Latitude: 56°30'59"N
Longitude: 132°3'39"W
Location: The AMAX Molybdenum prospect consists of 4 deep holes drilled between 1976 and 1981 by Amax Exploration Inc. The holes extend along a line about 5,000 feet long trending about N 40 W. The location is at about the center of this line of holes, near the site of one of the holes. Still and others (2002) locate the holes precisely on their Plate 3. The center of the line of holes is at an elevation of about 3,000 feet about 1.3 miles southwest of Mount Waters and about 0.6 mile south-southwest of the center of section 6, T. 62 S., R. 85 E., in Groundhog Basin. The location is accurate.
Geology: The rocks in the prospect area are part of a belt of Mesozoic or Paleozoic sedimentary and volcanic rocks that have been metamorphosed to schist and gneiss. The belt is about 1 1/2 mile wide and strikes northwest (Brew, 1997; George and Wyckoff, 1973). The metamorphic rocks are bounded on the east by a thick, regionally extensive, 60 to 70 Ma tonalite sill and on the west by a 90 Ma granodiorite pluton (Brew, 1997 Still and others, 2002). On the north side of Groundhog Basin adjacent to the lines of drill holes that define this prospect, the metamorphic rocks are intruded by a 16.3 Ma biotite 'tin' granite pluton about 1,000 by 2,0000 feet in size. The granite is probably the source of the numerous rhyolite dikes and sills that extend from it and the mineralization in the area (Newberry and Brew, 1989). From 1976 to 1981, AMAX Exploration Inc. drilled four holes, 506 to 2,727 feet deep, to test the molybdenum potential of the small biotite granite exposed on the ridge northeast of the drill holes. During surface mapping in the area, AMAX collected samples that contained up to 5,000 parts per million (ppm) molybdenum in the biotite granite stock and gneiss (AMAX Exploration Inc., 1981a, 1981b). The mineralization consists of thin fractures with molybdenite in the granite and gneiss. The molybdenite is associated with quartz and fluorite in stringers and vugs, sericite-chlorite alteration, and some tungsten in the assays. The four holes that AMAX drilled were oriented to penetrate the granite at depth and three of the holes did so. Mineralization was cut in several of the holes but the best interval contained only 69 parts per million molybdenum. Still and others (2002) examined the area as part of a Bureau of Land Management mineral assessment of the area but their work was confined to a few surface samples.
Workings: From 1976 to 1981, AMAX Exploration Inc. drilled four holes, 506 to 2,727 feet deep, to test the molybdenum potential of the small biotite granite pluton exposed on the ridge northeast of the drill holes. They also did considerable surface mapping in the area. A few surface samples collected by Still and others (2002).
Age: Associated with a 16.3 Ma granite.
Alteration: The molybdenite is associated with quartz and fluorite in stringers and vugs and sericite-chlorite alteration.
Reserves: None.
Commodities (Major) - Mo; (Minor) - W
Development Status: None
Deposit Model: Porphyry molybdenum.
References
AMAX Exploration Inc., 1981a, Ground Hog Basin project geochemical maps, 2 sheets (Unpublished maps on file at the Minerals Information Center, Bureau of Land Management, Juneau, Alaska). AMAX Exploration Inc., 1981b, Whistlepig property sample location map, 1 sheet, scale 1:12,000 (Unpublished report on file at the Minerals Information Center, Bureau of Land Management, Juneau, Alaska). George, R.H., and Wyckoff, B.S., 1973, Whistlepig mineral exploration program, Alaska, Final report 1972 (with attached diamond drill hole logs and analyses): Unpublished El Pas National Gas Company report 109 p. 12 sheets (available at the Bureau of Land Management, Minerals Information Center, Juneau Alaska). Newberry, R.J., and Brew, D.A., 1989, Epigenetic hydrothermal origin of the Groundhog Basin-Glacier Basin silver-tin-lead-zinc deposits, southeastern Alaska: U.S. Geological Survey Bulletin 1903, p. 113-121. Still, J.C., Bittenbender, P.E., Bean, K.W., and Gensler, E.G., 2002 Mineral assessment of the Stikine area, central Southeast Alaska: U.S. Bureau of Land Management Technical Report 51, 560 p.
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