United States

Sierrita Mine

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Categories

Overview

Mine TypeOpen Pit
Commodities
  • Copper
  • Molybdenum
  • Gold
  • Silver
Mining Method
  • Truck & Shovel / Loader
Production Start... Lock
Mine Life2086
ShapshotSierrita mine is an open-pit copper and molybdenum mining complex. The Sierrita operation includes a concentrator that produces copper and molybdenum concentrate. Sierrita also produces copper from a ROM oxide-leaching system. The Sierrita operation also has molybdenum facilities consisting of a leaching circuit, two molybdenum roasters and a packaging facility. The molybdenum facilities process molybdenum concentrate produced by Sierrita, from Freeport's other mines and from third-party sources.

Owners

SourceSource
CompanyInterestOwnership
Freeport-McMoRan Inc. 100 % Indirect
Freeport-McMoRan Sierrita Inc. (operator) 100 % Direct
Freeport-McMoRan owns 100% of the Sierrita mine through its wholly-owned subsidiary Freeport-McMoRan Sierrita.

Contractors

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Deposit type

  • Porphyry

Summary:

The Sierrita mine is a porphyry copper deposit that has oxide, secondary sulfide and primary sulfide mineralization. The predominant oxide copper minerals are malachite, azurite and chrysocolla. Chalcocite is the most important secondary copper sulfide mineral, and chalcopyrite and molybdenite are the dominant primary sulfides.

Sierrita is located in the Basin and Range physiographic province, on the west margin of the Santa Cruz Basin and along the east flank of the Sierrita Mountains (ELMA 2001, ELMA and Dames and Moore 1994). The principal geologic/hydrogeologic units at the Site include the alluvial deposits, the basin fill deposits, and the bedrock complex.

Alluvial Deposits
Unconsolidated Quaternary and late Tertiary deposits cover most of the eastern base (the piedmont) of the Sierrita Mountains. The term “piedmont” is used in the Esperanza Mill Quadrangle (Spencer et al. 2003) and refers to the area east of the immediate mine area. The alluvium was deposited by larger streams that originated in the mountains and then was reworked by smaller streams that originate on the piedmont. Alluvial deposits occur as thin, discontinuous deposits throughout the Site, typically within natural drainage channels including Demetrie Wash, Amargosa Wash, Esperanza Wash, and Tinaja Wash. However, there are unconsolidated deposits across the mine site that overlie bedrock; the soil and sediment samples were collected from the unconsolidated deposits (Arcadis 2013b). The deposits consist of coarse-grained, unconsolidated silty sand and gravel of Quaternary age. Based on investigation work from 2001, the thickness of the alluvial deposits ranges from 0 to 30 feet.

Basin Fill Deposits
At the Site, basin fill deposits occur generally east of Demetrie Wash, trending from the northwest and extending east below the tailings impoundments, and are not present in the Sierrita pit or plant areas. The basin fill deposits are Tertiary to Quaternary in age and consist of poorly consolidated sand, gravel, silt, and clay in varying proportions. The thickness of the basin fill deposits increases to the east up to more than 1,000 feet near the southeast corner of the Sierrita Tailings Impoundment.

Bedrock Complex
The Sierrita-Esperanza deposit is composed of igneous rocks; the oldest in the area are the Ox Frame Volcanics. The Ox Frame Volcanics were intruded by the Harris Ranch Quartz Monzonite, which was overlain by the Demetrie Volcanics. Later intrusive rocks, including the Ruby Star Granodiorite, intruded the existing volcanic and intrusive rocks and formed a large batholith. The bedrock complex consists of several formations, including the Tinaja Peak Formation, the Pantano Formation, the Tertiary Intrusives, Ruby Star Granodiorite, Demetrie Volcanics, Harris Ranch Quartz Monzonite, and Ox Frame Volcanics.

Reserves

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Mining Methods

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Comminution

Crushers and Mills

Milling equipment has not been reported.

Processing

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Production

CommodityUnits2023202220212020201920182017
Copper M lbs 000000000000000152160
Molybdenum M lbs 00000000001615

Operational metrics

Metrics202320222021202020192018
Daily mining capacity 000000000000000000000000000000175,000 t
Daily milling capacity 000000000000000000000000000000100,000 t of ore (in concentrator)
Annual production capacity 000000000050 M lbs of copper cathode

Production Costs

Commodity production costs have not been reported.

Heavy Mobile Equipment

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EV - Electric

Personnel

Mine Management

Source Source
Job TitleNameProfileRef. Date
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Total WorkforceYear
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Aerial view:

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