Unnamed (on Surprise Creek)

Prospect, Inactive

Commodities and mineralogy

Main commodities Cu
Other commodities Ag
Ore minerals bornite; chalcocite; chalcopyrite; chrysocolla; pyrite
Gangue minerals epidote; quartz

Geographic location

Quadrangle map, 1:250,000-scale VA
Quadrangle map, 1:63,360-scale B-1
Latitude 61.4018
Longitude -144.2522
Nearby scientific data Find additional scientific data near this location
Location and accuracy This prospect is on Surprise Creek, a south tributary to Nerelna Creek. It is at an elevation of about 3,200 feet, in the SW1/4 section 25, T. 5 S., R. 6 E., of the Copper River Meridian. This prospect is approximately located, perhaps to within a mile or more. It is locality 58 of Cobb and Matson (1972) and locality 49 of Winkler and others (1981 [OFR 80-892-B]).

Geologic setting

Geologic description

Fractures in shattered greenstone contain quartz and epidote (Moffit, 1914, p. 52). Bornite, chalcocite, chalcopyrite, chrysocolla, and pyrite are in the quartz and are locally disseminated in the host greenstone. A short adit was driven. The mineralization is similar to that in the Nikolai Greenstone of the northeast Valdez quadrangle, but this geologic unit has not been mapped in this area. Uplands in the headwaters of Surprise Creek are metamorphic rocks of the Paleozoic Skolai Group; a Jurassic intermediate-composition pluton is present to the west (Winkler and others, 1981 [OFR 80-892-A]). However, exposures are limited on lower Surprise Creek, and this prospect may be in unrecognized Nikolai Greenstone. The copper mineralization may be related to the regional mineralizing event that produced the rich Kennecott copper deposits in the McCarthy quadrangle (MacKevett and others, 1997).
Geologic map unit (-144.254280471666, 61.4013268480785)
Mineral deposit model Thin veins, impregnations, and fracture fillings in greenstone; may be related to Kennecott-type copper deposits (Mackevett and others, 1997)
Age of mineralization The copper mineralization may be related to the mineralizing event that produced the rich Kennecott copper deposits in the McCarthy quadrangle to the east (MacKevett and others, 1997). This event is interpreted to have accompanied Late Jurassic or Early Cretaceous deformation and metamorphism (MacKevett and others, 1997, p. 88).

Production and reserves

Workings or exploration A short adit was driven before 1912 (Moffit, 1914).
Indication of production None

Additional comments

This prospect is in Wrangell-St. Elias National Park.

References