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Mahoney

Past Producer in Alaska, United States with commodities Lead, Zinc, Silver, Gold, Cadmium, Copper
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Sections on this page
  1. Identification information
  2. Geographic coordinates
  3. Site location context
  4. Geographic areas
  5. Commodities
  6. Materials information
  7. Host and associated rocks
  8. Nearby scientific data
  9. Economic information about the deposit and operations
  10. Mining district
  11. Reserves and resources
  12. Links to other databases
  13. Bibliographic references
  14. General comments
  15. Reporter information

Geologic information

Identification information

Deposit ID 10001580
MRDS ID A012333
Record type Site
Current site name Mahoney
Alternate or previous names Ash, Asche
Related records 10161186

Geographic coordinates

Geographic coordinates: -131.50983, 55.4278 (WGS84)
Relative position The Mahoney mine is less than 100 feet above sea level on the west shore of George Inlet. It is on the north side of the mouth of the creek draining Mahoney Lake. The site is in section 25, T. 74 S., R. 91 E., of the Copper River Meridian. It corresponds to loc. 76 in Elliott and others (1978), and to loc. 293 in Maas and others (1995). The location is accurate within a few hundred feet. ? Also see Additional comments.

Site location context

Political divisions (FIPS codes)

Ketchikan Gateway(Borough)

Alaska(state)

United States(country)

North America(continent)

Land(continent)

USGS map quadrangles

Ketchikan B-5(quadrangle 1:63,360 scale)

Ketchikan SW(quadrangle 1:100,000 scale)

Ketchikan(quadrangle 1:250,000 scale)

Hydrologic units (watersheds)

Ketchikan(hydrologic unit)

Southern Southeast Alaska(hydrologic accounting unit)

Southeast Alaska(hydrologic subregion)

Alaska(hydrologic region)

Federal lands

Tongass National Forest(National Forest)

National Forest FS(Type of land area)

FS(Federal land areas administered by FS)

Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Lead Primary
Zinc Critical Primary
Silver Secondary
Gold Secondary
Cadmium Secondary
Copper Secondary

Materials information

Materials Type of material
Galena Ore
Sphalerite Ore
Calcite Gangue
Quartz Gangue

Host and associated rocks

  • Host or associated Associated
    Rock type Plutonic Rock
  • Host or associated Host
    Rock type Metamorphic Rock > Schist

Nearby scientific data

(1) -131.50983, 55.4278
ListMap

Economic information

Comments on the geologic information

  • Geologic Description = The country rocks in this part of Revillagigedo Island are marine, pelitic phyllite and schist that are intruded by Cretaceous stocks, sills, and dikes of feldspar-porphyritic granodiorite, and by a stock and probably related plugs of Tertiary gabbro (Berg and others, 1988). The strata and some of the granodiorite were regionally metamorphosed to greenschist grade in Late Cretaceous time. These regionally metamorphosed rocks subsequently were locally contact metamorphosed to hornblende hornfels near the contacts of Cretaceous granodiorite plutons that were emplaced after the regional metamorphism, and then more widely remetamorposed to hornblende hornfels near the contacts of the Tertiary gabbro. The premetamorphic age range of the pelitic strata is uncertain. Berg and others (1988) assign them a Mesozoic or (Late) Paleozoic age; Brew and Ford (1998) and Crawford and others (in press) assign them to the Gravina belt, of Late Jurassic or Cretaceous age.? the Mahoney deposit consists of a pod or lens 6 inches to 3 feet thick and 350 feet long of massive sphalerite and galena, accompanied by interstitial quartz and calcite. The orebody formed by fracture filling in, and by minor replacement of, dark gray, graphitic, slaty to phyllitic metapelite (Robinson and Twenhofel, 1953; Cobb and Elliott, 1980, p. 71). The metapelite locally is intruded by feldspar-porphyritic dikes or sills. ? Maas and others (1995, p. 203-204) note that the deposit has a shallow dip and is slightly discordant to the gently-dipping foliation of the phyllite hostrock. The orebody thickens from west to east and its dip steepens from 17 to 54 degrees. They believe that the deposit was emplaced along a fault, or, more likely, that there has been fault movement along the boundary of the soft sulfides and the relatively hard phyllite. Where the massive sulfides are not present, the fault zone is filled with quartz and crushed phyllite.? the Mahoney deposit was discovered in the early 1900s and originally referred to as the Asche claim (Brooks, 1902, p. 63). The mine was developed mainly in the 1940s and included more than 600 feet of underground workings, along with several surface pits and trenches (Maas and others, 1995, p. 202). From 1947 to 1949, total recovery from about 400-500 tons of ore was 33.1 metric tons (mt) of Zn, 18.1 mt of Pb, 1.27 mt of Cu, 11.6 kg of Ag, and 0.25 kg of Au (Maas and others, 1995, p, 202). Resources are estimated at 2,500 tons of material averaging 6-7% Pb and about 28% Zn (Robinson and Twenhofel, 1953; Cobb and Elliott, 1980, p. 71).? Maas and others (1995, p. 210) collected one-foot-wide samples across the deposit for the first 118 feet of the main adit. These samples averaged 3.2% Pb, 7.6% Zn, and 25.5 ppm Ag. The weighted average of assays of 1.4-foot-long samples along 60 feet of the richest ore was 20.1% Zn, 8.0% Pb, 61 ppm Ag, and 0.69 ppm Au (Maas and others, p. 204). Some samples also contained up to 1200 ppm Cd. Maas and others' sampling showed a direct correlation between high lead and silver values.

Economic information about the deposit and operations

Development status Past Producer
Commodity type Metallic

Mining district

District name Ketchikan

Comments on the production information

  • Production Notes = From 1947 to 1949, total recovery from about 400-500 tons of ore was 33.1 metric tons (mt) of Zn, 18.1 mt of Pb, 1.27 mt of Cu, 11.6 kg of Ag, and 0.25 kg of Au (Maas and others, 1995, p, 202). Resources are estimated at 2,500 tons of material averaging 6-7% Pb and about 28% Zn (Cobb and Elliott, 1980, p. 71).

Reserves and resources

  • Type In-situ
    Estimate year 1953
    Remarks Entry carried over from Old MRDS or added later (i.e. it did not originate in ARDF)
    Commodity Subtype Grade units Group Importance Year
    Zinc Zn 28 wt-pct Zinc Major 1953
    Lead Pb 6 wt-pct Lead Major 1953

Comments on the reserve resource information

  • Reserves = Resources are estimated at 2,500 tons of material averaging 6-7% Pb and about 28% Zn (Robinson and Twenhofel, 1953; Cobb and Elliott, 1980, p. 71).

Comments on the workings information

  • Workings / Exploration = The Mahoney deposit was discovered in the early 1900s and originally referred to as the Asche claim (Brooks, 1902, p. 63). The mine was developed mainly in the 1940s and included more than 600 feet of underground workings, along with several surface pits and trenches (Maas and others, 1995, p. 202). From 1947-49, total recovery from about 400-500 tons of ore was 33.1 metric tons (mt) of Zn, 18.1 mt of Pb, 1.27 mt of Cu, 11.6 kg of Ag, and 0.25 kg of Au (Maas and others, 1995, p, 202). ? Maas and others (1995, p. 210) collected one-foot-wide samples across the deposit for the first 118 feet of the main adit. These samples averaged 3.2% Pb, 7.6% Zn, 25.5 ppm Ag. The weighted average of assays of 1.4-foot-long samples along 60 feet of the richest ore was 20.1% Zn, 8.0% Pb, 61 ppm Ag, and 0.69 ppm Au (Maas and others, p. 204). Some samples also contained up to 1200 ppm Cd. Maas and others' sampling showed a direct correlation between high lead and silver values.

Reference information

Bibliographic references

Comments on the references

  • Primary Reference = Robinson and Twenhofel, 1953; Maas and others, 1995

General comments

Subject category Comment text
Deposit Model Name = Stratiform, massive-sulfide replacement body
Deposit Other Comments = Early reports refer to this property as the Asche, or Ash, claim (Brooks, 1902, p. 63-64; Cobb and Elliott, 1980, p. 71).

Reporter information

Type Date Name Affiliation Comment
Reporter 03-JUL-99 H.C. Berg U.S. Geological Survey

Beyond USGS

Supplemental information added by qvyshift.com. Not part of the original USGS MRDS record.

External references

Maps centered on this site

Authoritative Alaska resources

These are landing pages for further research — the state agencies don't currently expose per-mine deep links.