Baultoff

Prospect, Inactive

Commodities and mineralogy

Main commodities Cu
Other commodities Ag; Au; Mo
Ore minerals chalcopyrite; pyrite
Gangue minerals albite; actinolite; quartz; sericite

Geographic location

Quadrangle map, 1:250,000-scale NB
Quadrangle map, 1:63,360-scale A-1
Latitude 62.111
Longitude -141.182
Nearby scientific data Find additional scientific data near this location
Location and accuracy This prospect is at an elevation of about 5,100 feet on a low ridge along the east side of a small south tributary valley to Baultoff Creek. It is 4,500 feet northwest of peak 6142 and 6,500 feet northeast of peak 7821. The site is in the SW1/4 of section 21, T. 4 N., R. 23 E. of the Copper River Meridian. This is locality 4 of Richter and others (1973), locality 53 of Richter and others (1975), and National Park Service locality WRST-87 (unpublished data). Cobb and Richter (1980) included this prospect under the name 'Baultoff'. It is located to within a few hundred feet.

Geologic setting

Geologic description

At the Baultoff prospect, disseminated pyrite and chalcopyrite occur in hornblende diorite and quartz porphyry of the mid-Cretaceous, Klein Creek pluton (Matson and Richter, 1971 [OFR 71-202]: Richter and others, 1975; Hollister and others, 1975). A 400- by 1,000-meter central altered zone is characterized by albite, chlorite, sericite and late anhydrite veins. It is within a 2,000- by 3,000-meter outer zone marked by abundant sericite and pyrite. Local actinolite veins and disseminations are present in the alteration zones. A post-mineralization fault bounds the alteration zone to the east. Surface samples contain less than 0.25 percent copper, and average 0.10 percent copper and less than 0.01 percent molybdenum (Richter and others, 1975). Low amounts of gold and silver are also present. The deposit is estimated to contain 160 million tons with an average grade of 0.20 percent copper and very low amounts of molybdenum (Richter and others, 1975). The diorite and porphyry that host the deposit are part of the Klein Creek pluton which has a K/Ar date of 111 +/- 3.6 Ma (Richter, Lanphere, and Matson, 1975).
Geologic map unit (-141.218036357552, 62.1050798117359)
Mineral deposit model Porphyry Cu-Mo (Cox and Singer, 1986; model 21a)
Mineral deposit model number 21a
Age of mineralization Mid-Cretaceous; the diorite and porphyry that host the deposit are part of the Klein Creek pluton which has a K/Ar date of 111 +/- 3.6 Ma (Richter, Lanphere, and Matson, 1975).
Alteration of deposit A 400- by 1,000-meter central altered zone is characterized by albite, chlorite, sericite and late anhydrite veins. It is within a 2,000- by 3,000-meter outer zone marked by abundant sericite and pyrite. Local actinolite veins and disseminations are present in the alteration zones. A post-mineralization fault bounds the alteration zone to the east (Richter and others, 1973).

Production and reserves

Workings or exploration Surface exploration and some diamond drilling have been used to evaluated this deposit.
Indication of production None
Reserve estimates The deposit is estimated to contain 160 million tons with an average grade of 0.20 percent copper and very low amounts of molybdenum (Richter and others, 1975).

Additional comments

The prospect is in the Wrangell-St. Elias National Preserve.

References

MRDS Number A011423

References

Hollister, V.F., Anzalone, S.A., and Richter, D.H., 1975, Porphyry copper belts of southern Alaska and contiguous Yukon Territory: Canadian Mining and Metallurgical Bulletin, v. 68, no. 756, p. 104-112.
Richter, D.H., Lanphere, M.A., and Matson, N.A., Jr., 1975, Granite plutonism and metamorphism, eastern Alaska Range, Alaska: Geological Society of American Bulletin, v. 86, p. 819-820.
Reporters Travis L. Hudson (Applied Geology)
Last report date 11/24/2002