Unnamed (on upper Alteration Creek)

Occurrence, Inactive

Commodities and mineralogy

Main commodities Ag; Au; Cu
Ore minerals azurite; chalcopyrite; malachite; pyrite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale MH
Quadrangle map, 1:63,360-scale A-1
Latitude 63.02
Longitude -144.2578
Nearby scientific data Find additional scientific data near this location
Location and accuracy Alteration Creek is a south-southeast-flowing tributary of the Slana River, which it enters about 5 miles south of Gillett Pass. The occurrence is on the west side of Alteration Creek at an elevation of about 3,800 feet. It is near the center SW1/4 section 3, T. 14 N., R. 6 E., Copper River Meridian. The occurrence corresponds to locality 2 of Richter and others (1977) and locality 144 in table 2 of Nokleberg and others (1991) and is near locality 32 on figure 6 of Cobb (1979, [OFR 79-238)].

Geologic setting

Geologic description

The rocks in the vicinity of this occurrence consist of intensely hydrothermally altered Tetelna Volcanics of Pennsylvanian age (Richter and others, 1977). (Richter [1967] originally mapped the country rocks as Slana basalt.) The Tetelna Volcanics are mainly composed of flows, avalanche deposits, and tuff interbedded with lesser amounts of fine-grained volcaniclastic rock. A granitic pluton of Cretaceous (?) age crops out about a mile east of the altered zone and could underlie it.
The occurrence consists of azurite- and malachite-stained quartz veins that cut intensely iron stained silicified volcanic rocks. The veins contain small amounts of chalcopyrite and pyrite. A sample collected from a chalcopyrite-bearing vein assayed 1.5 percent copper, 0.02 ounce of gold per ton, and 0.54 ounce of silver per ton (Richter, 1967).
Geologic map unit (-144.260025963526, 63.0196115424182)
Mineral deposit model Porphyry Cu, distal (Cox and Singer, 1986; model 20c).
Mineral deposit model number 20c
Age of mineralization Possibly Pennsylvanian to Permian, on the basis of the age of the host rocks; may be related to a nearby Cretaceous (?) intrusion.
Alteration of deposit Silicification and pyritization of Tetelna Volcanics. Oxidation of iron sulfides has been so extensive that primary rock textures are largely obliterated (Richter, 1967).

Production and reserves

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

References