Unnamed (upper Portage Creek)

Occurrences, Inactive

Commodities and mineralogy

Main commodities Ag; Au; Cu
Other commodities Hg
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale TK
Quadrangle map, 1:63,360-scale D-4
Latitude 62.9848
Longitude -148.8355
Nearby scientific data Find additional scientific data near this location
Location and accuracy This site is a 1.5-mile-long, northeast-trending area of mineral occurrences near the headwaters of Portage Creek. The center of the area is at an elevation of about 3,700 feet, in the NE1/4NW1/4 sec. 26, T. 22 S., R. 7 W., Fairbanks Meridian. The location is accurate.

Geologic setting

Geologic description

The occurrences at the southwest end of the area are quartz-veined, mafic(?), aphanitic and hornfelsed volcanic rocks and rusty weathering argillite; at the northeast end, they are brecciated tuffs(?) (J. Schmidt, written communication, 2001). Samples of the hornfelsed volcanic rocks contain 260 parts per million copper, 0.5 part per million gold, 0.4 part per million silver, and 0.27 part per million mercury. Argillite samples contain 1 part per million silver; and the breccia contains 0.4 part per million silver and 215 parts per million copper. (The 0.5-part-per-million gold value is an ICP analysis from XRAL Laboratories; a fire assay of the same sample gives less than 0.005 part per million gold. The cause of the discrepancy is not known.)
Geologic map unit (-148.837759070278, 62.9843290421398)
Alteration of deposit Iron-oxide alteration.

Production and reserves

Workings or exploration Only surface sampling by U.S. Geological Survey (J. Schmidt, written communication, 2001).
Indication of production None

Additional comments

MAS/MILS number 20760109.