Unnamed (on Portage Creek)

The Unnamed (on Portage Creek) is a copper, gold, and molybdenum mine located in Alaska.

About the MRDS Data:

All mine locations were obtained from the USGS Mineral Resources Data System. The locations and other information in this database have not been verified for accuracy. It should be assumed that all mines are on private property.

Mine Info

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Site Name

Primary: Unnamed (on Portage Creek)

Commodity

Primary: Copper
Primary: Gold
Primary: Molybdenum
Secondary: Arsenic

Location

State: Alaska
District: Yentna

Land Status

Not available

Holdings

Not available

Workings

Not available

Ownership

Not available

Production

Not available

Deposit

Record Type: Site
Operation Category: Occurrence
Operation Type: Unknown
Years of Production:
Organization:
Significant:

Physiography

Not available

Mineral Deposit Model

Model Name: Porphyry Cu

Orebody

Not available

Structure

Not available

Alterations

Not available

Rocks

Not available

Analytical Data

Not available

Materials

Ore: Pyrite
Ore: Molybdenite
Ore: Gold
Ore: Chalcopyrite
Ore: Arsenopyrite

Comments

Comment (Geology): 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a porphyritic phase with potassium feldspar phenocrysts up to 10 millimeters in size (Cominco American Incorporated, unpublished report). Cominco American Incorporated (unpublished report) describes chalcopyrite, pyrrhotite, arsenopyrite, molybdenite and pyrite as joint coatings, in veins, and as disseminations adjacent to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.

Comment (Reference): Primary Reference = This record

Comment (Geology): 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.

Comment (Workings): 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).

Comment (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).

References

Reference (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.

Reference (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.

Reference (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.

Reference (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.

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