Rapid River

Site Name

Primary: Rapid River

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Commodity

Primary: Beryllium
Primary: Fluorine-Fluorite
Secondary: Tin
Secondary: Zinc
Secondary: Copper
Secondary: Silver
Secondary: Lead

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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

Not available

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Orebody

Not available

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Structure

Not available

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Alterations

Alteration Type: L
Alteration Text: Some lamprophere dikes have tactite borders but these may not be related to mineralization. The origin of dolomite and dolomite breccia is also not clear here. Mass balance calculations show significant SiO2, Al2O3, alkali, and fluorine enrichment with mineralization (Sainsbury, 1968, p. 1567).

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Rocks

Not available

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Analytical Data

Not available

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Materials

Ore: Bertrandite
Ore: Cassiterite
Ore: Chrysoberyl
Ore: Euclase
Ore: Fluorite
Ore: Galena
Ore: Phenacite
Ore: Sphalerite
Gangue: Diaspore
Gangue: Hematite
Gangue: Tourmaline
Gangue: Silica
Gangue: Mica

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Comments

Comment (Exploration): Status = Inactive

Comment (Reference): Primary Reference = Sainsbury, 1963; Sainsbury, 1968; Sainsbury, 1969

Comment (Reserve-Resource): Reserves = Not defined

Comment (Workings): Workings / Exploration = A few dozer trenches and several diamond drill holes have been completed on the prospect.

Comment (Deposit): Model Name = Fluorite- and beryllium-bearing veins and replacements in Ordovician limestone (Sainsbury, 1968)

Comment (Geology): Geologic Description = Banded fluorite-chrysoberyl veinlets, veins, pipes, and irregular replacements are present in Lower Ordovician limestone and dolomite in the footwall of the Rapid River fault. Sainsbury (1969; 1972) maps the Rapid River fault as a 12-mile long east-west trending thrust fault in the southern part of the York Mountains although stratigraphic relations across the fault suggest normal displacement. The fluorite-chyrsoberyl mineralization is locally present over an area 4,400 feet long (east-west) and about 1,000 feet wide. Lamprophyre dikes are also common in this area and some dike borders localize fluorite-chyrsoberyl replacements. Individual veins are generally 1 to 3 inches wide and spaced 6 to 18 inches apart but some irregular replacements are up to 25 feet across. Structures with a general east-west orientation, such as joints, small faults, and dike borders are a dominant control on mineralization. The mineralization includes minor euclase, bertrandite, and phenakite (?). Gangue minerals are diaspore, white mica, tourmaline, and hematite; fine-grained silica is locally present along the mineralized zones. BeO contents of 12 samples range from 0.15 to 1.05%; fluorite content of two samples is 57% (Sainsbury, 1963, p. 11). Diamond-drilling by Newmont Mining Company in 1963 encountered mineralization in the footwall of the Rapid River fault a few hundred feet below the surface. This drilling encountered sulfide mineralization in the cores of some veins. The sulfide minerals include galena and sphalerite; minor cassiterite is associated with the sulfides (Sainsbury, 1969, p. 77). Newmont attempted to find this early drill data in 1998 but was unsuccessful. However, the old project files did contain a report on metallugical testing of samples obtained by the 1963 drilling (Porter, 1964). One sample, a composite from drill holes 9 through 14, weighed 100 pounds and containted 12.0% CaF2 , 0.086% BeO, and 56.4% CaCO3. A second sample, a composite from drill holes 2, 8, 21, 22, and a 10-foot channel in a surface trench, weighed 50 pounds and contained 27.4% CaF2, 0.22% BeO, and 34.5% CaCO3. Bench-scale sink-float tests showed that this material could be upgraded to about 50% CaF2 and 0.35% BeO. The metallugical test results indicated that the beryllium was associated with silicate minerals and did not directly follow fluorite through the procedures.

Comment (Commodity): Gangue = white mica

Comment (Geology): Age = 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).

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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): 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): Sainsbury, C.L., 1968, Tin and beryllium deposits of the central York Mountains, Alaska, in Ridge, J. D., ed., Ore deposits in the United States, 1933-67: American Institute of Mining, Metallurgy, and Petroleum Engineers, v. 2, p. 1555-1572.

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): 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): Sainsbury, C.L., 1963, Beryllium deposits of the western Seward Peninsula, Alaska: U.S. Geological Survey Circular 479, 18 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.

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