Rat Deposit

Site Name

Primary: Rat Deposit
Secondary: Rat Pit

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Commodity

Primary: Gold
Tertiary: Mercury

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Location

State: Nevada
County: White Pine
District: Bald Mountain District

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Land Status

Land ownership: BLM Administrative Area
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: Ely BLM district

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Holdings

Not available

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Workings

Not available

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Ownership

Owner Name: Barrick Gold Corp.
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 disseminated gold
Operation Type: Surface
Year First Production: 1993
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: Distal disseminated Ag-Au

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Orebody

Form: tabular to irregular

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Structure

Type: R
Description: The Bald Mountain district is located in an area of thinned crust along the eastern side of the Late Proterozoic rift that split the North American craton. It is also in the west-central portion of the Late Devonian-Early Mississippian Antler foreland basin, and near the eastern edge of deformation related to the late Paleozoic Humboldt orogeny To the west of the Bald Mountain district, geologic interpretations are dominated by recognition of Paleozoic deformation, whereas to the east, interpretations emphasize Mesozoic contraction and plutonism and Tertiary extension.

Type: L
Description: NW-striking normal faults that dip steeply west and east, with lesser N-striking faults.

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Alterations

Alteration Type: L
Alteration Text: The porphyry dikes were sericitized, argillized and silicified.

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Rocks

Name: Sedimentary Rock
Role: Host
Description: calcareous
Age Type: Host Rock
Age Young: Cambrian

Name: Clastic Sedimentary Rock
Role: Host
Description: fine grained
Age Type: Host Rock
Age Young: Late Cambrian

Name: Limestone
Role: Host
Age Type: Host Rock
Age Young: Late Cambrian

Name: Siltstone
Role: Host
Description: sandy
Age Type: Host Rock
Age Young: Late Cambrian

Name: Porphyry
Role: Associated
Description: quartz-feldspar porphyry stock with satellitic dikes and sills
Age Type: Associated Rock
Age in Years: 159.000000+-
Age Young: Late Jurassic

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Analytical Data

Not available

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Materials

Ore: Gold
Gangue: Pyrite
Gangue: Clay
Gangue: Limonite
Gangue: Quartz

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Comments

Comment (Deposit): The deposit is hosted in the lowermost part of the Dunderberg Shale. Ore was structurally controlled and adjacent to and locally within NW-striking dikes of quartz-feldspar porphyry. Interbedded limestone and siltstone are altered to marble and hornfels adjacent to the dikes. Silicification and decalcification are concentrated in the lower Dunderberg above its contact with the underlying Hamburg, and in faults and fractures in the Dunderberg. The Hamburg is silicified along bedding and fracture networks in the Rat deposit. Pervasive sericitization and weak argillization (mainly supergene) affected the dike, and spotty silicification is along the margins of the dike and in the adjacent Dunderberg. Fine-grained disseminated gold is associated with silica, clay, carbonaceous material, iron oxides, and secondary iron-arsenic minerals. Ore zones are characterized by quartz veining, stockwork formation, and silicified breccia. The ore zone is overlain b a blanket of barren remobilized carbon.

Comment (Geology): The Rat deposit has a low to non-existent base metal signature with higher Hg, As, and Sb values. The Rat deposit is characterized by Au, As, and Sb; the deposits are Au rich, with high Au/Ag ratios, values of As to about 2,000 ppm and Sb as much as 1,300 ppm, and low base metals.

Comment (Identification): The Rat Deposit is part of Placer Dome?s Bald Mountain Mine project.

Comment (Location): The Rat deposit is located in the southern part of the Bald Mountain district about 1.5 mile southeast of the RBM deposit and 1.5 mile southwest of the Top/Mahoney Canyon/Sage Flat deposit area.

Comment (Workings): open pit

Comment (Development): Placer Dome began exploration in the Bald Mountain mine area in 1977 and the Rat deposit was discovered by 1978. In 1993, mining started in the Rat pit. In 2006, Barrick Gold Corp. acquired the Rat property through its acquisition of Placer Dome U. S., Inc.

Comment (Economic Factors): Production from the Rat deposit as of the end of 1995 was about 3 million tons of ore grading 0.09 ounces of gold per ton for a total contained 270,000 ounces of gold. The orebody was nearing depletion at that time with about 100,000 tons of 0.10 opt ore remaining.

Comment (Commodity): Ore Materials: free gold

Comment (Commodity): Gangue Materials: pyrite, clay, limonite, jasperoid, quartz

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References

Reference (Deposit): NBMG mining district files 323, press clippings

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

Reference (Deposit): GSN 1985 meeting and fall field trip road log

Reference (Deposit): Adamson, T.J., 1987, in Bulk Mineable Precious Metal Deposits of the Western U.S., 1987 GSN, Field Trip Guidebook and Technical Volume.

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

Reference (Deposit): Hitchborn and others, 1996, Geology and Gold Deposits of the Bald Mountain Mining District, White Pine County, Nevada, in Geology and Ore Deposits of the American Cordillera Symposium Proceedings, eds. A. Coyner and P. Fahey.

Reference (Deposit): The Geological Society of Nevada 1996 Spring Field trip, Geology and Gold Deposits of Eastern Nevada, GSN Special Publication No. 23.

Reference (Deposit): BLM, 2004, Bald Mountain Mine Exploration Program Programmatic Environmental Assessment NV040-04-023, Case File # N78825.

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): Nutt, C.J., Hofstra, A.H., Hart, K.S., and Mortensen, J.K., 2000, Structural setting and genesis of gold deposits in the Bald Mountain-Alligator Ridge area, east-central Nevada, in Cluer, J.K., Price, J.G., Struhsacker, E.M., Hardyman, R.F., and Morris, C.L., eds., Geology and Ore Deposits 2000: The Great Basin and Beyond: Geological Society of Nevada Symposium Proceedings, May 15-18, 2000, p. 513-537.

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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.