Name of the Mine
Mantos Blancos mine.

Location
Antofagasta province, Región de Antofagasta, 900 m above sea level.

Mine Owner/s
Capstone Copper Corp.

Brief Description
The Mantos Blancos property includes 135 mining concessions, covering an area of 27 236 ha and 73 exploration rights claims totalling 32 600 ha.

The operation currently mines and processes sulphide and oxide ores. Following the completion and current ramp-up of the Mantos Blancos concentrator debottlenecking development project (MBCDP), the mine will primarily treat sulphide ore in an expanded concentrator.

The openpit operation includes one large openpit (Santa Barbara) that provides most of the sulphide feed for the concentrator and the oxide feed for the dump leach. Material is also sourced from four oxide-leach stockpiles. Higher-grade sulphide material is sent to the plant and lower-grade sulphide material is stockpiled to be processed later in the mine life.

Brief History
Mantos Blancos has been in operation since 1960 and is one of the major copper mines in the Antofagasta region.

Primary Metals/Minerals
Mantos Blancos production is primarily copper in concentrate and copper cathode produced from run-of-mine leaching and solvent extraction and electrowinning (SX/EW) production.

Secondary Metals/Minerals
Silver.

Geology/Mineralisation
The Mantos Blancos deposit is interpreted as a stratabound copper/silver deposit; this deposit type is also known as a Chilean mantos-style deposit. 

Rock types consist of a rhyolitic dome and magmatic–hydrothermal breccias that are intruded by dioritic and granodioritic stocks and sills. The dioritic and granodioritic stockwork locally grade upwards into variably mineralised magmatic–hydrothermal breccias. Mineralised bodies, which are structurally controlled, form irregular 100– to 200-m-thick lenses. Mineralisation has a distinct vertical zonation, with specularite at the top, followed by oxide copper (atacamite with minor chrysocolla) and at depth, sulphides (chalcocite–bornite). A zone of lower-grade copper mineralisation typically surrounds these lenses, and transitions, at depth, to a pyrite-rich zone. 

Sulphide mineralisation is primarily disseminated and comprises chalcocite (and/or digenite), covellite, bornite, chalcopyrite, pyrite, specularite, magnetite, galena, and lesser sphalerite. Oxide mineralisation occurs as disseminations and fracture fills, with the most common minerals being atacamite, chrysocolla and minor malachite, antlerite, tenorite, cuprite and almagres. Silver occurs in the crystal structure of the copper sulphides and occasionally as native silver. 

Reserves
As at December 31, 2023, Mantos Blancos had total proven and probable reserves of sulphides and mixed reserves of 111.40-million tonnes grading 0.65% total copper and 5 g/t silver. Total proven and probable oxides and mixed reserves were estimated at 3.95-milllion tonnes grading 0.28% copper.

Resources
Total measured and indicated sulphide and mixed resources were estimated, as at December 31, 2023, at 202.09-million tonnes grading 0.64% copper and 4.92 g/t silver. Inferred resources were estimated at 22.45-million tonnes grading 0.47% copper and 3.25 g/t silver.

Total measured and indicated oxides and mixed resources were estimated, as at December 31, 2023, at 117.75-million tonnes grading 0.20% copper. Inferred resources were estimated at 23.57-million tonnes grading 0.19% copper.

Type of Mine
Openpit.

Mining Method
Mantos Blancos uses conventional openpit mining methods, with material extracted from the Santa Barbara pit. The operation uses a stockpiling strategy for sulphides and oxides, with sulphide ore sent to the flotation plant and oxide ore to the dump-leach pads.

Major Infrastructure/Equipment
The infrastructure for the Mantos Blancos mine is developed and in service. The main facilities for the mine include: the Santa Barbara pit; the Argentina Norte, Phase 8, Este, and Oeste dumps, a concentrator, leach vats, a coarse tailings deposit, a fine tailings deposit, the Mercedes stockpile, the Mercedes dump, secondary leaching pads and heaps, an SX/EW plant and a back-up power plant.

Ancillary facilities include workshops, warehouses, administrative buildings and offices, explosives storage, chemical/reagent storage, policlinic and two canteen buildings with kitchens.

Prospects
The MBCDP was completed in late 2021 to extend the mine’s life and expand sulphide ore treatment capacity from 4.2-million tonnes a year to 7.3-million tonnes a year. Mantos Blancos Phase II represents the mine’s next leg of growth, which is analysing the potential to further increase the concentrator plant’s throughput to at least 27 000 t/d, by using existing and unused or underused process equipment. The plan also includes extending cathode production beyond the current plan to use the existing 60 000 t/y cathode capacity.

Contact Details
Capstone Copper Corp
Tel +1 604 684 8894
Email info@capstonecopper.com

Mantos Blancos Mine
Tel +56 55 269 3001
Email MB.comunicaciones@capstonecopper.com

Sources
Mantos Blancos. Website: https://capstonecopper.com