Mantoverde is an open-pit mine located in the Atacama region of Chile. It is currently comprised of four pits situated along the Mantoverde fault, each of which contains both sulfide and oxide ores. Mantoverde currently mines and processes only the oxide ore. Mining is performed using truck-and-shovel technology.

The high-grade oxide ore is crushed and leached on heaps and low-grade oxide ore is sent directly to leach dumps as run-of-mine ore. The resultant solution is collected and sent to the SX-EW plant, which selectively removes the copper and leaves behind the remaining ions in the aqueous solution. The electrowinning process uses electrolysis to produce high-purity LME Grade “A” copper cathodes.

Mantoverde owns a state-of-the-art desalination plant, which is located on the coast approximately 40 kilometers west of the mine. Our desalination plant supplies all water requirements for our current operations at Mantoverde with 120 liters per second and will supply all water requirements for our expanded operation following the completion of the MV Development Project with 380 liters per second.

Annual production

The SX-EW plant has a production capacity of 60 thousand tonnes per annum of high-purity copper cathodes, with current production in the range of approximately 40 to 50 thousand tonnes per annum.

MV Development Project (Expansion Project)

The MV Development Project (MVDP) is the brownfield expansion project at Mantoverde. The project’s $784 million projected capital expenditure costs are fully financed and completion is expected to enable us to process 236 million tonnes of copper sulfide reserves with a current 21-year expected mine life, in addition to our existing oxide mining process.

Upon completion of the MV Development Project, we expect to increase the production at Mantoverde to approximately 122 thousand tonnes of copper in 2024 at an AISC of US$1.64 per payable pound; AISC will benefit from approximately 31 thousand ounces of gold per year in by-product over the life of the mine, beginning in the first year following completion of the project.

The MVDP will involve the addition of a sulfide concentrator and tailings storage facility, and the expansion of our existing state-of-the-art desalination plant. Given the scarcity of water in Chile, particularly for use at mining operations, we believe that our ability to supply Mantoverde with consistent and expandable levels of water from our desalination plant provides us with a competitive advantage.

HIghlights of the Expansion Project

  • The feasibility study for the MVDP was completed in June 2018, and the Environmental Impact Assessment was approved by the authorities during that same year. Construction is subject to a “lump sum turnkey” engineering, procurement and construction contract with Ausenco that significantly limits our construction cost risk.
  • The capital cost of the project is estimated to be US$783 million and represents a capital intensity of approximately US$12,500 per tonne, which is substantially lower than the Latin American industry average of approximately US$20,000 per tonne as calculated by Wood Mackenzie [need to indicate the date of the report]. This is due to the relatively high grade of the ore together with the benefit of leveraging substantial existing infrastructure.
  • In February 2021, we secured a US$572 million debt financing package to fund the construction of the MVDP with a lending syndicate of international banks and export credit agencies, which comprises senior secured amortizing project debt facilities in an aggregate amount of US$520 million and a US$52 million senior secured closure bonding facility.
  • In addition, as part of the financing of MVDP, Mitsubishi Materials acquired a 30% interest in Mantoverde for US$275 million, subject to an additional contingent payment of US$20 million upon the satisfaction of technical requirements related to the increase in project ore reserves containing 500,000 tonnes of contained copper.
  • Mitsubishi Materials also agreed to provide a US$60 million cost overrun facility in exchange for additional offtake of copper concentrate production. Construction on the MVDP commenced in February 2021 and is scheduled to be completed by 2024.

Mantoverde/Santo Domingo Synergies Analysis

In Q4 2021, we started work to identify and refine potential synergies between the Mantoverde and Santo Domingo Project. The Santo Domingo Project is located ~35 kilometres northeast of the Mantoverde mine and offers significant potential synergies opportunities for:

  • Infrastructure sharing (including power, water, pipelines, port),
  • Transportation synergies for concentrate shipment,
  • Potential enabling of product lines (additional iron or cobalt production from Mantoverde, processing oxide ore from Santo Domingo),
  • Potential integrated operating approach, and
  • Construction synergies (including project teams and camp).

We expect to release a synergies study and integration plan in September 2022.

Additional Growth Opportunities

The MV Phase II Expansion is an opportunity to add a second ball mill to potentially provide incremental production of approximately 30 thousand tonnes of copper per year by 2026, which would increase production at Mantoverde to over 136 thousand tonnes of copper per year.

The estimated capital cost of the MV Phase II Expansion is US$326 million, which represents a capital intensity of approximately US$11,800 per tonne.

As an alternative to the MV Phase II Expansion, the MV Second Line Expansion is an opportunity to add a second 32-thousand-tonne-per-day concentrator to provide incremental production of approximately 50 thousand tonnes of copper per year, which we expect would increase production at Mantoverde to over 186 thousand tonnes of copper per year.

In addition to the MV Phase II Expansion and the MV Second Line Expansion, there is opportunity to extract approximately 500 thousand tonnes per annum of magnetite and 800 tonnes per annum of cobalt from waste streams, which would be by-products that contribute to a reduction of AISC.

Geology and Mining

Geological setting Iron oxide–copper–gold (IOCG) deposit located within the Atacama Fault System
Economic Mineralization Oxide - Two types of oxidized copper ores are recognized. Breccias in the sloping fault block contain hematite with brochantite, minor antlerite, chrysocolla, malachite and atacamite in a specularite matrix.
Mineralization is disseminated and in veinlets or patches.
Copper mineralization is oxidized to approximately 200 m depth.
Weak supergene enrichment (3 m to 5 m thick) includes native copper, cuprite, tenorite and chalcocite (±covellite) partially replacing the hypogene sulphides.
Hypogene – disseminated chalcopyrite mineralization below 200m in a specularite matrix.
Mining method Open pit
Recovery methods Heap and dump leaching of oxide ore
Proposed flotation of sulphide (hypogene) ore
Primary product mined Copper
By-products mined Gold

Mineral Reserves & Resources

Mantoverde Mine Mineral Reserves as at December 31, 2020

  Classification Tonnes
Copper Metal
Gold metal
Sulphides + Mixed (Flotation) Proven 170,000 0.63 0.11 1,071 580
Probable 65,700 0.53 0.11 347 228
 Total 235,700 0.60 0.11 1,419 807
Oxides + Mixed (Dump + Heap>) Proven 189,800 0.25 - - -
Probable 65,800 0.21 - - -
Total 255,600 0.24 - - -

Carlos Guzman, RM CMC, FAusIMM, an employee of NCL, is the independent Qualified Person for the Mantoverde Mineral Reserve effective December 31, 2020. Mineral Reserves are reported on a 100% basis using average off-site costs (selling cost) of US$0.28/lb for sulphides and US$0.30 for oxides. Mineral Reserves are contained within an optimized pit shell. Mining will use conventional open pit methods and equipment and use a stockpiling strategy (direct mining costs are estimated by geological unit, averaging US$1.85/t of material mined). Processing costs were estimated by geometallurgical units (from UG1 to UG10) averaging US$7.28/t of milled material, including concentrator, tailings storage facility, port and desalination costs. Processing cost for material sent to the heap leach was US$6.24/t. For material sent to the run-of-mine dump leach, the processing cost was US$2.12/t. Total copper recoveries average 88.4% for sulphides and gold recoveries average 71.2%. Soluble copper recoveries average 76.4% for material sent to the heap leach and 45.8% for material sent to the dump leach process. Inter-ramp angles vary from 26˚ to 60˚. The life-of-mine strip ratio is 2.12 to 1.

Mantoverde Mineral Resources as at December 31, 2020

  Classification Tonnes
Copper Metal
Gold metal
Sulphides + Mixed
Measured 224,300 0.57 0.10 1,276 708
Indicated 369,200 0.41 0.10 1,504 1,176
M&I 593,500 0.47 0.10 2,780 1,884
Inferred 571,500 0.37 0.08 2,103 1,459
Oxides + Mixed
(Dump + Heap)
Measured 298,600 0.23 - 696 -
Indicated 235,700 0.19 - 438 -
M&I 534,300 0.21 1,134 -
Inferred 75,600 0.15 - 116 -

Ronald Turner, MAusIMM (CP), a Golder Associates S.A. employee, is the Qualified Person responsible for the Mantoverde Mineral Resource estimate effective December 31, 2020. Mineral Resources are reported on a 100% basis. The attributable percentage to Capstone Copper is 69.993%. COG varies per zone and recovery process:

Flotation: Sulphide: TCu ≥0.20%, Mixed: TCu ≥0.23% and SCu/TCu ≤50%.

Dump Leach: Oxide: 0.10%≤SCu<0.17%, Mixed: 0.10%≤SCu<0.17% and SCu/TCu >50%.

Heap Leach: Oxide: SCu≥.17%, Mixed: SCu≥0.17% and SCu/TCu >50%.

Flotation recovery is based on a geometallurgical model, 89.36%TCu and 71.41% Au average. Heap Leach recovery is 79.2% average. Dump recovery is based on operating data 39.4%SCu. The Mineral Resource pit is based on US$3.77/lb Cu.