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Bluff

Producer in Alaska, United States with commodities Gold, Tungsten
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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 10308293
Record type Site
Current site name Bluff

Geographic coordinates

Geographic coordinates: -163.75225, 64.57032 (WGS84)
Relative position The Bluff lode gold deposits are located in the seacliffs just east of the mouth of Daniels Creek and inland about 4,700 feet to the north. Daniels Creek is a 1-mile drainage that flows south to its mouth on Norton Sound at Bluff. This is locality 21 of Cobb (1972, MF 445; 1978, OF 78-181).

Site location context

Political divisions (FIPS codes)

Alaska(state)

United States(country)

North America(continent)

Land(continent)

USGS map quadrangles

Solomon C-4 SW(quadrangle 1:24,000 scale)

Solomon NE(quadrangle 1:100,000 scale)

Solomon C(quadrangle 1:250,000 scale)

Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Gold Primary
Tungsten Critical Secondary

Materials information

Materials Type of material
Arsenopyrite Ore
Chalcopyrite Ore
Gold Ore
Pyrite Ore
Scheelite Ore
Clay Gangue
Quartz Gangue

Alteration

  • (Local) The surface and near-surface gold-bearing rocks are oxidized, iron-staining is common, clay in quartz veins and veinlets is developed, and remnants of more massive arsenopyrite and pyrite are locally preserved. Quartz veining apparently accompanied gold mineralization. At the nearby Saddle prospect, alteration minerals in the host schist include plagioclase, chlorite, carbonate, white mica, biotite, titanite, and tourmaline.

Mineral occurrence model information

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

Nearby scientific data

(1) -163.75225, 64.57032
ListMap

Economic information

Comments on the geologic information

  • Geologic Description = The lode gold deposits at Bluff are preferentially developed in metasedimentary schist that is intercalated in Paleozoic marble (Collier and others, 1908; Cathcart, 1922; Herried, 1965; Mulligan, 1971; Till and others, 1986). The quartz mica (+/- graphite and chlorite) schist is locally iron-stained, sulfide impregnated (especially with arsenopyrite and pyrite), and cut by small, irregular quartz veins and veinlets. Exposures of the mineralization occur in the seacliffs 1,000 feet east of the mouth of Daniels Creek; also locally in old prospect pits and shafts, for a distance of 4,700 feet inland from the coast, and in a few dozer trenches. The seacliff exposures include a subhorizontal, massive arsenopyite-pyrite lens 4 feet wide and 20 feet long that pinches down to a foot or less at its ends. The east end of this lens becomes a foot-wide quartz vein. Elsewhere in this area, the schist is iron-stained and contains disseminated sulfides; a 100-foot-long chip sample across a sulfide-bearing part of this outcrop contained 0.045 ounces Au per ton and 0.08 ounces Ag per ton (Mulligan, 1971). A 4-foot chip sample across the massive sulfide lens contained 0.18 ounces Au per ton and 0.35 ounces per Ag ton (Herried, 1965). Other grab samples from the seacliff exposures contained 0.02 to 0.42 ounces Au per ton and 0.16 to 0.55 ounces Ag per ton (Herried, 1965). A sample of oxidized arsenopyrite-rich dump material beside an old shaft inland from the beach contained 2.76 ounces Au per ton and 1.49 ounces Ag per ton; eight other samples of dump materials contained 0.03 to 0.23 ounces Au per ton and 0.03 to 1.57 ounces Ag per ton (Herried, 1965). Herried (1965) reports that scheelite can be panned from some dump materials. Composite chip samples from four dozer trenches cut across the north-trending schist belt inland from the beach were locally mineralized and included some 10-foot intervals with up to 0.04 ounces Au per ton (Mulligan, 1971). Quartz-clay veinlets were common in the mineralized parts of the trench exposures. . The nearby Saddle prospect (SO175) is probably similar to the lode gold deposits at Bluff. The Saddle prospect is known from the work of Ford (1993) and Ford and Snee (1996). A large gold and arsenic anomaly in soils led to its discovery. Gold-bearing quartz veins are localized in extensional joints in quartz-muscovite schist that strike easterly and dip moderately to the south. The veins are discontinuous and commonly less than 3 inches thick. Gold grades are irregularly distributed; vein intersections up to 3.3 feet across have contained up to 1.8 ounces Au per ton. Minerals identified in the veins include arsenopyrite, biotite, carbonate, chlorite, fluorite, marcasite, plagioclase, pyrite, pyrrhotite, quartz, titanite, and white mica. Alteration minerals in the host schist include plagioclase, chlorite, carbonate, white mica, biotite, titanite, and tourmaline. The white mica in the veins is
  • Geologic Description = muscovite and that in the schist is phengite. A sample of vein white mica gave a Ar/Ar plateau age of 109.3 +/- 0.3 Ma and metamorphic white mica in the host schist gave Ar/Ar plateau ages of 122.6 +/- 0.4 Ma and 122.4 +/- 0.2 Ma (Ford and Snee, 1996). The host schist is similar to that at the nearby Bluff (SO135), Swede Creek (SO133) and Koyana Creek (SO136) lode prospects. This schist is a band intercalated in Paleozoic marble (Herried, 1965; Mulligan, 1971; Till and others, 1986). . This deposit is also probably mid-Cretaceous, the age of some other lode gold deposits on southern Seward Peninsula. The southern Seward Peninsula lode gold deposits formed as a result of mid-Cretaceous metamorphism (Apodoca, 1994; Ford, 1993, Ford and Snee, 1996; Goldfarb and others, 1997) that accompanied regional extension (Miller and Hudson, 1991) and crustal melting (Hudson, 1994). This higher temperature metamorphism was superimposed on high pressure/low temperature metamorphic rocks of the region.
  • Age = Mid-Cretaceous; at the nearby Saddle prospect (SO175) which is probably of the same age, a sample of vein white mica gave a Ar/Ar plateau date of 109.1 +/- 0.2 Ma and metamorphic white mica in the host schist gave Ar/Ar total-gas dates of 122.6 +/- 0.4 Ma and 122.4 +/- 0.2 Ma (Ford and Snee, 1996).

Economic information about the deposit and operations

Development status Producer

Comments on exploration

  • Status = Active?

Mining district

District name Council

Comments on the production information

  • Production Notes = Mulligan (1971) notes that the small volume of waste dumps scattered about the area suggests that very little ore was mined and processed. However, an old mill here indicates that some production probably took place.

Comments on the workings information

  • Workings / Exploration = Over 50 small prospect pits and shafts are scattered northward for 4,700 feet inland from the coast. This prospecting started in the early 1900's as the first lode claims were staked in 1900. Mulligan (1971) exposed bedrock in four dozer trenches totalling 3,300 feet in length. A short, adit, not caved, was driven in the seacliff exposures. Diamond drilling has probably occurred on this property since the 1970's but the operator and results are not known.

Reference information

Bibliographic references

Comments on the references

  • Primary Reference = Ford, 1993

General comments

Subject category Comment text
Deposit Model Name = Discontinuous, irregular quartz veins and veinlets with dissemminated arsenopyrite and pyrite in metasedimentary schist; low sulfide-Au quartz vein (Cox and Singer, 1986; model 36a).

Reporter information

Type Date Name Affiliation Comment
Reporter 19-AUG-99 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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