Mantos Blancos

Mantos Blancos is an open-pit mine located in the Antofagasta region of Chile. The mine is located within a one-hour drive of port facilities at Antofagasta and Mejillones, and the Glencore-owned Altonorte copper smelter. There is no on-site accommodation as all staff live off-site, mainly in the city of Antofagasta. The mine currently mines and processes both sulfide and oxide ores. Following the completion and current ramp up of the Mantos Blancos Concentrator Debottlenecking Development Project (“MBCDP”, or “Mantos Blancos Expansion”), the mine will primarily treat sulfide ore in an expanded concentrator.

The current sulphide concentrator has a capacity of 4.2 million tonnes of sulphide ore per year, with three stage crushing followed by ball milling and flotation plant. The oxide run-of-mine ore is leached on dumps, and the solution sent to an SX-EW plant with a production capacity of 60 thousand tonnes per year of high purity copper cathodes.

Annual production

Mantos Blancos produces in the range of approximately 40 to 50 thousand tonnes of copper in concentrates and cathodes per year.

Mantos Blancos Expansion

The Expansion Project was completed in 2021 and is currently ramping up to increase throughput capacity from 11 thousand tonnes per day to 20 thousand tonnes per day and will shift the focus of the mine towards the higher-grade, lower-cost sulfide deposit.

Following completion of the MB Debottlenecking Project, we expect to increase Mantos Blancos’ production to approximately 55,000 tonnes of copper in 2024 at an AISC of $1.97 per payable pound. As of March, 2022, the capital cost of the project is estimated to be US$249 million and represents a capital intensity of approximately US$11,900 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].

In 2019, Mantos Copper secured a US$250 million financing package to fund the construction of the MBCDP, which comprises a US$150 million facility from Glencore (associated with an offtake agreement with Glencore and Complejo Metalurgico Altonorte S.A.), a US$50 million copper royalty agreement with Southern Cross (a subsidiary of Anglo Pacific), a US$25 million upsized silver production agreement with Osisko, and a US$25 million equity injection by Orion Mining Finance. Construction on the MBCDP commenced in 2019 and was completed in late 2021.

Other Growth Projects

At Mantos Blancos,after completion of the MBCDP, we intend to focus on delivering the next phase of growth with the MB Phase II Expansion, which is an opportunity to use existing ball mills and processing equipment to increase sulfide throughput, as well as incremental oxide ore leaching from mine and waste dumps, to provide incremental production of approximately 20 thousand tonnes of copper per year by 2023.

The MB Phase II Expansion which would increase production at Mantos Blancos to over 80 thousand tonnes of copper per year by 2025. The estimated capital cost of the MB Phase II Expansion is US$80 million, which represents a capital intensity of approximately US$6,500 per tonne.

Geology and Mining

Geological setting Jurassic volcanic-hosted Cu-Ag stratabound deposit, Chilean Manto Type, associated with the La Negra Formation
Economic Mineralization Oxide mineralization includes atacamite, chrysocolla and minor malachite, antlerite, tenorite, cuprite and almagres, disseminated and as fracture fill.
Hypogene mineralization includes irregular chalcocite (and/or digenite) rich centre lenses transitioning to disseminated bornite and chalcopyrite. Silver occurs in the crystal structure of the copper sulphides and occasionally as native silver.
Mining method Open pit
Recovery methods Flotation of sulphide (hypogene) ore
Dump leaching of oxide ore
Primary product mined Copper
By-products mined Silver

Technical Reports

Download item year list

Mineral Reserves & Resources

Mantos Blancos Mine Mineral Reserves as at December 31, 2020

  Classification Tonnes
(kt)
Copper
(%)
Silver
(g/t)
Copper Metal
(kt)
Silver Metal
(koz)
Sulphides + Mixed
(Flotation)
Proven 72,600 0.78 6 567 14,968
Probable 50,000 0.57 5 288 7,339
Total 122,600 0.69 6 854 22,307
Oxides + Mixed
(Dump + Heap)
Proven 2,800 0.36 - 10 -
Probable 8,500 0.20 - 17 -
Total 11,300 0.24 - 27 -

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. Figures may not sum exactly due to rounding.

Mantos Blancos Mineral Resources as at December 31, 2020

  Classification Tonnes
(kt)
Copper
(%)
Silver
(g/t)
Copper Metal
(kt)
Silver Metal
(koz)
Sulphides + Mixed
(Flotation)
Measured 104,400 0.75 6 783 20,234
Indicated 106,500 0.58 4 618 15,099
M&I 210,900 0.66 5 1,400 35,334
Inferred 20,000 0.48 3 96 2,151
Oxides + Mixed
(Dump + Heap)
Measured 22,800 0.34 - 78 -
Indicated 38,700 0.24 - 92 -
M&I 61,600 0.28 - 171 -
Inferred 18,400 0.21 - 38 -

NOTE: Mineral Resources are classified according to CIM (2014) definitions, estimated following CIM (2019) guidelines and have an effective date of December 31, 2020. Ronald Turner, MAusIMM (CP), a Golder Associates S.A. employee, is the Qualified Person responsible for the Mantos Blancos Mineral Resource estimate effective December 31, 2020. Mineral Resources are reported on a 100% basis. The attributable percentage to Capstone Copper is 99.993%. COG varies by metallurgical process: Flotation at 0.22% Insoluble Cu, Dump Leach at 0.10% Soluble Cu. The Mineral Resource pit is based on US$3.77/lb Cu and US$17.00/oz Ag. Flotation recovery is based on a geometallurgical model, 83% TCu and 76.5% Ag as average. Dump recovery is based on operation data 40% SCu. Through the Osisko silver production agreement, Osisko Gold has the right to buy 100% of the silver production in concentrate, less specified deductions, until reaching 19,300,000 ounces and subsequently 40% paying 92% of the market price. Stockpile material in the oxide dump leach Indicated Mineral Resource includes the Mercedes Stockpile with 6,300 kt at 0.18% SCu and the NE Dump Stockpile with 3,900 kt at 0.19% SCu. Stockpile material in the oxide dump leach Inferred Mineral Resource includes the Mercedes Stockpile with 2,300 kt at 0.19% SCu, F2 Este Dump with 3,100 kt at 0.19% SCu and the NE2 Dump with 4,400 kt of 0.17% SCu.