Salmon River

Mine, Active

Commodities and mineralogy

Geographic location

Quadrangle map, 1:250,000-scale HG
Quadrangle map, 1:63,360-scale D-6
Latitude 58.9205
Longitude -161.715
Nearby scientific data Find additional scientific data near this location
Location and accuracy This placer mine is along the Salmon River, which is the main drainage on the east side of Red Mountain. Its mouth is on Kuskokwim Bay is about 10 miles south of the community of Platinum. Dredge mining took place from the mouth of Boulder Creek (HG026), downstream for about five miles to within 11/4 mile of the mouth of the river. The map site is at the approximate midpoint of the dredge tailings near the center of section 36, T. 14 S, R. 75 W.

Geologic setting

Geologic description

This placer mine is located in the present valley of Salmon River. Dredge mining took place from the mouth of Boulder Creek (HG026), a west tributary, downstream about five miles to within 11/4 mile of the mouth of the river. The dredge tailings commonly are a few hundred feet wide and confined to the active drainage. The pay streak was 300 to 450 feet wide, except near the mouth of Platinum Creek (HG014) where it was up to 600 feet wide (Mertie, 1969). Overburden gravel, sand, and silt deposits vary from 30 to 80 feet thick and do not change systematically in thickness. The gravels are mostly well-rounded pebbles and cobbles up to 2 feet across interbedded with sand and silt; clay is not present. The pay is on an uneven, non-weathered bedrock surface that is locally incised up to 20 feet; in the overlying 2 feet of gravels; and in 2 feet of fractured bedrock. The tenor of the worked pay streak was 0.002 to 0.026 ounce of platinum group metals (PGM) per cubic yard (Fechner, 1988). PGM grains become smaller southward through the Salmon-River pay streak, from 0.2 to less than 0.002 inch in diameter. Four samples of tailings from this mine contained up to 0.0037 ounce of PGM per cubic yard (Fechner, 1988, p. 190, 193). PGM grains from Salmon River valley and bench tailings contain 0.6 to 1.1 percent rhenium, 0.4 to 0.7 percent ruthenium, 60.3 to 85.5 percent platinum, 3.8 to 25.6 percent iridium, 1.2 to 6.3 percent osmium, and 5.9 to 8.9 percent iron (Fechner, 1988). The PGM-bearing phases identified in these samples included iron-platinum alloy containing 8 to 30 percent iron; iron-platinum alloy with minor osmiridium inclusions; and osmiridium, sperrylite, and tetraferroplatinum (Fechner, 1988). Small amounts of cinnabar and traces of native mercury have been identified in dredge concentrates (Mertie, 1976). Two small diamonds were identified in the nondissolved residue from 8 PGM granules (Mertie, 1976). The Salmon River placer is continuous with the placer in Platinum Creek (HG014) and with the placers in some of its other west tributaries. The pay streak apparently ends or becomes uneconomic at the south end of the mine workings. The workings there are all below 150 feet in elevation and their proximity to the coastline and low elevation suggests that Quaternary sea level changes could have influenced placer development.
XP Platinum Ltd. purchased the property which consisted of 1,531 Federal placer mining claims and 42 Federal lode mining claims in 2007 and by 2008 all permits had been approved to begin mining (Amarant Mining, 2011, 2012). In 2009, XP Platinum Ltd. began a sampling program of the tailings. Watts, Griffis, and McQuat collected samples with a 10-inch drill and operated a 300-ton-per-hour processing plant from July to October (Szumigala and others, 2010). In 2011, a recovery plant with a single production line capable of producing 1,700 ounces of platinum group metals (per season?) was in operation and produced an unstated but probably substantial amount of PGMs. As of November, 2011, Amarant Mining Ltd. has taken control of XP Platinum by ownership of more than 50 percent of its stock (Amarant Mining, 2011, 2012).
Amarant Mining (2011, 2012) estimates the resources of their ground on the Salmon River and its tributaries as 65 million of material with an average grade of 0.0258 ounce of PGM per ton, i.e, 1,677,000 ounces of PGM. About 45 million tons of the resources are in the old dredge tailings; the other 20 million tons are in virgin ground.
Geologic map unit (-161.717225269115, 58.9197160114962)
Mineral deposit model PGM-gold placer (Cox and Singer, 1986; model 39b).
Mineral deposit model number 39b
Age of mineralization Quaternary.

Production and reserves

Workings or exploration The Salmon River valley paystreak was worked by dredge starting in 1937, and several parallel channels that total about 15 to 20 miles of workings up to 60 feet deep have been made. Considerable exploration drilling was completed to delineate the paystreak. In 2009, XP Platinum Ltd. began a sampling program of the tailings. Watts, Griffis, and McOuat collected samples with a 10-inch drill and operated a 300-ton-per-hour processing plant from July to October (Szumigala and others, 2010). In 2011, a recovery plant with a single production line capable of producing 1,700 ounces of platinum group metals (per season?) was in operation and produced an unstated but probably substantial amount of PGMs.
Indication of production Yes; medium
Reserve estimates
Fechner (1988) concluded that since the dredge recovered only about 60 percent of the PGMs that went through it, the mine tailings were a low-grade resource. He estimated that over 40 million cubic yards of tailings were present that could contain 0.0013 to 0.017 ounce of PGM per cubic yard.
Amarant Mining (2011, 2012) estimates the resources of their ground on the Salmon River and its tributaries as 65 million of material with an average grade of 0.0258 ounce of PGM per ton, i.e, 1,677,000 ounces of PGM. About 45 million tons of the resources are in the old dredge tailings; the other 20 million tons are in virgin ground.
Production notes A large part of the 650,000 ounces of PGM and 15,600 ounces of Au produced from the Salmon River area was recovered from the Salmon River. In 2009, XP Platinum Ltd. began a sampling program of the tailings. Watts, Griffis, and McQuat collected samples with a 10-inches drill and operated a 300-ton-per-hour processing plant from July to October. An unknown amount of platinum-group metals was recovered. In 2011, a recovery plant with a single production line capable of producing 1,700 ounces of platinum group metals was in operation and produced an unstated but probably substantial amount of PGMs.

References