Dexter High Bench

Past Producer in Alaska, United States with commodities Gold, Silver

Geologic information

Identification information

Deposit ID 10002087
MRDS ID A012946
Record type Site
Current site name Dexter High Bench

Geographic coordinates

Geographic coordinates: -165.35605, 64.58595 (WGS84)
Relative position This record describes a complex, high-level gold placer deposit centered on the divide at the head of Deer Gulch. Other shaft mines in the Dexter divide area are described in records NM238-243. The map location is at an elevation of about 550 feet in the SW1/4 section 30, T. 10 S., R. 33 W., Kateel River Meridian. This location is included in locality 117 of Cobb (1972 [MF 463], 1978 [OFR 78-93]).
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Geographic areas

Country State
United States Alaska

Commodities

Commodity Importance
Gold Primary
Silver Secondary

Materials information

Materials Type of material
Gold Ore

Mineral occurrence model information

Model code 119
USGS model code 39a
BC deposit profile C01. C02
Deposit model name Placer Au-PGE
Mark3 model number 54

Host and associated rocks

  • Host or associated Host
    Rock type Metamorphic Rock > Schist
  • Host or associated Host
    Rock type Sedimentary Rock > Carbonate > Limestone

Nearby scientific data

(1) -165.35605, 64.58595

Comments on the geologic information

  • Geologic Description = The Dexter High Bench placer deposit is one of three similar deposits. The others are the Summit deposit (NM247) and the deposit at the head of Dry Creek (NM248). The Dexter high-level deposit includes the relatively low-grade auriferous gravel that mantles the divide between Nekula and Deer Gulches and extends southward onto the flanks of Dexter Peak and northward to Kings Mountain. It also includes two buried paystreaks. The northern paystreak extends southeasterly, approximately from the Madeline mine (NM239) to the Gold Hill drift mine (NM243). The southern paystreak extends southeasterly from Nekula Gulch (lower Mattie, NM240) to upper Deer Gulch. The paystreaks were exceptionally rich, and Collier and others (1908, p. 199) proposed that if water could be gotten to the high-level gravels outside the paystreaks then, 'all these deposits of gravel could be sluiced at a profit.' the lower Mattie in Nekula Gulch was the first discovery; it produced 90,000 dollars in gold in 1900, its first season (Collier and others, 1908, p. 201). The lower Mattie, and probably the Caribou Bill (NM238), developed the northwest end of the southern paystreak. According to Moffit (1913, p. 102-103), the southern paystreak was almost exposed in Nekula Gulch but was buried to a depth of 135 feet at Dexter Station. It was mined nearly continuously from Nekula Gulch to Deer Gulch. The northern paystreak was worked in the upper Mattie (NM239), Snowflake (NM241), Sugar (NM242), and Gold Hill (NM243) drift mines.? the presence in the Nome district of elevated benches that could contain gold was first pointed out by Schrader and Brooks (1900, p. 12, 16, and 20). The discovery of gold in the high-level gravel at Nekula Gulch followed this report. Some of the gold recovered in the Dexter deposits was crystalline; the gold also had quartz and calcite attached and was regarded as of local origin. One gold nugget having crystalline faces weighed more than 9 ounces (Collier and others, 1908, p. 204; Moffit, 1913, p. 105).? the origin of the high-level gravel deposits has been interpreted in various ways. Collier and others (1908, p. 198) regarded them as elevated remnants of deposits of an older drainage system ' . . which have been dissected and for the most part removed.' In recent years, the deposits have been interpreted as glacier-margin channels and spillways (Hopkins and others, 1960; David M. Hopkins, cited by Cobb, 1973 [B 1374], p. 83; Nelson and Hopkins, 1972). Granite boulders possibly of glacial origin, are in the deposits, but at Dexter the boulders are at the surface, not in the pay gravels (Moffit , 1913, p. 104). Collier and others (1908, p. 199) proposed that at least some of the boulders were ice-rafted during a period of submergence. The age and origin of the high-level gravels thus still seem in question. The richness of some of the placers suggests extensive reworking, proximity to lode sources, or both.? Bedrock underlying the Dexter high-level gravels possibly includes some marble and graphitic schist (Hummel, 1962 [MF 247]; Sainsbury, Hummel, and Hudson, 1972 [OFR 72-326]), rocks apparently younger than the 'mixed unit' of Till and Dumoulin (1994). Most of the saddle area, however, is underlain by feldspathic orthogneiss and metavolcanic schist (Bundtzen and others, 1994). The Dexter area was proposed as a center of silicic volcanism similar to that at Aurora Creek (NM140). The metavolcanic rocks could be the source of some of the gold in the placer deposits.
  • Age = Quaternary, but possibly late Tertiary.

Economic information

Economic information about the deposit and operations

Development status Past Producer
Commodity type Metallic

Comments on exploration

  • Status = Probably inactive

Mining district

District name Nome

Comments on the production information

  • Production Notes = Production from the high-level gravels of the general area totaled about 100,000 ounces by 1903 (Collier and others, 1908). The high level gravels at Dexter were mostly worked out by 1906.

Comments on the workings information

  • Workings / Exploration = Gold was discovered in Nekula Gulch in 1900. About 90,000 dollars worth of gold (about 4,500 ounces) was mined in 1900. The area was developed rapidly; it was active when visited by Collier and others (1908) in 1903 and by Moffit (1913) in 1905 and 1906. The Caribou Bill probably was the richest deposit ever found in the district; some pans there contained about an ounce of gold. Material excavated from that rather small deposit (30 x 50 feet x 90 feet deep) contained about 50 ounces of gold per cubic yard. Two main, largely buried paystreaks were mined. Material hoisted from most mines contained more than 0.25 ounce of gold per cubic yard.? Erosion and reworking of the high gravel deposits appears to have been a main source of gold in upper Anvil and Dexter Creeks.

Reference information

Links to other databases

Agency Database name Acronym Record ID Notes
USGS Mineral Resources Data System MRDS A012946
USGS Alaska Resource Data File ARDF NM246

Bibliographic references

  • Deposit

    Schrader, F.C., and Brooks, A.H., 1900, Preliminary report on the Cape Nome gold region, Alaska: U.S. Geological Survey Special Publication, 56 p.

  • Deposit

    Brooks, A.H., Richardson, G. B., and Collier, A. J., 1901, Reconnaissance in the Cape Nome and Norton Bay regions, Alaska, in 1900: U.S. Geological Survey Special Publication, p. 1-180.

  • Deposit

    Collier, A. J., Hess, F.L., Smith, P.S., and Brooks, A.H., 1908, The gold placers of parts of Seward Peninsula, Alaska, including the Nome, Council, Kougarok, Port Clarence, and Goodhope precincts: U.S. Geological Survey Bulletin 328, 343 p.

  • Deposit

    Moffit, F.H., 1913, Geology of the Nome and Grand Central quadrangles, Alaska: U.S. Geological Survey Bulletin 533, 140 p.

  • Deposit

    Hopkins, D.M., MacNeil, F.S. and Leopold, E.B., 1960, The coastal plain at Nome, Alaska, A late Cenozoic type section for the Bering Sea region, in Chronology and climatology of the Quaternary: International Geological Congress, 21st, Copenhagen , Proceedings, Part 4, p. 46-57.

  • Deposit

    Hummel, C.L., 1962, Preliminary geologic map of the Nome C-1 quadrangle, Seward Peninsula, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-247, 1 sheet, scale 1:63,360.

  • Deposit

    Sainsbury, C.L., Hummel, C.L., and Hudson, Travis, 1972, Reconnaissance geologic map of the Nome quadrangle, Seward Peninsula, Alaska: U.S. Geological Survey Open-File Report 72-326, 28 p., 1 sheet, scale 1:250,000.

  • Deposit

    Cobb, E.H., 1972, Metallic mineral resources map of the Nome quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-463, 2 sheets, scale 1:250,000.

  • Deposit

    Nelson, C.H., and Hopkins, D.M., 1972, Sedimentary processes and distribution of particulate gold in the northern Bering Sea: U.S. Geological Survey Professional Paper 689, 27 p., 1 plate.

  • Deposit

    Cobb, E.H., 1973, Placer deposits of Alaska: U.S. Geological Survey Bulletin 1374, 213 p.

  • Deposit

    Cobb, E.H., 1978, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Nome quadrangle, Alaska: U.S. Geological Survey Open-File report 78-93, 213 p.

  • Deposit

    Till, A.B., and Dumoulin, J.A, 1994, Geology of Seward Peninsula and St. Lawrence Island, in Plafker, G., and Berg, H.C., eds., The Geology of Alaska: Geological Society of America, The Geology of North America, DNAG, v. G-1, p. 141-152.

  • Deposit

    Bundtzen, T.K., Reger, R.D., Laird, G.M., Pinney, D.S., Clautice, K.H., Liss, S.A., and Cruse, G.R., 1994, Progress report on the geology and mineral resources of the Nome mining district: Alaska Division of Geological and Geophysical Surveys, Public Data-File 94-39, 21 p., 2 sheets, scale 1:63,360.

Comments on the references

  • Primary Reference = Collier and others, 1908

General comments

Subject category Comment text
Deposit Model Name = Alluvial placer Au (Cox and Singer, 1986; model 39a).

Reporter information

Type Date Name Affiliation Comment
Reporter 10-JUL-00 Hawley, C.C. Hawley Resource Group
Reporter 10-JUL-00 Travis L. Hudson Hawley Resource Group