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Unnamed Occurrence (ARDF - LH011; head of Hartman River), McGrath District, Bethel Borough, Alaska, USA

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Location: This occurrence is on a ridge along the north side of the upper Hartman River valley. It is at an elevation of 6,000 feet, one mile north of the glacier in the northwest headwater tributary of Hartman River. The map site is in the NE1/4 section 19, T 19 N, R 24 W, of the Seward Meridian. This is locality 3 of Cobb (1972 [MF 412]; 1976 [OF 76-485]) and and Cobb and Reed (1981). The location is probably accurate to within a quarter of a mile.
Geology: Reed and Elliott (1970, p. 22) reported that a 2-inch-wide quartz vein containing less than 2 percent finely disseminated molybdenite crosscuts quartz diorite at this locality. A sample of this vein also contained 300 ppm tungstenand 3.2 ppm gold. Allen and others (1990, samples 104, 111, 112) collected several samples from the south flank of the ridge where this vein was found. These samples were of graywacke containing disseminated pyrite; limonite-stained quartz veins containing pyrite and some chalcopyrite; and quartz-calcite veins in granitic rock. These samples contained as much as 3.5 ppm gold, 200 ppm silver, 700 ppm copper, 150 ppm antimony, and greater than 10,000 ppm arsenic. The sedimentary rocks are Jurassic and Lower Cretaceous, and the Upper Cretaceous or Tertiary granitic rocks are part of the Alaska-Aleutian Range batholith (Reed and Lanphere, 1973; Nokleberg and others, 1994).
Workings: Reconnaissance surface observation and sampling has been completed at this locality (Reed and Elliott, 1970).
Age: Late Cretaceous or Tertiary. The veins crosscut granitic rocks of the Upper Cretaceous or Tertiary part of the Alaska-Aleutian Range batholith.
Alteration: Silicification and oxidation.

Commodities (Major) - Au, Mo, W; (Minor) - Ag, Cu, Sb
Development Status: None
Deposit Model: Polymetallic veins (Cox and Singer, 1986, model 22c)

Mineral List



6 entries listed. 5 valid minerals.

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References

Allen, M. S., Malcolm, M. J., Motooka, J. M., and Slaughter, K. E., 1990, Geologic description, chemical analyses, and sample locality map for rock samples collected from the eastern part of the Lime Hills quadrangle, Alaska: U.S. Geological Survey Open-File Report 90-69, 49 p., 1 sheet, scale 1:250,000. Cobb, E.H., 1972, Metallic mineral resources map of the Lime Hills quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-412, 1 sheet, scale 1:250,000. Cobb, E.H., 1976, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Iliamna, Lake Clark, Lime Hills, and McGrath quadrangles, Alaska: U.S. Geological Survey Open-File Report 76-485, 101 p. Cobb, E.H., and Reed, B.L., 1981, Summaries of data on and lists of references to metallic and selected nonmetallic mineral occurrences in the Iliamna, Lake Clark, Lime Hills, and McGrath quadrangles, Alaska; Supplement to Open-File Report 76-485; Part A, Summaries to January 1, 1981: U.S. Geological Survey Open-File Report 81-1343-A, 25 p. Nokleberg, W.J., and (seven) others, 1994, Metallogeny and major mineral deposits of Alaska and Metallogenic map of significant metalliferous lode deposits and placer districts of Alaska, in Plafker, G. and Berg, H.C., eds., The Geology of Alaska: Geological Society of America, DNAG, The Geology of North America, Vol.. G1, p. 855-904, Plate 11, scale 1:2,500,000. Reed, B.L., and Elliott, R.L., 1970, Reconnaissance geologic map, analyses of bedrock and stream sediment samples, and an aeromagnetic map of parts of the southern Alaska Range: U.S. Geological Survey Open-File Report 70-217, 145 p., 1 sheet, scale 1:250,000. (Also published as U.S. Geological Survey Open-File Report 413) Reed, B.L., and Lanphere, M.A., 1973, Alaska-Aleutian Range batholith--Geochronology, chemistry, and relation to circum-Pacific plutonism: Geological Society of America Bulletin, v. 84, no. 8, p. 2583-2610.

 
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