Poorman Creek

Mine, Undetermined

Alternative names

Kast
Nelson And Larson

Commodities and mineralogy

Main commodities Au
Other commodities Cu; Pt; Sn; Th; U; Zr
Ore minerals cassiterite; gold; ilmenite; iridium; iridosmine; magnetite; platinum; pyrite

Geographic location

Quadrangle map, 1:250,000-scale TL
Quadrangle map, 1:63,360-scale C-2
Latitude 62.59
Longitude -150.81
Nearby scientific data Find additional scientific data near this location
Location and accuracy Poorman Creek is a tributary to Cottonwood Creek, which in turn flows southwest into Peters Creek. The location of this placer is given by Mertie (1919, p. 257), as the confluence of Poorman and Dandy Creeks, where the paystreak was reported to be widest (150 feet). Placer claims extend at least one-half mile downstream from this location as shown by the U.S. Bureau of Mines (1998). Also shown as locality 29 in Clark and Cobb (1972) and locality 85 in Reed and others (1978).

Geologic setting

Geologic description

Poorman Creek drains across the contact between Mesozoic slate and argillite (KJs) cut by Tertiary (?) soda rhyolites with associated quartz stringers and continentally derived Tertiary sedimentary rocks of the Kenai Group (Mertie, 1919; Reed and Nelson, 1980). The discovery claim is underlain by Mesozoic sedimentary rocks that strike N35E and dip 55NW (Mertie, 1919; Robinson and others, 1955; Reed and others, 1978).
Mining on Poorman Creek began at least as early as 1907 when six men recovered 1,329 ounces of gold (Garrett, 1998). Mertie (1919) reported that a bench deposit near the mouth of Dandy Creek, covered 2500 square feet and averaged 25 feet thick, or about 2300 cubic yards of gravel.
Concentrates contain cassiterite, gold, ilmenite, iridium, Ir-rich osmium, magnetite, platinum, pyrite, garnet, quartz, and zircon (Cobb and Reed, 1980). Grades of 0.09% U, 0.06% ThO2, 0.229% eU, and 0.22% Cu are reported from the concentrates (Mertie, 1919). The U.S. Geological Survey analyzed a sample of platinum metals weighing 41.6 grains, with specific gravity of 18.1, which contained 32% Ir-rich osmium, 11% iridium, 1.4% rhodium, 47.3% platinum, trace palladium, and 8.3% other elements. Concentrates were reported to run 36.54% tin, equivalent to 46% cassiterite (Mertie, 1919; Robinson and others, 1955). According to Mertie (1919), gold and cassiterite were likely to have been derived from mineralized bedrock within the drainage. He also reported that Poorman Creek contained the most platinum of any placer in the Kahiltna valley. Clark and Hawley (1968) indicate that platinum-group minerals in the Yentna District may be derived from altered mafic or ultramafic dikes that cut the Mesozoic sedimentary rocks.
Also see Peters Creek (TL045).
Geologic map unit (-150.812288847066, 62.5894826533783)
Mineral deposit model Placer Au-PGE (Cox and Singer, 1986; model 39a).
Mineral deposit model number 39a
Age of mineralization Pleistocene.

Production and reserves

Workings or exploration Garrett (1998) reports current placer mining by mechanical cut-and-fill techniques and feed hopper, trommel and sluice processing. Garrett (1998) reports current placer mining by mechanical cut-and-fill techniques and feed hopper, trommel and sluice processing. Exploration has been conducted by test drilling and pits. Hydraulic and hand-mining operations were conducted in the past.
Indication of production Yes; small
Production notes A bench deposit near the mouth of Dandy Creek mined in 1917 (Mertie, 1919) covered 2500 square feet and averaged 25 feet thick, or about 2300 cubic yards of gravel. Concentrate contained 0.09% U, 0.06% ThO2, 0.229% Eu, and 0.22% Cu. The U.S. Geological Survey analyzed a sample of platinum metals weighing 41.6 grains, with specific gravity of 18.1, which contained 32% iridosmium, 11% iridium, 1.4% rhodium, 47.3% platinum, trace palladium, and 8.3% other elements. Concentrates were reported to run 36.54% tin, equivalent to 46% cassiterite (Mertie, 1919; Robinson and others, 1955).

Additional comments

This placer ground is shown by C.C. Hawley and Associates, Inc. (1978) as part of the reserve area held by the Peters Creek Mining Corporation. See also Peters Creek (TL045).

References

MRDS Number M045408

References

Garrett, D. R., 1998, The Blue Ribbon mine, Yentna mining district, Alaska: Worldwide Web URL http://www.alaska.net/~freegold/brm.html.
U.S. Bureau of Mines, 1998, Minerals Availability System/Minerals Industry Location System (MAS/MILS), Talkeetna quadrangle: Worldwide Web URL http://imcg.wr.usgs.gov/data.html.
Reporters Madelyn A. Millholland (Millholland & Associates)
Last report date 8/10/1998