Unnamed (southeast of hill 2910, west of Chitsia Creek)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Ag; Zn
Other commodities Au; Mo; Pb
Ore minerals galena; limonite; pyrite; sphalerite

Geographic location

Quadrangle map, 1:250,000-scale MM
Quadrangle map, 1:63,360-scale D-1
Latitude 63.9309
Longitude -150.3955
Nearby scientific data Find additional scientific data near this location
Location and accuracy
This occurrence is a mineralized bedrock unit several hundred feet across that trends northeasterly about a half-mile southeast of hilltop 2910. The hill is about 3.5 miles southwest of Chitsia Mountain. For this record, the location is at an elevation of about 2200 feet, in the SE1/4 of section 25, T. 11 S., R. 15 W., Fairbanks Meridian. The site is the approximate midpoint of the mineralized outcrop, which is partly in section 25, and partly in section 30, T. 11S., R. 14 W. The location is accurate.
The occurrence described in this record includes 'gossan 2' and 'gossan 3' (numbers 71 and 72) of Bundtzen, Smith, and Tosdal (1976), and numbers 80b and 81 of Bundtzen (1981). It is briefly noted by Cobb (1980 [OFR 80-363]).

Geologic setting

Geologic description

This occurrence is a zone of pyritic schist marked on the surface by limonitic gossan. The most strongly mineralized part of the zone can be followed ENE for more than 3000 feet. The schist is a unit in metarhyolite tuff of the Upper Devonian and Mississippian Totatlanika Formation (Bundtzen, 1981).
The area was mapped and sampled in 1976 as part of a U. S. Bureau of Mines-sponsored evaluation of lands adjacent to then McKinley National Park (Hawley and Associates, 1978, fig. 4.1-A(3)). Samples of soil overlying the gossan suggest that the deposit is at least 400 feet across and trends east-northeast. On an eastern soil line, in a 400-foot-wide zone, the soil contained 45-195 ppm lead, 130-600 ppm zinc, and 0.02-1.2 ppm silver. On a soil line 3000 feet to the west, values were as much as 220 ppm lead, 210 ppm zinc, 1.0 ppm silver, and 0.03 ppm gold (Hawley and Associates, 1978, fig. and table no 4.1-A(3)). Samples of the gossan collected by Bundtzen (1981) contained as much as 330 ppm molybdenum, 0.52 percent zinc, and 10 ppm silver. Lead and zinc values this high indicate galena and sphalerite, or their oxidation products. Bundtzen, Smith, and Tosdal (1976) identified microscopic sphalerite, exsolved in pyrite. The deposit may extend to the west, but is covered by colluvium. Stream- sediment samples collected from drainages west of the deposit contained as much as 810 ppm zinc.
The deposit is probably of syngenetic or diagenetic origin, roughly contemporaneous with deposition of the Totatlanika metarhyolite tuff.
Geologic map unit (-150.397825765593, 63.9304075909375)
Mineral deposit model Mineralized metarhyolite tuff.
Age of mineralization Probably Late Devonian and Mississippian, the depositional age of the Totatlanika Formation (Bundtzen, 1981).
Alteration of deposit Iron-oxide alteration.

Production and reserves

Workings or exploration There are no workings. The area has been reconnaissance mapped and sampled by Bundtzen, Smith, and Tosdal (1976), Hawley and Associates (1978), and Bundtzen (1981).
Indication of production None

Additional comments

This occurrence is in Denali National Park and Preserve.

References