Cape Creek

Mine, Inactive

Alternative names

American Tinfields, Inc.

Commodities and mineralogy

Main commodities Sn
Ore minerals cassiterite

Geographic location

Quadrangle map, 1:250,000-scale TE
Quadrangle map, 1:63,360-scale C-6
Latitude 65.571
Longitude 167.931
Nearby scientific data Find additional scientific data near this location
Location and accuracy Cape Creek, the principal drainage on the east side of the Cape Mountain upland, has headwaters in the contact zone of the Late Cretaceous Cape Mountain biotite granite (Hudson and Arth, 1983) with Mississippian marble (Sainsbury, 1972). The creek flows south about 2 miles from its headwaters at the continental divide to its mouth at Tin City on the Bering Sea coast. The upper reaches of the creek include a west fork with headwaters in the uplands of Cape Mountain and an east fork with headwaters against the continental divide. First Chance Creek (TE007) is a short (0.5 mile long) tributary that enters from the west 0.75 mile upstream from the mouth of Cape Creek. This is locality 25 of Cobb and Sainsbury (1972). Cobb (1975) summarized relevant references under the names 'Cape Cr.' and 'American Tinfields, Inc.'.

Geologic setting

Geologic description

Cape Creek, the principal drainage on the east side of the Cape Mountain upland, has headwaters in the contact zone of the Late Cretaceous Cape Mountain biotite granite (Hudson and Arth, 1983) with Mississippian marble (Sainsbury, 1972). Private company and USBM churn-drill holes defined upper and lower pay sections along most of Cape Creek including the lower part of the east fork. The upper pay streak was related to the active stream drainage, did not have extensive overburden, and contained a few to several ponds of tin per cubic yard. The lower pay streak, separated from the upper by up to 65 feet of silt and minor sand containing marine shells, was 7 feet or less in thickness, developed on and adjacent to bedrock, and high grade in most places. Grades to over 30 pounds of tin per cubic yard were reported by Mulligan and Thorne (1959, p. 40). Mining during the 1970s and 1980s by Lost River Mining Company verified grades of about 30 pounds of tin per cubic yard over large parts of this pay streak (R. Murray, personal communication in Hudson and Reed, 1997, p. 451). Development of these high grades has been attributed to reworking during the marine transgression that flooded the area and led to the thick silt-rich marine section in Cape Creek (Hudson and Reed, 1997, p. 451-452).
Some of the detrital cassiterite is very coarse grained. Washing plant operations in 1982 included a 1.5 inch grizzley and hand picking of the oversize conveyor belt was required to collect coarse aggregates of cassiterite crystals. The largest cassiterite aggregate found in this way weighed 142 pounds (R. Murray, personal communication in Hudson, 1984, p. 8). Some of the cassiterite aggregates are an assemblage of cassiterite, muscovite, quartz, and feldspar (Hudson, 1984, p. 16). The character of this material is consistent with its derivation from lode deposits on slopes above the west headwater of Cape Creek (Mulligan and Thorne, 1959; Mulligan, 1966)
Geologic map unit (-167.933769349833, 65.5702181781893)
Mineral deposit model Alluvial tin placer (Cox and Singer, 1986; model 39e)
Mineral deposit model number 39e
Age of mineralization Quaternary

Production and reserves

Workings or exploration
A churn-drill exploration program defined both upper and lower pay streaks before larger scale mining (Mulligan and Thorne, 1959).
Early mining was by hand in the west headwater. Power shovels were used later and the recovered pay was hauled by truck to the beach for washing. The latest mining used a dragline to remove overburden, a dozer to consolidate pay in the pit, and a front-end loader to transport pay to a nearby washing plant. Cassiterite-bearing concentrate was placed in 55 gallon barrels and transferred by crane to barges on the beach for transfer to a coastal freighter anchored nearby.
Indication of production Yes
Reserve estimates Unkown but extensive mining took place in the 1970's and 1980's. Most of the placer deposits, especially the higher grade portions, are probably mined out (Bundzten and others, 1990, p. 33).
Production notes Most of the recorded 1,650 short tons of tin production from the Cape Mountain area (Hudson and Reed, 1997, p. 452) has come from Cape Creek; over 60% of the total production (1,036 tons) took place between 1979 and 1989 (Bundzten and others, 1990, p. 33). Goodwin Gulch, with between 132 and 650 tons of tin production, has been the only other significant placer source in this area.

References

MRDS Number 10308383

References

Hudson, T.L., 1984, Tin systems of Seward Peninsula, Alaska: Anchorage, Anaconda Minerals Company internal report, 51 p. (Report held by Cook Inlet Region Inc., Anchorage, Alaska)
Hudson, T.L., and Arth, J. G., 1983, Tin granites of Seward Peninsula, Alaska: Geological Society of America Bulletin, v. 94, p. 768-790.
Hudson, T.L., and Reed, B.L., 1997, Tin deposits of Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral Deposits of Alaska: Economic Geology Monograph 9, p. 450-465.
Reporters Travis L. Hudson (Applied Geology)
Last report date 5/10/1998