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Canada
Mount Polley Mine

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 Location:
56 km NE from Williams Lake, British Columbia, Canada

  Project Contacts:
PO Box 12
Likely
British Columbia, Canada
V0L 1N0
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  • Overview
  • Owners
  • Geology
  • Mining
  • Processing
  • Production
  • Reserves
  • Costs & Financials
  • Fleet
  • Personnel
  • Filings & News

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Overview

StageRestarting
Mine TypeOpen Pit & Underground
Commodities
  • Copper
  • Gold
  • Silver
Mining Method
  • Truck & Shovel / Loader
  • Longhole open stoping
  • Cemented backfill
Processing
  • Filter press plant
  • Dewatering
  • Flotation
Mine Life2026
Mount Polley mine was placed on care and maintenance status effective May 30, 2019.

In the fourth quarter of 2021, MPMC took the initial steps towards recommencement of operations at the Mount Polley mine. Stripping operations began to enable milling operations to restart in 2022. Mechanical and electrical contractors began on refurbishing the plant, including work on the tailings slurry and reclaim water pipelines and pumps, crushers, conveyors, screens, grinding mills, flotation and plant water systems. The crushing plant was commissioned by year end providing crush material for winter road maintenance.

Outlook for 2022 includes continued stripping of Springer Pit, building of an ore stockpile and a plant restart by the end of the second quarter 2022.
Latest NewsImperial Celebrates Renewed Participation Agreement     April 12, 2022


Owners

Source: p. 16
CompanyInterestOwnership
Imperial Metals Corp. 100 % Indirect
The Mount Polley copper/gold mine in south-central British Columbia is owned by Mount Polley Mining Corporation, a subsidiary of the Imperial Metals Corp.

Deposit Type

  • Porphyry


Summary:

Mount Polley is an alkalic porphyry copper-gold deposit. It lies in the tectono-stratigraphic Quesnel terrane or Quesnellia, which is characterized by a Middle Triassic to Early Jurassic assemblage of volcanic, sedimentary and plutonic rocks which formed in an island arc tectonic setting outboard of the ancestral North American continental margin. Quesnellia hosts several major porphyry copper deposits such as Highland Valley, Copper Mountain, AftonAjax, Gibraltar and Mount Milligan, all generated by early Mesozoic, calc-alkalic or alkalic arc magmatism.

In the Mount Polley region, the Triassic arc rocks are assigned to the Nicola Group and comprise alkalic basaltic to andesitic volcanics and sedimentary rocks, which are intruded by sub-volcanic stocks; all are overlain by post-Nicola, Early Jurassic clastic rocks and rare volcanics. Mount Polley itself is a complex of alkalic intermediate porphyritic intrusions and related magmatic-hydrothermal breccias. It was emplaced into the Nicola Group in the Late Triassic around 205 million years ago. The intrusive complex is about 6 km long (north-northwest) and 3 km wide, lying between Polley Lake in the east and Bootjack Lake in the west. The intrusions range from diorite (oldest) to monzonite (youngest) and are marginally undersaturated in silica. The Mount Polley Intrusive Complex is in the centre of the Mount Polley property; the remainder of the property is underlain mainly by Nicola Group volcanics and post-Nicola conglomerate, and small intrusions in which no economic mineralization has been found to date.

Mineralization in the Mount Polley Intrusive Complex (“MPIC”) is primarily hosted by irregular zones of hydrothermal breccia, which are closely related to the porphyry intrusions and were formed by magmatic devolatization processes. Mineralization and brecciation were accompanied by potassic or calc-potassic, albite, and magnetite alteration; the MPIC is bounded on most sides by propylitic country rocks. As in many alkalic porphyry systems, there is no single or simple zoned mineralization pattern, but instead a number of copper-gold zones of various size, shape and grade characteristics, distributed around the MPIC from the far north to the south. There is no clear structural control on the location of these mineralized breccia zones, although the greatest continuity and the bulk of the past and present resources occur in the centre of the MPIC (e.g. Springer, Cariboo, Bell zones) between two pre-mineral diorite intrusions. Dimensions of mineralized breccias in the MPIC range up to many hundred metres in length and width, such as in the Springer zone. Elsewhere, smaller zones (generally less than 100 m across) may form mineable bodies if grades and other factors are favourable. Post-mineral faulting probably did not disrupt the continuity of mineralized zones very significantly, except in the Northeast zone where deeper mineralization was offset along a fault a few hundred metres laterally and dropped vertically slightly.

In the deposits, the degree of brecciation and associated hydrothermal alteration is usually a reliable guide as to grade. There is relatively little post-mineralization dike dilution. Chalcopyrite is the dominant copper mineral, typically accompanied by pyrite; bornite is relatively uncommon in the centre of the MPIC. Here, copper sulfides occur as disseminations or veins and fracture coatings in brecciated intrusion, or they are disseminated in the matrix of breccias, in both cases precipitated along with alteration minerals. Mineralization has been traced by deep drilling in the Springer zone to a depth of around 900 m (from pre-mining surface).

In the north of the MPIC are much higher grade orebodies, namely the Northeast (mined in the Wight pit, 2005- 2009) and Boundary zones, where copper grades can reach several percent per tonne. Chalcopyrite and significant bornite form coarse-grained infill in breccias, and intense vein and microvein stockworks. As in the zones in the centre of the MPIC, gold and silver occur mainly as microscopic inclusions in the copper sulfides and in pyrite.

Exploration has always proceeded alongside mining at Mount Polley, leading to the expansion and deepening of known deposits, or to the discovery of new zones, or raising the status or resource category of marginal prospects, potentially towards feasibility for profitable mining. Geological and geotechnical logging of drill core is integrated with down-hole assay data and used with software for computation of the resource block model and mine design. In addition, exploration and research since the restart of operations in 2004-2005 have considerably advanced understanding of geology, structure and deposit genesis at Mount Polley, improving interpretation of mineralization geometry and the design of drill programs. New underground development is followed where appropriate by wall mapping and rib sampling to further characterize the mineralization, fill gaps in the resource model, and help guide stope design.

Airborne and ground magnetic signature is regarded as the most important geophysical tool for identifying new mineralization, although tellingly it was not effective in the Northeast zone, possibly delaying discovery of that highgrade but magnetite-poor orebody until 2003. An 11-line Titan-24 deep Induced Polarization-Magnetotelluric survey was completed by Quantec Geoscience Ltd. in Fall 2009 to potentially locate blind sulfide targets and guide exploration drilling where appropriate. Outlying parts of the Mount Polley property, away from the mine site, have been explored by geological mapping, sampling and trenching and by soil surveys over intrusive bodies, with no significant results to date. Mineral potential remains most promising within the MPIC itself, or possibly buried beneath the unconformity with cover rocks (conglomerate, breccia) immediately to its north.


Mining Methods

  • Truck & Shovel / Loader
  • Longhole open stoping
  • Cemented backfill


Summary:

Mining Methods - conventional shovel, truck and open pit mine. With a developing underground mine.

Open Pit Mining Equipment
The current open pit mining operation at Mount Polley utilizes a conventional truck and shovel fleet with drilling and blasting prior to excavation. The fleet includes a mixture of diesel and electrically powered equipment for drilling, excavating and dewatering.

Material Handling
Ore mined from the pits is hauled to either the primary gyratory crusher located immediately adjacent to the mill or to nearby stockpiles.

Waste material at Mount Polley occurs in one of two types: non-acid generating waste (NAG), and potentially acid-generating waste (PAG). NAG/PAG designations are made on the basis of the neutralizing potential ratio (NPR) of a given material. This NPR is calculated by performing acid-base accounting (ABA) using carbon and sulfur assays from blasthole cutting samples. Sampling is performed on a one sample per 20,000 tonnes basis. All rock with an NPR less than 2.0 and a sulfur content greater than 0.1% is designated as PAG and stockpiled.

PAG waste is estimated to constitute approximately 27% of the waste tonnage in the life-of-mine plan. PAG waste, as a condition of operating permits, must be submerged for long-term storage at the end of mine life. As such, all PAG rock is selectively mined and temporarily stored in the Northwest PAG Stockpile. This stockpile will be rehandled into the exhausted pits at the end of mine life. NAG waste is hauled to either the southeast rock dump (SERD), or to the Tailings Storage Facility (TSF) for construction purposes.

Pit Slope Design Parameters
Bench heights in the Main Zone are 12m, while the Boundary Zone Pit will be mined with 10m bench heights in waste and 5m spilt benches in ore.

The strength of the overall rock mass around the pits is generally good with the exception of faults and late-stage mafic dykes which can be of poorer quality. Jointing in the rock mass is semi-consistent through different rock units, resulting in pit slope design criteria being dominated by the orientation of the pit face in question, and specifically how this open face interacts with the local jointing regime.

Pit wall design parameters employed for mining at Mount Polley are provided by Golder Associates Ltd., and are based on historical mining experience.

Underground Mining Methods
The Primary Underground mining method at Mount Polley is mechanized long-hole open stoping followed by backfill with cemented rock before mining the next stope.

The three noteworthy zones which are currently being mined or planned to be mined are; the Boundary, Halo and Zuke Zones. The majority of the Mineral Reserve base is contained in the Boundary Zone (81% of the 312,000 tonnes of underground Mineral Reserves).

The larger Boundary Zone with approximate dimensions of 80m long by 20m wide and 100m tall has been divided into four stoping blocks (A, B, C, and D). Individual stoping blocks are approximately 20m by 20m in plan, and between 35m and 100m in height and are aligned.

The final stoping blocks (C and D) will be filled with un-cemented rock fill as required. Mining of the smaller Halo and Zuke Zones will not require backfill.


Crushing and Grinding
Flow Sheet: Source
Crusher / Mill TypeModelSizePowerQuantity
Gyratory crusher 42" x 65" 1
Cone crusher 7' 1
Cone crusher 3
Ball mill 3
Regrind 1
Rod mill 2
Pebble mill 3

Summary:

In the Mount Polley mine mill, run-of-mine ore from the open pits and underground is hauled to the crusher. The crusher has three stages of crushing involving five crushers, twenty conveyors and four sets of screens. Ore is deposited by rock trucks into the feed pocket of the primary gyratory crusher and is then crushed in three stages to produce a product for the grinding circuit. Pebbles obtained from the triple deck screen in the crushing plant are used as grinding media in the pebble mills. Periodically, the crusher is also used for production of aggregates used in TSF construction and other tasks.

The grinding circuit consists of two parallel rod mill/ball mill circuits and a pebble mill circuit. Crusher product is first split between two rod mills where water is added, and a slurry is formed to grind the product down to a sand like texture. The rod mill discharge is pumped to the primary hydrocyclones that classify the particles by size. The larger particles flow to feed the ball mills while the fine particles report to two flash flotation cells. The ball and pebble mills are in “closed circuit”, meaning that the discharge is pumped to the classifying units (primary hydrocyclones) and the particles will not pass to the next stage until the particle sizes are fine enough. The flash flotation product can report directly to the dewatering circuit or to the cleaner circuit for further upgrading. The overflow from the pebble mill hydrocyclones reports to the flotation circuit.


Processing

  • Filter press plant
  • Dewatering
  • Flotation

Flow Sheet: Subscription required

Summary:

The mill at Mount Polley was commissioned in June 1997. The mill uses conventional rod and ball mills with a flotation and dewatering circuit to produce a copper /gold concentrate. The mill has a capacity to process 17,800 to 22,000 tonnes per day (tpd) of ore depending on hardness. Mount Polley concentrates are trucked to facilities at the Port of Vancouver and then shipped to overseas smelters.

The flotation circuit separates the valuable minerals from the rest of the ground particles. With the addition of reagents, the valuable minerals, mostly in the form of sulphides, are separated by flotation and are collected and upgraded to produce a concentrate. Initial separation is completed in a rougher/scavenger circuit, where the remaining minerals are discarded as tailings (which flow by gravity to the TSF). Rougher concentrate is reground in a regrind mill and further upgraded in a cleaner circuit to produce the final concentrate product. Cleaner tailings report to the cl ........

Recoveries & Grades:

CommodityParameter201920182017201620152014
Copper Recovery Rate, %  ......  Subscription required52.964.569.769.676
Copper Head Grade, %  ......  Subscription required0.210.20.250.290.32
Gold Recovery Rate, %  ......  Subscription required67.368.969.871.668.1
Gold Head Grade, g/t  ......  Subscription required0.280.320.310.380.26

Projected Production:

CommodityUnits201920182017201620152014
Copper lbs  ......  Subscription required14,973,63119,070,93225,338,8578,007,32824,489,725
Gold oz  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required
Silver oz  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required
All production numbers are expressed as metal in concentrate.
Subscription required - Subscription is required.

Operational Metrics:

Metrics2019201820172016201520142013
Tonnes milled 2,231,119 t6,195,760 t6,723 kt6,685 kt1,782 kt4,548 kt7,957 kt
Daily milling rate 14,776 t16,975 t18,420 t18,265 t11,958 t21,056 t21,799 t
Stripping / waste ratio 3.12 2.87 2.57

Reserves at January 1, 2019:
As of January 1, 2020, the reported Mount Polly's mineral reserves and mineral resources have not changed.

CategoryTonnage CommodityGradeContained Metal
Proven & Probable 53,772,000 t Copper 0.337 % 400,000,000 lbs
Proven & Probable 53,772,000 t Gold 0.299 g/t 517,000 oz
Proven & Probable 53,772,000 t Silver 0.899 g/t 1,554,000 oz
Measured 103,193,000 t Copper 0.319 % 725,000,000 lbs
Measured 103,193,000 t Gold 0.3 g/t 996,000 oz
Measured 103,193,000 t Silver 0.823 g/t 2,730,000 oz
Indicated 91,127,000 t Copper 0.266 % 534,000,000 lbs
Indicated 91,127,000 t Gold 0.269 g/t 787,000 oz
Indicated 91,127,000 t Silver 0.619 g/t 1,814,000 oz
Measured & Indicated 194,320,000 t Copper 0.294 % 1,259,000,000 lbs
Measured & Indicated 194,320,000 t Gold 0.285 g/t 1,783,000 oz
Measured & Indicated 194,320,000 t Silver 0.727 g/t 4,544,000 oz
Inferred 5,619,000 t Copper 0.374 % 46,000,000 lbs
Inferred 5,619,000 t Gold 0.276 g/t 50,000 oz
Inferred 5,619,000 t Silver 2.187 g/t 395,000 oz

Commodity Production Costs:

CommodityUnits201920182017201620152014
Cash costs Copper USD  ......  Subscription required† 1.94 / lb† 2.32 / lb† 1.83 / lb† 2.26 / lb† 1.16 / lb†
† Net of By-Product.
Subscription required - Subscription is required.

Financials:

Units202020192018201720162015
Capital expenditures M CAD  ......  Subscription required  ......  Subscription required13.3   27.7   26.7   30.3  
Revenue M CAD  ......  Subscription required  ......  Subscription required104.4   163.5   131.5   23.3  
After-tax Income M CAD  ......  Subscription required  ......  Subscription required-35   -27.2   -19.3   -5.6  
Subscription required - Subscription is required


Heavy Mobile Equipment as of May 20, 2016:
HME TypeModelSizeQuantity
Bolter ....................... Subscription required ....................... Subscription required
Bulldozer ....................... Subscription required ....................... Subscription required
Bulldozer ....................... Subscription required ....................... Subscription required
Drill ....................... Subscription required ....................... Subscription required
Drill ....................... Subscription required ....................... Subscription required
Drill ....................... Subscription required
Drill jumbo (two boom) ....................... Subscription required
Excavator ....................... Subscription required ....................... Subscription required
Grader ....................... Subscription required ....................... Subscription required
Loader (FEL) ....................... Subscription required ....................... Subscription required
Scissor Lift ....................... Subscription required
Scoop Tram ....................... Subscription required
Scoop Tram ....................... Subscription required
Shovel ....................... Subscription required ....................... Subscription required
Shovel ....................... Subscription required ....................... Subscription required
Truck (haul) ....................... Subscription required ....................... Subscription required
Truck (haul) ....................... Subscription required ....................... Subscription required
Truck (underground) 25 t ....................... Subscription required
Subscription required - Subscription is required.

Mine Management:

Job TitleNameProfileRef. Date
....................... Subscription required ....................... Subscription required Subscription required Aug 26, 2021
....................... Subscription required ....................... Subscription required Subscription required Aug 26, 2021
....................... Subscription required ....................... Subscription required Subscription required Aug 26, 2021
Subscription required - Subscription is required.

Staff:

EmployeesYear
Subscription required 2018
Subscription required 2017

Corporate Filings & Presentations:

DocumentYear
................................... Subscription required 2021
................................... Subscription required 2021
................................... Subscription required 2020
................................... Subscription required 2020
................................... Subscription required 2019
................................... Subscription required 2019
Annual Information Form 2018
Annual Report 2018
Annual Information Form 2017
Annual Report 2017
Press Release 2017
Annual Information Form 2016
Annual Report 2016
Technical Report 2016
Annual Information Form 2015
Annual Report 2015
Other 2015
Year-end Mineral Reserves 2015
Annual Information Form 2014
Annual Report 2014
Subscription required - Subscription is required.

News:

NewsDate
Imperial Celebrates Renewed Participation Agreement April 12, 2022
Imperial Reports Final Drill Hole Assays from Mount Polley 2020 Exploration February 23, 2021
Imperial Drilling Intersects 502.5 Metres Grading 0.70 g/t Gold and 0.33% Copper at Mount Polley February 8, 2021
Imperial Announces Suspension of Operations at Mount Polley Mine January 7, 2019

Aerial view:

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