Horsfeld

Site Name

Primary: Horsfeld
Secondary: Horsfall

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Commodity

Primary: Copper
Secondary: Silver
Secondary: Molybdenum
Secondary: Gold

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Location

State: Alaska
District: Chisana

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Land Status

Not available

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Holdings

Type: Located Claim

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Workings

Not available

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Ownership

Owner Name: Oil Development Co. of Texas
Home Office: Texas
Info Year: 1984

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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: Y

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Physiography

Not available

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Mineral Deposit Model

Model Name: Porphyry Cu
Model Name: Porphyry Cu-Mo

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Orebody

Not available

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Structure

Not available

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Alterations

Alteration Type: L
Alteration Text: Argillic, propylitic. Central altered zone 200 m by 700 m characterized by K-feldspar, actinolite and magnetite.

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Rocks

Not available

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Analytical Data

Not available

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Materials

Ore: Magnetite
Ore: Pyrite
Ore: Chalcopyrite
Gangue: Actinolite
Gangue: Quartz
Unknown: Orthoclase
Unknown: Molybdenite
Unknown: Bornite

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Comments

Comment (Age): Mid-Cretaceous. The diorite of the Klein Creek pluton that hosts the deposits has a K/Ar date of 111 +/- 3.6 Ma (Richter, Lanphere, and Matson, 1975).

Comment (Geology): At the Horsfeld prospect, pyrite and chalcopyrite occur in quartz veinlets and as disseminations in monzonite and monzonite porphyry of the mid-Cretaceous, Klein Creek pluton (Richter and others, 1973; 1975). This porphyry copper and molybdenum deposit has a central 200- by 700-meter zone of potassium feldspar, actinolite, and magnetite alteration, and a 800- by 1,500-meter outer zone of unspecified hydrothermal alteration. Surface samples contain less than 0.5 percent copper, and average 0.10 percent copper and less than 0.01 percent molybdenum (Hollister and others, 1975; Richter and others, 1975). Gold and silver were detected in some surface samples (Matson and Richter, 1971 [OFR 71-202]). The deposit is estimated to contain 60 million tons with an average grade of 0.20 percent copper and very low amounts of molybdenum (Richter and others, 1975). The deposit is in the Klein Creek pluton near its contact with Jurassic or Cretaceous siliciclastic rocks; the associated hydrothermal alteration zone extends across this contact (Richter and others, 1973).

Comment (Workings): Surface exploration and some diamond drilling have been used to evaluated this deposit. Average grade from surface sampling: 0.10% Cu (all samples were below 0.5% Cu) and less than 0.10% Mo (Richter and others, 1975, USGS MF-655K, loc. 52). Au and Ag detected in analysis (Matson and Richter,, 1971, USGS OF 471, samples 148, 149).

Comment (General): One of 8 porphyry copper deposits which make up the known principal potential mineral resource of the Nabesna quadrangle. The prospect is in the Wrangell-St. Elias National Preserve.

Comment (Reference): Primary Reference = Richter, D.H., Lanphere, M.A., and Matson, N.A., Jr., 1975, Granite plutonism and metamorphism, eeastern Alaska Range, Alaska: Geological Society of American Bulletin, v. 86, p. 819-820.

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References

Reference (Deposit): MacKevett, E.M., Jr., and Holloway, C.D., 1977, Map showing metalliferous and selected nonmetalliferous mineral deposits in the eastern part of southern Alaska: U.S. Geological Survey Open-File Report 77-169-A, 99 p., 1 sheet, scale 1:1,000,000.

Reference (Deposit): Engineering & Mining Journal 7905, p.83, No. 144

Reference (Deposit): Richter, D.H., and Matson, N.A., Jr., comps., 1972, Metallic mineral resources map of the Nabesna Quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies 422, 1 sheet, scale 1:250,000.

Reference (Deposit): Matson, N.A., Jr., and Richter, D.H., 1971, Geochemical data from the Nabesna A-1 quadrangle, Alaska: U.S. Geological Survey Open-File Report 71-0202, 10 p.

Reference (Deposit): Cobb, E.H., and Richter, D.H., 1980, Summaries of data on and list of references to metallic and selected nonmetallic mineral deposits in the Nabesna quadrangle, Alaska: U.S. Geological Survey Open-File Report 80-927, 117 p.

Reference (Deposit): Richter, D.H., Lanphere, M.A., and Matson, N.A., Jr., 1975, Granite plutonism and metamorphism, eeastern Alaska Range, Alaska: Geological Society of American Bulletin, v. 86, p. 819-820.

Reference (Deposit): Hollister, V.F., Anzalone, S.A., and Richter, D.H., 1975, Porphyry copper belts of southern Alaska and contiguous Yukon Territory: CIM (Canadian Mining and Metallurgical) Bulletin, v. 68, no. 756, p. 104-112.

Reference (Reserve-Resource): Engineering & Mining Journal 7905, p. 83
Pages: 83

Reference (Deposit): Matson, N.A., and Richter, D.H., 1971, Geochemical data from the Nabesna A-1 quadrangle, Alaska: U.S. Geological Survey Open-File Report 71-0202, 10 p.

Reference (Reference): Primary reference = Richter, D.H., Singer, D.A., and Cox, D.P., 1975, Mineral resources map of the Nabesna quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-655-K, 1 sheet, scale 1:250,000.

Reference (Deposit): Richter, D.H., Singer, D.A., and Cox, D.P., 1975, Mineral resources map of the Nabesna quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-655-K, scale 1:250,000.

Reference (Deposit): Richter, D.H., Matson, N.A., Jr., and Smoll, H.R., 1973, Reconnaissance geologic map of the Nabesna A-1 quadrangle, Alaska: U.S. Geological Survey Miscellaneous Investigations Series Map 1-807, scale 1:63,360.

Reference (Deposit): MTA 82 No. E-55

Reference (Ownership): Alaska Kardex 078-106

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