Canada

Mount Milligan Mine

Click for more information

Categories

Overview

Mine TypeOpen Pit
Commodities
  • Copper
  • Gold
  • Silver
Mining Method
  • Truck & Shovel / Loader
Production Start... Lock
Mine Life... Lock
ShapshotThe Mount Milligan Mine is a conventional truck shovel open-pit copper and gold mine and process plant. The Mount Milligan Mine is currently permitted by the Province of British Columbia to operate at an average of 60,000 tpd over a calendar year.

As a result of the Additional Royal Gold Agreement, the mine life has been extended by two years to 2035, subject to normal course permitting, and has declared mineral resources of 510 million tonnes, inclusive of reserves.

With the announcement of the agreement, Centerra described a three-part strategy to further increase the Mount Milligan mine life that includes the completion of a Preliminary Economic Assessment (“PEA”) in the first half of 2025 to evaluate mine life extension opportunities, further exploration drilling, and a site optimization program that began in the fourth quarter of 2023.

Owners

SourceSource
CompanyInterestOwnership
Centerra Gold Inc. 100 % Indirect
Thompson Creek Metals Company Inc. (operator) 100 % Direct
Centerra Gold Inc.'s wholly-owned subsidiary, Thompson Creek Metals Company Inc., is the holder of the rights to the Mount Milligan Mine.

Contractors

Lock

- subscription is required.

Deposit type

  • Porphyry
  • Vein / narrow vein
  • Breccia pipe / Stockwork

Summary:

The Mount Milligan deposits are categorized as silica-saturated alkalic Cu-Au porphyry deposits (Lang et al., 1995; Panteleyev, 1995) associated with alkaline monzodioritic-to-syenitic igneous rocks and are recognized in only a few mineral provinces worldwide (Deyell and Tosdal, 2004).

Mineralization at the Mount Milligan deposit consists of two styles, early-stage porphyry gold-copper (Au-Cu) and late-stage high-gold low-copper (HGLC). The early-stage porphyry Au-Cu mineralization comprises mainly chalcopyrite and pyrite, occurs with potassic alteration and early-stage vein types and is spatially associated with composite monzonite porphyry stocks (especially at their hanging-wall and footwall margins), hydrothermal breccia, and narrow dyke and breccia complexes. Late-stage, structurally controlled pyritic HGLC style mineralization is associated with carbonate-phyllic alteration and intermediate- to late-stage vein types, and is spatially associated with faults, fault breccias and faulted lithological contacts (i.e. faulted monzonite porphyry dyke margins). It crosscuts and overprints the earlier stage porphyry Au-Cu mineralization.

Porphyry style Au-Cu mineralization occurs in the hanging-wall and footwall zones of the MBX, Saddle, Southern Star, and Goldmark stocks. Disseminated and vein/veinlet-hosted mineralization is associated with the composite monzonite stocks, their brecciated margins and variably altered volcanic host rocks. Core zones of auriferous chalcopyrite-pyrite mineralization with magnetite rich potassic alteration transition laterally and vertically to pyrite rich HGLC zones within the inner propylitic (albitic) and carbonate-phyllic alteration shells; the latter appear to be late stage and exhibit strong structural control.

Brownfield target areas west of the mine have mainly peripheral alteration and mineralization signatures; these include near surface HGLC zones proximal to structures. Narrow intrusive units, dykes or pencil porphyries, are common and are locally Au-Cu mineralized. The Heidi target farther west and outside the mine lease is a shallow copper prospect with low gold.

Hypogene Mineralization
The bulk of the mineralization consists of disseminated and vein-hosted chalcopyrite (in potassic and sodic-calcic alteration assemblages) and disseminated and vein-hosted pyrite (in all alteration assemblages). Late stage polymetallic (subepithermal) veins are rare, but most pronounced in the DWBX zone. These veins contain sphalerite, galena and sulfosalt in addition to chalcopyrite and pyrite.

Chalcopyrite
Chalcopyrite is associated with potassic alteration at the contact margin between volcanic and intrusive rocks. It occurs most commonly as fine-grained disseminations and fracture fillings, and less commonly as veinlets and in veinlet selvages. Adjacent to the MBX stock, chalcopyrite may be accompanied by pyrite to form coarse sulphide aggregates. Chalcopyrite-bearing veins contain pyrite and magnetite in a gangue of potassium feldspar, quartz, and calcite. In massive trachytic rocks, chalcopyrite occurs with pyrite along curviplanar partings and as disseminations. Chalcopyrite also occurs in gold-bearing early quartz veins in the Southern Star, WBX and DWBX zones.

Pyrite
Pyrite content increases with distance from the MBX and Southern Star stocks and is most abundant in propylitically altered rocks. Pyrite occurs as disseminations, veinlets, large clots, patches, and as replacements of mafic minerals. Gold mineralization in the 66 zone is associated with 10-20% pyrite. Cross-cutting vein relationships indicate several generations of pyrite mineralization.

Gold
Gold occurs as grains from 1 to 100 µm in size, as observed in process samples. Grains occur as microfracture fillings and are attached to pyrite, chalcopyrite, or bornite (Ditson, 1997). Gold also forms inclusions within pyrite, chalcopyrite, and magnetite grains. SEM work indicates electrum throughout the deposit with varying gold to silver ratios.

Silver
Silver is a minor metal found in the Mount Milligan deposits. Polymetallic gold-silver bearing sulphide and sulfosalt rich veins are present in volcanic rocks peripheral to the MBX and Southern Star stocks. Tetrahedrite is the most widespread Ag-bearing sulfosalt mineral at Mount Milligan. Silver is also known to occur throughout the deposits in conjunction with copper and gold mineralization, from micron-scale electrum grains and inclusions.

Polymetallic Veins
Gold- and silver-bearing sulphide, sulfosalt and carbonate-rich veins are present in andesitic volcanic rocks peripheral to the MBX and Southern Star stocks on the western margin of the deposit, in the DWBX and Saddle zones. They comprise pyrite with lesser chalcopyrite, sphalerite, galena, molybdenite, arsenopyrite, tetrahedrite-tennantite, and minor quartz and carbonate. Alteration envelopes are not always present but are recognized to consist of chlorite-sericite-carbonate in propylitically altered andesitic volcanic rocks. Polymetallic veins intersected in the DWBX zone exhibit subepithermal textures (Sillitoe, 2010).

Supergene Mineralization
Supergene enrichment is poorly developed at Mount Milligan. It is recognized in the MBX, WBX, and Southern Star zones, and is deeper and more extensive in the MBX and WBX zones than in Southern Star (Placer Dome, 1991). Supergene enrichment is restricted to the sporadic occurrence of secondary copper minerals including sulphides (covellite, chalcocite, and djurleite), oxides (cuprite and tenorite), carbonates (malachite and azurite) and native copper. The secondary sulphides occur as rims around chalcopyrite. Oxides, especially cuprite, occur as surface coatings on native copper.

Secondary copper minerals commonly occur with iron oxides (goethite, magnetite, and hematite) and iron carbonate (siderite), particularly where malachite and azurite are present. Hydrous iron oxides, which are generally referred to as limonite and include goethite, commonly replace chalcopyrite and pyrite. Limonite either completely replaces sulphide minerals or occurs as coatings on surfaces of fractures and hairline cracks. Limonitic coatings commonly occur at depths greater than those at which pyrite or chalcopyrite are completely replaced. Supergene enrichment is best represented in the MBX and WBX zones between 6109150N to 6109800N, and between 434000E to 434850E, where it is partially developed over a 20 m thickness. Locally, the supergene mineralization reaches 50-60 m in thickness, particularly along the north and eastern margins of the MBX stock.

Length Width Continuity
Mount Milligan is a roughly tabular, near-surface silica-saturated alkalic gold-copper porphyry deposit that measures approximately 2,500 m north-south, 1,500 m east-west, and extends to a vertical depth greater than 500 m. There is 1 to 50 m depth of till overburden in the deposit area. Within this system, the overall shapes of the mineralized bodies are irregular and gradational. The two principal deposits, MBX Main and Southern Star, are centred on composite monzonite porphyry stocks. The MBX Main deposit has been subdivided into zones based on structural boundaries and/or changes in alteration-mineralization. These zones include the MBX, WBX, DWBX and 66. The Southern Star deposit has not been subdivided into zones but may be considered to include the Saddle zone at its northern end. The limits of these mineralized zones can vary greatly in size and shape depending on which grade cut-offs are used. The known deposit extents are limited by the lack of drill hole information and could potentially be extended down-dip of monzonite porphyry stocks to the west, down-dip of stratigraphy to the east, and to the north and south along the linear trend of the stock cluster.

Reserves

Lock

- subscription is required.

Mining Methods

Lock

- subscription is required.

Comminution

Crushers and Mills

Lock

- subscription is required.

Processing

Lock

- subscription is required.

Production

CommodityProductUnits2024202320222021202020192018201720162015
Copper Payable metal M lbs  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe7147545771
Gold Payable metal koz  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe183195223199218
Copper Concentrate kt  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe160106122126141
^ Guidance / Forecast.

Operational metrics

Metrics202320222021202020192018201720162015
Daily milling rate  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe53,000 t44,214 t
Daily milling capacity  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe60,000 t60,000 t
Ore tonnes mined  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe15,736 kt13,461 kt21,501 kt17,994 kt
Total tonnes mined  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe39,466 kt33,225 kt41,966 kt
Tonnes milled  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe16,350 kt13,556 kt17,743 kt19,277 kt16,138 kt
Waste  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe23,730 kt19,764 kt20,363 kt14,413 kt
Daily mining rate  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe110,000 t
Stripping / waste ratio  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe0.8

Production Costs

CommodityUnits20242023202220212020201920182017
Cash costs (sold) Copper USD  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe 1.46 / lb  
Cash costs (sold) Gold USD  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe 746 / oz   672 / oz  
Cash costs (sold) Gold USD 519 / oz **   370 / oz **  
All-in sustaining costs (sold) Copper USD  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe 1.85 / lb   1.77 / lb   1.47 / lb  
All-in sustaining costs (sold) Gold USD  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe 950 / oz   751 / oz   663 / oz  
All-in sustaining costs (sold) Gold USD  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe 828 / oz **   764 / oz **   505 / oz **  
All-in costs Gold USD  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe
^ Guidance / Forecast.
** Net of By-Product.

Operating Costs

Currency202320222020201920182017
OP mining costs ($/t mined) USD 2.25  2.18  1.8  2.19  2.22  1.86  
Processing costs ($/t milled) USD  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe
G&A ($/t milled) USD  ....  Subscribe  ....  Subscribe
Total operating costs ($/t milled) USD  ....  Subscribe  ....  Subscribe

Financials

Units20242023202220212020201920182017
Capital expenditures (planned) M USD  ....  Subscribe
Capital expenditures M USD  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe 35.6   42.7   30  
Sustaining costs M USD  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe 35.6   42.7   30  
Revenue M USD  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe 335   263   368.8  
Operating Income M USD  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe
Earnings M USD  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe
Operating Cash Flow M USD  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe

Heavy Mobile Equipment

Lock

- subscription is required.

Personnel

Mine Management

Job TitleNameProfileRef. Date
....................... Subscription required ....................... Subscription required Subscription required Apr 24, 2024
....................... Subscription required ....................... Subscription required Subscription required Apr 24, 2024
....................... Subscription required ....................... Subscription required Subscription required Apr 24, 2024
....................... Subscription required ....................... Subscription required Subscription required Apr 24, 2024
....................... Subscription required ....................... Subscription required Subscription required Apr 24, 2024
....................... Subscription required ....................... Subscription required Subscription required Apr 24, 2024
....................... Subscription required ....................... Subscription required Subscription required Apr 24, 2024
....................... Subscription required ....................... Subscription required Subscription required Apr 24, 2024
....................... Subscription required ....................... Subscription required Subscription required Apr 24, 2024

Total WorkforceYear
...... Subscription required 2023
...... Subscription required 2022
...... Subscription required 2021
...... Subscription required 2020
...... Subscription required 2019

Aerial view:

Lock

- subscription is required.