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Purches Creek

Occurrence in Alaska, United States with commodities Gold, Silver, 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. Alteration
  8. Mineral occurrence model information
  9. Nearby scientific data
  10. Economic information about the deposit and operations
  11. Mining district
  12. Links to other databases
  13. Bibliographic references
  14. General comments
  15. Reporter information

Geologic information

Identification information

Deposit ID 10000936
MRDS ID A011605
Record type Site
Current site name Purches Creek
Alternate or previous names Purchase Creek

Geographic coordinates

Geographic coordinates: -149.35269, 61.80956 (WGS84)
Relative position 1,000 ft northwest of the head of Craigie Creek. Accurate within 2,500 ft. Locality 4 and 5 of Capps and Tuck (1935) and locality 7 of Cobb (1972).

Site location context

Political divisions (FIPS codes)

Matanuska-Susitna(Borough)

Alaska(state)

United States(country)

North America(continent)

Land(continent)

USGS map quadrangles

Anchorage D-7(quadrangle 1:63,360 scale)

Anchorage NW(quadrangle 1:100,000 scale)

Anchorage(quadrangle 1:250,000 scale)

Hydrologic units (watersheds)

Lower Susitna River(hydrologic unit)

Susitna River(hydrologic accounting unit)

South Central Alaska(hydrologic subregion)

Alaska(hydrologic region)

Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Gold Primary
Silver Secondary
Copper Secondary

Materials information

Materials Type of material
Chalcopyrite Ore
Gold Ore
Pyrite Ore
Silver Ore
Quartz Gangue

Alteration

  • (Local) Wall-rock alteration within a few inches of the veins is intense, but seldom extends more than 10 to 12 inches beyond the quartz filling. Sericitization and carbonate alteration predominate, but there is some pyritization and in the outer parts of the alteration zone chloritization is present (Ray, 1954).

Mineral occurrence model information

Model code 273
USGS model code 36a
Deposit model name Low-sulfide Au-quartz vein
Mark3 model number 27

Nearby scientific data

(1) -149.35269, 61.80956
ListMap

Economic information

Comments on the geologic information

  • Geologic Description = Two occurrences were reported by Capps and Tuck (1935). The first is a quartz vein exposed in a tributary on the divide between Craigie Creek and Purches Creek drainages (Capps and Tuck locality 4). The vein is 1 ft wide, strikes S 20 W, and dips 30 S, and can be traced for several hundred feet. It is composed of 'bull' quartz and contains chalcopyrite, gold, and silver. The second occurrence is a crushed piece of quartz float from the next tributary to the west (Capps and Tuck locality 5). It contained disseminated pyrite, gold, and silver. At the first locality described above, assays show the vein to contain 0.16 oz/ton Au and 0.2 oz/ton Ag. At the second locality described, the quartz float assayed 0.01 oz/ton Au and 0.2 oz/ton Ag.? These occurrences are located near the contact of the Willow Creek Pluton and an early Paleocene and Late Cretaceous granite body. The Willow Creek Pluton is a Late Cretaceous zoned pluton: the outer part consists of hornblende quartz diorite and lesser hornblende tonalite; the core consists of hornblende-biotite granodiorite, and lesser hornblende-biotite quartz monzodiorite and biotite quartz monzonite. The early Paleocene and Late Cretaceous granite is generally a biotite-muscovite granite with granodiorite and lesser quartz monzonite. Wall-rock alteration within a few inches of the veins is intense, but seldom extends more than 10 to 12 inches beyond the quartz filling. Sericitization and carbonate alteration predominate, but there is some pyritization and in the outer parts of the alteration zone chloritization is present (Ray, 1954).
  • Age = Late Cretaceous or younger based on the bedrock in the vicinity.

Economic information about the deposit and operations

Development status Occurrence
Commodity type Metallic

Comments on exploration

  • Status = Inactive

Mining district

District name Willow Creek

Comments on the workings information

  • Workings / Exploration = Two occurrences were sampled by Capps and Tuck (1935). At the first locality described above, assays show the vein to contain 0.16 oz/ton Au and 0.2 oz/ton Ag. At the second locality described, the quartz float assayed 0.01 oz/ton Au and 0.2 oz/ton Ag (Capps and Tuck, 1935).

Reference information

Bibliographic references

  • Deposit

    Capps, S.R., and Tuck, Ralph, 1935, The Willow Creek-Kashwitna District, Alaska: U.S. Geological Survey Bulletin 864-B, p. 95-113.

  • Deposit

    Cobb, E.H., 1979, Summary of references to mineral occurrences (other than mineral fuels and construction materials in the Anchorage quadrangle, Alaska: U.S. Geological Survey Open-File Report 79-1095, 184 p.

  • Deposit

    Cobb, E.H., 1972, Metallic mineral resources map of the Anchorage quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-409, 1 sheet, scale 1:250,000.

Comments on the references

  • Primary Reference = Capps and Tuck, 1935

General comments

Subject category Comment text
Deposit Model Name = Low-sulfide Au-quartz veins (Cox and Singer, 1986; model 36a)
Deposit Other Comments = Capps and Tuck (1935) also mention that on the lower Purches Creek there are numerous pegmatite dikes, but no minerals of value were found in them. Purches Creek has also been labeled Purchase Creek on some older maps.

Reporter information

Type Date Name Affiliation Comment
Reporter 30-JUL-1998 D.P. Bickerstaff U.S. Geological Survey
Reporter 30-JUL-1998 S.W. Huss U.S. Geological Survey

Beyond USGS

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

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.