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  3. Mineral Resource Data System (MRDS)

Unnamed (on Portage Creek)

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

Geologic information

Identification information

Deposit ID 10308453
Record type Site
Current site name Unnamed (on Portage Creek)

Geographic coordinates

Geographic coordinates: -152.90279, 62.00849 (WGS84)
Relative position This occurrence is located in Portage Creek at about 3100 feet in the southwest quarter of Section 11, T. 22 N., R. 20 W., of the Seward Meridian.

Site location context

Political divisions (FIPS codes)

Matanuska-Susitna(Borough)

Alaska(state)

United States(country)

North America(continent)

Land(continent)

USGS map quadrangles

Talkeetna A-6(quadrangle 1:63,360 scale)

Talkeetna SW(quadrangle 1:100,000 scale)

Talkeetna(quadrangle 1:250,000 scale)

Hydrologic units (watersheds)

Yentna 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
Copper Primary
Molybdenum Primary
Arsenic Critical Secondary

Materials information

Materials Type of material
Arsenopyrite Ore
Chalcopyrite Ore
Gold Ore
Molybdenite Ore
Pyrite Ore

Mineral occurrence model information

Model code 53
USGS model code 17
Deposit model name Porphyry Cu
Mark3 model number 4

Nearby scientific data

(1) -152.90279, 62.00849
ListMap

Economic information

Comments on the geologic information

  • Geologic Description = The area is underlain by Mesozoic marine sedimentary rocks (KJs) that are intruded by the granodiorite of Mount Estelle (Te) (Reed and Nelson, 1980). At this locality the granodiorite has a leucocratic equigranular phase and a porphyritic phase with potassium feldspar phenocrysts up to 10 millimeters in size (Cominco American Incorporated, unpublished report). Cominco American Incorporated (unpublished report) describes chalcopyrite, pyrrhotite, arsenopyrite, molybdenite and pyrite as joint coatings, in veins, and as disseminations adjacent to northwest-striking mineralized joint sets. Sulfide-bearing rock samples from this site contain gold which ranges from 60 ppb to greater than 1.0 oz/ton. Silver values are generally below detection (less than 0.4 ppm); however isolated values of up to 11 ppm were recorded. The granodiorite of Mt. Estelle probably reflects the same plutonic event as the composite plutons (Tcp) to the north described by Reed and Nelson (1980). Altered granodiorite float about 2 miles S72W of this location location contains gold-bearing veinlets of arsenopyrite and pyrite (TL063). Curtin, Karlson, O'Leary, Day, and McDanal (1978) report pan concentrate samples with visible gold from Quaternary gravels about one mile downstream from this locality at site TL052. Similar gold-sulfide veins are present in the Estelle pluton (TY019) to the south in the Tyonek quadrangle.
  • Age = Late Cretaceous/early Tertiary; mineralization is interpreted to be linked to the granodiorite of Mount Estelle (Te) for which Reed and Nelson (1980) give hornblende ages of about 65 and 66 m.y.

Economic information about the deposit and operations

Development status Occurrence

Mining district

District name Yentna

Comments on the workings information

  • Workings / Exploration = Rock chip sampling and mapping at 1:12,000 scale by Cominco American Incorporated was conducted in the late 1980's (unpublished report). Reconnaissance mapping, stream silt and pan concentrate sampling was done in the area by the U.S. Geological Survey (Reed and Elliot, 1970; Curtin, Karlson, O'Leary, Day, and McDanal, 1978; Reed and Nelson, 1980). Sulfide-bearing rock samples from this site contain gold which ranges from 60 ppb to greater than 1.0 oz/ton. Silver values are generally below detection (less than 0.4 ppm); however isolated values of up to 11 ppm were recorded (Cominco American Incorporated, unpublished report).

Reference information

Bibliographic references

  • Deposit

    Reed, B.L., and Elliot, R.L., 1970, Reconnaissance geologic map, analyses of bedrock and stream sediment samples, and an aeromagnetic map of parts of the southern Alaska Range: U.S. Geological Survey Open-file Report 70-271, 24 p., 4 plates, scale 1:250,000.

  • Deposit

    Curtin, G.C., Karlson, R.C., O'Leary, R.M., Day, G.W., and McDanal, S.K., 1978, Geochemical and generalized geologic map showing the distribution of gold and silver, Talkeetna quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-870-E, 2 sheets, scale 1:250,000.

  • Deposit

    Reed, B.L., Nelson, S.W., Curtin, G.C., and Singer, D.A., 1978, Mineral resources map of the Talkeetna Quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-870-D, 1 sheet, scale 1:250,000.

  • Deposit

    Reed, B.L., and Nelson, S.W., 1980, Geologic map of the Talkeetna quadrangle: U.S. Geological Survey Miscellaneous Investigations Map I-1174, scale 1:250,000.

Comments on the references

  • Primary Reference = This record

General comments

Subject category Comment text
Deposit Model Name = This occurrence does not specifically fit any of those defined by Cox and Singer (1986). It may be a variation of the Porphyry copper model (Cox and Singer, 1986; model 17).

Reporter information

Type Date Name Affiliation Comment
Reporter 10-AUG-98 Madelyn A. Millholland Millholland & Associates

Beyond USGS

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

Maps centered on this site

Authoritative Alaska resources

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