Dalcoath Dike

Site Name

Primary: Dalcoath Dike

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Commodity

Primary: Tin

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Location

State: Alaska
District: Port Clarence

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Land Status

Not available

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Holdings

Not available

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Workings

Not available

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Ownership

Not available

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Production

Not available

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Deposit

Record Type: Site
Operation Category: Prospect
Operation Type: Unknown
Years of Production:
Organization:
Significant:

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Physiography

Not available

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Mineral Deposit Model

Model Name: Sn skarn
Model Name: Replacement Sn
Model Name: Sn greisen
Model Name: Sn veins

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Orebody

Not available

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Structure

Not available

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Alterations

Alteration Type: L
Alteration Text: The strongly altered lamprophyre dike has abundant white mica, arsenopyrite, quartz, tourmaline, danburite in places, chlorite, pyrite, and some topaz.

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Rocks

Not available

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Analytical Data

Not available

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Materials

Ore: Cassiterite
Gangue: Mica
Gangue: Tourmaline
Gangue: Pyrite
Gangue: Danburite
Gangue: Chlorite
Gangue: Arsenopyrite

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Comments

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

Comment (Exploration): Status = Inactive

Comment (Reserve-Resource): Reserves = Not defined

Comment (Workings): 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.

Comment (Geology): 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).

Comment (Commodity): Gangue = white mica

Comment (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).

Comment (Geology): 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).

Comment (Deposit): Model Number = 14b, 14c, 15b, 15c

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References

Reference (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.

Reference (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).

Reference (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.

Reference (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.

Reference (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).

Reference (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.

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

Reference (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.

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

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