Unnamed (head of Chathenda Creek)

Prospect, Inactive

Commodities and mineralogy

Main commodities Cu
Other commodities Au; Mo
Ore minerals chalcopyrite; molybdenite; pyrite

Geographic location

Quadrangle map, 1:250,000-scale NB
Quadrangle map, 1:63,360-scale A-2
Latitude 62.1096
Longitude -141.6273
Nearby scientific data Find additional scientific data near this location
Location and accuracy This prospect is on the south side of the uppermost headwaters of Chathenda Creek. It is at an elevation of about 6,200 feet, 1.6 miles northeast of peak 7372. The site is in the SE1/4 of section 19, T. 4 N., R. 21 E. of the Copper River Meridian. This is locality 3 of Richter and Matson (1970 [OFR 70-275]), locality 44 of Richter and others (1975), and National Park Service locality WRST-72 (unpublished data). Cobb and Richter (1980) included this prospect under the name 'Johnson Cr.'. It is located to within a few hundred feet.

Geologic setting

Geologic description

At this prospect, pyrite and chalcopyrite are disseminated in a small diorite stock and surrounding hornfels (Richter and others, 1975). The sulfide-bearing rocks are limonite stained and also locally contain abundant copper-staining along fractures (Richter and Matson, 1970 ([OFR 70-275]). Richter and others (1975) estimate that the area of hydrothermal alteration in diorite and hornfels is about 300 by 300 feet in size. The average grade of surface samples is about 0.15 percent copper and less than 0.01 percent molybdenum. A grab sample of copper-stained diorite and a grab sample representing 500 feet of pyrite-bearing argillite talus respectively contained 0.2 parts per million (ppm) and 0.04 ppm gold (Richter and Matson, 1970 [OFR 70-275]). The deposit has been estimated to contain 8 million tons with an average grade of 0.20 percent copper and very low amounts of molybdenum (Richter and others, 1975). The host diorite is inferred to be Cretaceous in age; it intrudes Jurassic or Cretaceous siliciclastic rocks (Richter and Jones, 1973).
Geologic map unit (-141.629437568137, 62.1092565391914)
Mineral deposit model Porphyry Cu-Mo (Cox and Singer, 1986; model 21a)
Mineral deposit model number 21a
Age of mineralization Cretaceous? The age of the host diorite is inferred to be Cretaceous (Richter and Jones, 1973).
Alteration of deposit Quartz-pyrite (+/- sericite?) veining and replacement; oxidation has resulted in iron- and copper-staining.

Production and reserves

Workings or exploration Surface prospecting has occurred since 1967.
Indication of production None
Reserve estimates The deposit is estimated to contain about 8 million tons of material with a grade of 0.20 percent copper and very low amounts of molybdenum (Richter and others, 1975).

Additional comments

The prospect is in the Wrangell-St. Elias National Preserve.

References