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Gold Acres Deposit

Producer in Lander county in Nevada, United States with commodities Gold, Tungsten, Copper, Antimony, Arsenic, Mercury, Thallium, Lead, Zinc, Molybdenum
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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 10310461
MRDS ID W002496
MAS/MILS ID 0320150008
Record type Site
Current site name Gold Acres Deposit
Alternate or previous names Little Gold Acres, Old Kennecott Group, Lime Point Claim, Lakin Claim, Maloney Claim, Little Squirt Claim
Related records 10069103, 10125727, 10246211

Comments on the site identification

  • This record includes all material from earlier record W002496 plus additional material. Older records #M232510 and #M232517 have been deleted.

Geographic coordinates

Geographic coordinates: -116.73982, 40.25213 (WGS84)
Elevation 1700
Relative position Gold Acres is located 47 km southeast of Battle Mountain, Nevada.\n

Site location context

Political divisions (FIPS codes)

Lander(county)

Nevada(state)

United States(country)

North America(continent)

Land(continent)

USGS map quadrangles

Tenabo(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

Public Land Survey System information

Meridian Township Range Section Fraction State
Mount Diablo 028N 046E 36 Nevada
Mount Diablo 028N 046 E 31 Nevada

Comments on the location information

  • Gold Acres is located on the eastern flank of the Northern Shoshone Range. UTM is to the historic Little Gold Acres Mine workings.

Commodities

Commodity Importance
Gold Primary
Tungsten Critical Secondary
Copper Secondary
Antimony Critical Tertiary
Arsenic Critical Tertiary
Mercury Tertiary
Thallium Tertiary
Lead Tertiary
Zinc Critical Tertiary
Molybdenum Tertiary

Comments on the commodity information

  • Ore Materials: native gold, molybdenite, and scheelite, pyrite, arsenopyrite, sphalerite, galena, pyrrhotite

Materials information

Materials Type of material
Gold Ore
Molybdenite Ore
Scheelite Ore
Pyrite Ore
Arsenopyrite Ore
Sphalerite Ore
Galena Ore
Pyrrhotite Ore

Alteration

  • (Local) Alteration of the deposit consists of carbonization, silicification, argillization, oxidation, and skarn formation. Carbonization (up to 3% by weight organic carbon) is the dominant alteration type in the deposit and can give a sooty appearance to the rocks. Silicification is strongest at the northern end of the deposit and decreases to the south. Argillization is primarily confined to fractures in lower plate carbonates associated with carbonization. The clays are generally illitic. Supergene oxidation is evident throughout the deposit area as limonitic and hematitic staining along fractures. Skarn development is associated with the emplacement of a Cretaceous granitic stock. Two prograde, skarn zones are developed, both barren of gold. A retrograde skarn alteration mineral assemblage consists of chlorite, tremolite, epidote, calcite, quartz, illite, nontronite, smithsonite(?), pyrite, pyrrhotite, chalcopyrite, sphalerite, arsenopyrite, and galena. Gold is not associated with the retrograde assemblage.

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 Mountains Fm
    Stratigraphic age (youngest) Early Devonian
    Stratigraphic age (oldest) Wenlock
  • Host or associated Host
    Rock type Sedimentary Rock > Chemical Sediment > Chert
    Rock type qualifier siliceous
    Rock unit name Valmy Fm
    Stratigraphic age (youngest) Ordovician
    Stratigraphic age (oldest) Late Cambrian
  • Host or associated Host
    Rock type Sedimentary Rock > Clastic Sedimentary Rock > Shale
    Rock unit name Valmy Fm
    Stratigraphic age (youngest) Ordovician
    Stratigraphic age (oldest) Late Cambrian
  • Host or associated Host
    Rock type Sedimentary Rock > Clastic Sedimentary Rock > Sandstone
    Rock unit name Elder Sandstone
    Stratigraphic age (youngest) Silurian
  • Host or associated Host
    Rock type Plutonic Rock > Porphyry
    Rock type qualifier quartz porphyry dikes
    Stratigraphic age (youngest) Middle Eocene
    Chronological age 40
    Stratigraphic age (youngest) Early Oligocene
    Chronological age 30
  • Host or associated Associated
    Rock type Plutonic Rock > Granitoid > Quartz Monzonite
    Rock type qualifier sill
    Stratigraphic age (youngest) Late Cretaceous
    Chronological age 98

Economic information

Geologic structures

Type of structure Regional
Structure description Gold Acres is exposed at the western margin of the Gold Acres window along the NW-trending Roberts Mountains thrust, Cortez-Uinta axis. It lies along the Eureka-Battle Mountain trend of aligned deposits and mineralization.
Type of structure Local
Structure description High angle normal faulting of various orientations has broken the mineralized zone into three parts: the main Gold Acres orebody, the Little Squirt orebody, and the Little Gold Acres orebody.

Ore body information

  • General form tabular; stratabound

Controls for ore emplacement

  • Carbonaceous silty limestone of Roberts Mountains Formation provided a favorable host for gold deposition. Northeast-striking high angle normal faults served as conduits for mineralizing fluids. The majority of gold was deposited in an imbricated thrust zone below the Roberts Mountains Thrust within the Roberts Mountains Formation. The upper skarn may have acted as a caprock.

Economic information about the deposit and operations

Operation type Surface-Underground
Development status Producer
Commodity type Metallic
Deposit size Medium
Significant Yes
Discovery year 1920
Discoverer Lee Lakin
Year of first production 1935
Year of last production 1996
Production years 1936-1961; 1973-1983; 1987-1996

Mining district

District name Bullion District

Land status

Ownership category Private
Ownership category BLM Administrative Area
Area name Battle Mountain BLM-administrative district

Ownership information

  • Type Owner-Operator
    Owner Cortez Joint Venture: Placer Dome, Inc.
    Interest 60
    Year 2004
  • Type Owner-Operator
    Owner Cortez Joint Venture: Kennecott Explorations
    Interest 40
    Year 2004

Comments on the workings information

  • There are both old underground workings and more recent open pit mines. There were over 3000 feet of underground workings. The historic Little Gold Acres mine is now part of the Gold Acres open pit.

Comments on other economic factors

  • Gold Acres and Little Gold Acres reserves:
    1987: 4.8 million tons of ore grading 0.105 ounces of gold per ton
    1988: 5.4 million tons of ore grading 0.093 ounces of gold per ton
    1992: reserves-3.1 million tons of ore grading 0.05 ounces of gold and 0.4 ounces of silver per ton
    Production:
    Gold Acres: 1942-84: 2.4 million tons of ore grading 0.13 oz ton Au/ton; 2 million tons, 0.041 ounces of gold per ton leached.
    Little Gold Acres: 800,000 tons of ore grading 0.124 ounces of gold per ton
    1988: 42,322 ounces of gold (includes Horse Canyon)
    1989: 39,993 ounces of gold , 12,234 ounces of silver (includes Horse Canyon)
    1990: 53,945 ounces of gold , 10,150 ounces of silver
    1991: 53,500 ounces of gold , 6,600 ounces of silver
    1992: 75,000 ounces of gold
    1993: 66,850 ounces of gold

Comments on development

  • Gold mining from the North Ore zone (Gold Acres) began in 1935, first by underground methods then by open pit after 1942. From 1942-1961, Gold Acres produced $10 million in gold and silver and was one of the largest gold producers in Nevada in the 1950s. Placer Dome U.S., Inc. began exploring the district in 1959 and consolidated the land position at Gold Acres in 1969 by and conducted a drilling program. By 1973, mineable reserves for what became the South Pit (Little Gold Acres) were estimated at 1.6 million tons grading 0.106 opt gold. Cortez Gold Mines mined Little Gold Acres from 1973-1976. Heap leaching and milling of the Gold Acres dumps and stockpiles followed until 1983. Development drilling continued from 1984-1986. In 1987, mining activity was reactivated at the North Pit where a refractory mineable reserve of 2.2 million tons/0.118 opt gold was exploited.
    In 2002, Cortez Gold Mines announced plans to reopen the old Gold Acres Mine to recover carbonaceous ore that was left unmined in the bottom of the old open pit. The ore was to be mined by a contractor and transported to Barrick?s Goldstrike
    The property is owned by Cortez Joint Venture: Placer Dome, Inc. (60%); Kennecott Explorations (40%) (2004).

Reference information

Bibliographic references

General comments

Subject category Comment text
Deposit The deposit is in the west edge of a window in the upper plate of the Roberts Mountains Thrust, and is localized in brecciated chert and limestone in the lower plate (siliceous, volcanic and carbonate rock assembles). The ore is localized in the Roberts Mountains thrust fault breccia zone, in a shear adjacent to a sill. The shear zone is between limestone and sill; sandstone and chert overlie sill. Blocks of tactite within the shear zone are mineralized, the zone is mineralized with native gold, molybdenite, and scheelite. The intrusive contains minor pyrrhotite. The breccia zone contains disseminated iron-oxides and gold as submicroscopic particles. The intrusives exposed in the pit have been dated as 98 my old. The surrounding country rocks have been pyrometasomatized to various degrees, with the introduction of some scheelite. Tactites zones best developed in the lower plate rocks. Epithermal gold mineralization may be overprinted on Cretaceous tactite Cu-Zn mineralization. The orebody strikes N40W, dipping nearly flat to the southwest. The ore limits are determined by assay values. Gold is hosted primarily in the Silurian Roberts Mountains Formation.
Age Age of mineralization is younger than 98.8, +/-2.0 Ma. Gold deposition postdates Cretaceous skarn development.

Reporter information

Type Date Name Affiliation Comment
Reporter 01-DEC-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.

External references

Maps centered on this site

Authoritative Nevada resources

These are landing pages for further research — the state agencies don't currently expose per-mine deep links.