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Pediment Gold Property

Past Producer in Lander county in Nevada, United States with commodities Gold, Silver, Mercury, Arsenic, Antimony
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Sections on this page
  1. Identification information
  2. Geographic coordinates
  3. Site location context
  4. Geographic areas
  5. Public Land Survey System information
  6. Commodities
  7. Materials information
  8. Alteration
  9. Mineral occurrence model information
  10. Host and associated rocks
  11. Nearby scientific data
  12. Geologic structures
  13. Ore body information
  14. Controls for ore emplacement
  15. Economic information about the deposit and operations
  16. Mining district
  17. Land status
  18. Ownership information
  19. Bibliographic references
  20. General comments
  21. Reporter information

Geologic information

Identification information

Deposit ID 10310459
Record type Site
Current site name Pediment Gold Property
Alternate or previous names Cortez Joint Venture, Cortez Pediment
Related records 10310435

Geographic coordinates

Point of reference Ore Body
Geographic coordinates: -116.6037, 40.1543 (WGS84)
Location accuracy 100(meters)
Relative position About 50 km SSW of Beowawe, NV, and about 1.5 km SSW of the Cortez Hills prospect. These coordinates are for the Piedmont property marker shown in the Lander County Yucca Mountain rail corridor study 2004 reference, p20.

Site location context

Political divisions (FIPS codes)

Lander(county)

Nevada(state)

United States(country)

North America(continent)

Land(continent)

USGS map quadrangles

Cortez(quadrangle 1:24,000 scale)

Crescent Valley(quadrangle 1:100,000 scale)

Winnemucca(quadrangle 1:250,000 scale)

Hydrologic units (watersheds)

Northern Big Smoky Valley(hydrologic unit)

Central Nevada Desert Basins(hydrologic accounting unit)

Central Nevada Desert Basins(hydrologic subregion)

Great Basin(hydrologic region)

Federal lands

Bureau of Land Management(Bureau of Land Management NV)

Bureau of Land Management NV BLM(Type of land area)

BLM(Federal land areas administered by BLM)

Geographic areas

Country State County
United States Nevada Lander
United States Nevada Eureka

Public Land Survey System information

Meridian Township Range Section Fraction State
Mount Diablo 027N 048E 31 Nevada

Comments on the location information

  • The property is located XX and is part of the Cortez Joint Venture which operates Cortez, Pipeline, and South Pipeline mines.

Commodities

Commodity Importance
Gold Primary
Silver Primary
Mercury Tertiary
Arsenic Critical Tertiary
Antimony Critical Tertiary

Comments on the commodity information

  • Commodity Info: Gold is submicroscopic (micron to submicron-sized particles of native gold), occurring in minute specks of arsenian pyrite.
  • Ore Materials: native gold, pyrite
  • Gangue Materials: hematite, goethite; gangue: quartz, carbonate, clays

Materials information

Materials Type of material
Gold Ore
Pyrite Ore
Goethite Ore
Quartz Ore
Clay Ore
Hematite Gangue

Alteration

  • (Local) Host rocks have been decalcified, silicified, leached, bleached, argillized, and oxidized. This phase of low grade hydrothermal alteration occurred after intrusion of the porphyry sill, and removed most of the carbon. A decalcification halo extends into the host rock surrounding the mineralized area. Mineralization is associated with silicification.

Mineral occurrence model information

Model code 173
USGS model code 26a.1
Deposit model name Sediment-hosted Au
Mark3 model number 17

Host and associated rocks

  • Host or associated Host
    Rock type Sedimentary Rock > Carbonate > Limestone
    Rock unit name Roberts Mountain
    Stratigraphic age (youngest) Early Devonian
    Stratigraphic age (oldest) Wenlock
  • Host or associated Host
    Rock type Sedimentary Rock > Clastic Sedimentary Rock > Siltstone
    Rock unit name Roberts Mountain
    Stratigraphic age (youngest) Early Devonian
    Stratigraphic age (oldest) Wenlock
  • Host or associated Host
    Rock type Sedimentary Rock > Clastic Sedimentary Rock > Sandstone
    Rock unit name Roberts Mountain
    Stratigraphic age (youngest) Early Devonian
    Stratigraphic age (oldest) Wenlock
  • Host or associated Host
    Rock type Sedimentary Rock > Carbonate > Limestone
    Rock unit name Wenban Limestone
    Stratigraphic age (youngest) Devonian
  • Host or associated Associated
    Rock type Plutonic Rock > Porphyry
    Rock type qualifier BIOTITE-QUARTZ PORPHYRY DIKES and sills
    Rock unit name Mill Canyon quartz monzonite stock
    Stratigraphic age (youngest) Oligocene
  • Host or associated Associated
    Rock type Plutonic Rock > Granitoid > Quartz Monzonite
    Rock type qualifier STOCK
    Rock unit name Mill Canyon quartz monzonite stock
    Stratigraphic age (youngest) Oligocene
  • Host or associated Associated
    Rock type Volcanic Rock (Aphanitic) > Intermediate Volcanic Rock > Andesite
    Rock type qualifier FLOWS
    Rock unit name Caetano Tuff
    Stratigraphic age (youngest) Late Eocene
    Chronological age 34
  • Host or associated Associated
    Rock type Volcanic Rock (Aphanitic) > Felsic Volcanic Rock > Rhyolite
    Rock type qualifier PLUG
    Rock unit name Caetano Tuff
    Stratigraphic age (youngest) Late Eocene
    Chronological age 34

Nearby scientific data

Ore Body (1) -116.6037, 40.1543
ListMap

Economic information

Geologic structures

Type of structure Regional
Structure description The deposit lies within the Cortez Window of the Roberts Mountain Thrust (Cortez Range).
Type of structure Local
Structure description The deposit occurs within the Cortez Window in the Roberts Mountain Thrust.

Ore body information

  • General form Irregular

Controls for ore emplacement

  • Gold is localized where limestone was faulted, brecciated and folded along the margin of a Tertiary intrusive.

Comments on the geologic information

  • The deposit is also associated with the Horse Canyon volcanics (andesite flows, rhyolite plug) and the Roberts Mountain Limestone (silty, argillaceous, carbonaceous, pyrite-bearing limestone).

Economic information about the deposit and operations

Operation type Surface
Development status Past Producer
Commodity type Metallic
Deposit size Large
Significant Yes
Discovery year 1998

Mining district

District name Cortez District

Land status

Ownership category BLM Administrative Area
Area name Battle Mountain BLM Administrative District

Ownership information

  • Type Owner-Operator
    Owner Cortez Joint Venture: Placer Dome
    Interest 60
  • Type Owner-Operator
    Owner Cortez Joint Venture: Kennecott Explorations
    Interest 40

Comments on the workings information

  • The deposit will probably be developed as an open pit mine.

Comments on other economic factors

  • As of year-end 2003, the proven and probable reserve for Cortez Hills is 5.25 million contained ounces (41.3 M tons @ 0.127 opt) @ $325/gold. An additional 1.58 million contained ounces (12.112 M tons @ 0.114) of measured, indicated and inferred resource is calculated. Delineation of this new discovery continues with expansion potential evident to the west and at depth.

    As reported at December 31, 2003, the Cortez Hills deposit, hosts proven and probable gold mineral reserves of 5.2 million ounces, measured and indicated gold mineral resources of 0.5 million ounces, and inferred gold mineral resources of 1.0 million ounces

    Cortez currently has 7.5 million ounces of gold reserves in Cortez Hills and another 1.2 million ounces at Pediment (Elko Daily Free Press, 9/04)
    Pediment deposit currently estimated at 1.2 million ounces consisting of 1.1 million ounces proven (35.4 tonnes at average grade of 0.99 g/t) and 0.1 million ounces probable (3.5 million tonnes at average grade of 0.74 g/t).

Comments on development

  • Gold was discovered in 1966 following geochemical studies of the Cortez Window by the U.S.G.S. Subsequent drilling by Placer Dome U.S. (formerly AMEX) led to the outlining of the Cortez gold deposit. In 1968 a joint venture among American Exploration and Mining Co., Bunker Hill Co., Vernon Taylor and Webb Resources announced reserves of 3.4 million tons ore at 0.29 oz/ton gold. Open pit mining began in 1969 with processing in a 1500 t.p.d. mill. Reserves were exhausted and mining ceased in 1976. In 1981-1983, Cortez Gold mines reworked low-grade stockpile ore from the open pit directly above the millsite. This ore was further separated into low and high-grade piles, crushed to -3/4 and then decarbonized and heapleached with cyanide. In 1983 the entire operation employed 104 persons. New mining by Cortez Gold Mine commenced in 1988 and continued until 1993. Total production to that time was about 873,000 ounce of gold from about 6.4 million tons of ore. Estimated additional unmined mineralized material remaining in 1999 totalled about 362,000 ounces.

    ?1983 ownership was Cortez Gold Mines, Art Walsh, General Manager, Crescent Valley, NV 89821; later a joint venture with Placer Amax, Idaho Mining Co., Vernon F. Taylor, Jr.

    Cortez is approximately 113km south west of Elko, Nevada. It consists of three distinct units: the Cortez open pit and two Carlin-type disseminated gold deposits - Pipeline and South Pipeline. The operation is owned 60% by Placer Dome Inc and 40% by Rio Tinto. Production began at Cortez in 1969 with the Pipeline deposits, where mining is now centered, being discovered subsequently. In 2000, the Cortez complex produced 1,009,922oz of gold at a cash cost of $60/oz (total cost $136/oz), making the mine the lowest-cost gold producer in North America.

    Placer Dome is the operator and owner of a 60% joint venture interest in the Cortez Joint Venture("Cortez"). The remaining 40% is held by Kennecott Explorations (Australia) Ltd. All production by Cortez is subject to a 1.5% gross smelter return ("GSR") royalty payable to the grantees of Idaho Resources Corp.

    June 2004, Placer announced that they had drilled a hole in the area between the Cortez Hills and the Pediment deposits that had returned 1.5 ounces per ton over more than 400 feet.

    Cortez Pediment discovered during the fall of 1998.
    The Pediment Project, which will allow for the construction and mining of a new ore deposit in 2004, requires a newly developed
    EIS. Permitting of the Pediment Project is in process with baseline environmental studies, cultural resource evaluations, dewatering and water treatment studies and other environmental permitting activities. Kennecott website 12/03

Reference information

Bibliographic references

  • Deposit

    Roberts, R.J. et al, (1967) Geology and Mineral Deposits of Eureka Co. Nev., N.B.M. Bull. 64

  • Location

    Lander County Mineral Impact Assessment, Crescent Valley Area - Update, Along the Department of Energy (DOE), Yucca Mountain Project - Proposed Rail Corridor, October 2004. Two parts. The location map showing Pidement and Cortez Hills properties are in section 2, p. 20.

  • Deposit

    Wells J.D., Stoiser, L.R., and Elliot, J.E., (1969) Geology and Geochemistry of the Cortez Gold Deposit, Economic Geology v. 64, p. 526

  • Deposit

    Stager, H.K., (1977) Geology and Mineral Deposits of Lander Co., N.B. of M. Bull. 88

  • Deposit

    Division of Mine Inspection, Dec. 1983, Directory of Nevada Mine Operations Active in Calendar Year 1983.

  • Deposit

    NBMG, 1983, Map 84, Active Mines and Oil Fields.

  • Deposit

    NBMG, 1983, Active Mines and Oil Fields, Map 84.

  • Deposit

    Bentz, J. and Smith, P., 1982, Field Examination Report, July 12, 1982.

  • Deposit

    Metal Market Consultants, Inc., 1987, Gold Situation Map

  • Deposit

    Nevada Dept. of Minerals, 1993.95-2

  • Deposit

    .Geological Society of Nevada 1997 Spring Field Trip: Geology and Ore Deposits of Northeastern Nevada, Special Publication No. 25

  • 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.

  • Deposit

    Geology and Ore Deposits of the American Cordillera, Field Trip Guidebook Compendium of the April 1995 Geological Society of NevadaSymposium; 501 p

  • Deposit

    Robert C. Hays, Jr., 2003, The Cortez Hills Deposit, a recent discovery in an historic mining district, Lander County, Nevada, abstract for Geological Society of Nevada talk given in spring 2004.

General comments

Subject category Comment text
Deposit The Cortez Pediment deposit has one primary mineralized zone that is about 45 metres below the surface on the southern portion of the deposit and about 170 metres below the surface on the northern end of the deposit. The average thickness of the low-angle tabular zone is about 75 metres. The deposit occupies area approximately 1,000 metres in a northerly direction and about 180 metres in an easterly direction.
Gold is localized where limestone was faulted, brecciated and folded along margin of Tertiary intrusive, gold is micron-to sub-micron-size.
The upper portion of the Devonian carbonate sequence beneath the Roberts Mountains thrust hosts the nearby Cortez Hills deposit. Pervasive oxidation and marble development are key alteration types associated with gold deposit.

Reporter information

Type Date Name Affiliation Comment
Reporter 01-JUL-2004 LaPointe, D. D. Nevada Bureau of Mines and Geology
Editor 01-SEP-2007 Schruben, Paul G. U.S. Geological Survey Converted from S&A FileMaker format to Oracle. Edit checks on rocks, units, and ages with Geolex search, and other fields.

Beyond USGS

Supplemental information added by qvyshift.com. Not part of the original USGS MRDS record.

Maps centered on this site

Authoritative Nevada resources

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