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Ann Mason Copper Deposit

Prospect in Lyon county in Nevada, United States with commodities Copper, Gold, Molybdenum, Silver
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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. Mineral rights holdings
  18. Land status
  19. Ownership information
  20. Reserves and resources
  21. Workings at the site
  22. Links to other databases
  23. Bibliographic references
  24. General comments
  25. Reporter information

Geologic information

Identification information

Deposit ID 10310385
MRDS ID MP90062
Record type Deposit
Current site name Ann Mason Copper Deposit
Alternate or previous names Ann Mason Copper Gold Molybdenum Project, Ludwig, Douglas Hill, Cast, Blue Hills, McConnell, Minnesota, Shamrock
Related records 10048830, 10222434

Comments on the site identification

  • All material in earlier MRDS record MP90062 has been incorporated into the current record, as well as additional new information.

Geographic coordinates

Geographic coordinates: -119.27098, 38.95991 (WGS84)
Relative position The Ann Mason deposit is located about 5 miles west of the town of Yerington, Nevada.

Site location context

Political divisions (FIPS codes)

Lyon(county)

Nevada(state)

United States(country)

North America(continent)

Land(continent)

USGS map quadrangles

Artesia Lake(quadrangle 1:24,000 scale)

Smith Valley(quadrangle 1:100,000 scale)

Walker Lake(quadrangle 1:250,000 scale)

Hydrologic units (watersheds)

West Walker(hydrologic unit)

Walker(hydrologic accounting unit)

Central Lahontan(hydrologic subregion)

Great Basin(hydrologic region)

Geographic areas

Country State County
United States Nevada Lyon

Public Land Survey System information

Meridian Township Range Section Fraction State
Mount Diablo 013N 025E 19 Nevada

Comments on the location information

  • The Ann Mason project consists of a total of 80 unpatented mining claims located in the Buckskin (Singatse) Range west of Yerington. The deposit is located about 2 miles WSW of the main Yerington open pit mine.
  • DEPOSITS ALSO LOCATED IN SECTIONS 13, 15, AND 24, T13N, R24E. * DEPOSIT IS ABOUT 3 MILES WEST OF THE OLD YERINGTON AND IS BURIED UNDER 300 TO 1500 FEET OF TERTIARY VOLCANICS. *

Commodities

Commodity Importance
Copper Primary
Gold Secondary
Molybdenum Secondary
Silver Secondary

Materials information

Materials Type of material
Bornite Ore
Chalcopyrite Ore
Pyrite Ore
Chalcocite Ore
Apatite Unknown
Biotite Unknown
Feldspar Unknown
Hornblende Unknown
Ilmenite Unknown
Magnetite Unknown
Quartz Unknown
Sphene Unknown
Zircon Unknown

Alteration

  • (Local) Above the porphyry Cu?Mo orebodies (at 1 to 4 km depth), sericitic and local advanced argillic alteration dominate along structural zones that funneled magmatic fluids upward from the deep cupolas, and may be time-equivalent to deeper K-silicate alteration.

Mineral occurrence model information

Model code 53
USGS model code 17
Deposit model name Porphyry Cu
Mark3 model number 4

Host and associated rocks

  • Host or associated Host
    Rock type Plutonic Rock > Granitoid > Granite
    Rock type qualifier Granite porphyry dikes within the cogenetic Luhr Hill Granite
    Rock unit name Luhr Hill granite
    Stratigraphic age (youngest) Middle Jurassic
    Chronological age 168.5
    Dating method U-Pb (zircon)
  • Host or associated Associated
    Rock type Volcanic Rock (Aphanitic) > Alkalic Volcanic Rock
    Stratigraphic age (youngest) Triassic
  • Host or associated Associated
    Rock type Sedimentary Rock
    Stratigraphic age (youngest) Triassic
  • Host or associated Associated
    Rock type Volcanic Rock (Aphanitic)
    Stratigraphic age (youngest) Late Cretaceous
  • Host or associated Host
    Rock type Plutonic Rock > Granitoid > Quartz Monzonite
    Rock type qualifier 3 phases oldest to youngest: McLeod Hill quartz monzodiorite, Bear quartz monzonite, Luhr Hill Granite
    Rock unit name Yerington batholith
    Stratigraphic age (youngest) Middle Jurassic
    Chronological age 169.4
    Dating method U-Pb (zircon)

Nearby scientific data

(1) -119.27098, 38.95991
ListMap

Economic information

Geologic structures

Type of structure Regional
Structure name Batholith

Ore body information

  • Name Ann Mason
    General form Massive
    Strike N04E
    Dip 76E
    Thickness 400M
    Length 1000M
    Width 100M
    Area 117HA
    Depth to top 400M

Controls for ore emplacement

  • granitic intrusive body

Comments on the geologic information

  • Magmatic fluids responsible for porphyry copper hydrothermal alteration-mineralization separated from cupolas atop the Luhr Hill granite at depths ranging from ~3 km at the Yerington Mine to ~4.5 km at the Ann-Mason deposit.
  • NOTE---CHALCOPYRITE CONCENTRATION (M-AMO) IS AN ORE BODY AVERAGE AND INCLUDES REPORTED BORNITE. * MINERALS ARE NOT REPORTED IN ORDER OF ABUNDANCE. *

Economic information about the deposit and operations

Operation type Surface
Development status Prospect
Deposit size Large
Significant Yes
Discovery year 1960
Discoverer Anaconda Company (1971)
Mining method Open Pit
Milling method Flotation

Mining district

District name Yerington District

Mineral rights holdings

Type of mineral rights Patented
Type of mineral rights Located Claim

Land status

Ownership category BLM Administrative Area
Area name Carson City BLM Administrative District

Ownership information

  • Type Owner-Operator
    Owner PacMag Metals Limited
    Year 2006
  • Type Owner
    Owner Anaconda Minerals Co
    Interest 100
    Last year 1976
  • Type Owner
    Owner Arco
    Interest 100
    First year 1976
    Last year 1982
  • Type Owner
    Owner Tibbles Construction Co. (Don and Joy Tibbles)
    Interest 100
    Home office Nevada
    Year 1991
    First year 1982
    Last year 1990
  • Type Owner
    Owner Arimetco International, Inc.
    Interest 100
    Home office Arizona
    First year 1990
    Last year 2003
  • Type Owner
    Owner Giralia
    Interest 100
    First year 2003
  • Type Owner
    Owner Entree Gold
    Interest 100
    Year 2009
    First year 2009

Reserves and resources

  • Type In-situ
    Estimate year 2007
    Inferred 810000000mt
    Remarks Entree Gold press release 7_Feb_2011. Cu cutoff grade 0.3%
    Commodity Subtype Grade units Group Importance Year
    Molybdenum Mo 0.004 wt-pct Molybdenum Secondary 2007
    Copper Cu 0.4 wt-pct Copper Primary 2007
  • Type In-situ
    Estimate year 1996
    Indicated 449000000mt
    Total resources 449000000mt
    Commodity Subtype Grade units Group Importance Year
    Copper Cu 0.4 wt-pct Copper Primary 1996
  • Type In-situ
    Estimate year 1982
    Total resources 495000000mt
    Commodity Subtype Grade units Group Importance Year
    Gold Au 0.03 g/mt Gold Secondary 1982
    Molybdenum Mo 0.01 wt-pct Molybdenum Secondary 1982
    Silver Ag 0.17 g/mt Silver Secondary 1982
    Copper Cu 0.4 wt-pct Copper Primary 1982
  • Type In-situ
    Estimate year 1970
    Total resources 449000000mt
    Remarks Anaconda 1970 Annual Report; Long, 1995

Comments on the reserve resource information

  • ARCO - ANACONDA MERGER FILING, SEPTEMBER 1976, P 67,82 HIGH GRADE TONNAGE - 100,000,000 MT @ 0.51 % CU. NOT INCLUDED I 1978 SUPPLY ANALYSIS. SHOULD BE CONSIDERED FOR FUTURE AVAILABILITY STUDIES.

Workings at the site

  • Type of workings Underground
    Overall depth 900M

Comments on the workings information

  • Surface drilling and other exploration
  • MAS Development Schedule #: 1
    Mining Record # : 1
    Status of Mining Method : PROPOSED
    Mining Method : FILLED STOPES
    Percent Waste Rock : 0
    Percent Recovery : 100
    Hardness of Rock : HARDROCK FISSURED WITH MODERATE WATER
    Rock Characteristics : MULTIPLE SYSTEMS OF WEAKNESS PLANES
    Rock Support Chars. : SUPPORTINGMine Support Chars. : UNKNOWN
    umber of Shafts : 1
    Length of Inclines (m) : 2100
    Slope of Inclines : 85
    Number of Inclines : 3
    Avg. Length of Adits (m) : 18000
    Number of Adits : 9
    Capacity : 15373
    Capacity Units : MT ORE/DAY
    Unit Production Cost : 8.6
    Units of Production : $/MT ORE
    Operating Days per Year : 350
    Operating Shifts per Day : 3
    Year of Information : 1985

Comments on other economic factors

  • The Ann Mason deposit was estimated in the 1970s to contain 4.4 billion pounds of copper.
    In about 2002 the Ann Mason deposit was estimated to contain reserves of 495 million tons of ore grading 0.4% copper.
    In fall 2006, PacMag Metals Ltd. announced that based on recent drill results at the Ann Mason Project, total resources aggregate 891,000,000 tons grading 0.40% copper and 0.004% molybdenum inferred while the high grade core aggregates 243,100,000 tons grading 0.51% copper and 0.004% molybdenum inferred.

Comments on development

  • The deposit was originally discovered by the Anaconda Copper Company (?Anaconda?) in the 1960s and was subject to exploration by Anaconda until 1978. It is one of a cluster of deposits in the Yerington porphyry copper district. During the 1950s and 1960s significant production was recorded at both the MacArthur and Yerington open pits within 10 kilometers of Ann Mason.

    In 2005, Giralia Resources NL purchased 100% interest in MIM (USA) Inc., an offshore subsidiary of the MIM group of companies now controlled by Xstrata. MIM (USA) Inc's assets include the Ann Mason porphyry copper deposit in the Yerington district. Nevada. The Ann Mason deposit (estimated at 495 million tons @ 0.4% copper) was discovered in 1971 by the Anaconda Copper Company. The deposit reportedly has a stripping ratio of 3.5:1 and copper recoveries of 90% by flotation. The deposit is known from Anaconda sampling to contain silver and molybdenum credits, and limited resampling of old drillcore by MIM in 2002 returned gold grades to 0.28 g/t Au, along with up to 2.64 g/t silver and 259 ppm molybdenum. Potential for extensions to the deposit and evidence of a higher grade core at Ann Mason is indicated by holes D316: 196 meters at 1.14% Cu, and D317: 152 meters at 0.8% Cu, located on the south-west margin of the deposit.
    MIM (USA) Inc acquired the Ann Mason property in 2002 and completed a geophysical survey using MIM's proprietary MIMDAS system. The survey indicated a major chargeability anomaly, which remains effectively untested by drilling on the western flank of the known copper deposit and adjacent to the high grade zone.
    In 2006, the deposit was controlled by PacMag Metals Limited, who commissioned Golder Associates to complete a new resource estimate for the Ann Mason deposit.
    In fall 2006, PacMag Metals Ltd. announced that based on recent drill results at the Ann Mason Project, total resources aggregate 891,000,000 tons @ 0.40% Cu, 0.004% Mo inferred while the high grade core aggregates 243,100,000 tons @ 0.51% Cu, 0.004% Mo inferred.

Reference information

Bibliographic references

General comments

Subject category Comment text
Deposit The deposit is not exposed on the surface.
Deposit MAS Matrix # : 1 MAS Column # : 1
Type of Orebody #1 : DISSEMINATED
Shape of Orebody #1 : MASSIVE
Type of Orebody #2 : FISSURE VEIN
Primary mode of Origin : HYDROTHERMAL
Primary Ore Control : CONTACT ZONE
Secondary Ore Control : FRACTURING
Degree of Wallrock Alter. : INTENSE
Type of Wallrock Alter. #1 : POTASSIC
Strike And Dip : N04E:76E
Minimum Depth to Top : 0
Avg. Thick. Unconsol. Mat. : 400
Min. Thick. Unconsol. Mat. : 0
Date of Last Modification : 850913
Deposit Associated Minerals: actinolite, albite, biotite, bornite, chalcopyrite, chlorite, epidote, hematite, magnetite, molybdenite, pyrite, rutile, sericite, tourmaline
Deposit Associated Rock: andesite dike, granite porphyry, rhyolite dike;andesite, argillite, gypsum, ignimbrite, rhyolite, sandstone, volcaniclastic rocks;breccia, dolomite, granite, limestone, quartz monzodiorite, quartz monzonite, skarn
Deposit Associated Deposits: Casting Copper (skarn), Douglas Hill (skarn), Bluestone (skarn), Mason Valley (skarn), McConnel Mine (skarn), MacArthur (porphyry), Bear-Lagomarsino (porphyry), Buckskin Mine (Au-Cu veins), Ludwig Mine (carbonate replacement/skarn)
Deposit Major Ore Minerals and Assemblages: chalcopyrite, bornite, chalcocite, pyrite.
Pyrite-chalcopyrite, chalcopyrite, chalcopyrite-bornite assemblages.
Major Vein types and Relative Ages: Common veins oldest to youngest in ore zone: quartz?K-feldspar; chalcopyrite ? pyrite or bornite ?quartz ? chlorite; epitdote ? quartz ? chlorite + chalcopyrite ? pyrite or bornite; epidote + quartz ? chlorite + chalcopyrite ? pyrite or bornite; pyrite ? quartz ? chalcopyrite ? tourmaline
Major Alteration Types: Pre-main stage endoskarn (garnet, albite ? clinopyroxene); main stage potassic (biotite ? K-feldspar), sodic-calcic (actinolite, sodic plagioclase), propylitic (actinolite, chlorite); late stage sericitic, sodic, chloritic
Alteration Zoning: Likely contemporaneous central potassic with deeper and lateral sodic-calcic with peripheral propylitic; albitic (albite-chlorite) and sericitic alteration overprint the earlier alteration with sericitic alteration increasing at shallower levels. Ann-Mason has late albite alteration strongly developed along pre-tilt western side of Cu zone
Metal Zoning: For Ann-Mason: Large central zone of chalcopyrite ?bornite, ?pyrite to outer pyrite, magnetite minor to absent. Highest Cu grades associated with greatest potassic alteration.

Reporter information

Type Date Name Affiliation Comment
Reporter 01-FEB-05 LaPointe, D.D. Nevada Bureau of Mines and Geology
Editor 01-SEP-07 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.
Reporter 09-JUL-97 Spear, James M U.S. Bureau of Mines
Reporter 18-AUG-95 Tanikawa, Saciko U.S. Geological Survey
Updater 01-FEB-10 Anderson, Claire U.S. Geological Survey

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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