Silver Creek

Prospect, Inactive

Commodities and mineralogy

Main commodities Ag
Other commodities Au; Cu; Pb; Zn
Ore minerals chalcopyrite; galena; limonite; malachite; pyrite; sphalerite; tetrahedrite
Gangue minerals carbonate; quartz

Geographic location

Quadrangle map, 1:250,000-scale GU
Quadrangle map, 1:63,360-scale C-1
Latitude 62.733
Longitude -144.055
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Silver Creek prospect (Cobb, 1979 [OFR 79-1247]) is at an elevation of about 2,800 feet in Silver Creek about 1/2 mile above its junction with Ahtell Creek . The location is number 8 of Richter (1966; fig. 5), locality 12 of Richter and Matson (1972), and locality 11 of MacKevett and Holloway (1977). The location is accurate to within 500 feet; it is the NW1/4SW1/4, section 14, T. 11 N., R. 7 E., Copper River Meridian.

Geologic setting

Geologic description

The Silver Creek prospect consists of highly altered, pyritic rock and veins that occur along cross-fractures to a major fault zone. The fault zone is 100 or more feet wide, strikes N 10-20 E and dips 65 to 80 degrees to the west. The fault appears to cut and displace a dike-like Jurassic(?) diorite that intrudes sedimentary and volcanic rocks of the Pennsylvanian to Permian, Slana Spur Formation (Richter 1964; 1966; Richter, Lanphere, and Matson, 1975; and Kirk Stanley, written communication, 2000).
Rocks within the fault zone are yellowish, carbonate- and gouge-rich hornfels that contain fine-grained disseminated pyrite. Quartz-carbonate veins as much as five-feet thick cross the fault zone; veins locally contain concentrations of galena, tetrahedrite, chalcopyrite, pyrite, and sphalerite. Limonite and malachite are abundant in near surface exposures (Thorne, 1946; Richter, 1966; Kirk Stanley, written communication, 2000).
Individual cross-veins described by Richter (1964; 1966, p. 32-33) strike NW and dip NE. Locally, they are enriched in silver, probably mainly in tetrahedrite. Thorne (1946, p. 8, fig. 4) reported that a one-foot-thick vein from the uppermost workings assayed a trace of gold, 17.5 ounces of silver per ton, some lead, and 1.59 percent copper. Another sample from caved workings contained 0.04 ounce of gold per ton with only a trace of copper. The prospect was reopened and drilled in about 1969-70. Samples collected from small diameter (AX) drill holes locally contained more than 50 ounce of silver per ton. Low-angle BX holes drilled across the veins encountered occasional high silver values, but indicated that the average grade across the fault zone was less than 5 ounces of silver per ton. No substantial work has been done since 1970 (Kirk Stanley, written communication, 2000).
Geologic map unit (-144.057183586672, 62.73260837585)
Mineral deposit model Polymetallic vein (Cox and Singer, 1986; model 22c)
Mineral deposit model number 22c
Age of mineralization Emplaced subseqent to or is related to the border phase of the Pennsylvanian to Permian, Ahtell pluton.
Alteration of deposit Country rocks near veins are altered to carbonates and are iron-stained; hornfels in the fault zone has been argillized and pyritized.

Production and reserves

Workings or exploration The prospect has been known since about 1908 (Kirk Stanley, written communication, 2000). When visited by Moffit (1938) and Thorne (1946), most workings were caved. Renewed interest in the prospect began about 1962 and continued until about 1970, The property was trenched beginning in 1962, and drilled by the Ptarmigan Company in 1969 or 1970. It has been inactive since.
Indication of production None

Additional comments

The most recent exploration data on the property was summarized in: 'Slana Mineral Belt Prospects Review' by Kirk Stanley, a report for Ahtna Minerals Corporation (Wes Nason, Ahtna Minerals, written communication, 2000). Additional information can be obtained from Ahtna Minerals in Anchorage, Alaska.

References

MRDS Number A011842

References

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.
Reporters W.T. Ellis (Alaska Earth Sciences), C.C. Hawley (Hawley Resource Group), and W.J. Nokleberg (U.S. Geological Survey)
Last report date 12/5/2000