McMahon Ridge

Site Name

Primary: McMahon Ridge

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Commodity

Primary: Gold
Secondary: Silver
Secondary: Copper
Secondary: Lead
Tertiary: Potassium
Tertiary: Antimony
Tertiary: Tin
Tertiary: Bismuth

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Location

State: Nevada
County: Esmeralda
District: Goldfield 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.
Administrative Organization: Tonopah District BLM

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Holdings

Not available

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Workings

Not available

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Ownership

Owner Name: Metallic Ventures Inc.
Info Year: 2004

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Production

Not available

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Deposit

Record Type: Site
Operation Category: Producer
Deposit Type: silicified zones at shear intersections
Operation Type: Surface-Underground
Year First Production: 1904
Year Last Production: 1970
Discovery Year: 1902
Years of Production:
Organization:
Significant: Y
Deposit Size: M

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Physiography

Not available

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Mineral Deposit Model

Model Name: Epithermal quartz-alunite Au

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Orebody

Form: Irregular to tabular or knobby

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Structure

Type: L
Description: The most productive mines in Goldfield form an arcuate belt that trends generally north from the Goldfield Main District, then northeast through the Adams and Conqueror mines area, and then easterly through McMahon Ridge and Black Butte. This belt of gold deposits coincides with the western and northern limits of an inferred intrusive-related, ring-fracture system and is host to nearly all of the most productive gold ore bodies known in the District.

Type: R
Description: Tertiary deposits are domed and faulted by steeply dipping post Miocene: N-S and E-W faults.

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Alterations

Alteration Type: L
Alteration Text: Large envelopes of intense argillic alteration surround most of the ore zones with silicification of core ore zones.

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Rocks

Name: Andesite
Role: Host
Age Type: Host Rock
Age Young: Miocene

Name: Rhyodacite
Role: Host
Description: porphyritic
Age Type: Host Rock
Age Young: Tertiary

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Analytical Data

Not available

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Materials

Ore: Gold
Gangue: Gypsum
Gangue: Limonite
Gangue: Kaolin
Gangue: Quartz
Gangue: Alunite
Gangue: Barite

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Comments

Comment (Commodity): Ore Materials: gold

Comment (Commodity): Gangue Materials: quartz, alunite, barite, gypsum, limonite, kaolin

Comment (Deposit): The drill-defined part of the McMahon Ridge mineralized area has the following dimensions: 4,800 ft long and open, 800 ft down dip and open, and average 100 ft thick. The mineralized area at McMahon Ridge is formed by a series of east-west trending and northeast trending veins and breccia zones hosted by Milltown andesite. Almost all of the precious and base metal production recorded from the Goldfield mining district has come from rich epithermal bonanza ore bodies in the area northeast of the Goldfield town site. These ore bodies occur within silicified hydrothermal alteration zones. Mineralization in the argillized wall rock envelopes appears to be leakage zones emanating from core silicified zones. Ore zones are commonly associated with silicification and/or free quartz surrounded by large envelopes of intense argillic alteration. In the main district, gold-copper ores were found in a series of pipe-like shoots referred to locally as ledges, the most productive of which occurred where the east-west striking Goldfield structural trend intersects a mile-long arcuate section of inferred intrusive-related ring-fracture zone. Although the major ore bodies are hosted in a complex intersecting set of faults and fracture zones, the ore-bearing structures are generally north-south trending and sub-parallel to the strike of the ring-fracture zone in that location.

Comment (Geology): The Goldfield mining district is located at the site of a complex and long-lived igneous intrusive and volcanic center that is defined by eruptive vents and curviplanar faults. The local volcanic stratigraphy, a moderately well-defined ring-fracture zone, concentric structural doming, high sulfidation-style quartz-alunite hydrothermal alteration, and widespread copper-gold mineralization are all genetically related to the emplacement of a large dominantly andesitic igneous complex and the most significant components of which are late Oligocene to early Miocene in age.

Comment (Identification): This new record is for the current McMahon Ridge deposit of Metallic Ventures, which is one of three Metallic Ventures properties in the historic Goldfield District: Goldfield Main, McMahon Ridge, and Gemfield, each of which has its own record since they are separate and discrete deposits a few miles apart. The older MRDS record W002900 describes the historic Goldfield District.

Comment (Location): The McMahon Ridge Area is about two-and-a-half miles northeast of the town of Goldfield along a well-graded gravel road.

Comment (Workings): Older workings were predominantly underground with later surface workings.

Comment (Development): At McMahon Ridge, Metallic Ventures was running a 25,000-foot drilling program in 2004 and was planning to implement a feasibility study of the Gemfield and McMahon Ridge deposits by the third quarter of 2004. In April 2004, high-grade gold was intersected during infill drilling at McMahon Ridge and along structures in the main district at its Goldfield Project in Nevada. Highlights of the McMahon infill drilling include RC drill hole MCM-333 intersecting 30 ft grading 15.04 g/t Au including 5 ft grading 68.72 g/t Au, MCM-343 intersecting 115 ft grading 4.11 g/t Au including 5 ft grading 22.29 g/t Au, and MCM-344 intersecting 115 ft grading 15.09 g/t Au including 15 ft grading 98.4 g/t Au. The McMahon Ridge drill hole data base will be taken into a prefeasibility study whereby minable ounces of gold will be calculated in 2004.

Comment (Economic Factors): Historic recorded production from the main Goldfield district is 4,190,133 ounces of gold at an average 0.541 oz/ton gold, including about 160,800 ounces of gold from reworked tailings. 1994 reserves of the McMahon Ridge area were reported at 1.6 million tons of ore grading 0.45 opt Au.for a total of about 70,000 ounces of gold,but recent high grade drill results should expand these reserves in 2004.

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References

Reference (Deposit): Ransome, F. L. 1909, Geol. and Ore Deposits of Goldfield, Nev.: USGS Prof. Paper 66, 258 p.

Reference (Deposit): Searls, F. Jr., 1948, Geol and Ore Deposits of Goldfield, Nev.: Nevada Univ. Bull., v.42, no. 5, Geology and Mining Ser. 48, 24 p.

Reference (Deposit): Koschmann, A. H. and Bergendahl, M. H., 1968; Principal Gold Producing Districts of the United States: USGS Prof. Paper 610

Reference (Deposit): Spurr, J E, 1905, The Ores of Goldfield, Nev.: USGS Bull. No. 260, p. 132-139.

Reference (Deposit): Lincoln, F C, 1923, Mining Dist and Min. Res. Nev.: Reno, Nev. Newsletter Pub., p. 67-73

Reference (Deposit): Albers, J.P. and Stewart, J.H., 1972, Geology and Mineral Deposits of Esmeralda County, Nevada: NBMG Bull. 78, p. 67-69

Reference (Deposit): Steven Ristorcelli, Scott Hardy, and Neil Prenn, 2003, Geology and Mineralization of the Goldfield Area, Esmeralda,County, Nevada; Geological Society of Nevada Special Publication No. 37: Spring 2003 Field Trip Guidebook Gold Deposits of the Goldfield, Midway and Thunder Mountain Areas

Reference (Deposit): Internet website for Metallic Ventures Inc.

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): NBMG MI-80 through MI-99

Reference (Deposit): NBMG Map 91 1st, 2nd, 3rd

Reference (Deposit): MAS, 1984

Reference (Deposit): Amer. Mines (1990-2001)

Reference (Deposit): NBMG Bull 78

Reference (Deposit): www.romarco.com

Reference (Deposit): Metallic Ventures Inc., press release, 12/23/02.

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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.