Unnamed Occurrence (ARDF - SM010; head of Trapper Creek), Aniak Mining District, Bethel Census Area, Alaska, USAi

Regional Level Types
Unnamed Occurrence (ARDF - SM010; head of Trapper Creek)	- not defined -
Aniak Mining District	Mining District
Bethel Census Area	Census Area
Alaska	State
USA	Country

Location: 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.
Geology: 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swarm that intrudes shale and sandstone of the Upper Cretaceous, Kuskokwim Group (Cady and others, 1955; J.R. Riehle, unpublished data, 1998).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.
Workings: The occurrence was investigated by the U.S. Geological Survey in 1998 (J. Riehle, unpublished data, 1998).
Age: Unknown. Similar dikes in the Donlin Creek deposit (ARDF ID XXX) in the Iditarod quadrangle vary in age from 65 to 70 Ma (Bundtzen and Miller, 1997).
Alteration: Sericitic alternation of dikes and sediments.

Commodities (Major) - Bi, Hg, Sb; (Minor) - Au, W
Development Status: None
Deposit Model: Polymetallic vein (Cox and Singer, 1986; model 22c).

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Link to USGS - Alaska:	SM010

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References