Arnold

Site Name

Primary: Arnold

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Commodity

Primary: Gold
Secondary: Lead
Secondary: Tungsten
Secondary: Copper
Secondary: Molybdenum

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Location

State: Alaska
District: Marshall

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Land Status

Not available

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Holdings

Not available

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Workings

Not available

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Ownership

Not available

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Production

Not available

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Deposit

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

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Physiography

Not available

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Mineral Deposit Model

Model Name: Polymetallic veins

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Orebody

Not available

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Structure

Not available

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Alterations

Alteration Text: Silicification, oxidation, sericitization, iron-carbonate development, and potassic replacement(?).

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Rocks

Role: Host
Age Type: Host Rock
Age Young: Early Cretaceous

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Analytical Data

Not available

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Materials

Ore: Anglesite
Ore: Scheelite
Ore: Pyrrhotite
Ore: Pyrite
Ore: Molybdenite
Ore: Malachite
Ore: Magnetite
Ore: Hematite
Ore: Gold
Ore: Galena
Ore: Chalcopyrite
Gangue: Calcite
Gangue: Limonite
Gangue: Quartz

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Comments

Comment (Commodity): Gangue = iron carbonate

Comment (Production): Production Notes = A test shipment of high-grade material returned $80 per ton in 1915.

Comment (Exploration): Status = Active

Comment (Reference): Primary Reference = Turner, 1987

Comment (Workings): Workings / Exploration = The Arnold prospect has been explored with surface trenches, pits, and dozer cuts several times since it was first staked in 1914. Drilling has not been reported. Surface mapping and sampling was completed for Calista Corporation in the 1980's (Turner, 1987), and additional sampling, including a soil grid, was completed in 1997 (Bull and Schneider, 1997).

Comment (Geology): Geologic Description = The Arnold prospect was first staked in 1914 (Harrington, 1918). It has been explored with surface trenches and pits at several times since, but mining has not occurred. The deposit is quartz veins, quartz vein stockworks, and quartz-cemented breccia in pyrite-bearing mafic volcanic rocks intruded by quartz porphyry. As mapped by Turner (1987), the breccia is commonly in quartz porphyry but also includes greenstone fragments. The largest stockwork and (or) breccia zone is about 200 feet wide and 700 feet long, but exposure is mostly slope rubble. Most geologic units trend northwest, including well-developed shears and small faults; contacts are commonly slickensided. The quartz veins contain as much as 2 percent sulfide minerals, including chalcopyrite, galena, molybdenite, pyrite, pyrrhotite, and sphalerite. Other minerals in the veins include magnetite, hematite, anglesite, malachite, limonite, scheelite, and calcite. The best gold grades are in quartz veins. Selected quartz veins contain as much as 2.72 ounces of gold per ton but altered greenstone with or without quartz veins commonly contains a few tens to a few hundreds parts per billion gold (Turner, 1987). Homestake collected 78 rock, 5 stream sediment, and 70 soil samples in the general area, but almost all anomalous samples were from the Arnold prospect (Bull and Schneider, 1997). The anomalous rock and soil samples mostly contained a few tens to hundreds of parts per billion gold, although one quartz vein with visible gold contained 63.5 grams of gold per ton. Copper, in the 100 to 835 ppm range, was the element most commonly anomalous in these samples. Molybdenum, as much as 126 ppm, was locally anomalous, and lead, zinc, silver, antimony, and arsenic were present in low amounts in most of the samples. A reconnaissance examination of the prospect for radioactive minerals did not find any material containing more than 0.001 percent equivalent uranium (West, 1954). The general area is one where mafic volcanic rocks are intruded by a variety of intermediate to felsic igneous rocks (Hoare and Coonrad, 1959; Turner, 1987; Bull and Schneider, 1997). Mineralization appears to be dominantly associated with felsic intrusive rocks.

Comment (Deposit): Model Name = Polymetallic veins (Cox and Singer, 1986: model 22c)

Comment (Geology): Age = Cretaceous or Tertiary. The altered and mineralized host volcanic rocks are part of the Gemuk Group that includes rocks as young as Early Cretaceous (Hoare and Coonrad, 1959). The felsic intrusive rocks in the prospect area may be part of a Upper Cretaceous and Lower Tertiary suite of igneous rocks that are widespread in southwest Alaska (e.g., Box and others, 1993).

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References

Reference (Deposit): Hoare, J M., and Cobb, E.H., 1972, Metallic mineral resources map of the Russian Mission quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-444, 1 sheet, scale 1:250,000.

Reference (Deposit): Hoare, J.M., and Coonrad, W.L., 1959, Geology of the Russion Mission quadrangle, Alaska: U.S. Geological Survey Miscellaneous Geologic Investigations Map I-292, 1 sheet, scale 1:250,000.

Reference (Deposit): Bull, Katharine, and Schneider, Craig, 1997, 1997 Summary report for Calista Corporation: Unpublished report prepared for Calista Corporation, Anchorage, 10 pages plus tables.

Reference (Deposit): Box, S.E, Moll-Stalcup, E.J., Frost, T.P., and Murphy, J.M., 1993, Preliminary geologic map of the Bethel and southern Russian Mission quadrangles, southwestern Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-2226-A, 20 p., scale 1:250,000.

Reference (Deposit): Turner, T.R., 1987, The geology and geochemistry of the Arnold prospect, Marshall district, Alaska: Anchorage, Alaska, Calista Corporation, unpublished report, 13 p.

Reference (Deposit): West, W.S., 1954, Reconnaissance for radioactive deposits in the lower Yukon-Kuskokwim region, Alaska, 1952: U.S. Geological Survey Circular 328, 10 p.

Reference (Deposit): Hoare, J.M., and Cobb, E.H., 1977, Mineral occurrences (other than mineral fuels and construction materials) in the Bethel, Goodnews, and Russian Mission quadrangles, Alaska: U.S. Geological Survey Open-File Report 77-156, 98 p.

Reference (Deposit): Hoare, J M., and Cobb, E.H., 1972, Metallic mineral resources map of the Russian Mission quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-444, scale 1:250,000.

Reference (Deposit): Harrington, G.L., 1918, The Anvik-Andreafsky region, Alaska (including the Marshall district): U.S. Geological Survey Bulletin 683, 70 p.

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