Unnamed (head of Trapper Creek)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Bi; Hg; Sb
Other commodities Au; W
Ore minerals pyrite; stibnite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale SM
Quadrangle map, 1:63,360-scale D-6
Latitude 61.95573
Longitude -158.1566
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is located on an east-west trending, gently undulating ridge at the head of Trapper Creek. It is at an elevation of about 1,450 feet, about 0.6 mile west of hill 1526 in the NW1/4 sec. 31, T. 22 N., R. 48 W., of the Seward Meridian. The location is accurate.

Geologic setting

Geologic description

This occurrence is associated with a felsic dike and sill swarm that intrudes shale and sandstone of the Upper Cretaceous, Kuskokwim Group (Cady and others, 1955; J.R. Riehle, unpublished data, 1998). The dikes and sills, most of which are sericitically altered, extends across the top of an east-west-trending ridge for at least 2 miles. The mineral occurrence is near the central portion of the dike swarm. The mineralization consists of thin quartz veinlets in an altered granite porphyry dike or sill and in altered calcareous sandstone. According to J. Riehle (oral communication, 1998), the mineralization is about 16 feet wide and the alteration zone with it can be traced along the strike of the ridge for about 100 feet. A few percent of sulfides, mainly pyrite and a few blades of stibnite, were identified in hand specimens. Six grab samples of quartz, pyrite, and sericite alteration contained 1.45 to 7.44 parts per million (ppm) mercury, up to 100 parts per billion (ppb) gold, 1,250 ppm antimony, 13.0 ppm bismuth, and 14.9 ppm tungsten. A grab sample collected about a mile west of the occurrence in the same dike and sill swarm contained 111 ppm antimony, 2.82 ppm mercury, 17 ppm bismuth, and 16 ppb gold.
Geologic map unit (-158.159002854271, 61.9550330485881)
Mineral deposit model Polymetallic vein (Cox and Singer, 1986; model 22c).
Mineral deposit model number 22c
Age of mineralization Unknown. Similar dikes in the Donlin Creek deposit (ARDF number ID167) in the Iditarod quadrangle vary in age from 65 to 70 Ma (Bundtzen and Miller, 1997).
Alteration of deposit Sericitic alteration of dikes and sediments.

Production and reserves

Workings or exploration The occurrence was investigated by the U.S. Geological Survey in 1998 (J. Riehle, unpublished data, 1998).
Indication of production None

References

References

Bundtzen, T.K., and Miller, M.L., 1997, Precious metals associated with Late Cretaceous-early Tertiary igneous rocks of southwestern Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral Deposits of Alaska: Economic Geology Monograph 9, p. 242-286.
Reporters T.K. Bundtzen (Pacific Rim Geological Consulting, Inc.) and M.L. Miller (U.S. Geological Survey)
Last report date 5/8/2003