Fortitude Mine

Site Name

Primary: Fortitude Mine

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Commodity

Primary: Gold
Primary: Silver
Secondary: Copper
Secondary: Lead
Secondary: Zinc
Tertiary: Chromium
Tertiary: Manganese
Tertiary: Bismuth
Tertiary: Tellurium
Tertiary: Arsenic
Tertiary: Mercury
Tertiary: Molybdenum
Tertiary: Antimony
Tertiary: Cobalt
Tertiary: Nickel

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Location

State: Nevada
County: Lander
District: Battle Mountain District

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Land Status

Land ownership: Private
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: Newmont Mining Corp.
Info Year: 2004

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Production

Year: 1994
Time Period: to 1993
Year: 1987
Mined: 1008000.000 mt
Material type: ore
Year: 1985
Mined: 1079000.000 mt
Material type: ORE
Description: Ap_Grade: ^0.21 Opt Au, 1.19 Opt Ag
Year: 1993
Time Period: 1985-93
Mined: 10860000.000 mt
Material type: AU ORE
Description: Cp_Grade: ^0.194 Opt Au., Approx. 2.3 Million Oz. Au; Cp_Grade: ^0.9 Opt Ag., Approx. 10.8 Million Oz.
Year: 1986
Mined: 1020000.000 mt
Material type: ore
Description: Ap_Grade: ^0.24 Opt Au, 1.50 Opt Ag

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Deposit

Record Type: Site
Operation Category: Past Producer
Deposit Type: replacement
Operation Type: Surface
Year First Production: 1984
Year Last Production: 1993
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: Skarn Cu

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Orebody

Form: tabular

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Structure

Type: L
Description: Virgin Fault

Type: R
Description: Golconda Thrust

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Alterations

Alteration Type: L
Alteration Text: Skarn formation began with the alteration of clastic rich sedimentary rocks to biotite/skarn hornfels. Introduction of metasomatic fluids further extended the biotite halo, flooding the system with k and fe, and adding orthoclase to the biotite hornfels assemblage. This assemblage replaced much of the protolith regardless of original composition. Continued metasomatism at high temperature (300C - 550C) formed garnet and pyroxene in calcareous rocks and overprinted the biotite-orthoclase hornfels. Sulfide minerals, dominated by pyrrhotite, began to precipitate with the garnet-pyroxene skarn and continued as temperatures declined. Gold mineralization began at 300C-400C and continued to lower temperatures along with minor arsenopyrite, pyrite, marcasite, sphalerite, galena, bismuth, and tellurides. During cooling of the hydrothermal system, the garnet-pyroxene skarn was altered to actinolite, prehnite, and chlorite.

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Rocks

Name: Granodiorite
Role: Associated
Age Type: Associated Rock
Age in Years: 38.500000+-
Dating Method: K-Ar
Age Young: Middle Eocene

Name: Granodiorite
Role: Associated
Age Type: Associated Rock
Age in Years: 38.000000+-
Dating Method: K-Ar
Age Young: Middle Eocene

Name: Siltstone
Role: Host
Description: calcareous
Age Type: Host Rock
Age Young: Middle Pennsylvanian

Name: Conglomerate
Role: Host
Age Type: Host Rock
Age Young: Middle Pennsylvanian

Name: Conglomerate
Role: Host
Age Type: Host Rock
Age Young: Early Permian
Age Old: Middle Pennsylvanian

Name: Limestone
Role: Host
Description: silty
Age Type: Host Rock
Age Young: Early Permian
Age Old: Late Pennsylvanian

Name: Conglomerate
Role: Associated
Age Type: Associated Rock
Age Young: Late Permian

Name: Limestone
Role: Associated
Age Type: Associated Rock
Age Young: Late Permian

Name: Sandstone
Role: Associated
Description: calcareous
Age Type: Associated Rock
Age Young: Late Permian

Name: Quartzite
Role: Associated
Age Type: Associated Rock
Age Young: Middle Pennsylvanian

Name: Shale
Role: Associated
Description: calcareous
Age Type: Associated Rock
Age Young: Middle Pennsylvanian

Name: Conglomerate
Role: Associated
Age Type: Associated Rock
Age Young: Middle Pennsylvanian

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Analytical Data

Analytical Data: REPRESENTATIVE GEOCHEMISTRY VALUES FROM THE 6075 LEVEL OF THE FORTITUDE DEPOSIT ARE:AU-0.15 OPT, CU< 0.1%, AG-30 PPM, AS-1426 PPM, BI-68 PPM, CD-25 PPM, CO-17 PPM, CR-48 PPM, HG-657 PPB, MN-2784 PPM, MO-8 PPM, NI-28 PPM, PB-2316 PPM, SB-74 PPM, W-5 PPM, ZN-2523 PPM. METALS ARE ZONED RELATIVE TO THE GRANODIORITE PORPHYRY STOCK WITH CU, MO, CO, CR, AND NI OCCURRING PROXIMAL TO THE STOCK (E.G. THE WEST OREBODY) AND AU, AS, TE, BI, SB, CD, MN, AND HG OCCURRING IN THE MAIN FORTITUDE ORE ZONE.

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Materials

Ore: Bismuth
Ore: Gold
Ore: Electrum
Ore: Pyrrhotite
Ore: Pyrite
Ore: Chalcopyrite
Ore: Arsenopyrite
Ore: Marcasite
Ore: Galena
Ore: Sphalerite
Ore: Hedleyite
Ore: Jonesite
Ore: Volynskite
Gangue: Prehnite
Gangue: Hedenbergite
Gangue: Andradite
Gangue: Diopside
Gangue: Actinolite
Gangue: Chlorite
Gangue: Grossularite
Gangue: Garnet
Gangue: Epidote
Gangue: Calcite
Gangue: Quartz

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Comments

Comment (Identification): The current record incorporates material from previous MRDS records # W700375 and #W700601 for the Fortitude Mine as well as additional new information.

Comment (Location): The Fortitude Mine is located in Copper Canyon, in the Battle Mountain Range.

Comment (Workings): Ore is extracted from the Fortitude and Upper Fortitude open pits.

Comment (Development): The Fortitude Deposit was discovered in late 1980 north of the West orebody at Battle Mountain Gold?s operations. After three years of pre-production striping and miing of the upper Fortitude ore zone, the larger, higher-grade lower Fortitude ore zone began production in late 1984. Mining ceased in 1993 after the reserves were depleted. In November, 1988 Dighem flew a test line over the exposed sulfide body at Fortitude at a bird height of 30-50 m. The magnetic anomaly over ore in the pit was 500 nt. The massive sulfide ore also gave a strong inphase em response with a high inphase-to-quadrature ratio. The apparent resistivity of ore measured 0.1 ohm-m in contrast to 10-100 ohm-m for limestone host rock. ; econ.com: production costs per equivalent ounce of gold after byproduct credits and including depreciation were $206 in 1985, $172 in 1986, and $156 in 1987. Battle Mountain Gold Co. pays no royalties on production from the Fortitude deposit.

Comment (Economic Factors): The Fortitude deposit produced 10.86 million metric tons of ore averaging 6 grams per tonne gold and 28 grams per tonne silver.

Comment (Commodity): Gangue Materials: hedenbergite, andradite garnet (with grossularlite rims), diopside, actinolite, chlorite, epidote, prehnite, calcite, quartz

Comment (Deposit): The Fortitude Deposit is a world-class gold-silver skarn deposit in the main Battle Mountain District. The deposit was comprised of an upper and a lower ore zone, formed in place, but separated by the N-striking, W-dipping Virgin Fault and by a granodiorite porphyry dike intruded along the fault. The upper ore zone in and east of the footwall of the fault formed in host rocks calcareous siltstone and conglomerate of the Battle Formation. The larger lower ore zone that formed the major portion of the deposit formed in host Antler Peak Limestone west of and in the hanging wall of the Virgin Fault. Discontinuous upper zone ore consisted of selective sulfide replacement of thin calc-silicate pods and lenses concentrated along faults or at fault interesections. Lower zone ore was a more continuous stratiform and stratabound orebody elongated northeast, up to 600 meters long, averaging 150 meters wide and 25-30 meters thick. Native gold is common and is most frequently associated with arsenopyrite, native bismuth, and tellurides. The highest gold concentrations occur in the pyrrhotite-dominant sulfide zones which contain only minor chalcopyrite.

Comment (Geology): Skarn minerals are zoned in abundance and composition relative to the granodiorite porphyry stock. Proximal skarn near the pluton contact is garnet and copper rich, relatively oxidized, and formed at high temperatures. Distal skarn, up to 1.5 km from the pluton contact, is pyroxene and gold-rich, relatively reduced, and formed at lower temperatures. Average garnet-pyroxene ratios and pyroxene iron-manganese contents are useful guides to position within the skarn system and to gold and copper grades. The reduced nature of the Copper Canyon porphyry, indicated by very low ferric/ferrous iron ratio (Fe +3/Fe +2 < 0.5), is an important characteristic of this gold-enriched system and distinguishes it from other gold-poor igneous/hydrothermal systems. Doebrich notes that contouring of blast hole assay maps shows strong N-S and NNE- linear trends in gold concentration. These higher grade gold zones correspond to garnetiferous skarn within an overall pyroxene skarn zone. Conglomerate hosts ore in the upper zone.

Comment (Production): 1985-1987 ANNUAL PRODUCTION: BATTLE MOUNTAIN GOLD CO., 1988, ANNUAL REPORT FOR 1987. CUMULATIVE PRODUCTION FIGURES FROM DOEBRICH, WRITTEN COMMUNICATION, JUNE 1993, FROM COMPANY SOURCES. NBMG MI-1993

Comment (Commodity): Ore Materials: native gold, electrum, pyrrhotite, pyrite, chalcopyrite, arsenopyrite, marcasite, galena, sphalerite, native bismuth, hedleyite, joesite, volnyskite

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References

Reference (Reserve-Resource): 1985 -1987 RESERVE FIGURES: BATTLE MOUNTAIN GOLD CO., 1988, ANNUAL REPORT FOR 1987. NBMG MI-1993

Reference (Production): 1985-1987 ANNUAL PRODUCTION: BATTLE MOUNTAIN GOLD CO., 1988, ANNUAL REPORT FOR 1987. CUMULATIVE PRODUCTION FIGURES FROM DOEBRICH, WRITTEN COMMUNICATION, JUNE 1993, FROM COMPANY SOURCES. NBMG MI-1993

Reference (Deposit): Doebrich, Jeff, 1995, Geology and Mineral Deposits of the Antler Peak n7.5-minute quadrangle, Lander County, Nevada, NBMG Bull 109, 44 p.

Reference (Deposit): WOTRUBA, P.R., BENSON, R.G., AND SCHMIDT, K.W., 1988, GEOLOGY OF THE FORTITUDE GOLD-SILVER SKARN DEPOSIT, COPPER CANYON, LANDER COUNTY, NEVADA IN SCHAFER, R.W., COOPER, J.J., AND VIKRE, P.G., EDS., BULK MINEABLE PRECIOUS METAL DEPOSITS OF THE WESTERN UNITED STATES SYMPOSIUM PROCEEDINGS, GEOLOGICAL SOCIETY OF NEVADA, RENO, NEVADA, APRIL 6-8, 1987, P.150-171.

Reference (Deposit): NEVADA DIVISION OF MINERALS, 1994

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

Reference (Deposit): NBMG, 1994, MI-1993

Reference (Deposit): DOEBRICH, JEFF, 1993, ORAL AND WRITTEN COMMUNICATIONS CONCERNING THIS RECORD, BASED ON HIS FIELD WORK AND PROFESSIONAL CONTACTS, MAY AND JUNE 1993

Reference (Deposit): BATTLE MOUNTAIN GOLD CO., 1988, ANNUAL REPORT FOR 1987.

Reference (Deposit): WOTRUBA, P.R., BENSON, R.G., AND SCHMIDT, K.W., 1986, BATTLE MOUNTAIN DESCRIBES THE GEOLOGY OF THE FORTITUDE GOLD-SILVER DEPOSIT AT COPPER CANYON: MINING ENGINEERING, V. 38, N. 7 (JULY), P495-499

Reference (Deposit): Wendt, Clancy, 2004, Technical Report on the ICBM/COPPER BASIN Property, Lander and Humboldt Counties, Nevada, Staccato Gold website, : http://www.staccatogold.com/i/pdf/icbm-43-101.pdf
URL: http://www.staccatogold.com/i/pdf/icbm-43-101.pdf

Reference (Deposit): Geological Society of Nevada, 1999, Geology and Gold Mineralization of the Buffalo Valley Area, Northwestern Battle Mountain Trend; GSN Special Publication No. 31, 1999 Fall field trip Guidebook.

Reference (Deposit): ROCKY MOUNTAIN PAY DIRT, MAY, 1988, P. 6A-8A.

Reference (Deposit): MYERS, G.L., 1990, ALTERATION ZONATION OF THE FORTITUDE GOLD SKARN DEPOSIT, LANDER COUNTY, NEVADA, MINING ENGINEERING, VOL. 42, NO. 4, P. 360-368.

Reference (Deposit): TAYLOR, R. S., 1990 AIRBORNE EM RESISTIVITY APPLIED TO EXPLORATION FOR DISSEMINATED PRECIOUS METAL DEPOSITS, GEOPHYSICS; THE LEADING EDGE OF EXPLORATION, VOL. 9, NO. 2, P. 34-41.

Reference (Deposit): MINING MAGAZINE, JANUARY, 1989, P. 44.

Reference (Deposit): MYERS, G. L. AND MEINERT, L.D., 1991, ALTERATION, MINERALIZATION, AND GOLD DISTRIBUTION IN THE FORTITUDE GOLD SKARN, IN RAINES, G.L., ET AL, EDS., GEOLOGY AND ORE DEPOSITS OF THE GREAT BASIN, THE GEOLOGICAL SOCIETY OF NEVADA, RENO, P. 407-417.

Reference (Deposit): METAL MARKET CONSULTANTS, INC., 1987, GOLD SITUATION MAP.

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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.