Doby George Deposit

Site Name

Primary: Doby George Deposit
Secondary: Doby Deposit

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Commodity

Primary: Silver
Primary: Gold

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Location

State: Nevada
County: Elko
District: Aura 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

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Holdings

Not available

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Workings

Not available

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Ownership

Owner Name: Western Exploration and Development Ltd

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Production

Not available

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Deposit

Record Type: Site
Operation Category: Past Producer
Deposit Type: Sediment-hosted gold
Operation Type: Surface
Discovery Year: 1983
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: pods, irregular

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Structure

Type: L
Description: In mineralized areas, numerous high-angle fault sets trend N, NE, and WNW, standing out topographically as prominent silicified ribs.

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Alterations

Alteration Type: L
Alteration Text: Host rocks are silicified and often sericitized. The diorite is weakly argillized in places

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Rocks

Name: Diorite
Role: Associated
Description: quartz
Age Type: Associated Rock
Age Young: Mesozoic
Age Old: Tertiary

Name: Diorite
Role: Associated
Age Type: Associated Rock
Age Young: Mesozoic
Age Old: Tertiary

Name: Chert
Role: Host
Age Type: Host Rock
Age Young: Mississippian

Name: Siltstone
Role: Host
Description: siliceous and calcareous
Age Type: Host Rock
Age Young: Mississippian

Name: Sandstone
Role: Host
Age Type: Host Rock
Age Young: Mississippian

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Analytical Data

Not available

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Materials

Ore: Gold
Ore: Electrum
Gangue: Quartz
Gangue: Sericite

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Comments

Comment (Geology): Mineralization preceded the local volcanic event here, unlike at the nearby Wood Gulch deposit, where the mineralizing system affected the 40-million year old volcanics.

Comment (Location): The mineralization occurs on both sides of the canyon south of a spring located a half mile due south of Columbia Summit.

Comment (Workings): Surface exploration, drill roads

Comment (Development): The discovery claims were first staked and leases acquired in the Doby George area in 1983 by Felmont Oil Company, following the discovery of anomalous gold and trace elements as a result of a reconnaissance geochemical sampling program in the Maggie Summit area. More focused sampling and geologic mapping followed in 1984 resulting in a drilling program in 1985 after Homestake purchased Felmont. Ore grade intercepts were encountered early in the drilling, leading to an expanded drilling program in the late 1980s that delineated the three orebodies. Exploration and development proceeded under a 60/40 joint venture agreement between Homestake and Bargold in 1990. Independence Mining Company acquired the Doby George property in the early1990s, but by the end of 1995, Atlas Corp. had completed the purchase of the project from Independence Mining Co. Preliminary studies in 1995 indicated a reserve of 3.7 million tons at a grade of 0.060 opt Au. The three near-surface deposits that contain the majority of the indicated reserve still remain open. The Doby land position covers 14 square miles of public land. In addition to the main mineralization, five other zones of mineral potential have been identified. In early 1997, Atlas Corp. reported that it had granted an exclusive option to Aquaterre Mineral Development Ltd. to purchase Doby George for $3 million. Later in 1997, Atlas Corp. sold the Doby George property to Western Exploration and Development Ltd. for $1.6 million. Western had recently also acquired certain rights to the 84,000-acre IL Ranch in the Doby George area. Western was continuing exploration and development on the Doby George and surrounding property in 1999 (personal communication).

Comment (Commodity): Ore Materials: native gold, electrum

Comment (Commodity): Gangue Materials: quartz, sericite

Comment (Deposit): The deposit consists of three shallow oxidized pods of gold-silver mineralization with five other zones of anomalous gold mineralization identified. Fine-grained native gold occurs in a silicified matrix of siltstone and sandstone. Bedding in the host rocks strikes NNW to NE and dips gently west. Gold also occurs locally as inclusoins within goethite pseudomorphs after pyrite. The grade and thickness of the ore zones generally increases toward major structures, but small pods of mineralization traverse stratigraphic horizons with no apparent relationship to structure. Quartz veining typically accompanies mineralization and alteration. Host rocks are silicified and often sericitized. The mineralization predates the volcanic rocks present. Deeper drilling (to 1600 feet) encountered anomalous gold in calcareous rocks of the Schoonover Formation

Comment (Economic Factors): In 1994, the Doby George deposit was estimated to contain a remaining resource of 3300 kilotonnes of ore containing 6.7 tonnes of gold (Long and others, 1998). The total resource was reported as 250,000 troy ounces of gold in 1997.

Comment (Commodity): Commodity Info: Au:Ag ratios are strongly gold-biased, in contrast to the nearby Wood Gulch deposit

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References

Reference (Deposit): Baker, D.J., Stanley, W. R., and Dickerson, R.B., 1990, Geology of the Wood Gulch Mine Area and the Doby Prospect, Northern Independence Range, Elko County, Nevada, unpulished report, NBMG files

Reference (Deposit): Denver Mining Record, 7/23/95

Reference (Deposit): Skillings Mining Review, 8/26/95

Reference (Deposit): Northern Miner, 9/11/95

Reference (Deposit): Miing Engineering, 10/1/95

Reference (Deposit): Denver Mining Record, 11/15/95

Reference (Deposit): Denver Mining Record, 1/29/97

Reference (Deposit): Elko Daily Free Press, 10/11/97

Reference (Deposit): Rocky Mountain Pay Dirt, June, 1989.

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): Western Exploration and Development Ltd., 1999, personal communication.

Reference (Deposit): Western Exploration and Development Ltd., 1999, personal communication.

Reference (Deposit): Rocky Mountain Pay Dirt, June, 1989.

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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.