Unnamed (west wall of Yankee Creek)

Prospect, Inactive

Commodities and mineralogy

Main commodities Ag; Cr
Other commodities Ni
Gangue minerals mariposite

Geographic location

Quadrangle map, 1:250,000-scale ID
Quadrangle map, 1:63,360-scale D-1
Latitude 62.98522
Longitude -156.41433
Nearby scientific data Find additional scientific data near this location
Location and accuracy This prospect is west of Yankee Creek at an elevation of about 1,500 feet. It is near the northwest corner of section 1, T. 33 N ., R 38 W., of the Seward Meridian. The location is accurate.

Geologic setting

Geologic description

This prospect is in a highly altered, northeast-trending mafic (ultramafic?) dike that intrudes sandstone and siltstone of the Upper Cretaceous, Kuskokwim Group (Bundtzen and Laird, 1983; Miller and Bundtzen, 1994). The dike is brown to tan in color and is almost completely altered to silica-carbonate minerals and mariposite. Rubble-crop suggests that the dike is 6 to 25 feet wide; it it can be traced along strike for about 500 feet in old prospect pits and rubble crop (Bundtzen and Laird, 1983). A grab sample of the altered dike contained 5.0 parts per million (ppm) silver, 200 ppm nickel, and 2,000 ppm chromium (Bundtzen and Laird, 1983).
This occurrence is an example of chromium, nickel, and occasional precious metal enrichment that occurs in altered mafic and ultramafic? dikes in the Ganes -Yankee Creek fault zone and in other areas of the Iditarod quadrangle. The abundant chromite and magnesiochromite found in panned concentrates from Yankee Creek (ID037) and Ganes Creek (ID011) may be derived from occurrences of this type (Bundtzen, Cox, and Veach, 1987).
Geologic map unit (-156.416691920867, 62.9845878353845)
Age of mineralization Undated; similar mafic dikes near the DeCourcy Mountain Mine (ID158) have 40K/40Ar dates of 71 to 76 Ma (Miller and Bundtzen, 1994).
Alteration of deposit Pervasive alteration of mafic to ultramafic dikes to silica and carbonate minerals and mariposite.

Production and reserves

Workings or exploration The altered dike at this unnamed prospect has been explored by several old prospect pits.
Indication of production None



Reporters T.K. Bundtzen (Pacific Rim Geological Consulting, Inc.), M.L. Miller (U.S. Geological Survey); and C.C. Hawley (Hawley Resource Group)
Last report date 5/16/2003