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Cortez Hills 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 10310435
Record type Site
Current site name Cortez Hills Gold Property
Alternate or previous names Cortez Joint Venture
Related records 10310459

Geographic coordinates

Geographic coordinates: -116.60257, 40.16899 (WGS84)
Elevation 1520
Relative position The prospect area is located about 50 km south of Beowawe near the crest of the Cortez Hills.

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)

Middle Humboldt(hydrologic unit)

Humboldt(hydrologic accounting unit)

Black Rock Desert-Humboldt(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
Hematite Gangue
Goethite Gangue
Quartz Gangue
Clay 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. Pervasive oxidation and marble development are key alteration types associated with gold deposition

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 type qualifier silty, argillaceous, carbonaceous, pyrite-bearing
    Rock unit name Roberts Mountain Formation
    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 Formation
    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 Formation
    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) Early Oligocene
    Chronological age 33.8
  • Host or associated Associated
    Rock type Volcanic Rock (Aphanitic) > Felsic Volcanic Rock > Rhyolite
    Rock type qualifier PLUG, dikes, and sills
    Rock unit name Caetano Tuff
    Stratigraphic age (youngest) Early Oligocene
    Chronological age 33.8

Nearby scientific data

(1) -116.60257, 40.16899
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 2002

Mining district

District name Cortez District

Land status

Ownership category BLM Administrative Area
Area name Battle Mountain 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 reserves for the Cortez Hills deposit are 5.25 million contained ounces of gold (41.3 million tons of ore grading 0.127 ounces per ton.) An additional 1.58 million contained ounces of gold (12.112 million tons of ore grading 0.114 ounces per ton) of measured, indicated and inferred resource is calculated.

Comments on development

  • Placer Dome is the operator and owner of a 60% joint venture interest in the Cortez Joint Venture (CJV). The remaining 40% is held by Kennecott Explorations (Australia) Ltd. The recent Cortez Hills discovery is the result of focused exploration efforts by CJV staff along an extensive high-angle fault corridor that localizes the distribution of gold in the Cortez area. Projection of this structural corridor under cover, coupled with gravity data, were the key exploration techniques that led to the discovery of Cortez Hills.
    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.

Reference information

Bibliographic references

  • Deposit

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

  • 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 recent Cortez Hills discovery is the result of focused exploration efforts along an extensive high-angle fault corridor that localizes the distribution of gold in the Cortez area. Projection of this structural corridor under cover, coupled with gravity data, were the key exploration techniques that led to the discovery of Cortez Hills. 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 Cortez Hills deposit. Pervasive oxidation and marble development are key alteration types associated with gold deposit.
The Cortez Hills deposit is hosted in the upper portion of the Devonian carbonate sequence. It has a strike length of more than 300 m and is approximately 200 m wide. The mineralized zone starts approximately 120 m below surface and continues up to 460 m. The deposit remains open with expansion potential evident to the west and at depth.

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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