Location: This site represents six occurrences on and near Red Mountain on northern Annette Island. The occurrences are in sections 21, 27, and 34, T. 76 S., R. 91 E., of the Copper River Meridian. They are at elevations ranging from about 500-2000 feet, and are distributed along a northwest-trending line 1.7 miles long, that extends from the southeast foot of Red Mountain to the northwest foot. The coordinates are for the approximate center of the estimated two-square-mile area that contains these occurrences. The site corresponds to loc. 4a-f in Karl (1992). The location is accurate within 0.2 mile.

Geology: The country rocks in the area of Red Mountain are Upper Jurassic or Cretaceous andesitic or basaltic metavolcanic rocks that are gradationally interbedded with subordinate flyschlike metasedimentary rocks (Berg, 1972 [I 684]; Berg and others, 1988). The bedded rocks are intruded by a Jurassic or Cretaceous diorite stock and related dikes. The rocks were regionally metamorphosed to greenschist-grade phyllite and semischist in Late Cretaceous time. The occurrences consist of ubiquitously disseminated pyrite and pyrrhotite in metadiorite, argillite, metagraywacke, and metatuff (Karl, 1992, loc. 4a-f). The sulfides commonly make up as much as 10 volume percent, and locally up to 40 volume percent, of the hostrocks. In places, a little galena or chalcopyrite accompany the other sulfides. A sample of augite crystal metatuff contained 1.5 ppm Ag; samples of the metadiorite contained up to 700 ppm Cu and 100 ppm Pb; a sample of slate contained 10 ppm Mo; and samples of phyllitic gritstone and sandstone contained up to 200 ppm Pb (Karl, 1992, loc. 4a-f). The distribution and setting of the disseminated sulfide mineralization suggest that it may in part be cogenetic with Late Jurassic or Cretaceous deposition of the volcanic-sedimentary hostrocks.

Workings: A sample of augite crystal metatuff contained 1.5 ppm Ag; samples of the metadiorite contained up to 700 ppm Cu and 100 ppm Pb; a sample of slate contained 10 ppm Mo; and samples of phyllitic gritstone and sandstone contained up to 200 ppm Pb (Karl, 1992, loc. 4a-f).

Age: Disseminated sulfide mineralization may in part be cogenetic with Late Jurassic or Cretaceous deposition of volcanic-sedimentary hostrocks.

Alteration: Sulfidization of country rocks.

Commodities (Major) - Cu, Pb; (Minor) - Ag

Development Status: None

Deposit Model: Disseminated sulfide deposit of volcanogenic origin?

Other Databases

Link to USGS - Alaska:	KC161

Other Regions, Features and Areas containing this locality

References