Big Springs Mine

Site Name

Primary: Big Springs Mine
Secondary: Mac Ridge
Secondary: North Sammy Creek
Secondary: South Sammy Creek
Secondary: 701 deposit
Secondary: 131 deposit
Secondary: 401 deposit
Secondary: 601 deposit
Secondary: Mesona claims
Secondary: Jack Creek project
Secondary: Bull Run

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Commodity

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

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Location

State: Nevada
County: Elko
District: Jerritt Canyon District

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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: Humboldt National Forest, Mountain City Ranger District

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Holdings

Not available

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Workings

Not available

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Ownership

Owner Name: Queenstake Resources
Info Year: 2006

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Production

Not available

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Deposit

Record Type: Site
Operation Category: Producer
Deposit Type: Sediment-hosted Au
Operation Type: Surface
Discovery Year: 1982
Years of Production:
Organization:
Significant: Y
Deposit Size: S

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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: Irregular

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Structure

Type: R
Description: Deformation related to the Antler Orogeny is the earliest tectonic event recorded in the Big Springs rocks, during which siliceous western assemblage rocks were emplaced over eastern assemblage carbonate and siltstone along the Roberts Mountain thrust fault. Compressional deformation of the Sonoma Orogeny occurred in the late Permian, during which the foredeep accumulated Schoonover Sequence was thrust over both the allochthonous western and autochthonous eastern assemblage rocks. Sonoma tectonism in the Big Springs area is evidenced by SE-verging overturned folds and imbricate thrust faults, all of which have been cut by later normal faults. A strong N75W fabric is manifested in folds and shears throughout the Independence Range and may be related to the Wells fault. This structural zone may have been reactiviated during the formation of the NW-striking Northern Nevada Rift Zone and Basin and Range extensional faulting.

Type: L
Description: Deposits are structurally controlled at intersections of NE-trending and E-W-trending fault zones and fold axes. The E-W structure is part of a large ore-controlling shear zone that also truncates the northern mineralized zone at Big Springs. Many of the dikes occur along the NE-trending and E-W-trending fault intersections. A strong N75W fabric is manifested in folds and shears throughout the Independence Range and may be related to the Wells fault. This structural zone may have been reactiviated during the formation of the NW-striking Northern nevada Rift Zone and Basin and Range extensional faulting.

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Alterations

Alteration Type: L
Alteration Text: Propylitic alteration is common throughout the volcanic rocks of the Dorsey Creek member. Gold mineralization occurs locally when the propylitically altered rocks are overprinted by quartz-sericite-pyrite-dolomite alteration

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Rocks

Name: Diorite
Role: Host
Age Type: Host Rock
Age Young: Jurassic

Name: Limestone
Role: Host
Description: fossiliferous
Age Type: Host Rock
Age Young: Permian
Age Old: Devonian

Name: Limestone
Role: Host
Description: massive
Age Type: Host Rock
Age Young: Permian
Age Old: Devonian

Name: Sedimentary Rock
Role: Host
Description: arenite
Age Type: Host Rock
Age Young: Permian
Age Old: Devonian

Name: Siltstone
Role: Host
Age Type: Host Rock
Age Young: Permian
Age Old: Devonian

Name: Conglomerate
Role: Host
Age Type: Host Rock
Age Young: Permian
Age Old: Devonian

Name: Chert
Role: Host
Age Type: Host Rock
Age Young: Permian
Age Old: Devonian

Name: Argillite
Role: Host
Description: cherty
Age Type: Host Rock
Age Young: Permian
Age Old: Devonian

Name: Quartz Monzonite
Role: Host
Age Type: Host Rock
Age Young: Jurassic

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Analytical Data

Not available

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Materials

Ore: Gold
Ore: Marcasite
Ore: Arsenopyrite
Ore: Pyrite
Ore: Sphalerite
Ore: Chalcopyrite
Ore: Stibnite
Gangue: Pyrite

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Comments

Comment (Identification): The Big Springs Mine is composed of seven deposits developed by Freeport-McMoran Gold Co. (later Independence Mining Co., now Anglo Gold): Mac Ridge, M242936; North Sammy Creek, W700398; South Sammy Creek, W700399; 701 deposit, 131 deposit, 401 deposit, and 601 deposit.

Comment (Location): Most of the mined deposits are located within a one-square mile area between Sammy Creek and Beadles Creek, south of North Fork of the Humboldt River. The Mac Ridge deposit lies about a half mile farther to the southest on the east side of Mac Ridge. The UTM given is for the approximate center of the largest deposit, North Sammy Creek.

Comment (Workings): The mine was developed by several open pits and a heap-leaching facility.

Comment (Development): The area was first explored in the early 1980s by Freeport- McMoRan Gold Company. Extensive drilling, mapping, sampling, and construction of access roads were completed by Freeport by 1982. Mining of the Big Springs deposit was initiated by a joint venture between Freeport- McMoRan Gold Company (later Independence Mining Company) and Bull Run Gold Mines, Ltd. The mine was placed into production in September, 1987 and was fully operational by October, 1987. Initial production was from heap-leaching oxidized ore, but second phase construction provided a fluid-bed roasting system and conventional ore-milling facilities. Initially, Freeport planned to process 400,000 tons/year from three deposits at Big Springs to produce about 60,000 oz/year gold. The deposit was mined out in 1994, having produced a total of 386,000 troy ounces of gold from seven separate deposits on the property. Most of the gold was contained in refractory sulfide ore requiring a pre-oxidizing roasting method to enable conventional CIL recovery. Big Springs Project. In 2004, Gateway Gold Corp. continued work on its Big Springs project. A new geological model was developed based on the results of last year?s drilling and the company expects drilling this year will validate the model. In 2006, Gateway Gold Corp. announced that based on recent drill results at the Big Springs Project, resources aggregate 914,000 tons grading 0.345 ounces of gold per ton inferred using a 0.2 opt Au cutoff. (was 904,200 tons grading 0.288 ounces of gold per ton measured+indicated prior to the new round of drilling.)

Comment (Economic Factors): Reserves in 1987 were listed as 3.3 million short tons of ore (1.7 million tons of mill ore and 1.6 million tons of heap leach ore) grading 0.18 opt. From 1987 to 1995 the mine produced more than 13 metric tonnes of gold and 0.44 metric tonnes of silver from over 1,743 metric tonnes of ore (Long and others, 1998). In 2006, Gateway Gold Corp. announced that based on recent drill results at the Big Springs Project, resources aggregate 914,000 tons grading 0.345 ounces of gold per ton inferred using a 0.2 opt Au cutoff. (was 904,200 tons grading 0.288 ounces of gold per ton measured+indicated prior to the new round of drilling.)

Comment (Geology): The deposits occur primarily in allochthonous rocks of the Devonian to Permian Schoonover Sequence, which are cut by diorite and quartz monzonite intrusives which also host ore.

Comment (Commodity): Gangue Materials: pyrite, marcasite,arsenopyrite, arsenical pyrite, sphalerite, chalcopyrite, stibnite

Comment (Commodity): Ore Materials: gold

Comment (Deposit): The Big Springs mine consists of seven distinct deposits (Mac Ridge, North Sammy Creek, South Sammy Creek, 701 deposit, 131 deposit, 401 deposit, and 601 deposit) plus many additional resource areas of anomalous gold mineralization which were not mined. The deposits are characterized by disseminated, near-surface gold mineralization within 400 feet of the surface. Mineralization is structurally controlled and occurs primarily in allochthonous rocks of the Dorsey Creek and Mikes Creek members of the Schoonover Sequence. Host rocks include thin-bedded to cherty argillite, chert, conglomerate, siltstone, arenite, massive limestone, and fossiliferous limestone. Deposits are structurally controlled at intersections of NE-trending and E-W-trending fault zones and fold axes. The E-W structure is part of a large ore-controlling shear zone that also truncates the northern mineralized zone at Big Springs.

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References

Reference (Deposit): NBMG, 1988, MI-1987.

Reference (Deposit): Adams, O. F., 1996, Stratigraphy, structure, and exploration potential of the Big Springs gold deposits, Northern Independence Range, Nevada in Coyner, A. R., and Fahey, P.L., eds., Geology and Ore Deposits of the American Cordillera: Geological Society of Nevada Symposium Proceedings, Reno/Sparks, Nevada, April, p.1-13.

Reference (Deposit): Youngerman, A., 1992, Structural control, alteration, and primary mineralization at the Big Springs gold mine, Elko County, Nevada, unpublished M. Sc. Thesis, University of Nevada, 80p.

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): Gateway Gold Corp. press release, 9/16/2004).

Reference (Deposit): LaPointe, D. D., Tingley, J. V., Jones, R. B., 1991, Mineral Resources Of Elko County, Nevada, NBMG Bulletin 106.

Reference (Deposit): NBMG MI-1986 - 2004, The Nevada Mineral Industry, 1986.

Reference (Deposit): Bonham, H.F., 1986, NBMG Map 91.

Reference (Deposit): EIS Report - Big Springs Project, on file at NBMG

Reference (Deposit): Prospectus - Freeport Gold, Co. 1985.

Reference (Deposit): 1983 Annual Report to Stockholders of Bull Run Gold Mines, Ltd.

Reference (Deposit): USDA Forest Service, 1987, Environmental Assessment - Big Springs Project, Elko County, Nevada.

Reference (Deposit): Numerous Press Releases, NBMG Mining District File 79-A.

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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.