Dalcoath Dike

Prospect in Alaska, United States with commodity Tin

Geologic information

Identification information

Deposit ID 10308416
Record type Site
Current site name Dalcoath Dike

Geographic coordinates

Geographic coordinates: -167.15041, 65.48827 (WGS84)
Relative position The Dalcoath dike prospect is about 1 mile north of the Lost River Mine (TE048-TE051). It is on the south side of the ridge separating Crystal Creek and the headwaters of Cassiterite Creek, both east tributaries to Lost River in the York Mountains. The surface trace of the dike, which trends N 50 E and dips about 65 degrees north, has been mapped by Sainsbury (1969, plate 1) at elevations of 600 to over 1,000 feet. This location was not identified separately by Cobb and Sainsbury (1972) or Cobb (1975).
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Geographic areas

Country State
United States Alaska


Commodity Importance
Tin Primary

Comments on the commodity information

  • Gangue = white mica

Materials information

Materials Type of material
Cassiterite Ore
Arsenopyrite Gangue
Chlorite Gangue
Danburite Gangue
Pyrite Gangue
Tourmaline Gangue
Mica Gangue


  • (Local) The strongly altered lamprophyre dike has abundant white mica, arsenopyrite, quartz, tourmaline, danburite in places, chlorite, pyrite, and some topaz.

Mineral occurrence model information

Model code 43
USGS model code 14b
Deposit model name Sn skarn
Model code 44
USGS model code 14c
Deposit model name Replacement Sn
Model code 47
USGS model code 15b
Deposit model name Sn veins
Model code 49
USGS model code 15c
Deposit model name Sn greisen

Nearby scientific data

(1) -167.15041, 65.48827

Comments on the geologic information

  • Geologic Description = The 2- to 3-foot wide, Dalcoath dike has been mapped for over a mile of length and is highly altered for about 2,000 feet of this length. It intrudes Ordovician limestone and is one of the set of lamprophyre dikes locally present throughout the Lost River area. Faulting has deformed limestone, dike rock, and altered rocks; fault gouge is well developed in some places. The dike may have originally been emplaced along a fault but some movement has post-dated emplacement, alteration, and mineralization. Six-inch wide limestone selvages adjacent to both sides of the dike are recrystallized and contain minor topaz and scattered tremolite. Some tremolite mats are developed along bedding. Cassiterite, intergrown with danburite, is locally abundant in this altered limestone (Knopf, 1908, p. 51). Alteration of the dike includes disseminated replacement by quartz, white mica, tourmaline, arsenopyrite, and pyrrhotite. Arsenopyrite-rich replacement is well developed along the hanging wall contact and small cassiterite grains are disseminated in the highly altered rocks (Knopf, 1908, p. 51). Samples of quartz-tourmaline rock contain up to 1.9% tin but only 3 ppm tungsten (Hudson, 1983). . Layered tactite is well developed on the lower slopes south of the Dalcoath dike. This tactite is also present on the lower part of the west side of the ridge cut by the Dalcoath dike in the area of the Hidden dike prospect (TE053). A positive magnetic anomaly detected by an airborne survey (McDermott, 1983) is developed in the Dalcoath dike area (Hudson, 1983).
  • Age = the age of the mineralization is assumed to be related to the development of tin systems in the Lost River area and therefore Late Cretaceous, the age of the tin-mineralizing granites there (Hudson and Arth, 1983).

Economic information

Economic information about the deposit and operations

Development status Prospect

Comments on exploration

  • Status = Inactive

Mining district

District name Port Clarence

Comments on the reserve resource information

  • Reserves = Not defined

Comments on the workings information

  • Workings / Exploration = Prospect pits scattered along the dike, a 100-foot long adit, and a 25-foot deep shaft were completed by 1918 (Steidtmann and Cathcart, 1922, p. 76-77). There has been only occasional surface observation and sampling since.

Reference information

Links to other databases

Agency Database name Acronym Record ID Notes
USGS Alaska Resource Data File ARDF TE052

Bibliographic references

  • Deposit

    Knopf, Adolph, 1908, Geology of the Seward Peninsula tin deposits, Alaska: U.S. Geological Survey Bulletin 358, 71 p.

  • Deposit

    Steidtmann, Edward, and Cathcart, S. H., 1922, Geology of the York tin deposits, Alaska: U.S. Geological Survey Bulletin 733, 130 p.

  • Deposit

    Cobb, E.H., and Sainsbury, C.L., 1972, Metallic mineral resource map of the Teller quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-426, 1 sheet, scale 1:250,000.

  • Deposit

    Sainsbury, C.L., 1972, Geologic map of the Teller quadrangle, Seward Peninsula, Alaska: U.S. Geological Survey Map I-685, 4 p., 1 sheet, scale 1:250,000.

  • Deposit

    McDermott, M.M., 1983, Investigation of the magnetic contact aureoles of the Khotol and Black Mountain granites, Alaska: Anchorage, Alaska, Anaconda Minerals Company internal report (Report held by Cook Inlet Region, Inc., Anchorage, Alaska).

  • Deposit

    Hudson, T.L., and Arth, J. G., 1983, Tin-granites of Seward Peninsula, Alaska: Geological Society of America Bulletin, v. 94, p. 768-790.

  • Deposit

    Sainsbury, C.L., 1969, Geology and ore deposits of the central York Mountains, western Seward Peninsula, Alaska: U.S. Geological Survey Bulletin 1287, 101 p.

  • Deposit

    Cobb, E.H., 1975, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Teller quadrangle, Alaska: U.S. Geological Survey Open-File Report 75-587, 130 p.

  • Deposit

    Hudson, T.L., 1983, Interim report on the Lost River district, Seward Peninsula, Alaska: Anchorage, Alaska, Anaconda Minerals Company internal report (Report held by Cook Inlet Region, Inc., Anchorage, Alaska).

Comments on the references

  • Primary Reference = Knopf, 1908 (USGS B 358); Hudson, 1983

General comments

Subject category Comment text
Deposit Model Name = Alteration and mineralization along lamprophyre dike in Ordovician limestone. Deposit analog is not clear; possibly tin vein model (15b), or at depth, tin skarn, replacement, or greisen models(14b, 14c, and 15c) after Cox and Singer (1986).
Deposit Model Number = 14b, 14c, 15b, 15c

Reporter information

Type Date Name Affiliation Comment
Reporter 10-MAY-98 Travis L. Hudson Applied Geology