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United States
Arctic Project

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 Location:
36 km NE from Kobuk, Alaska, United States

  Project Contacts:
1150 - 609 Granville Street
Vancouver
British Columbia, Canada
V7Y 1G5
Phone  ...  Subscription required
Fax604-638-0644
EmailEmail
WebsiteWeb
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  • Owners
  • Geology
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  • Fleet
  • Personnel
  • Filings & News

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Overview

StageFeasibility
Mine TypeOpen Pit
Commodities
  • Copper
  • Zinc
  • Lead
  • Gold
  • Silver
Mining Method
  • Truck & Shovel / Loader
Processing
  • Flotation
  • Cyanide (reagent)
Mine Life12 years (as of Jan 1, 2020)
Latest NewsTrilogy Metals Files NI 43-101 Technical Report for the Arctic Feasibility Study     October 2, 2020


Owners

Source: p. 28
CompanyInterestOwnership
Trilogy Metals Inc. 50 % Indirect
South32 Limited 50 % Indirect
The Project is directly held by Ambler Metals LLC, a 50/50 joint venture formed between South32 Limited and Trilogy Metals Inc. in February 2020. Upon the formation of the joint venture, Trilogy Metals contributed all of its Alaskan assets, including the Project and Trilogy’s agreement with NANA, to Ambler Metals in exchange for a 50% membership interest and at the same time, South32 contributed $145 million in cash for a 50% membership interest.

Deposit Type

  • VMS


Summary:

The mineralization at the Arctic Deposit and at several other known occurrences within the Ambler Sequence stratigraphy of the Ambler District, consists of Devonian age, polymetallic (zinc-copper-lead-silver-gold) VMS-like occurrences.

VMS deposits are formed by and associated with sub-marine volcanic related hydrothermal events. These events are related to spreading centres such as fore arc, back arc or mid-ocean ridges. VMS deposits are often stratiform accumulations of sulphide minerals that precipitate from hydrothermal fluids on or below the seafloor. These deposits are found in association with volcanic, volcaniclastic and/or siliciclastic rocks. They are classified by their depositional environment and associated proportions of mafic and/or felsic igneous rocks to sedimentary rocks.

In the Ambler District, VMS-like mineralization occurs in the Ambler Sequence schists over a strike length of approximately 110 km. These deposits are hosted in volcaniclastic, siliciclastic and calcareous metasedimentary rocks interlayered with mafic and felsic metavolcanic rocks. Sulphide mineralization occurs above the mafic metavolcanic rocks but below the Button schist, a distinctive district wide felsic unit characterized by large albite porphyroblasts after relic phenocrysts. The presence of the mafic and felsic metavolcanic units is used as evidence to suggest formation in a riftrelated environment, possibly proximal to a continental margin.

A sulphide-smoker occurrence has been tentatively identified near Dead Creek northwest of the Arctic Deposit and suggests local hydrothermal venting during deposition. However, the lack of stockworks and stringer type mineralization at the Arctic Deposit suggest that the deposit may not be a proximal vent type VMS. Although the deposit is stratiform in nature, it exhibits characteristics and textures common to replacement-style mineralization. At least some of the mineralization may have formed as a diagenetic replacement.

At Arctic, sulphides occur as semi-massive (30 to 50% sulphide) to massive (greater than 50% sulphide) layers, typically dominated by pyrite with substantial disseminated sphalerite and chalcopyrite and trace amounts of galena and tetrahedrite. The Arctic Deposit sulphide accumulation is thought to be stratigraphically correlative to those seen at the Dead Creek and Sunshine deposits up to 12 km to the west.

There is also an occurrence of epithermal discordant vein and fracture hosted base metal (lead-zinc-copper) mineralization with significant fluorite mineralization identified at the Red prospect in the Kogoluktuk Valley, east of the Arctic Deposit. Although not yet fully understood, the genesis of this occurrence is considered to be related to the regional system that formed the VMS deposits in the Ambler District.

Mineralization occurs as stratiform SMS to MS beds within primarily graphitic chlorite schists and fine-grained quartz sandstones. The sulphide beds average 4 m in thickness but vary from less than 1 m up to as much as 18 m in thickness. The bulk of the mineralization is within five modelled zones lying along the upper and lower limbs of the Arctic isoclinal anticline. All of the zones are within an area of roughly 1 km2 with mineralization extending to a depth of approximately 250 m below the surface. There are five zones of MS and SMS that occur at specific pseudo-stratigraphic levels which make up the bulk of the mineral resources. The other three zones also occur at specific pseudo-stratigraphic levels, but are too discontinuous to confidently model as resources.

Unlike more typical VMS deposits, mineralization is not characterized by steep metal zonation or massive pyritic zones. Mineralization is dominantly sheet-like zones of base metal sulphides with variable pyrite and only minor zonation usually on an extremely small scale.

Mineralization is predominately coarse-grained sulphides consisting mainly of chalcopyrite, sphalerite, galena, tetrahedrite, arsenopyrite, pyrite and pyrrhotite. Trace amounts of electrum and enargite are also present. Gangue minerals associated with the mineralized horizons include quartz, barite, white mica, black chlorite, talc, calcite, dolomite and cymrite.


Mining Methods

  • Truck & Shovel / Loader


Summary:

The Arctic Project is designed as a conventional truck–shovel operation assuming 144 t trucks, and15 m³ shovels. The pit design includes three nested phases to balance stripping requirements while satisfying the concentrator requirements.

The design parameters include a ramp width of 28.5 m, maximum road grades of 10%, bench height of 5 m, targeted mining width of between 70 and 100 m, berm interval variable by sector, variable slope angles by sector and a minimum mining width of 30 m.

The smoothed final pit design contains approximately 43.4 Mt of ore and 298.3 Mt of waste for a resulting stripping ratio of 6.9:1. Within the 43.4 Mt of ore, the average grades are forecast to be 2.24% Cu, 3.12% Zn, 0.54% Pb, 0.47 g/t Au and 34.7 g/t Ag.

The scheduling constraints set the maximum mining capacity at 36 Mt/a and the maximum process capacity at 10 kt/d. The production schedule results in a LOM of 12 years. The mine will require three years of pre-production before the start of operations in the processing plant.


Crushing and Grinding
Crusher / Mill TypeModelSizePowerQuantity
Jaw crusher 1.07m x 1.22m 187 kW 1
SAG mill 6.1m x 4.9m 3000 kW 1
Ball mill 6.1m x 9.1m 6000 kW 1
Regrind / Stirred mill 337 kW 2

Summary:

Crushing Plant
ROM material will be trucked to the crushing station and dumped into a 200 t receiving bin protected with a 1000 mm aperture stationary grizzly screen. Ore will be reclaimed from the bin with an apron feeder and scalped of fines with a vibrating grizzly. Grizzly oversize will be passed to a 200 kW jaw crusher. The designed nominal crushing rate is 641 t/h at 65% availability.

The combined grizzly undersize and jaw crusher discharge product is expected to be 80% passing 80 mm. The crusher product will be conveyed to a 5,000 t live capacity stockpile, providing up to 12 hours of live storage for the grinding/flotation plant.

A dust collection system will be provided to control fugitive dust generated during dumping, crushing, and transport of the materials. A belt magnet will be provided over the crusher discharge conveyor to remove any tramp iron.

The main equipment in the crushing area will include:
• One 1000 mm stationary grizzly.
• One primary apron feeder, 1,500 mm wide by 7,000 mm long.
• One vibrating grizzly (1,600 mm wide x 6,100 mm long, 100 mm aperture)
• One jaw crusher, 1,067mm x 1,270mm; driven by a 187kW motor.
• One belt scale.
• One belt magnet.
• One jaw crusher discharge conveyor.
• One stockpile feed conveyor.
• One baghouse/dust collector.

Coarse Ore Storage
The coarse ore stockpile will have a live capacity of 5,000 t equivalent to approximately 12hrof mill feed at the nominal mill feed rate.The stockpile dead capacity will be approximately 20,000t.The coarse ore stockpile will be a covered facility equipped with a dust collector to effectively control dust losses and to mitigate freezing of the stockpiled material. The coarse ore stockpile building access will allow for the operation of mobile equipment to work the pile as required.Reclaim of ore from the stockpile will be accomplished using two 1000 mm wide by 4,800 mm long apron feeders at a nominal rate of 226 t/h per feeder. Reclaimed material from the apron feeders will be discharged onto a 900 mm wide by 125m long SAG mill feed conveyor.

Primary Grinding and Classification
Crushed ore reclaimed from the coarse ore stockpile will feed the SAG mill at a rate of 453 t/h. The initial lime and zinc sulphate addition to establish downstream flotation chemistry will be added here. The SAG mill will be a 6.1 m diameter by 4.9 m long unit equipped with a classifying trommel screen. The installed power on the SAG mill will be 3000 kW provided by a single motor and variable speed drive.

The SAG mill trommel undersize will flow by gravity to a pump box which will feed the classifying cyclones. Oversized pebbles from the SAG mill trommel will be returned to the SAG mill for additional grinding. The circulating load of oversize from the SAG mill trommel is estimated at 20% of SAG mill feed. As required, steel balls will be added to the SAG mill to maintain mill power.

Secondary Grinding and Classification
The secondary grinding circuit will include a single ball mill operated in closed circuit with a classifying cyclone cluster. The ball mill will be a 6.1 m diameter by 9.1 m effective grinding length (EGL) ball mill, powered by a 6,000 kW motor. The SAG mill trommel undersize will be combined with ball mill discharge to feed the classifying cyclone cluster. The cyclone underflow will gravity-flow to the ball mill, while the cyclone overflow, with a solids content of 36.5%, will gravitate to the flotation plant. The designed circulation load for the ball mill is approximately 300%. The flotation feed slurry is estimated to have a particle size of 80% passing 70 µm.

As required, steel balls will be added into the ball mill to maintain the required mill power.


Processing

  • Flotation
  • Cyanide (reagent)

Flow Sheet: Subscription required

Summary:

Mineral Processing
A 10,000 t/d process plant was designed to process the massive and semi-massive sulphide mineralization. The process plant will operate two shifts per day, 365 d/a with an overall plant availability of 92%. The process plant will produce three concentrates: 1) copper concentrate, 2) zinc concentrate, and 3)lead concentrate. Gold and silver are expected to be payable at a smelter; silver is expected to be payable in the copper and lead concentrates, with gold expected to be payable in the lead concentrate only. The process plant feed will be supplied from the proposed Arctic open pit mine.

The process plant will consist of the following unit operations:
• Crushing:
o Primary (jaw) crushing.
o Stockpile and reclaim system.
o Associated conveying and dust collection systems.
• Grinding:
o Primary grinding using a SAG mill with pebble recycle.
o Secondary grinding using a closed-circuit ball mill.
• Talc pre-flotati ........

Recoveries & Grades:

CommodityParameterAvg. LOM
Copper Recovery Rate, %  ......  Subscription required
Copper Head Grade, % 2.24
Copper Concentrate Grade, %  ......  Subscription required
Zinc Recovery Rate, %  ......  Subscription required
Zinc Head Grade, % 3.12
Zinc Concentrate Grade, %  ......  Subscription required
Lead Recovery Rate, %  ......  Subscription required
Lead Head Grade, % 0.54
Lead Concentrate Grade, %  ......  Subscription required
Gold Head Grade, g/t 0.47
Silver Head Grade, g/t 34.7
Subscription required - Subscription is required.

Projected Production:

CommodityProductUnitsAvg. AnnualLOM
Copper Payable metal M lbs 1551,864
Copper Concentrate kt 2412,892
Zinc Concentrate kt  ......  Subscription required  ......  Subscription required
Zinc Payable metal M lbs  ......  Subscription required  ......  Subscription required
Lead Concentrate kt  ......  Subscription required  ......  Subscription required
Lead Payable metal M lbs  ......  Subscription required  ......  Subscription required
Gold Payable metal koz  ......  Subscription required  ......  Subscription required
Silver Payable metal koz  ......  Subscription required  ......  Subscription required

Operational Metrics:

Metrics
Stripping / waste ratio  ......  Subscription required
Daily ore mining rate  ......  Subscription required
Annual mining capacity  ......  Subscription required
Waste tonnes, LOM  ......  Subscription required
Ore tonnes mined, LOM  ......  Subscription required
Total tonnes mined, LOM  ......  Subscription required
Daily processing capacity  ......  Subscription required
Tonnes processed, LOM  ......  Subscription required
Annual processing capacity  ......  Subscription required
* According to 2020 study.
Subscription required - Subscription is required.

Reserves at August 20, 2020:
The base case cut-off grade is 0.5% copper equivalent: CuEq = (Cu% x 0.92) + (Zn% x 0.290) + (Pb% x 0.231)+(Au g/t x 0.398)+(Ag g/t x 0.005).

CategoryTonnage CommodityGradeContained Metal
Probable 43,443 kt Copper 2.24 %
Probable 43,443 kt Zinc 3.12 %
Probable 43,443 kt Lead 0.54 %
Probable 43,443 kt Gold 0.47 g/t
Probable 43,443 kt Silver 34.7 g/t
Indicated 36 Mt Copper 3.07 % 2,441 M lbs
Indicated 36 Mt Zinc 4.23 % 3,356 M lbs
Indicated 36 Mt Lead 0.73 % 581 M lbs
Indicated 36 Mt Gold 0.63 g/t 728 koz
Indicated 36 Mt Silver 47.6 g/t 55 M oz
Inferred 3.5 Mt Copper 1.71 % 131 M lbs
Inferred 3.5 Mt Zinc 2.72 % 210 M lbs
Inferred 3.5 Mt Lead 0.6 % 47 M lbs
Inferred 3.5 Mt Gold 0.36 g/t 40 koz
Inferred 3.5 Mt Silver 28.7 g/t 3 koz

Commodity Production Costs:

CommodityUnitsAverage
Cash costs Copper USD  ......  Subscription required *†
All-in costs Copper USD  ......  Subscription required *†
Assumed price Lead USD  ......  Subscription required *
Assumed price Zinc USD  ......  Subscription required *
Assumed price Copper USD  ......  Subscription required *
Assumed price Silver USD  ......  Subscription required *
Assumed price Gold USD  ......  Subscription required *
* According to 2020 study / presentation.
† Net of By-Product.
Subscription required - Subscription is required.

Operating Costs:

Units2020
OP mining costs ($/t milled) USD 18.5 *
Processing costs ($/t milled) USD  ......  Subscription required
G&A ($/t milled) USD  ......  Subscription required
Total operating costs ($/t milled) USD  ......  Subscription required
* According to 2020 study.
Subscription required - Subscription is required.

2020 Study Costs and Valuation Metrics :

MetricsUnitsLOM Total
Initial CapEx $M USD  ......  Subscription required
Sustaining CapEx $M USD  ......  Subscription required
Closure costs $M USD  ......  Subscription required
Total CapEx $M USD  ......  Subscription required
OP OpEx $M USD  ......  Subscription required
Processing OpEx $M USD 795.3
G&A costs $M USD 223.5
Total OpEx $M USD  ......  Subscription required
Income Taxes $M USD  ......  Subscription required
Gross revenue (LOM) $M USD  ......  Subscription required
Pre-tax Cash Flow (LOM) $M USD  ......  Subscription required
After-tax Cash Flow (LOM) $M USD  ......  Subscription required
Pre-tax NPV @ 8% $M USD  ......  Subscription required
After-tax NPV @ 8% $M USD  ......  Subscription required
Pre-tax IRR, %  ......  Subscription required
After-tax IRR, %  ......  Subscription required
Pre-tax payback period, years  ......  Subscription required
After-tax payback period, years  ......  Subscription required
Subscription required - Subscription is required.

Proposed Heavy Mobile Equipment as of August 20, 2020:
HME TypeSizeQuantity
Backhoe 106 kW 1
....................... Subscription required ....................... Subscription required 1
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....................... Subscription required ....................... Subscription required 18
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....................... Subscription required ....................... Subscription required 1
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Subscription required - Subscription is required.

Mine Management:

Job TitleNameProfileRef. Date
....................... Subscription required ....................... Subscription required Subscription required Aug 20, 2020
....................... Subscription required ....................... Subscription required Subscription required Aug 20, 2020
Subscription required - Subscription is required.

Staff:

EmployeesContractorsTotal WorkforceYear
Subscription required Subscription required Subscription required 2020

Corporate Filings & Presentations:

DocumentYear
Corporate Presentation 2021
................................... Subscription required 2020
Corporate Presentation 2017
Form 10-K 2017
Press Release 2017
Technical Report 2017
Corporate Presentation 2016
Corporate Presentation 2016
Preliminary Economic Assessment 2013
Subscription required - Subscription is required.

News:

NewsDate
Trilogy Metals Files NI 43-101 Technical Report for the Arctic Feasibility Study October 2, 2020
Trilogy Metals Announces Positive Feasibility Study Results for the Arctic Project Located in Alaska, USA August 20, 2020
Trilogy Metals: Final Environmental Impact Statement filed for the Ambler Access Road March 27, 2020
Trilogy Metals Provides Update on Project Activities January 16, 2020
Trilogy Metals Inc.: Bureau of Land Management Extends Draft Environmental Impact Statememt Comment Period for the Ambler Road September 30, 2019
Draft Environmental Impact Statement and Environmental and Economic Analysis filed for the Ambler Road August 26, 2019
Trilogy Metals Announces Increase in 2019 Exploration Budget at the Upper Kobuk Mineral Projects February 6, 2019
Trilogy Metals Announces Pre-Feasibility Study Results and Reserves for the Arctic Project, Alaska February 21, 2018
Trilogy Metals Reports Year End Results February 2, 2018

Subscription required - Subscription is required.

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