Prospect in Alaska, United States with commodities Gold, Lead, Zinc

Geologic information

Identification information

Deposit ID 10001585
MRDS ID A012340
Record type Site
Current site name Baltic

Geographic coordinates

Geographic coordinates: -131.19287, 55.38281 (WGS84)
Relative position The Baltic prospect is at an elevation of about 150-200 feet, 0.3 mile east of the shore of Thorne Arm, and 0.5 mile west of Star Lake. The site is in section 7, T. 75 S., R. 94 E., of the Copper River Meridian. It corresponds to loc. 87 in Elliott and others (1978), and to loc. 299 in Maas and others (1995). The location is accurate within 0.1 mile. Elliott and others, following an error in Wright and Wright (1908, p. 148), erroneously called the site 'Baltic Star.'
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Geographic areas

Country State
United States Alaska


Commodity Importance
Gold Primary
Lead Secondary
Zinc Secondary

Materials information

Materials Type of material
Galena Ore
Gold Ore
Pyrite Ore
Sphalerite Ore
Quartz Gangue


  • (Local) According to Maas and others (1995, p. 215), the wallrocks of the auriferous veins in the Sea Level mine area are hydrothermally altered to bluish-gray carbonate-sericite-pyrite rock, called 'blue porphyry' in some early reports (for example, Brooks, 1902; Wright and Wright, 1908) (also see KC095).

Mineral occurrence model information

Model code 273
USGS model code 36a
Deposit model name Low-sulfide Au-quartz vein
Mark3 model number 27

Host and associated rocks

  • Host or associated Host
    Rock type Metamorphic Rock > Schist

Nearby scientific data

(1) -131.19287, 55.38281

Comments on the geologic information

  • Geologic Description = The country rocks in this part of Revillagigedo Island are marine, interbedded, andesitic and basaltic metavolcanic rocks and subordinate pelitic metasedimentary rocks that are intruded by stocks, sills, and dikes of Cretaceous feldspar-porphyritic granodiorite (Berg and others, 1988). The strata and some of the granodiorite were regionally metamorphosed to greenschist grade in Late Cretaceous time. These regionally metamorphosed rocks subsequently were locally remetamorphosed to hornblende hornfels near the contacts of Cretaceous granodiorite plutons that were emplaced after the regional metamorphism. The premetamorphic age of the strata is uncertain. Berg and others (1988) assign them a Mesozoic or (late) Paleozoic age. Berg (1982) and Crawford and others (in press) assign them to the Gravina belt, of Late Jurassic or Cretaceous age, or to the Taku terrane, of late Paleozoic to Late Triassic age. The metamorphic and intrusive rocks locally are overlain by basalt and andesite lava flows of Quaternary or Tertiary age.? According to Wright and Wright (1908, p. 148), the Baltic prospect (which they erroneously called 'Baltic Star') consists of a 1.5-foot-thick quartz fissure vein in mineralized schist. The vein, which was traced on the surface for 300 feet, strikes NE and dips 75 SE, and contains small amounts of pyrite, sphalerite, and galena, in addition to low values in gold. The northeast end of the Baltic claim abuts against a Quaternary basalt lava flow.? Maas and others (1995, p. 215) interpret the 'mineralized schist' in the Sea Level mine area as hydrothermally altered mafic metavolcanic rock (see Alteration, below; also see KC095). They also note that the quartz in the veins in this area is not recrystallized; the veins thus are probably younger than most or all of the Late Cretaceous regional metamorphism.
  • Age = Maas and others (1995, p. 215) note that the quartz in the veins in this area is not recrystallized; the veins thus are probably younger than most or all of the Late Cretaceous regional metamorphism.

Economic information

Economic information about the deposit and operations

Development status Prospect
Commodity type Metallic

Mining district

District name Ketchikan

Reference information

Links to other databases

Agency Database name Acronym Record ID Notes
USGS Mineral Resources Data System MRDS A012340
USGS Alaska Resource Data File ARDF KC090

Bibliographic references

  • Deposit

    Wright, F.E., and Wright, C.W., 1908, The Ketchikan and Wrangell mining districts, Alaska: U.S. Geological Survey Bulletin 347, 210 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

    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.

  • Deposit

    Crawford, M.L., Crawford, W.A., and Gehrels, G.E., 2000, Terrane assembly and structural relationships in the eastern Prince Rupert quadrangle, British Columbia, in H.H. Stowell and W.C.McClelland, eds., Tectonics of the Coast Mountains, southeastern Alaska and British Columbia: Boulder, Colorado, Geological Society of America Special Paper 343, p. 1-21.?

Comments on the references

  • Primary Reference = Wright and Wright, 1908; Maas and others, 1995

General comments

Subject category Comment text
Deposit Model Name = Low-sulfide gold-quartz veins (Cox and Singer, 1986; model 36a)
Deposit Other Comments = the Baltic prospect was erroneously called 'Baltic Star' by Wright and Wright (1908, p. 148) and by Elliott and others (1978, loc. 87).

Reporter information

Type Date Name Affiliation Comment
Reporter 03-JUL-1999 H.C. Berg U.S. Geological Survey