MacArthur Copper Deposit

Site Name

Primary: MacArthur Copper Deposit

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Commodity

Primary: Copper

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Location

State: Nevada
County: Lyon
District: Yerington District

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Land Status

Land ownership: Private
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.

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Holdings

Not available

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Workings

Not available

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Ownership

Owner Name: Quaterra Resources Inc.
Info Year: 2006

Owner Name: Arimetco International, Inc.
Percent: 50.00
Home Office: Tuscon, AZ
Info Year: 1992

Owner Name: Holcorp Mines Ltd.
Percent: 50.00
Info Year: 1992

Owner Name: Anaconda Co.
Percent: 100.0
Info Year: 1975

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Production

Not available

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Deposit

Record Type: Deposit
Operation Category: Past Producer
Deposit Type: disseminated
Operation Type: Surface-Underground
Year First Production: 1995
Year Last Production: 1997
Years of Production:
Organization:
Significant: Y
Deposit Size: L

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Physiography

Not available

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Mineral Deposit Model

Model Name: Porphyry Cu

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Orebody

Not available

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Structure

Not available

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Alterations

Alteration Type: L
Alteration Text: Green-stained outcrops of copper-rich rock occur in the mine area.

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Rocks

Name: Granodiorite
Role: Associated
Age Type: Associated Rock
Age Young: Jurassic
Age Old: Triassic

Name: Quartz Monzonite
Role: Host
Age Type: Host Rock
Age Young: Jurassic
Age Old: Triassic

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Analytical Data

Analytical Data: As of 1976, 6.5 Mt of Oxide ore

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Materials

Ore: Chalcocite
Ore: Chalcopyrite
Gangue: Pyrite

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Comments

Comment (Development): Small-scale high-grade copper production began in 1943. The major period of porphyry copper exploration in the Yerington area began in the 1950s. The area was again extensively explored in the 1960s and in the 1970s Anaconda mined the main Yerington deposit. Copper mining in the historically active Yerington district in Lyon county ceased in the late 1970s. In 1992 Arimetco International Inc. of Tucson, AZ. acquired a 50% interest (Holcorp Mines Ltd. owned 50%) in the Yerington property and began mining. Arimetco mined, stacked and leached ore at a rate of almost 2 million tons annually. In 1994 Arimetco International produced 10 million pounds of copper from the Yerington mine, equal to 1993 production. This figure was expected to increase when production from the nearby MacArthur property began. Permits for development of the MacArthur copper deposit were finally received by Arimetco International and development of the deposit started. MacArthur crops out at the surface and contains estimated proven and probable oxide copper reserves of 97 million tons containing 0.21% Cu. Yerington mine had an open-pit oxide reserve of about 15 million tons averaging 0.32% copper at that time. In 1994, Arimetco entered into an agreement with Billiton Metals Inc. for Billiton to finance an expansion of the Yerington-MacArthur solvent extraction-electrowinning plant for cathode copper from 50,000 pounds per day to 80,000 pounds per day. Arimetco planned to complete the expansion by the end of 1994. Copper production increased by 30% from 1994 to 1995 as Arimetco, Inc. opened its new MacArthur Mine near its Yerington facility. 1995 copper production by Arimetco International Inc. from the Yerington and MacArthur Mines in Lyon County totaled almost 13 million pounds, up from 10 million pounds in 1994. In 1995, Arimetco International Inc. began operations at its MacArthur deposit from a 12-million-ton starter pit with an average grade of 0.33% copper. Ore was being trucked to leach facilities at Arimetco's nearby Yerington Mine. At the Yerington Mine, Arimetco planned to begin a 2-year project for dewatering the pit, preparatory to mining sulfide ore left by Anaconda, and permitting was underway for a 20,000 ton-per-day mining, crushing, and concentrating operation. Arimetco reported that the Yerington pit contained provable and developed sulfide ore of 50 million tons grading 0.49% copper with a 0.70:1 tripping ratio. Meanwhile, Arimetco was processing 18.5 million tons of low-grade oxide dump material by heap-leaching, yielding about 5,000 pounds of copper per day. In 1996, Copper production by Arimetco International Inc. from the Yerington and MacArthur Mines in Lyon County totaled 15 million pounds. In 1997 low copper prices caused Arimetco, Inc. to curtail mining at its MacArthur project after producing slightly over 10.5 million pounds from the combined Yerington operations in 1997. Quaterra Resources Inc acquired the MacArthur property and in 2006 planned to drill it and develop it. Quaterra began a first phase program consisting of data review and compilation in late 2006. During the first half of 2007 Quaterra plansa limited confirmation drilling program to validate the historic resource, calculate an oxide resource and complete a technical report. Drilling will also be initiated to determine the size and grade of the porphyry system beyond the pit boundaries.

Comment (Location): The MacArthur property is located about five miles NNW of the Yerington open pit copper mine in the Singatse Range about a mile south of Carson Hill.

Comment (Workings): The mine area is developed by extensive trenching and diamond drilling, open pit mine and heap leach operation

Comment (Economic Factors): In 1994, MacArthur was reported to contain an estimated proven and probable oxide copper reserve of 97 million tons containing 0.21% Cu. In 1995, MacArthur was reported to contain an estimated 51 million tons of oxide copper ore with an average grade of 0.26% copper. In 2006, the MacArthur oxide deposit was reported to contain a remainng resource of 29 million tons grading 0.28% copper, including 13 million tons of +0.40% copper.

Comment (Identification): All material in earlier MRDS record N000424 has been incorporated into the current record, as well as additional new information.

Comment (Commodity): Ore Materials: chalcocite, chalcopyrite

Comment (Commodity): Gangue Materials: pyrite

Comment (Deposit): The MacArthur mine occurs in a quartz monzonite intrusive of Jurassic age that has been intruded by a series of northwesterly-trending steeply dipping quartz monzonite porphyry, rhyolite and andesite dikes. The copper mineralization is zoned, with a chalcopyrite-rich (low iron to copper ratio) eastern area grading into a pyrite halo (high iron to copper ratio) to the north and west. Oxide mineralization overlies the chalcopyrite-rich area and consists of copper oxides and silicates (malachite, chrysocolla), copper wad and iron oxides

Comment (Development): A MAJOR EXPLORATION IN 1950. AREA WAS AGAIN EXTENSIVELY EXPLORED IN THE 1960'S AND 1975. ; ECON.COM: PRODUCTION : 14 CARLOADS OF ORE, AVERAGING 1.22 PERCENT COPPER, WAS SHIPPED IN 1943. ARIMETCO SAYS THAT ORES WILL BE MINED, STACKED AND LEACHED AT A RATE OF ALMOST 2 MILLION TONS ANNUALLY TO PRODUCE 4,400 TONS OF COPPER. WHEN PROJECT DEVELOPMENT IS COMPLETED IT WILL ADD 6.4 TONS PER DAY TO YERINGTON'S CURRENT RATE OF 12 TONS PER DAY. ( ROBERTO,1992)

Comment (Deposit): SAMPLE 4414 WAS A RANDOM SAMPLE FROM THE NORTH-SOUTH TRENCHES. SAMPLE 4415 WAS FROM ONE OF THE INCLINES SUNK ON A QUARTZ VEIN IN THE NORTHERN PART OF THE DEPOSIT.

Comment (Deposit): AT THE SURFACE, THE DEPOSIT HAS A WIDESPREAD IRON-OXIDE CAPPING WITH MANY GREEN STAINED OUTCROPS OF COPPER COVERING AN AREA ABOUT ONE-HALF MILE WIDE.

Comment (Workings): EXTENSIVE TRENCHING AND DIAMOND DRILLING. HEAP LEACH.

Comment (Commodity): Associated Minerals: actinolite, azurite/malachite, biotite, chalcocite, chalcopyrite, chrysocolla, goethite/limonite, pyrite, tenorite

Comment (Commodity): Associated Rock: granite porphyry, quartz monzonite porphyry;argillite, gypsum, ignimbrite, rhyolite, sandstone, volcaniclastic rocks;andesite, granite, hornfels, quartz monzonite, skarn

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References

Reference (Deposit): Anonymous, 1994, MacArthur permits in hand; The Northern Miner, January 3 issue, p. 3.

Reference (Deposit): Northern Miner, 5/15/95.

Reference (Deposit): Jurassic Magmatism and Metal Deposits in Western Nevada, 2002, Spring Field Trip Guidebook, Geological Society of Nevada Special Publication No. 35.

Reference (Deposit): Anonymous, 1993e, Arimetco boosts MacArthur interest: The Northern Miner, May 31, p. 6.

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): 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): Einaudi, M.T., 1982, Description of skarns associated with porphyry copper plutons, in Titley, S.R., ed., Advances in geology of the porphyry copper deposits, southwestern North America: Tucson, University of Arizona Press, p. 139-183.

Reference (Deposit): Heatwole, D.A., 1978, Controls of oxide copper mineralization, MacArthur property, Lyon County, Nevada: Arizona Geological Society Digest, v. 11, Tucson, p. 59?66.

Reference (Reserve-Resource): Arimetco 1993 Annual Report

Reference (Deposit): Steininger, R.C., 1995, Great Basin, exploration review: SEG (Society of Economic Geologists) Newsletter, no. 22, July, p. 26.

Reference (Deposit): NBMG MI-1995.

Reference (Deposit): NBMG MI-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.

Reference (Deposit): Rocky Mountain Pay Dirt, 5/1/95

Reference (Deposit): Engineering & Mining Journal, 5/1/95

Reference (Deposit): Denver Mining Record, 8/31/94

Reference (Deposit): Skillings 9/19/92

Reference (Deposit): northern Miner Sept. 18, 1989 And Oct.7, 1991

Reference (Deposit): Roberto, Marguerite, 1992, USBM Minerals Today, Oct. 1992, p. 28.

Reference (Deposit): Telluride Claims, Yerington Mining District, Lyon County, Quade Visit Site 7-11-89,NBMG Unpublished Mining District Files (Tingley Files).

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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.