Submarine Beach Mine, Nome Mining District, Nome Census Area, Alaska, USAi

Regional Level Types
Submarine Beach Mine	Mine
Nome Mining District	Mining District
Nome Census Area	Census Area
Alaska	State
USA	Country

Location: Submarine Beach is a composite abrasion-platform gold deposit that can be traced from Dry Creek at Nome west as far as Jess Creek (a minor drainage about a mile east of the mouth of Penny River). It is richest and best developed west of Nome near the Nome airport. The map location in the northeast corner of section 28, T. 11 S., R. 34 W., Kateel River Meridian, represents the general area between two composite elements, the so-called Inner and Outer Submarine Beaches. The Inner Beach is one-quarter to one-half mile inland from the modern beach and is about about 20 feet below sea level. The Outer Beach is 300 to 1,000 feet inland from the modern beach and is at an elevation of about 35 feet below sea level. Submarine Beach is locality 139 of Cobb (1972 [MF 463], 1978 [OFR 78-93]).
Geology: Submarine Beach is the oldest recognized placer deposit that developed on the abrasion platform of the Third Beach strandline. It is irregular, but has a crudely linear trend from near the mouth of Dry Creek at Nome west as far as Jess Creek in the Nome C-2 quadrangle. Average elevations on the Inner and Outer elements of the beach are below sea level, at about -20 and -35 feet respectively, but the range of elevations is between about -10 and -40 feet (Metcalfe and Tuck, 1942, p. 36). Near Nome, the deposit is on silt false bedrock. Near its western recognized limit at Jess Creek, Submarine Beach is on schistose bedrock. In the area west of Nome, where the deposit has been dredged, the overall configuration suggests a fan-like placer gold deposit that could have accumlated at the mouth of an ancestral Anvil Creek. According to Metcalfe and Tuck (1942, p. 36), 'The wide distribution of gold in general indicates that it may have been the result of an old beachline that was higher than the sea that destroyed it.' In common with the other abrasion so called beaches, such as Center Creek (NM286), Intermediate (NM287), and Monroeville (NM257), sulfides are abundant in the placer concentrates, along with some scheelite. The sulfide minerals are principally arsenopyrite, chalcopyrite, and pyrite. Chalcopyrite was especially abundant in the 'Outer' beach (Moffit, 1913, p. 119). Garnet occurs, but it does not form the ruby sand lenses that typify the true strandline beaches, such as Present (NM254), Second (NM256), and Third (NM258). The sulfide minerals probably contain gold. In 1939, samples of the Submarine Beach deposit contained 1.059 pounds of sulfide per cubic yard in the interval above bedrock, and cleaned sulfide concentrate contained 14.10 dollars worth of gold per ton of concentrates. Although the sulfides were cleaned by panning and amalgamation, some of the gold probably is still present as very fine grained free gold. The placer gold of Submarine Beach was relatively coarse compared with other beach or abrasion deposits; numerous nuggets weighed as much as 0.5 ounce (Moffit, 1913, p. 118). The Submarine beaches were discovered in 1907 and were developed by shafts about 70 feet deep. One shaft in the 'Inner' beach bottomed at an elevation of about -20 feet (Smith, 1909, p. 271-273; Moffit, 1913, p. 118-119). The deposit consisted of alternating layers of sand and gravel, gravel predominating at depth. The gravel consisted mainly of 'slate' (their term), greenstone, schist, feldspathic schist, and limestone (marble). It also contained boulders of granite and quartz of as much as 2 feet across. The quartz boulders were semi-angular but with apparently water-rounded corners. Sand layers in the beach also contained mollusk shells, more broken, hence inferred to be older, than the shells in Intermediate Beach. The Submarine Bench deposits were mined from about 1908 into the 1990s. One large bucket-line dredge operated on Submarine Beach from about 1975 until 1995.
Workings: Submarine Beach was discovered in 1907 and was at first worked from underground drift mines in frozen ground. After the development of cold-water thawing in the 1920's, the deposit was worked by bucket-line dredges that mined the thaw-fields after one or two years of thawing. The Submarine Beach was reopened after gold was allowed to seek a free-market price (Kastelic, 1975). The mine was shut down in 1995, when thawing and other operating costs exceeded the value of the ground, which is on the order of 0.01 to 0.015 ounce of gold per cubic yard of mining section (Bundtzen and others, 1995). High-resolution seismic surveys and drilling related to the development of the offshore gold resource have contributed to the knowledge of the Submarine Beaches (Nelson and Hopkins, 1972; Tagg and Greene, 1973).
Age: Late Tertiary to Pleistocene. Fossils in the Submarine deposits were reported as late Miocene or Pliocene (Moffit, 1913, p. 45-48). Hopkins, MacNeil, and Leopold (1960) postulate that Submarine Beach could be as old as Pliocene.
Reserves: The Submarine Beach mine area contains a gold resource that could be mined under favorable economic conditions.

Commodities (Major) - Ag, Au; (Minor) - Cu, W
Development Status: Yes; small
Deposit Model: Marine placer gold deposit; intergrading marine abrasion and fan-like deposits

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Link to USGS - Alaska:	NM285

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References