El Tiro Open Pit Mine

Site Name

Primary: El Tiro Open Pit Mine
Secondary: Red Rock Group
Secondary: Silver Bell Mine

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Commodity

Primary: Copper
Secondary: Gold
Secondary: Lead
Secondary: Silver
Secondary: Molybdenum

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Location

State: Arizona
County: Pima
District: Silver Bell District

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Land Status

Land ownership: Unknown
Note: the land ownership field only identifies whether the area the mine is in is generally on public lands like Forest Service or BLM land, or if it is in an area that is generally private property. It does not definitively identify property status, nor does it indicate claim status or whether an area is open to prospecting. Always respect private property.

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Holdings

Not available

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Workings

Not available

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Ownership

Owner Name: Asarco (American Smelting And Refining Co.)

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Production

Year: 1931
Time Period: Pre-1931
Material type: ORE
Description: Cp_Grade: ^5% Cu, 0.2 Oz Ag/T, Minor Au & Pb

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Deposit

Record Type: Deposit
Operation Category: Past Producer
Deposit Type: Porphyry Cu
Operation Type: Underground
Year First Production: 1954
Discovery Method: Unknown
Years of Production:
Organization:
Significant: N
Deposit Size: L

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Physiography

General Physiographic Area: Intermontane Plateaus
Physiographic Province: Basin And Range Province
Physiographic Section: Sonoran Desert

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Mineral Deposit Model

Model Name: Porphyry Cu

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Orebody

Form: TABULAR

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Structure

Type: L
Description: Sheared Limestone, Parallel Fissures In Dacite Porphyry

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Alterations

Alteration Type: L
Alteration Text: Argillic; Partly Oxidized, Garnetized Limestone

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Rocks

Name: Quartz Monzonite
Role: Host
Age Type: Host Rock
Age Young: Late Cretaceous

Name: Dacite
Role: Associated
Description: dacite porphyry and an extensive mass of coarse grained alaskite
Age Type: Associated Rock
Age Young: Mesozoic

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Analytical Data

Analytical Data: TYPICAL ORE IS ALTERED ROCK & SULFIDES IN A RATIO OF ABOUT 10:1

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Materials

Ore: Chalcopyrite
Ore: Limonite
Ore: Molybdenite
Ore: Chalcocite
Ore: Pyrite
Ore: Cuprite

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Comments

Comment (Production): See Silver Bell Mine Record (D002948) For Open Pit Production

Comment (Development): Previous Operators Include: Arizona Mining Co, El Tiro Copper Co, El Tiro Leasing Co, Williams Western American Mines Co, Chemical Process Copper Co

Comment (Commodity): Chalcocite Blanket Formed By 2-3 Fold Enrichment Of The Copper Contained In The Protore

Comment (Deposit): Ore In Thin Quartz Sulfide Veinlets That Form A Disseminated Deposit In Aggregate. Large Size Refers To Silver Bell Property; Underground El Tiro Operations Prior To 1931 Were Small.

Comment (Geology): Cu Does Not Occur In Dacite Porphyry Where Shears Aren'T Parallel.

Comment (Identification): ***** SEE Silver Bell Deposit ID 10161929 for more info

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References

Reference (Geology): The Porter GeoConsultancy webpage for Silver Bell contains a description of the geology at El Tiro. Accessed on 8/12/2010. http://www.portergeo.com.au/
URL: http://www.portergeo.com.au/

Reference (Geology): Cook S S and Porter T M, 2005 - The Geologic History of Oxidation and Supergene Enrichment in the Porphyry Copper Deposits of Southwestern North America, in Porter T M, (Ed), Super Porphyry Copper and Gold Deposits: A Global Perspective, v1 pp 207-242

Reference (Deposit): Galey, 1979, Soc Econ Geol, Porphyry Cu Field Conf, 18 P.

Reference (Other Database): Cimri

Reference (Age): Kendrick, M.A., Burgess, R., Pattrick, R.A.D. and Turner, G., 2001, Halogen and Ar-Ar age determinations of inclusions within quartz veins from porphyry copper deposits using complementary noble gas extraction techniques; Chemical Geology, v. 177, p. 351-370.

Reference (Deposit): Keith, 1974, Abm Bull 189, P. 143.

Reference (Deposit): Hardwick, 1963, USBM Ic 8153.

Reference (Deposit): Kerr, 1951, Gsa Bull 62, P. 451-480.

Reference (Deposit): Richard and Courtright, 1966, Porph-Cu Volume Abm.

Reference (Deposit): S B Keith Ariz Bur Mines Bull 189 1974 P 143

Reference (Reserve-Resource): Browne, Q. J. and Miller, M. A., 2002, Use of geologic parameters for development of low-grade copper reserves, Silver Bell Mine, Arizona; In Society of Mining Engineers Annual Meeting and Exhibit, 2002, Technical Program, Society of Mining Engineers, p. 68.

Reference (Production): Long, K.R., 1995, Production and reserves of Cordilleran (Alaska to Chile) porphyry copper deposits; in Pierce, F.W. and Bolm, J.G., eds., Porphyry Copper Deposits of the American Cordillera, Arizona Geological Society, Digest 20, p. 35-68.

Reference (Geology): Lopez J A, Titley S R 1995 - Outcrop and capping characteristics of the supergene sulfide enrichment at North Silver Bell, Pima County, Arizona: in Pierce F W, Bolm J G (Eds), Porphyry Copper Deposits of the American Cordillera Arizona Geol. Soc. Digest 20 pp 424-435

Reference (Age): Barra, F., Ruiz, J., Valencia, V.A., Ochoa-Landin, L., Chesley, J.T. and Zurcher, L., 2005, Laramide porphyry Cu-Mo mineralization in northern Mexico: age constraints from Re-Os geochronology in molybdenite; Economic Geology, v. 100, p. 1605-1616.

Reference (Geology): Graybeal F T 1983 - Geology of the El Tiro area: in Titley S R 1983 Advances in Geology of the Porphyry Copper Deposits, Southwestern North America University of Arizona Press, Tucson pp 487-505

Reference (Geology): Richard K, Courtright J H 1966 - Structure and mineralization at Silver Bell, Arizona: in Titley S R, Hicks C L 1966 Geology of the Porphyry Copper Deposits, Southwestern North America University of Arizona Press, Tucson pp 157-163

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