trevali NB. Since that time, FTI, in its capacity as Receiver of Trevali NB, has been working to maximize value for those Trevali NB assets.

Contractors

ContractorContractDescriptionRef. DateSource
NB Power Power supply NB Power supplies incoming power under a long-term contact. Dec 31, 2017

Deposit type

  • VMS

Summary:

The Bathurst Mining Camp occupies a roughly circular area of approximately 70 kilometres diameter in the Miramichi Highlands of northern New Brunswick. The area boasts some 46 mineral deposits with defined tonnage and another hundred mineral occurrences, all hosted by Cambro-Ordovician rocks that were deposited in an ensialic back-arc basin.

The volcanogenic massive sulphide deposits in the Bathurst Mining Camp formed in a sediment-covered back-arc continental rift during periods when the basin was stratified with a lower anoxic water-column. The basin was subsequently intensely deformed and metamorphosed during multiple collisional events related to east-dipping subduction of the basin. The rocks in the Bathurst Mining Camp are divided into five groups: the Miramichi, Tetagouche, California Lake, Sheephouse Brook, and Fournier groups, which are largely in tectonic contact with one another. The lower part of each group is dominated by felsic volcanic rocks and the upper part by mafic volcanic rocks, which are overlain by carbonaceous shale and pelagic chert. The basalts are both tholeiitic and alkalic and show a progression from enriched, fractionated continental tholeiites to alkali basalts to more primitive, mantle-derived midocean ridge, tholeiitic pillow basalts. Most massive sulphide deposits of the Bathurst Mining Camp are associated with felsic volcanic rocks in each group.

The Caribou deposit is a VMS deposit, is located in the northern part of the Bathurst Mining Camp and occurs in the core of a synformal structure that plunges steeply (80°-85°) to the north. The Caribou deposit is a VMS typical of the Bathurst Mining Camp but is sufficiently distinct from the Brunswick type to warrant a subtype designation (Caribou type) within the Bathurst Mining Camp. Unlike the Brunswick-12 deposit, which is hosted by the Tetagouche Group, the Caribou deposit occurs in the California Lake Group near the base of a felsic volcanic rock sequence that comprises part of the Spruce Lake Formation. The Spruce Lake Formation volcanic rocks are petrologically and geochemically distinct from those of the Tetagouche Group. Furthermore, the Caribou deposit is not associated with the Algoma-type carbonate-oxide-silicate iron formation that overlies and is lateral to the Brunswick-12 and Heath Steele deposits.

Mineralization within the Caribou deposit is composed of seven en échelon lenses striking parallel to the Caribou fold numbered 10 to 80 that are zoned mineralogically and chemically from a copper-rich ventproximal 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. The zones typically 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. Individual lenses vary in thickness between a few metres to approximately 30 metres and extend over 1,000 metres along strike on the North Limb. Lenses on the Eastern Limb pinch at a depth of approximately 800 metres below the topographic surface while lenses along the North limb have been drilled to a depth of approximately 1,000 metres and are still open at depth.

Reserves at December 31, 2021

Mineral Reserve estimate is reported based on optimized stopes designed on an incremental net smelter return cut-off value of $80/tonne with average metal prices of: $1.25/lb zinc, $1.00/lb lead and $25.00/oz silver.
Mineral Resource estimate is reported based on a cut-off grade of 5% zinc equivalent.

Mineral Resources are reported inclusive of Mineral Reserves.
CategoryTonnage CommodityGradeContained Metal
Proven 1.75 Mt Zinc 6.13 % 236 M lbs
Proven 1.75 Mt Lead 2.21 % 85 M lbs
Proven 1.75 Mt Silver 65.92 g/t 3,707 koz
Probable 2.66 Mt Zinc 5.67 % 332 M lbs
Probable 2.66 Mt Lead 2.14 % 125 M lbs
Probable 2.66 Mt Silver 65.39 g/t 5,584 koz
Proven & Probable 4.41 Mt Zinc 5.85 % 568 M lbs
Proven & Probable 4.41 Mt Lead 2.17 % 211 M lbs
Proven & Probable 4.41 Mt Silver 65.6 g/t 9,291 koz
Measured 6.82 Mt Zinc 6.55 % 984 M lbs
Measured 6.82 Mt Lead 2.44 % 367 M lbs
Measured 6.82 Mt Silver 71.49 g/t 15,664 koz
Indicated 4.91 Mt Zinc 6.31 % 683 M lbs
Indicated 4.91 Mt Lead 2.49 % 270 M lbs
Indicated 4.91 Mt Silver 75.03 g/t 11,846 koz
Measured & Indicated 11.73 Mt Zinc 6.45 % 1,667 M lbs
Measured & Indicated 11.73 Mt Lead 2.46 % 636 M lbs
Measured & Indicated 11.73 Mt Silver 72.97 g/t 27,510 koz
Inferred 2.61 Mt Zinc 5.68 % 327 M lbs
Inferred 2.61 Mt Lead 2.4 % 138 M lbs
Inferred 2.61 Mt Silver 72.61 g/t 6,099 koz

Mining Methods

  • Avoca
  • Longitudinal retreat

Summary:

Access to the underground mine is via a connected, dual-ramp system, with an existing Main 2460 Portal located on the north side of the deposit, and an existing 2560 Portal located on the east side near the crusher pad, which connects to the main ramp near the top of the 2360 Level.

During past operations ore was skipped to surface using an existing shaft and then conveyed through a conveyor gallery to the Fine Mill-Feed Bins.

Trevali decided to use truck haulage over shaft hoisting.

During 2015, the construction of an underground ramp connection to the existing conveyor portal (approximately 400 m of development) was completed which allowed operational efficiencies by reducing the underground haul distance to a stockpile within approximately 100 m of the Fine Mill-Feed Bins versus the previous approximately 1.5 km surface haul route. This stockpile is the primary feed to the concentrator, and has a capacity of 50,000 tonnes.

All new ramps are designed at a maximum gradient of -15%, with dimensions of 5.0 m wide by 5.0 m high.

Modified Avoca is the main mining method, supplemented by uphole retreat for partial sill pillar recovery. This method uses development waste and surface-stockpiled waste as backfill. Modified Avoca is a longitudinal retreat mining method. Stope sequencing generally follows a retreat along strike from lens extremities or strategic starting points, and retreats to ramp access points.

The stopes are typically excavated 16 m along strike, and to a nominal height of 25 m floor-tofloor. Stope width is normally the same as the lens width. A standard stope will yield approximately 10,600 tonnes of ore, including the development tonnes.

Blast holes are 16 m to 20 m downholes drilled at 76 mm diameter with a 2.0 m burden x 2.0 m spacing pattern. Some drill holes are fanned out where lens width exceeds 5.0 m. On average, the drill factor is 11.0 ore tonnes per metre of drilling.

Blast holes are loaded with either emulsion or ammonium nitrate/fuel oil (ANFO), depending on local water conditions, to an average powder factor of 0.45 kg/t. Slots are opened by drop raising on only the first stope of each retreat mining front. On average, one slot raise will suffice for four stopes. Trevali is planning to convert to use 1.1 m diameter raisebore holes for slots in all stopes.

Production mucking is undertaken by 14 t capacity Load-Haul-Dump (LHD) mobile equipment. Ore mucked from drawpoints is trammed to remuck bays located on each level close to the main ramp, then loaded into 40 t capacity haul trucks. Loaded trucks then travel up the ramp and dump material on the surface crusher pad located adjacent to the mill (Main Feed) conveyor.

When stope mucking is completed, the mined-out stope is tightly filled with waste rock; no cement is used for the backfill material.

Comminution

Crushers and Mills

TypeModelSizePowerQuantity
SAG mill 6.7m x 2.1m 1491 kW 1
Ball mill 4.3m x 6.7m 1864 kW 1
Ball mill 3.0m x 6.7m 746 kW 1
Regrind IsaMill M1000 500 kW 3

Summary:

The plant feed is delivered as primary crushed ore at nominally 119 mm (4.5 in.) top size by inclined conveyor from the mine to two 2,000 tonne storage bins at the concentrator. Belt feeders discharge each bin individually, controlled by a variable frequency drive (VFD) located on each bin’s discharge conveyor.

The plant feed is delivered to the 6.7 m (22 ft) diameter by 2.1 m (7 ft) long Hardinge primary SAG mill, equipped with a 1,491 kW (2,000 hp) drive motor. A maximum ball charge of 15% is allowed in the mill to reduce the feed material to nominal 650 µm as feed to the secondary ball mill. The discharge from the SAG mill is pumped to a Derrick vibratory screen, with 3.2 mm (0.13 in.) apertures, to classify the mill discharge and recycle the oversize particles back to the SAG mill feed. Derrick screen undersize gravitates to the secondary ball mill cyclone feed pump for secondary classification in a battery of 508 mm (20 in.) diameter Krebs cyclones.

Overflow, at 80% passing nominal 30 µm to 35 µm, reports directly to flotation while the cyclone underflow will recycle to the 4.3 m (14 ft) diameter by 6.7 m (22 ft) long Nordberg secondary ball mill, equipped with a 1,864 kW (2,500 hp) drive motor, for further grinding.

Secondary ball mill discharge combines with the SAG mill product in the cyclone feed pump. Soda ash and sodium cyanide are added to the grinding circuit as pyrite and sphalerite depressants.

LEAD REGRIND
The combined rougher-scavenger concentrate passes to the lead regrind circuit, where it is classified in a battery of 152 mm (6 in.) cyclones to divert the plus 12 µm to 15 µm mineralization to an M1000 Isa regrind mill rated at 500 kW (670 hp). Previous operations required two M1000s in parallel owing to higher head grades. Current conditions have allowed Trevali to utilize the additional ISA mill as a spare

Isa mill discharge combines with the cyclone overflow at nominal 12 µm to 15 µm as feed to the primary cleaning.

The primary cleaner concentrate undergoes secondary regrind in an additional M1000 Isa mill using 100 mm (4 in.) diameter cyclones as classifiers. Product, at nominal 8 µm to -10 µm, passes to secondary cleaning.

ZINC REGRIND
The combined rougher and scavenger concentrate is pumped to a single-stage, 3.0 m (10 ft) diameter by 6.7 m (22 ft) long regrind ball mill, equipped with a 746 kW (1,000 hp) drive motor.

Processing

  • Crush & Screen plant
  • Flotation
  • Dewatering
  • Filter press

Summary:

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 trucked to the port at Belledune, New Brunswick, where it is subsequently shipped to designated smelters for processing.

Product from the grinding circuit, at nominal 35% solids by weight and pH 8.2, gravitates to the pre-aeration circuit for depression of the pyrite.

PRE-AERATION
The first two cells in the lead rougher bank are DR500 units which are used to pre-aerate the slurry and tarnish the iron minerals to aid in their depression. There is no flotation in this circuit, as the cells are simply to provide aeration of the pulp.

LEAD ROUGHER-SCAVENGER
Discharge from the pre-aerators passes directly to the lead rougher bank, which consists of five Outokumpu 16 m3 (565 ft3 ) units and three additional DR500 units for recovery of the lead mineralization. The collector (3418A) is used to recover the lead mineralization selectively from the zinc, with Methyl Isobutyl Carbinol (MIBC) being used as the frother. The combined rougher and scavenger concentrate is sent for regrinding, while the scavenger tailings forms the majority of the feed to the zinc circuit.

LEAD REGRIND
The combined rougher-scavenger concentrate passes to the lead regrind circuit. Isa mill discharge combines with the cyclone overflow at nominal 12 µm to 15 µm as feed to the primary cleaning.

The primary cleaner concentrate undergoes secondary regrind in an additional M1000 Isa mill using 100 mm (4 in.) diameter cyclones as classifiers. Product, at nominal 8 µm to -10 µm, passes to secondary cleaning.

LEAD CLEANING
The primary cleaner consists of an eight cell rougher and a six cell scavenger, with all cells being DR300 units. The rougher concentrate passes to secondary regrind, while the scavenger concentrate is recycled back to the head of the primary cleaner. Primary cleaner tailings report directly to the primary cleaner scavenger via gravity.

The lead secondary cleaner consists of six DR300 cells, with total secondary concentrate passing to tertiary cleaning. Secondary cleaner tailings combine with the rougher concentrate as feed to the regrind cyclone ahead of the primary cleaner.

The cleaner scavenger tailings join with the rougher scavenger tailings to make up the feed to the zinc circuit.

LEAD DEWATERING
The final lead concentrate from the fourth cleaner is pumped to a 4.6 m (15 ft) diameter conventional thickener for recovery of the excess water.

ZINC CIRCUIT
Combined lead rougher scavenger and cleaner scavenger tailings will combine as feed to the zinc circuit.

CONDITIONING
A single conditioner is utilized as a reagent addition stage to allow activation and promotion of the zinc mineralization, and to adjust the pH for pyrite depression.

ZINC ROUGHER-SCAVENGER
Overflow from the conditioners gravitates to a combined zinc rougher-scavenger circuit of eighteen cells, with the rougher being a bank of twelve DR300 cells, and the scavenger a bank of six DR500 units.

ZINC REGRIND
The combined rougher and scavenger concentrate is pumped to a single-stage regrind ball mill. All mill feed reports to the cyclone feed box for classification in a battery of 254 mm (10 in.) diameter Krebs cyclones, with a product of nominal 80% passing 14 µm. The cyclone underflow recycles to the regrind mill, maintaining the regrind in closed circuit. The cyclone overflow passes by gravity to the cleaner circuit for upgrading to final concentrate specification.

ZINC CLEANERS
The cleaner circuit consists of a four-stage cleaning plant, with the final three stages of cleaning operating in closed circuit, with the tailings of each cleaning stage reporting to the feed of the previous stage. The primary cleaner operates in open circuit, with the tailings passing directly to the cleaner scavenger feed.

The primary cleaner consists of a single bank of eleven DR500 cells, with total primary cleaner concentrate product passing directly to the secondary cleaner bank of seven DR300 cells. Tailings from the secondary cleaner recycles to the regrind mill, while the total secondary concentrate passes to the tertiary cleaner, a bank of five DR300 cells operating in open circuit. Tailings report to the second cleaner feed pump, while the third cleaner concentrate is delivered to the fourth cleaner of four DR300 cells, operating as the final cleaner bank. Tailings recycle to the third cleaner feed pump, while the product, as final concentrate, will be delivered to the dewatering section.

ZINC DEWATERING
The final zinc concentrate from the fourth cleaner is pumped to a 12 m (40 ft) diameter conventional thickener for recovery of the excess water. The underflow, at approximately 60% solids, is pumped to a holding stock tank ahead of the VPA 1515-33 plate and frame filter. Filtrate from the filter operation is recycled to the zinc thickener. Thickener overflow is pumped to the tailings pond.

Recoveries & Grades:

CommodityParameter20222021202020192018201720162015
Zinc Recovery Rate, % 76.778.478.179.175.6777765.8
Zinc Head Grade, % 5.25.55.55.75.95.945.975.31
Zinc Concentrate Grade, % 46.947.245.64746.9484748.3
Lead Recovery Rate, % 6161.762.263.661.8635848.3
Lead Head Grade, % 1.82.12.12.32.32.552.661.99
Lead Concentrate Grade, % 36.237.33638.738.8393937.6
Silver Recovery Rate, % 34.334.33337.636.43936
Silver Head Grade, g/t 5665.359.165.362.269.471.2
Silver Concentrate Grade, g/t 637.61664.36654.72

Production

On August 19, 2022, following review of its operations at the Caribou Mine in New Brunswick, Trevali Mining Corp. suspended operations due to operational and financial challenges.

On November 14, 2022, Trevali announced that it did not, and will not, file its interim financial statements for the three and nine months ended September 30, 2022.

All production and cost data for 2022, are given for the six months of the year ended June 30, 2022.
CommodityProductUnits20222021202020192018201720162015LOM (Projected)
Zinc Payable metal M lbs 2041157572803724584
Lead Payable metal M lbs 6.3135302531147.3205
Silver Payable metal koz 2004001007007008904021864,598
Zinc Concentrate kt 84914327
Lead Concentrate kt 3239179.5
Gold Payable metal oz 1,0054499,734
Zinc Equivalent Payable metal lbs 115,715,89555,173,589

Operational metrics

Metrics20222021202020192018201720162015
Ore tonnes mined 281,581 t518,639 t191,817 t909,298 t887,141 t937,459 t449,488 t280,183 t
Tonnes milled 280,613 t518,541 t195,305 t913,178 t884,529 t945,436 t436,730 t369,006 t
Daily milling capacity 3,000 t3,000 t3,000 t3,000 t3,000 t3,000 t
Daily mining capacity 3,000 t of ore
Daily milling rate 2,005 t

Production Costs

CommodityUnits202220212020201920182017
Total cash costs Zinc USD 1.77 / lb **   0.86 / lb **   1.42 / lb **   1.03 / lb **   0.85 / lb **   0.62 / lb **  
All-in sustaining costs (AISC) Zinc USD 2.2 / lb **   1.16 / lb **   1.71 / lb **   1.17 / lb **   1.14 / lb **   0.72 / lb **  
** Net of By-Product.

Operating Costs

Currency2019201820172016
Total operating costs ($/t milled) USD 73  68  58.6  57.5  

Financials

Units202220212020201920182017
Sustaining costs M USD 6.6  8.2  2.9   10.8   20.9   8.1  
Revenue M USD 21.2  54.4  11.9   75.2   0.08   118.4  
EBIT M USD -24.2  -6  -75.8   -11.6   -0.1   42.1  
EBITDA M USD -19  6.4  -73   1.4   0   56  

Heavy Mobile Equipment

Ref. Date: May 11, 2017

SourceSource
HME TypeModelSizeQuantity
Drill Sandvik DL421 1
Drill jumbo (two boom) Sandvik DD321 2
Scoop Tram Sandvik LH514 8 cu. yd 5
Truck (underground) Sandvik TH540 40 t 7

Personnel

Mine Management

Job TitleNamePhoneEmailProfileRef. Date
Managing Director Tom Powell +1-604-551-9881 tom.powell@fticonsulting.com LinkedIn Aug 28, 2023

EmployeesContractorsTotal WorkforceYear
124 149 273 2021
14 4 28 2020
259 90 349 2019
249 111 360 2018
252 115 367 2017
170 2016

Aerial view:

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