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McMahon Ridge

Producer in Esmeralda county in Nevada, United States with commodities Gold, Silver, Copper, Lead, Bismuth, Potassium, Antimony, Tin
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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 10310418
MRDS ID W002900
Record type Site
Current site name McMahon Ridge
Related records 10310328, 10310417, 10310419, 60001656

Comments on the site 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.

Geographic coordinates

Geographic coordinates: -117.23341, 37.71023 (WGS84)
Elevation 1830
Relative position The deposit is located about 2.5 miles northeast of the historic mining town of Goldfield about 28 miles south of Tonopah, near the east border of Esmeralda County

Site location context

Political divisions (FIPS codes)

Esmeralda(county)

Nevada(state)

United States(country)

North America(continent)

Land(continent)

USGS map quadrangles

Goldfield(quadrangle 1:24,000 scale)

Goldfield(quadrangle 1:100,000 scale)

Goldfield(quadrangle 1:250,000 scale)

Hydrologic units (watersheds)

Ralston-Stone Cabin Valleys(hydrologic unit)

Central Nevada Desert Basins(hydrologic accounting unit)

Central Nevada Desert Basins(hydrologic subregion)

Great Basin(hydrologic region)

Geographic areas

Country State County
United States Nevada Esmeralda

Public Land Survey System information

Meridian Township Range Section Fraction State
Mount Diablo 003S 043E 319 20 Nevada

Comments on the location information

  • The McMahon Ridge Area is about two-and-a-half miles northeast of the town of Goldfield along a well-graded gravel road.

Commodities

Commodity Importance
Gold Primary
Silver Secondary
Copper Secondary
Lead Secondary
Bismuth Critical Tertiary
Potassium Tertiary
Antimony Critical Tertiary
Tin Critical Tertiary

Comments on the commodity information

  • Ore Materials: gold
  • Gangue Materials: quartz, alunite, barite, gypsum, limonite, kaolin

Materials information

Materials Type of material
Gold Ore
Quartz Gangue
Alunite Gangue
Barite Gangue
Gypsum Gangue
Limonite Gangue
Kaolin Gangue

Alteration

  • (Local) Large envelopes of intense argillic alteration surround most of the ore zones with silicification of core ore zones.

Mineral occurrence model information

Model code 154
USGS model code 25e
Deposit model name Epithermal quartz-alunite Au
Mark3 model number 38

Host and associated rocks

  • Host or associated Host
    Rock type Volcanic Rock (Aphanitic) > Felsic Volcanic Rock > Rhyodacite
    Rock type qualifier porphyritic
    Stratigraphic age (youngest) Tertiary
  • Host or associated Host
    Rock type Volcanic Rock (Aphanitic) > Intermediate Volcanic Rock > Andesite
    Rock unit name Milltown andesite
    Stratigraphic age (youngest) Miocene

Nearby scientific data

(1) -117.23341, 37.71023
ListMap

Economic information

Geologic structures

Type of structure Local
Structure 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 of structure Regional
Structure description Tertiary deposits are domed and faulted by steeply dipping post Miocene: N-S and E-W faults.

Ore body information

  • General form Irregular to tabular or knobby

Controls for ore emplacement

  • The ore-bearing structures are generally north-south trending and sub-parallel to the strike of the ring-fracture zone.

Comments on the geologic information

  • 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.

Economic information about the deposit and operations

Operation type Surface-Underground
Development status Producer
Commodity type Both
Deposit size Medium
Significant Yes
Discovery year 1902
Discoverer Harry Stimler & Wm Marsh
Year of first production 1904
Year of last production 1970
Production years 1904-1970s

Mining district

District name Goldfield District:

Land status

Ownership category Private
Area name Tonopah District BLM
Ownership category BLM Administrative Area

Ownership information

  • Type Owner-Operator
    Owner Metallic Ventures Inc.
    Year 2004

Comments on the workings information

  • Older workings were predominantly underground with later surface workings.

Comments on other 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.

Comments on 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.

Reference information

Bibliographic references

General comments

Subject category Comment text
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.

Reporter information

Type Date Name Affiliation Comment
Reporter 01-MAY-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.

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.