Overview

Deposit type

• Skarn
• Porphyry

Summary:

The Bingham Canyon deposit is a classic porphyry copper deposit containing economic values of copper, molybdenum, gold, silver, and historic lead and zinc production. Peripheral copper-gold skarns, lead-zinc fissures, and disseminated gold deposits are also associated with this copper porphyry system.

Porphyry dikes, faults, and quartz veins are steeply dipping and have two dominant orientations; north-northeast– and northwest-striking. Dikes have a north-northeast strike but they thicken and develop northwest-trending apophyses and host high-grade copper-gold zones at intersections with northwest-faults, indicating that magmatic-hydrothermal fluids were focused by these structural intersections.

Vein truncation relationships coupled with abrupt changes in copper-gold grades, sulfide ratios, and potassic alteration intensity at porphyry intrusive contacts indicate that the mass of introduced copper and gold decreased significantly during successive porphyry intrusive-hydrothermal cycles, presumably due to depletion of metals and volatiles in the underlying magma chamber.

The Lower Commercial Skarn (LCS) deposit is located in the Bingham mining district southwest of Salt Lake City, Utah. The Bingham mining district is dominated by the Bingham Canyon copper-molybdenum-gold porphyry system, which consists of the Eocene monzonite-quartz monzonite Bingham Stock and deformed siliciclastic and carbonate country rock of the Paleozoic Bingham Mine Formation. The LCS deposit is hosted in mineralized skarn of the Lower Commercial Limestone (LCLS) unit of the Lower Bingham Mine Formation. This unit is proximal to the Bingham Canyon porphyry system and has been altered to copper-gold hosting calc silicate skarn through prograde metasomatism with localized retrograde massive sulphide and clay. This unit has been variably folded and faulted prior to mineralization, resulting in fold thickening and repetition of the units across faults.

The LCS deposit lies in the footwall of the southwest dipping Midas thrust fault, between the older northeast striking and steeply dipping oblique transverse Verona and Smelter faults. This structural block between the Verona and Smelter faults, and below the Midas, is referred to as the Middle Block. The Middle Block is bounded to the south by the Bingham Canyon porphyry monzonite, open to the north, and cut by late latite porphyry dikes on a northeast trend. Palaeozoic country rock within the Middle Block is folded in an asymmetric anticline, slightly overturned to the east, with a gentle plunge to the north. The LCS deposit is hosted in the gently dipping upper limb of the LCLS.

The LCS Mineral Resource is contained within a roughly tabular zone dipping gently north, approximately 40 to 100 m thick, extending 275 m along strike, and 450 m down dip.

The LCS Mineral Resource is located beneath the Bingham Canyon Mine open pit, at approximately the 3700 level (~1,128 m AMSL), immediately adjacent to the active underground drainage gallery workings.

Mining Methods

• Truck & Shovel / Loader
• Longhole open stoping
• Sub-level stoping

Summary:

Kennecott is a fully integrated mining operation just outside Salt Lake City, Utah, U.S.

Mining operations at Kennecott is deployed via conventional open pit method and is carried out a sequence of drilling, blasting, loading, hauling, crushing and conveying 24 hours a day, seven days a week, 52 weeks a year.

On average, 200 holes 55 feet deep are drilled in a typical day. Each hole is packed with 1,200 pounds of special blasting agents. Explosives are carried out twice a day.

Loading to 320 tons haulage trucks performed by electric shovels (the largest electric shovel has a 56-cubic-yard dipper).

In September 2022, was approved a $55 million investment in development capital to start underground mining and expand production at the Kennecott copper operations.

The selected underground mining method is bottom up, sub-level, long hole open stoping, using a primary secondary sequence with cemented backfill. This is a well-known and proven mining method and can be applied effectively within this deposit given the recommended geotechnical limitations.

Stope dimensions are set a 22.9 m high, 15.2 m wide, and a variable length between 15.2 to 9.1 m. Permanent development needed to access the deposit will be 5.9 m high by 5.5 m wide, reducing to 4.9 m high by 5.5 m wide. Stope ground support has been accounted for to aid in stability, this is planned for the backs and sides of the upper drift, as well as the brow from which mucking will occur.

Minimum mining widths have been established and applied to the mine design which underpins the estimate. These are based on the dimensions of the existing mechanized mining fleet, and the expected additional equipment needed to operate the mine (Including allowance for BEV equipment size).

Kennecott’s fleet of 90 haul trucks and all heavy machinery began to transition to renewable diesel in the first quarter of 2024, along with consumption from the concentrator, smelter, and refinery.

Comminution

Crushers and Mills

Summary:

At the In-pit gyratory crusher, approximately 150,000 tons of ore per day reduces to pieces about 10 inches in diameter. Then crushed ore is transported by a five-mile conveyor system: three miles through a tunnel in the mountain and two miles above ground to the Copperton Concentrator.

Processing

• Crush & Screen plant
• Dry Screening
• Smelting
• Flotation

Summary:

The operation includes Copperton concentrator, Garfield smelter, refinery, and precious metals plant and tailings storage facilities.

The crushed ore is turned into a slurry and transported to flotation cells. Additional reagents were added to produce a bubbly froth. Ore particles containing most of the valuable minerals adhere to the bubbles, which float over the sides of the flotation cells. Then the material is collected and filtered.

Production includes a froth flotation process to produce copper and molybdenum concentrates.

The concentrate, which contains about 26 percent copper and by-products such as gold and silver, moves through a pipeline to Kennecott’s smelter, located about 17 miles to the north, for further processing.

The next stage, smelting, is a process of heating and smelting the copper concentrates to cause a chemical reaction, which removes the copper from other elements in the ore. At the smelter, we produce large 750-pound anodes and transport them by rail to the Refinery. The copper is 99 percent pure at this stage.

The smelter at Kennecott captures 99.9 percent of the sulfur in the feed, making it one of the cleanest in the world. The smelter also recovers heat from the furnaces, which generates 60 percent of the facility’s total electricity.

At the refining stage, the copper is in anode form. We subject 750-pound copper anode plates to an electric current for ten days and turn them into two 300-pound copper cathodes. This further separates the copper from other metals – the result is copper that is 99.99 percent pure.

The last step in the production process is to stamp each bar with Kennecott's brand, the lot number, the weight and the fineness of the metal — that is, the percentage of gold or silver in the bar.

Pipelines and Water Supply

Summary:

Kennecott will reduce average annual imported water per ton of ore milled by 5% over the 2014-18 baseline of 393 gal/ton (1,487L/ton) at the Copperton Concentrator by 2023.

With the exception of 2019, annual concentrator water intensity has remained above the 2014-2018 target baseline. Required changes to the concentrator process during 2020 resulted in increased water usage compared to the initial target baseline. Kennecott’s water usage has trended down since the implementation of these changes. Kennecott’s commitment to improve water efficiency through the concentrator successfully reduced intensity in 2022 and 2023 to approximately 10% lower than the period peak recorded in 2021.

Production

Operational metrics

Personnel

Job Title	Name	Phone	Email	Profile	Ref. Date
Maintenance Superintendent	Thomas Dormenval				May 6, 2024
Manager Underground Technology	Ferrin Prince				May 6, 2024
Managing Director	Nathan Foster	+1-406-539-2563	nate.foster@riotinto.com		May 6, 2024
Mine Manager	Scott Farrell				May 6, 2024
Mine Operations Manager	Kieran McRae				May 6, 2024
Mine Scheduling and Projects Manager	Mark Smith				May 6, 2024