Unnamed (on Dubuque Mountain)

Occurrences, Undetermined

Commodities and mineralogy

Main commodities Ag; Mo
Ore minerals hematite; magnetite; pyrite
Gangue minerals quartz

Geographic location

Quadrangle map, 1:250,000-scale KC
Quadrangle map, 1:63,360-scale A-5
Latitude 55.118
Longitude -131.429
Nearby scientific data Find additional scientific data near this location
Location and accuracy This site represents two occurrences on Dubuque Mountain: one is at an elevation of 2100 feet, 0.1 mile northwest of the peak; the other is at an elevation of 1350 feet, 0.4 mile northwest of the peak. The occurrences are in section 8, T. 78 S., R. 93 E., of the Copper River Meridian. The map site is approximately midway between the occurrences. The site corresponds to loc. 31 in Berg (1972 [I 684]), and loc. 41a, b in Karl (1992). The location is accurate within 0.1 mile.

Geologic setting

Geologic description

The country rocks in the area of this site are undivided, metamorphosed Silurian and Ordovician volcanic, sedimentary, and intrusive rocks; and Silurian trondhjemite that intrudes the Silurian and Ordovician rocks (Berg, 1972, Berg and others, 1988). The rocks were regionally metamorphosed to greenschist-grade phyllite and semischist in Late Cretaceous time.
The occurrences consist of quartz fissure veins and iron-stained zones in foliated, sericitized trondhjemite, or associated with aplite and intermediate dikes that cut the trondhjemite (Berg, 1972, loc. 31; Karl, 1992, loc. 41a, b). One iron-stained zone is associated with a dark-green intermediate dike about 10 feet thick. The quartz veins contain pyrite and hematite, and the trondhjemite contains inch-long pods of magnetite and hematite. A sample of sulfide-bearing aplite contained 0.5 ppm Ag and 15 ppm Mo (Karl, 1992, loc. 41b).
Geologic map unit (-131.430679766114, 55.1176590700999)
Mineral deposit model Possibly low-sulfide Au-quartz veins (Cox and singer, 1986; model 36a). Disseminated magnetite mineralization of undetermined origin.
Mineral deposit model number 36a?
Age of mineralization The fissure veins probably are Late Cretaceous or younger. The mineralization associated with the dikes that cut the trondhjemite probably is Tertiary.
Alteration of deposit Schistose trondhjemite is intensely sericitized. One iron-stained zone is associated with a dark-green intermediate dike about 10 feet thick.

Production and reserves

Workings or exploration A sample of sulfide-bearing aplite contained 0.5 ppm Ag and 15 ppm Mo (Karl, 1992, loc. 41b).
Indication of production None

References