Unnamed (on lower Alteration Creek)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Au
Other commodities Cu
Ore minerals limonite; pyrite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale MH
Quadrangle map, 1:63,360-scale A-1
Latitude 63.0149
Longitude -144.2469
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is on the east side of Alteration Creek. It is near the north edge of the NW1/4NE1/4 section 10, T. 14 N., R. 6 E., Copper River Meridian, at an elevation of about 3,900 feet. The occurrence corresponds to locality 15 of Richter (1967).

Geologic setting

Geologic description

The rocks at this occurrence are highly altered Tetelna Volcanics of Pennsylvanian age (Richter and others, 1977). Earlier Richter [1967] mapped the rocks as Slana basalt. The Tetelna Volcanics are largely composed of flows, avalanche deposits, and tuff with lesser amounts of fine-grained volcaniclastic rocks. An extensive area extending easterly has been silicified and pyritized. Subsequent oxidation, acid leaching, and formation of secondary limonite has nearly obliterated primary volcanic textures in the rocks. Richter (1967) found a trace of gold in two of three samples collected at or near this site.
Two stream-sediment samples collected from Alteration Creek below the occurrence were weakly anomalous in copper (Richter, 1967). Extensive oxidation of pyrite at the site possibly resulted in acidic surface waters that mobilized copper and minimized the copper values in the stream-sediment samples.
Geologic map unit (-144.24912548699, 63.0145115930603)
Mineral deposit model Porphyry Cu, distal (Cox and Singer, 1986; model 20c).
Mineral deposit model number 20c
Age of mineralization Pennsylvanian to Permian on the basis of the age of the host rocks; may be related to and synchronous with a Cretaceous (?) intrusion about a mile to the east.
Alteration of deposit Intense silicification and pyritization of original volcanic rocks.

Production and reserves

Workings or exploration Only limited surface sampling.
Indication of production None

References