Bootstrap-Capstone-Tara Gold Mine

Site Name

Primary: Bootstrap-Capstone-Tara Gold Mine
Secondary: Antimony Pete (originally)
Secondary: Antimony Ike

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Commodity

Primary: Gold
Secondary: Silver
Secondary: Copper
Secondary: Lead
Secondary: Zinc
Tertiary: Antimony

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Location

State: Nevada
County: Elko
District: Carlin Trend

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Land Status

Land ownership: National Forest
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.
Administrative Organization: Elko BLM Administrative District

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Holdings

Not available

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Workings

Not available

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Ownership

Owner Name: Newmont Exploration Ltd.
Home Office: Carlin, NV

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Production

Not available

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Deposit

Record Type: Site
Operation Category: Producer
Deposit Type: Stockwork
Operation Type: Surface-Underground
Year First Production: 1918
Discovery Year: 1914
Years of Production:
Organization:
Significant: Y
Deposit Size: M

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Physiography

Not available

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Mineral Deposit Model

Model Name: Sediment-hosted Au

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Orebody

Form: Stockwork

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Structure

Type: R
Description: Roberts Mountains Thrust Fault

Type: L
Description: A complex fault zone is exposed along the crest of the Bootstrap window. Steep north trending faults have been intruded by dikes.

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Alterations

Alteration Type: L
Alteration Text: Host rocks have been affected by pervasive hydrothermal alteration: sericitization, silicification, and argillization. Dikes are sericitized. Within carbonate sediments, cherty replacement silicification along faults and joints diminishes laterally in intensity and grades into argillic alteration. Argillized zones grade into fresh country rock.

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Rocks

Name: Dacite
Role: Host
Description: dikes
Age Type: Host Rock
Age Young: Tertiary

Name: Quartz Latite
Role: Host
Description: dikes
Age Type: Host Rock
Age Young: Tertiary

Name: Siltstone
Role: Host
Description: calcareous
Age Type: Host Rock
Age Young: Devonian

Name: Mudstone
Role: Host
Description: Siliceous
Age Type: Host Rock
Age Young: Devonian

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Analytical Data

Not available

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Materials

Ore: Gold
Ore: Quartz
Gangue: Clay

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Comments

Comment (Workings): The mine was developed in the early days by a 24-ft. shaft, a 520-ft. adit, followed by open pits.

Comment (Geology): The Bootstrap deposits are aligned along the crest of a N-S-trending horst block, comprised primarily of carbonate rocks of the Devonian Popovich Formation and Siluro-Devonian Roberts Mountains Formation, and siliciclastic rocks of the Devonian Rodeo Creek unit. Within the horst block, rock strata are folded into a broad, S20E-trending gently plunging antiform. Resistant carbonate units and silicified rocks forming the east limb of the antiform form a 2-mile-long, 3000-foot wide, 600-foot high ridge known as the Bootstrap Window. Most of the west limb of the antiform has been down-droped by faults and is only exposed on the west side of the Tara deposit. Dikes are up to 15' wide. Gold occurs as microscopic particles along fractures in the dikes, and in the cherts & shales. Limestone in contact with the dike is hornfelsed and partially marbleized

Comment (Identification): The current deposit encompasses the area formerly mined as the Antimony Pete and Antimony Ike antimony mines, and is formed by three contiguous gold deposits, Bootstrap (MRDS record #M232818), Capstone (MRDS record #RE00026), and Tara.

Comment (Development): The first reported gold production from the Bootstrap deposit was in 1914 from a small underground operation near the NW corner of the present Bootstrap pit. In 1918, approximately 500 tons of stibnite ore were shipped to the railhead at Dunphy, NV. Gold production resumed in 1958 when Harry Treweek and Marion Fischer began mining a small dike immediately west of the present Bootstrap pit. It was the largest gold producer in Elko County in 1958. In 1967, the property was acquired by Newmont, who completed a development drilling program of 76 holes totalling 4,394 meters in 1969. Newmont began mining in 1974, producing 20,000 oz. gold over the next five years by milling and heap leaching. Intermittent mining of high grade zones continued from 1976-1984, produciing an additional 100,000 oz. gold. It was listed as an active open pit mine employing 2 persons in 1980. Capstone was discovered in 1985 by Newmont and heap-leaching of low grade ore continued in 1987. Additional exploration resulted in the discovery of Tara in 1990. The property was inactive in 1991. Production resumed in 1992 with the opening of the contiguous Capstone deposit, and mining began at the Tara deposit in 1997.

Comment (Economic Factors): Total production from 1948 through 1984 is estimated to be about 780 kilotonnes of ore containing 4 tonnes gold. Production from 1990-1995 was not reported separately. In 1995, the remaining resource was reported as 21,242 kilotonnes of ore containing approximately 35 tonnes gold. This resource includes the Tara deposit.

Comment (Location): The mine is located on the north slope of Round Mountain.

Comment (Commodity): Ore Materials: gold

Comment (Commodity): Gangue Materials: clay, quartz, carbonate

Comment (Deposit): Disseminated gold mineralization occurs along a NNE-trending , west-dipping fault zone over two miles long. Ore is localized on a north-striking, high angle fault developed along a competency contrast between massive Devonian Bootstrap carbonates and platform-slope talus debris within the Bootstrap Limestone. West-dipping, late Cretaceous to Tertiary dikes intruded along the fault. Later tectonism accentuated initial structural breaks, enhancing permeability and porosity.Gold occurs as microscopic particles along fractures in quartz latite and dacite dikes, chert, siliceous mudstone, calcareous siltstone, and shale.Host rocks have been affected by sericitization, silicification, and argillization. Dikes are sericitized. Within carbonate sediments, cherty replacement silicification along faults and joints diminishes laterally in intensity and grades into argillic alteration. Argillized zones grade into fresh country rock. Where several dikes are closely spaced, the ore is mineable by open pit methods.

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References

Reference (Deposit): Smith, R.M. (1976-56) Mineral Resources of Elko Co. Nev, USGS Open-File Report

Reference (Deposit): NBMG, 1987, The Nevada Mineral Industry 1986, NBMG Special Publication MI-1986

Reference (Deposit): Baker, E.D., 1991, Geology and Ore Deposits of the Bootstrap Subdistrict, Elko County, Nevada, in Geology And Ore Deposits of the Great Basin, Raines, G.L., et al., eds., the Geological Society of Nevada, Reno, p. 619-623.

Reference (Deposit): NBMG, 1991, The Nevada Mineral Industry 1990, NBMG Special Publication MI-1990.

Reference (Deposit): Newmont Gold 1985 SEC Form 10K

Reference (Deposit): E/MJ 8/1986 p. 41

Reference (Deposit): Geology and Ore Deposits of Northeastern Nevada; Geological Society of Nevada, 1997 Spring Field Trip Guidebook, Special Publication No. 25, p. 55.

Reference (Deposit): Long, K.R., DeYoung, J.H., Jr., and Ludington, S.D., 1998, Significant deposits of gold, silver, copper, lead, and zinc in the United States: U.S. Geological Survey Open-File Report 90-206A, 33 p.; 98-206B. one 3.5 inch diskette.

Reference (Deposit): Lawrence (1963) Antimony Deposits of Nev., NBMG Bull. 61.

Reference (Deposit): State Inspector of Mines (1981) Directory of Nevada Mine Operations Active In 1980

Reference (Deposit): Bonham, H.F., 1986, Bulk-Mineable Precious-Metal Deposits and Prospects In Nevada, NBMG Map 91.

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Nevada Gold

Nevada has a total of 368 distinct gold districts. Of the of those, just 36 are major producers with production and/or reserves of over 1,000,000 ounces, 49 have production and/or reserves of over 100,000 ounces, with the rest having less than 100,000 ounces. Read more: Gold Districts of Nevada.