Ann Mason Copper Deposit

Site Name

Primary: Ann Mason Copper Deposit
Secondary: Ann Mason Copper Gold Molybdenum Project
Secondary: Ludwig
Secondary: Douglas Hill
Secondary: Cast
Secondary: Blue Hills
Secondary: McConnell
Secondary: Minnesota
Secondary: Shamrock

---

Commodity

Primary: Copper
Secondary: Molybdenum
Secondary: Silver
Secondary: Gold

---

Location

State: Nevada
County: Lyon
District: Yerington District

---

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: Carson City BLM Administrative District

---

Holdings

Type: Located Claim
Type: Patented

---

Workings

Type: Underground

---

Ownership

Owner Name: Giralia
Percent: 100.0
Years: 2003 -

Owner Name: Arimetco International, Inc.
Percent: 100.0
Home Office: Arizona
Years: 1990 - 2003

Owner Name: Tibbles Construction Co. (Don and Joy Tibbles)
Percent: 100.0
Home Office: Nevada
Info Year: 1991
Years: 1982 - 1990

Owner Name: Arco
Percent: 100.0
Years: 1976 - 1982

Owner Name: Anaconda Minerals Co
Percent: 100.0

Owner Name: PacMag Metals Limited
Info Year: 2006

Owner Name: Entree Gold
Percent: 100.0
Info Year: 2009
Years: 2009 -

---

Production

Not available

---

Deposit

Record Type: Deposit
Operation Category: Prospect
Deposit Type: Porphyry copper
Operation Type: Surface
Mining Method: Open Pit
Milling Method: Flotation
Discovery Year: 1960
Years of Production:
Organization:
Significant: Y
Deposit Size: L

---

Physiography

General Physiographic Area: Intermontane Plateaus
Physiographic Province: Basin And Range Province
Physiographic Section: Great Basin
Physiographic Detail: Basin And Mountains

---

Mineral Deposit Model

Model Name: Porphyry Cu

---

Orebody

Name: Ann Mason
Form: Massive

---

Structure

Type: R
Structure: Batholith

---

Alterations

Alteration Type: L
Alteration Text: 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.

---

Rocks

Name: Quartz Monzonite
Role: Host
Description: 3 phases oldest to youngest: McLeod Hill quartz monzodiorite, Bear quartz monzonite, Luhr Hill Granite
Age Type: Host Rock Unit
Age in Years: 169.400000+-0.400000
Dating Method: U-Pb (zircon)
Age Young: Middle Jurassic

Name: Volcanic Rock (Aphanitic)
Role: Associated
Age Type: Host Rock
Age Young: Late Cretaceous

Name: Sedimentary Rock
Role: Associated
Age Type: Associated Rock
Age Young: Triassic

Name: Alkalic Volcanic Rock
Role: Associated
Age Type: Associated Rock
Age Young: Triassic

Name: Granite
Role: Host
Description: Granite porphyry dikes within the cogenetic Luhr Hill Granite
Age Type: Host Rock
Age in Years: 168.500000+-0.400000
Dating Method: U-Pb (zircon)
Age Young: Middle Jurassic

---

Analytical Data

Not available

---

Materials

Ore: Chalcocite
Ore: Pyrite
Ore: Bornite
Ore: Chalcopyrite
Unknown: Apatite
Unknown: Biotite
Unknown: Feldspar
Unknown: Hornblende
Unknown: Ilmenite
Unknown: Magnetite
Unknown: Quartz
Unknown: Sphene
Unknown: Zircon

---

Comments

Comment (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)

Comment (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.

Comment (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

Comment (Reserve-Resource): 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.

Comment (Deposit): Associated Minerals: actinolite, albite, biotite, bornite, chalcopyrite, chlorite, epidote, hematite, magnetite, molybdenite, pyrite, rutile, sericite, tourmaline

Comment (Location): 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. *

Comment (Geology): NOTE---CHALCOPYRITE CONCENTRATION (M-AMO) IS AN ORE BODY AVERAGE AND INCLUDES REPORTED BORNITE. * MINERALS ARE NOT REPORTED IN ORDER OF ABUNDANCE. *

Comment (Workings): 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

Comment (Geology): 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.

Comment (Identification): All material in earlier MRDS record MP90062 has been incorporated into the current record, as well as additional new information.

Comment (Location): 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.

Comment (Workings): Surface drilling and other exploration

Comment (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

Comment (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.

Comment (Deposit): The deposit is not exposed on the surface.

Comment (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.

---

References

Reference (Deposit): PROFFETT, J.M. JR. AND J.H. DILLES. GEOLOGIC MAP OF THE YERRINGTON DISTRICT NEVADA. NEVADA BUREAU OF MINES AND GEOLOGY MAP NO. 77. 1984.

Reference (Deposit): GALE, G.D. (LATE) METALLURGICAL ENGINEER, U.S. BUREAU OF MINES WESTERN FIELD OPERATION CENTER. MARGRET PROJECT. 1980.

Reference (Deposit): GEOLOGICAL SOCIETY OF AMERICA. THIRTY SIXTH ANNUAL MEETING- Deposit ROCKY MOUNTAIN SECTION. THE GEOLOGICAL SOCIETY OF AMERICA VOLUME 15, NO. 5, 1983, P. 277.

Reference (Deposit): BARBER, G.A. VICE PRESDENT-EXPLORATION AND GEOLOGY, ANACONDA MINERALS DIVISION. CONFIDENTIAL COMPANY INFO. 1979. DILLES, J.H., THE PETROLOGY AND GEOCHEMISTRY OF THE YERINGTON BATHOLITH AND THE ANN-MASON PORPHRY COPPER DEPOSIT, WESTERN NEVADA. PHD THESIS STANFORD UNIVERSITY Deposit 33 CA. 1983. 389 PP.

Reference (Deposit): WORLD MINING (SAN FRANCISCO) WHAT'S GOING ON IN WORLD MINING - UNITED STATES: NEVADA; YERINGTON DISTRICT WILL BE A MAJOR FUTURE PORPHYRY COPPER PRODUCER. V. 29, NO. 3, 1976, P. 82.

Reference (Deposit): STODDARD, C., AND J. A. CARPENTER. MINERAL RESOURCES OF STOREY AND LYON COUNTIES, NEVADA. NV BUREAU OF MINES AND GEOL. BULL. 49, 1950, P. 89.

Reference (Deposit): PROFFETT, J. M. AND J. H. DILLES. GEOLOGIC MAP OF THE YERINGTON DISTRICT, NEVADA. NV BUREAU OF MINES AND GEOL., UNIV. OF NV, RENO, MAP 77, 1984.

Reference (Deposit): MOORE, J. G. GEOLOGY AND MINERAL DEPOSITS OF LYON, DOUGLAS, AND ORMSBY COUNTIES, NEVADA. NV BUREAU OF MINES AND GEOL. BULL. 75, 1969, 45 PP.

Reference (Deposit): EINAUDI, M. YERINGTON SKARNS; FIELD TRIP 10, SKARN DEPOSITS. PAPER IN EXPLORATION FOR ORE DEPOSITS OF THE NORTH AMERICAN CORDILLERA. FIELD TRIP GUIDEBOOK, ED. BY J. L. JOHNSON. SYMP. OF ASSOC. EXPL. GEOCHEM., RENO, NV, MARCH 25-28, 1984, PP. 31-39.

Reference (Reserve-Resource): WORLD MINING (SAN FRANCISCO) ANACONDA - ATLANTIC RICHFIELD MUST DIVEST CU RESERVES. V. 32. NO. 5, 1979, P. 65. ARIMETCO INTERNATIONAL INCORPORATED. 1995 ANNUAL REPORT. P.11.

Reference (Reserve-Resource): Giralia Resources NL, 2004, AGM Presentation, 25 November, 2004, 26 p.: www.giralia.com.au/pdf/asx/AGMPresentationNov%202004.pdf

Reference (Deposit): EINAUDI, M. DESCRIPTION OF SKARNS ASSOCIATED WITH PORPHYRY COPPER PLUTONS. PAPER IN ADVANCES IN GEOLOGY OF THE PORPHYRY COPPER DEPOSITS, SOUTHWESTERN NORTH AMERICA, ED. BY S. R. TITLEY. UNIV. AZ PRESS, TUCSON, AZ, 1982, PP. 145-148.

Reference (Deposit): SECURITY AND EXCHANGE COMMISSION. FORM S-14 (STOCK REGISTRATION FORM). 1976, P. 60,67.

Reference (Deposit): U.S. DEPARTMENT OF COMMERCE NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION. MONTHLY NORMALS OF TEMPERATURE, PRECIP., AND HEATING AND COOLING DEGREE DAYS 1941-70, 1973, 10 P.

Reference (Deposit): Dilles, J.H., and Proffett, J.M., 1995, Metallogenesis of the Yerington batholith, Nevada, in Pierce, F.W., and Bolm, J.G., eds., Porphyry copper deposits of the American Cordillera: Tucson, Arizona Geological Society Digest 20, p. 306?315.

Reference (Deposit): Albino, G.V., 1995, Porphyry copper deposits of the Great Basin?Nevada, Utah, and adjacent California, in Pierce, F.W., and Bolm, J.G., eds, Porphyry copper deposits of the American Cordillera: Tucson, Arizona Geological Society Digest 20, p. 267?296.

Reference (Deposit): Pacific Magnesium Corp. Ltd., 2006, Ann Mason copper deposit ? new results, 4 p.: www.pacmag.com.au/aurora/assets/user_content/File/010606annmasonresults.pdf

Reference (Geology): Seedorff, E., Barton, M. , Stavast, W. and Maher D., 2008, Root Zones of Porphyry Systems: Extending the Porphyry Model to Depth: Econ. Geol. Vol 103 no, 5 p. 939-956

Reference (Deposit): 2006 press release

Reference (Geology): Proffett, J.M., Jr., and Dilles, J.H., 1984, Geologic map of the Yerington district, Nevada: Nevada Bureau of Mines and Geology Map 77, scale 1:24,000.

Reference (Deposit): Einaudi, Marco T., 1994, 6-km Vertical Cross Section Through Porphyry Copper Deposits, Yerington District, Nevada: Multiple Intrusions, Fluids, and Metal Sources; Society of Economic Geologists International Exchange Lecture - June 1994.Giralia Resources NL website, 2005, http://www.giralia.com.au/activities/annmason.htm
URL: http://www.giralia.com.au/activities/annmason.htm

Reference (Deposit): Dilles, J. H., and Einaudi, M. T., 1992, Wall-rock alteration and hydrothermal flow paths about the Ann-Mason porphyry copper deposit, Nevada--A 6 km vertical reconstruction: Economic Geology, v. 87, p. 1963-2001.

Reference (Deposit): Dilles, John H., 2002, Magmatic-Hydrothermal Fluids: A Summary of Temporal and Spatial Evolution from the 6 km Vertical Transect of the Porphyry Copper Systems in the Yerington Batholith, Nevada; GSA Abstracts with Programs.

Reference (Deposit): Dilles, J. H., Solomon, G.C., Taylor, H.P., Jr., and Einaudi, M.T., 1992, Oxygen and hydrogen isotope characteristics of the Ann-Mason porphyry copper deposit, Yerington district, Nevada: Economic Geology, v. 87, no. 1, p. 44-63.

Reference (Deposit): Dilles, John H., 1983, The petrology and geochemistry of the Yerington batholith and the Ann-Mason porphyry copper deposit, western Nevada, Ph.D. Thesis, Stanford University, CA.

Reference (Deposit): Dilles, J.H., Proffett, J.M., and Einaudi, M.T., 2000, Field Trip Day 2: Magmatic and hydrothermal features of the Yerington batholith with emphasis on the porphyry Cu-(Mo) deposit in the Ann-Mason area: in Thompson, T.B. ed., Society of Economic Geologists, Guidebook 32, p. 67-90.

Reference (Deposit): American Mines Handbook 1994

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.

---

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.