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Third of July

Prospect in Alaska, United States with commodity Tin
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Sections on this page
  1. Identification information
  2. Geographic coordinates
  3. Site location context
  4. Geographic areas
  5. Commodities
  6. Materials information
  7. Alteration
  8. Mineral occurrence model information
  9. Nearby scientific data
  10. Economic information about the deposit and operations
  11. Mining district
  12. Links to other databases
  13. Bibliographic references
  14. General comments
  15. Reporter information

Geologic information

Identification information

Deposit ID 10308418
Record type Site
Current site name Third of July

Geographic coordinates

Geographic coordinates: -167.04641, 65.51227 (WGS84)
Relative position The Third of July prospect is located at an elevation of 1,250 feet on the south side of an Ordovician limestone ridge that separates the headwaters of Anderson Creek and an unnamed 13-mile long stream that flows south to Brevig Lagoon. Anderson Creek, with headwaters on the southeast slopes of Brooks Mountain, flows east to the Don River. The prospect is on the south side of a prominent saddle (1,350 feet elevation) developed at the head of north and south draining gulches. The pass between Anderson Creek headwaters and the unnamed stream to the south, at 640 feet elevation, is 0.75 miles west of the prospect. This locality was not identified by Cobb and Sainsbury (1972) or Cobb (1975).

Site location context

Political divisions (FIPS codes)

Nome(Census area)

Alaska(state)

United States(country)

North America(continent)

Land(continent)

USGS map quadrangles

Teller C-5(quadrangle 1:63,360 scale)

Teller NE(quadrangle 1:100,000 scale)

Teller(quadrangle 1:250,000 scale)

Hydrologic units (watersheds)

Imuruk Basin(hydrologic unit)

Norton Sound(hydrologic accounting unit)

Northwest(hydrologic subregion)

Alaska(hydrologic region)

Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Tin Critical Primary

Comments on the commodity information

  • Gangue = sulfide minerals

Materials information

Materials Type of material
Cassiterite Ore
Mica Gangue
Quartz Gangue
Topaz Gangue
Tourmaline Gangue

Alteration

  • (Local) Thermal recrystallization of limestone, minor skarn in limestone, minor endoskarn in granite, fluorite-bearing veins and veinlets in both limestone and granite, and local greisenization of granite are all present in the prospect area.

Mineral occurrence model information

Model code 49
USGS model code 15c
Deposit model name Sn greisen

Nearby scientific data

(1) -167.04641, 65.51227
ListMap

Economic information

Comments on the geologic information

  • Geologic Description = This prospect is a 500 x 500 foot area of prophyritic granite intrusion in Ordovician limestone. Sainsbury (1969, plate 1) mapped the location of the granite and noted the presence of beryllium-bearing minerals here. Anaconda Minerals Company completed detailed mapping, sampling, and gravity and magnetic surveys in the prospect area during parts of the summers of 1982 and 1983 (Hudson and Wyman, 1983). This work indicates that the exposed granite is a small part of a larger granite body at depth. The exposed intrusion is porphyritic biotite granite with quartz and feldspar phenocrysts in an aplitic groundmass. Thin, 1 to 2.5 inch wide aplite dikes, some with disseminated purple fluorite, cut the porphyritic granite. The age of the mineralization is assumed to be similar to that of tin systems in the Lost River area and therefore Late Cretaceous, the age of the tin-mineralizing granites there (Hudson and Arth, 1983). . Ordovician limestone intruded by the granite has been thermally recrystallized over large areas. Thin quartz-fluorite, calcite-fluorite, or fluorite veins and veinlet stockworks are widespread and common within 300 feet of the granite contact. Minor skarn, developed locally along the limestone-granite contact, includes light green quartz, fluorite, epidote, calcite bands with purple fluorite veins and some sulfide minerals. Sulfide minerals include pyrite and pyrrhotite in altered limestone and granite. Endoskarn is locally developed where remnant quartz phenocrysts are present within light to dark green epidote-fluorite-sericite assemblages. Intense silicification of limestone is also locally present in the contact zone. The porphyritic granite is altered to greisen along structural zones and fractures. These altered rocks typically contain vuggy clots of tourmaline crystals in a light colored, aphanitic matrix (quartz and mica?). Vuggy quartz-tourmaline veins up to one-foot wide cut granite and greisen. The exposed granite is similar to precursor granites (Hudson and Reed, 1997, figure 3) and not the fine-grained, equigranular, and leucocratic granite more directly associated with tin metallization elsewhere on Seward Peninsula (Hudson and Arth, 1983). A mineralizing granite phase could be present in the subsurface of this area. Most cassiterite mineralization is associated with altered rocks within granite. Gossan fragments have up to 0.2% tin but only weakly anomalous lead and zinc (100 to 500 ppm). Arsenic, tungsten, and base metals are generally present at low levels; elevated tin, fluorine, and boron characterize the metasomatism here. Greisen samples contain up to 0.4% tin, 5,800 ppm fluorine, and greater than 20,000 ppm boron.
  • Age = the age of the mineralization is assumed to be similar to that 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 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 = Surface mapping and sampling and a few shallow hand-dug surface pits have been completed here. An airborne magnetic survey and a gravity survey have been completed over the prospect (McDermott in Hudson and Wyman, 1983, p. 68-71).

Reference information

Bibliographic references

  • 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

    Hudson, T.L., and Wyman, W. F., 1983, Interim report on areas of Seward Peninsula warranting further prospecting and evaluation: Anchorage, Anaconda Minerals Company internal report, 84 p., 7 plates. (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

    Hudson, T.L., and Reed, B.L., 1997, Tin deposits of Alaska, in Goldfarb, R.J., and Miller, L.D., eds., Mineral Deposits of Alaska: Economic Geology Monograph 9, p. 450-465.

  • 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

    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.

Comments on the references

  • Primary Reference = Hudson and Wyman, 1983.

General comments

Subject category Comment text
Deposit Model Name = Tin greisen in granite. (Cox and Singer, 1986; model 15c)

Reporter information

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

Beyond USGS

Supplemental information added by qvyshift.com. Not part of the original USGS MRDS record.

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Authoritative Alaska resources

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