Mystery Mountains East

Prospect, Inactive

Commodities and mineralogy

Main commodities Cu
Other commodities Ag; As; Sb
Ore minerals arsenopyrite; chalcopyrite; pyrite; trace stibnite
Gangue minerals quartz; tourmaline

Geographic location

Quadrangle map, 1:250,000-scale MD
Quadrangle map, 1:63,360-scale C-4
Latitude 63.524
Longitude -154.56
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Mystery Mountains East prospect is situated on a steep southerly flank of a southwest facing valley about 2 miles (3.2 km) north of Cottonwood Creek at an elevation of 3,400 feet (1,036 m) in Section 2, T. 23 S., R. 22 E., of the Kateel River Meridian. Location is accurate to within 500 feet (152 m).

Geologic setting

Geologic description

The Mystery Mountains East prospect is one of a number of porphyry-like copper-gold prospects that occur along a seven mile (11 km) long, northeast trending belt through the central Mystery Mountains. Mineralization consists of tourmaline quartz veins, breccia veins, and fractures associated with small monzonite and quartz porphyry bodies hosted in biotite hornfels (DiMarchi and others, 1997). Sulfides include arsenopyrite, chalcopyrite, pyrite, and traces of stibnite, within a 600 feet by 600 feet (183 m by 183 m) area. The Mystery Mountain East prospect is inferred to be Late Cretaceous, based on isotopic ages from Mystery Mountains plutonic rocks (Moll and others, 1981). Surface grab samples from the Mystery Mountains East prospect ran as high as 830 ppm arsenic, 203 ppm copper, 2.0 ppm silver, but contained no gold (DiMarchi and others, 1997).
Geologic map unit (-154.562343083563, 63.5234030498256)
Mineral deposit model Porphyry Cu-Au (Cox and Singer, 1986; model 20c).
Mineral deposit model number 20c
Age of mineralization The Mystery Mountain East prospect is inferred to be Late Cretaceous, based on isotopic ages from Mystery Mountains plutonic rocks (Moll and others, 1981).
Alteration of deposit Biotite, tourmaline, and quartz.

Production and reserves

Workings or exploration WGM Inc. located a number of porphyry-like prospects in the Mystery Mountains during the late 1970s (Andrews, 1978). From 1988 to 1990, ACNC conducted detailed exploration work, which included an airborne geophysical survey. ASA Inc. continued work from 1991 to 1997. Surface grab samples from the Mystery Mountains East prospect ran as high as 830 ppm arsenic, 203 ppm copper, 2.0 ppm silver, but contained no gold (DiMarchi and others, 1997).
Indication of production None
Reserve estimates None.

Additional comments

See Copenhagen Hill (MD030), Frozen Creek (MD032), Tarn (MD027), and Pork Chop (MD031) prospects.

References

MRDS Number 10307778

References

Andrews, Tom, 1978, Summary of Progress, Doyon Project, Mystery Mountains (Block 10): Anchorage, Alaska, WGM Inc., 24 p. (Held by Doyon, Limited, Fairbanks, Alaska, as proprietary report 78-42).
DiMarchi, J.J., and Frantz, P.S., 1997, Annual Report for 1997-Doyon Option Lands, Block 10: ASA Inc.-Montague Gold Joint Venture Report, Volume II: Unpublished report, 189 p. (Report held by Doyon, Limited, Fairbanks, Alaska.)
Reporters Bundtzen, T.K. (Pacific Rim Geological Consulting)
Last report date 6/6/1998