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Concord group

Prospect in Alaska, United States with commodities Silver, Gold, Copper, Zinc, Barium-Barite
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Geologic information

Identification information

Deposit ID 10094041
MRDS ID A012366
Record type Site
Current site name Concord group
Alternate or previous names Apex group, Concord no. 2, 3, 4, Blue Jay, Old Man, Sunrise

Geographic coordinates

Geographic coordinates: -131.74371, 55.17363 (WGS84)
Relative position The Concord group of prospects is at an elevation of about 300 feet near the south foot of Punch Hill . The prospects are in section 20, T. 71 S., R. 91 E., of the Copper River Meridian, about 0.8-1.0 mile north-northwest of the mouth of the unnamed creek at the north entrance to Dall Bay. The site corresponds to loc. 120 in Elliott and others (1978), and to loc. 312 in Maas and others (1995). The location is accurate within 0.1 mile.? Also see Additional comments.
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Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Silver Primary
Gold Primary
Copper Primary
Zinc Primary
Barium-Barite Secondary

Materials information

Materials Type of material
Barite Ore
Chalcopyrite Ore
Pyrite Ore
Sphalerite Ore
Calcite Gangue
Quartz Gangue

Alteration

  • (Local) Probably local silicification, carbonatization, pyritization, and introduction of hydrothermal hematite.

Mineral occurrence model information

Model code 85
USGS model code 22c
Deposit model name Polymetallic veins
Mark3 model number 46

Host and associated rocks

  • Host or associated Host
    Rock type Volcanic Rock (Aphanitic) > Felsic Volcanic Rock > Rhyolite

Nearby scientific data

(1) -131.74371, 55.17363
ListMap

Comments on the geologic information

  • Geologic Description = Southern Gravina Island is underlain by an assemblage of undivided Silurian or Ordovician metamorphosed bedded and intrusive rocks; a stock and associated dikes of Silurian trondhjemite that cuts the metamorphic assemblage; and a sequence of Upper Triassic carbonate, clastic, rhyolitic, and basaltic strata that unconformably overlies the older rocks (Berg, 1973, 1982; Berg and others, 1988). The rocks are complexly folded and are cut by high-angle faults and by low-angle thrust faults. In many places, the Triassic rhyolite and the rocks beneath it are permeated by microscopic particles of hydrothermal hematite, giving them a pink, purple, or red hue (Berg, 1973, p. 14).? Brooks (1902, p. 72-73) describes the deposits on the Concord group of claims as sulfide-bearing quartz-barite-carbonate veins at ?greenschist-pegmatite contacts. The veins contain chalcopyrite, sphalerite, probably pyrite, and low Ag and Au values. The Sunrise vein is 12-18 inches thick, strikes N75W and dips 80 SW, and was traced in outcrop for several hundred feet. The vein contained a conspicuous mass of chalcopyrite ore, which was said to carry values of $72 per ton, chiefly in Cu, and a little Ag and Au. ? Maas and others' (1995, p. 229) best samples of the Concord deposit were: 1.4% Cu in a 6-foot sample; 0.44% Cu in a 16-foot sample; and 0.24% Cu in a 38-foot sample. Workings that could be identified at the time of their investigation included 2 adits, one 11.5 feet long and one caved; a 20-foot flooded shaft; and several trenches.? Maas and others (1995, p. 227) description of the mineral deposits in the area north of Dall Bay probably applies in general to the Concord group of deposits. They report that chalcopyrite is associated with sheared, silicified zones, chiefly in trondhjemite. Small barite veins are also found in the area. About 0.6 mile north of Dall Bay, chalcopyrite occurs as clasts or pods in a siderite-hematite matrix in altered trondhjemite. One deposit that Maas and others assign to the Concord group is on a NE-striking, high-angle fault that forms the contact between the trondhjemite and the Silurian-Ordovician metamorphic rocks (Maas and others, 1995, loc. 312-1 on fig. 58). The characteristics and setting of the deposits suggest that they mainly are polymetallic veins of Late Triassic or younger age.
  • Age = Late Triassic or younger.

Economic information

Economic information about the deposit and operations

Development status Prospect
Commodity type Metallic

Mining district

District name Ketchikan

Comments on the workings information

  • Workings / Exploration = Early assays of a conspicuous mass of chalcopyrite ore were said to carry values of $72 per ton, chiefly in Cu, and a little Ag and Au (Brooks, 1902). ? Maas and others' (1995, p. 229) best samples of the Concord deposit were: 1.4% Cu in a 6-foot sample; 0.44% Cu in a 16-foot sample; and 0.24% Cu in a 38-foot sample. Workings that could be identified at the time of their investigation included 2 adits, one 11.5 feet long and one caved; a 20-foot flooded shaft; and several trenches.

Reference information

Links to other databases

Agency Database name Acronym Record ID Notes
USGS Mineral Resources Data System MRDS A012366
USGS Alaska Resource Data File ARDF KC123

Bibliographic references

  • Deposit

    Brooks, A.H., 1902, Preliminary report on the Ketchikan mining district, Alaska, with an introductory sketch of the geology of southeastern Alaska: U.S. Geological Survey Professional Paper 1, 120 p.

  • Deposit

    Berg, H.C., 1973, Geology of Gravina Island Alaska: U.S. Geological Survey Bulletin 1373, 41 p.

  • Deposit

    Elliott, R.L., Berg, H.C., and Karl, Susan, 1978, map and table describing metalliferous and selected nonmetalliferous mineral deposits, Ketchikan and Prince Rupert quadrangles, Alaska: U.S. Geological Survey Open-file Report, 78-73-B,17 p., scale 1:250,000.

  • Deposit

    Cobb, E.H., and Elliott, R.L., 1980, Summaries of data on and lists of references to metallic and selected nonmetallic mineral deposits in the Ketchikan and Prince Rupert quadrangles, Alaska: U.S. Geological Survey Open-File Report 80-1053, 154 p.

  • Deposit

    Berg, H.C., 1982, The Alaska Mineral Resource Assessment Program; guide to information about the geology and mineral resources of the Ketchikan and Prince Rupert quadrangles, southeastern Alaska: U.S. Geological Survey Circular 855, 24 p.

  • Deposit

    Berg, H.C., Elliott, R.L., and Koch, R.D., 1988, Geologic map of the Ketchikan and Prince Rupert quadrangles, southeastern Alaska: U.S. Geological Survey Mineral Investigations Series Map MF-1807,27 p., scale 1:250,000.

  • Deposit

    Maas, K.M., Bittenbender, P E., and Still, J.C., 1995, Mineral investigations in the Ketchikan mining district, southeastern Alaska: U.S. Bureau of Mines Open-File Report 11-95, 606 p.

Comments on the references

  • Primary Reference = Brooks, 1902; Maas and others, 1995

General comments

Subject category Comment text
Deposit Model Name = Polymetallic veins (Cox and Singer, 1986; model 22c)
Deposit Other Comments = Early reports describing the Concord group refer to it as the Apex group; the Concord no. 2, 3, and 4 (group); and the Blue Jay, Old Man, and Sunrise claims (Cobb and Elliott, 1980, p. 144-146).

Reporter information

Type Date Name Affiliation Comment
Reporter 05-JUL-1999 H.C. Berg U.S. Geological Survey