Unnamed (west of upper Davis River)

Occurrence, Undetermined

Commodities and mineralogy

Main commodities Cu
Other commodities Ag; Zn
Ore minerals chalcopyrite; pyrite; pyrrhotite

Geographic location

Quadrangle map, 1:250,000-scale KC
Quadrangle map, 1:63,360-scale D-2
Latitude 55.836
Longitude -130.409
Nearby scientific data Find additional scientific data near this location
Location and accuracy This occurrence is at an elevation of about 2700 feet in section 4, T70S, R98E. It is near the head of an east-flowing tributary to upper Davis River and about 1.2 miles north-northeast of an unnamed lake at 3038 feet elevation. The site is in section 4, T. 70 S., R. 98 E., of the Copper River Meridian. It corresponds to area M-7 in Berg and others (1977), and to loc. 15 in Elliott and others (1978). The location is accurate within about 0.1 mile.

Geologic setting

Geologic description

The country rocks in the area of this occurrence are Tertiary or Cretaceous foliated granodiorite of the Coast Range batholith, and pelitic paragneiss that forms metamorphic roof pendants and screens in the batholith (Berg and others, 1977, p. 10; Berg and others, 1988). The paragneiss consists chiefly of quartz, biotite, feldspar, garnet, and sillimanite. It probably represents marine argillaceous and clastic sedimentary rocks that underwent high-grade regional metamorphism in Cretaceous or Tertiary time. The premetamorphic age of the strata is uncertain, but they probably are mainly Paleozoic and may be as old as Precambrian (Berg and others, 1988, p. 26; Gehrels and others, 1990; Crawford and others, 2000).
The occurrence is a conspicuous zone of iron-stained paragneiss 120 feet wide and about 2 miles long (Berg and others, 1977, area M-7, p. 132 and pl. 2). The paragneiss contains small amounts of pyrite, pyrrhotite, and chalcopyrite that form small small pods parallel to the gneissic foliation. Two random chip samples across about half the width of the zone assayed up to 2 ppm Ag and 260 ppm Zn (Berg and others, 1977, p. 132).
Geologic map unit (-130.410703331894, 55.8356773675512)
Mineral deposit model Sparsely disseminated base-metal sulfides
Alteration of deposit Conspicuous iron-staining.

Production and reserves

Workings or exploration Two random chip samples across about 60 feet of the iron-stained zone assayed up to 2 ppm Ag and 260 ppm Zn (Berg and others, 1977, p. 132).
Indication of production None

Additional comments

Site is in Misty Fiords National Monument Wilderness.

References