Unnamed (east side of Spruce Peak)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Ag; Au
Other commodities As
Ore minerals arsenopyrite; goethite; jarosite; limonite; pyrite
Gangue minerals calcite; quartz

Geographic location

Quadrangle map, 1:250,000-scale MM
Quadrangle map, 1:63,360-scale C-2
Latitude 63.5814
Longitude -150.6966
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is on the east side of Spruce Peak, probably within 800 feet of the top. The location is uncertain. For this record, it corresponds to occurrence 88 of Thornsberry, McKee, and Salisbury (1984, fig. K-8), which is near the center of the E1/2 SW1/4 section 29, T. 15 S., R. 16 W., Fairbanks Meridian.

Geologic setting

Geologic description

At this occurrence, a weakly mineralized reverse(?) fault places metafelsite on the south against highly deformed graphitic schist or phyllite. Both rock types are probably units of the lower Paleozoic Spruce Creek sequence (Bundtzen, 1981). The fault zone is about 10-15 feet wide. It strikes about N 55 E and dips 65-75 N, and contains quartz -calcite veins. The zone and nearby country rocks are stained with limonitic minerals, including goethite and jarosite. The limonite probably replaces pyrite or arsenopyrite. Samples of the oxidized vein contain up to 1400 ppm arsenic, along with a trace each of gold and silver (Thornsberry, McKee, and Salisbury, 1984, v. 2, occurrence 88).
Geologic map unit (-150.698883908611, 63.5808996801812)
Mineral deposit model Low-sulfide Au-quartz vein (Cox and Singer, 1986; model 36a).
Mineral deposit model number 36a
Age of mineralization The deposit is assumed to be Eocene (see record MM091).
Alteration of deposit Silicification of a fault zone. Iron-oxide alteration.

Production and reserves

Workings or exploration There are no workings. The oxidized fault zone can be traced in outcrop (rubblecrop?) for several tens of feet.
Indication of production None

Additional comments

This occurrence is in Denali National Park and Preserve.