The Unnamed (on Threesome Mountain) is a molybdenum and tungsten 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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Unnamed (on Threesome Mountain) MRDS details
Site Name
Primary: Unnamed (on Threesome Mountain)
Commodity
Primary: Molybdenum
Primary: Tungsten
Secondary: Copper
Secondary: Silver
Location
State: Alaska
District: Juneau
Land Status
Not available
Holdings
Not available
Workings
Not available
Ownership
Not available
Production
Not available
Deposit
Record Type: Site
Operation Category: Prospect
Operation Type: Unknown
Years of Production:
Organization:
Significant:
Physiography
Not available
Mineral Deposit Model
Model Name: Porphyry Mo, low-F
Model Name: W skarn
Orebody
Not available
Structure
Not available
Alterations
Alteration Type: L
Alteration Text: Local iron staining.
Rocks
Name: Diorite
Role: Associated
Age Type: Associated Rock
Age Young: Pliocene
Analytical Data
Not available
Materials
Ore: Chalcopyrite
Ore: Molybdenite
Ore: Scheelite
Gangue: Quartz
Comments
Comment (Geology): Age = Tertiary.
Comment (Exploration): Status = Inactive
Comment (Deposit): Model Name = Porphyry molybdenum-tungsten deposit, similar to W skarn and porphyry Mo of Cox and Singer (1986; model 14a and 21b). Associated tactite. Porphyry deposit is mainly mineralized fracture surface type.
Comment (Deposit): Model Number = 14a, 21b
Comment (Deposit): Other Comments = the deposit is in Glacier Bay National Park and Preserve.
Comment (Geology): Geologic Description = This molybdenum-tungsten prospect is in a terrane composed mainly of Paleozic sedimentary rocks. The prospect is east of a major fault that separates the Paleozoic strata from granitic rock of Mesozoic age. The fault is concealed by Brady Glacier and is inferred to control the course of Taylor Bay to the south (Brew and others, 1978). The deposit is of porphyry-type. Molybdenite and scheelite, with minor chalcopyrite, occur in the roof-zone of a Tertiary granodiorite stock that intrudes volcanic and sedimentary rocks (limestone) of Devonian age. The molybdenite and scheelite occur in quartz veins and as fracture coatings on joints in the intrusion. Molybdenum-bearing vein density measured by the U.S. Bureau of Mines (Kimball and others, 1978, p. C-253-C256) was about eight veins per 100 feet. The maximum observed vein thickness was 0.2 foot, with an average of about 0.08 foot. Mineralized veins and fractures strike east-northeast and dip from 25 to 76 degrees northwest. Selected vein samples contained as much as 2000 ppm molybdenum, 4917 ppm tungsten, 7 ppm silver, and 330 ppm copper. Iron-stained hornfels near the granitic stock contains as much as 200 ppm copper and 50 ppm tungsten. The deposit has been drilled, and is a resource on the order of 0.0X percent equivalent molybdenum.? Richer tactite deposits could occur in nearby contact zones between the stock and the limestone.
Comment (Reference): Primary Reference = Kimball and others, 1978
Comment (Workings): Workings / Exploration = The deposit was discovered by Alvenco, Inc. in 1968, who staked 24 claims to cover it. Alvenco drilled three diamond drill holes to evaluate the deposit. The grades were in the low 0.0X range molybdenum equivalent . Selected samples collected by the Bureau of Mines contained as much as 2000 ppm molybdenum and more than 4000 ppm tungsten (Kimball and others, 1968).
Comment (Commodity): Ore Material = silver mineral
References
Reference (Deposit): Cobb, E.H., 1981, Summaries of data on and lists of references to metallic and selected nonmetallic mineral occurrences in the Mt. Fairweather quadrangle, Alaska; Supplement to Open-file Report 78-316; Part A, Summaries of data to January 1, 1980: U.S. Geological Survey Open-File Report 81-249-A, 20 p.
Reference (Deposit): Cobb, E. H., 1981, Summaries of data and lists of references to metallic and selected non-metallic mineral occurrences in the Mt. Fairweather quadrangle, Alaska, Supplement to Open-file Report 78-316: U. S. Geological Survey Open-File Report 81-249B, 15 p.
Reference (Deposit): Kimball, A.L., Still, J.C., and Rataj, J.L., 1978, Mineral resources, in Brew, D. A., and others, Mineral resources of the Glacier Bay National Monument wilderness study area, Alaska: U.S. Geological Survey Open-File Report 78-494, p. C1-C375.
Reference (Deposit): Brew, D.A., Johnson, B.R., Grybeck, D., Griscom, A., Barnes, D.F., Kimball, A.L., Still, J.C., and Rataj, J.L., 1978, Mineral resources of the Glacier Bay National Monument Wilderness Study Area, Alaska: U.S. Geological Survey Open-File Report 78-494, 670 p.
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