Joaquin Prospect, Iditarod District, Yukon-Koyukuk Borough, Alaska, USA
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Geology: The Joaquin prospect consists of thin quartz -sulfide veinlets and stringer zones in a small calcareous sandstone inclusion within the Upper Cretaceous, Mount Joaquin pluton (Malone, 1962; Bundtzen and Laird, 1983). The quartz veinlets contain disseminated grains of cinnabar and arsenopyrite. The prospect is exposed in lichen-covered talus near the toe of a talus fan; the mineralized zone can be traced for about 50 feet along strike and it is about 2 feet thick. The property was staked as a mercury prospect in 1957 but no production has been reported (Malone, 1962). One grab sample from the prospect dump contained 2.00 percent mercury, 240 parts per billion (ppb) gold, 800 ppb silver, and 2.00 percent arsenic (Miller, Bundtzen, and Gray, 2005).
Workings: The Mount Joaquin mercury prospect has appeared on many compilations of Alaskan mercury deposits (i.e., Sainsbury and MacKevett, 1965; Malone, 1962). The property was located as a mercury prospect by Knute P. Lind in 1957, but no production has been reported (Malone, 1962). In 1978, a crude pit about 15 feet square that was dug in talus in talus was still visible (T.K. Bundtzen, unpublished field data, 1978).
Age: Undated; may be related to emplacement of the Mount Joaquin pluton, which has a 40K/40Ar age of 70.6 Ma (Bundtzen and Laird, 1983).
Production: None recorded, but the site was equipped to be small scale mercury producer in the late 1950s (J. Murphy, oral communication, 1987). A retort was to be assembled on site. A small cabin in a state of disrepair in 1978 was about 1,000 feet from the prospect pit. The cabin contained mallets, sledge hammers, and a small crusher (T.K. Bundtzen, unpublished data, 1978).
Commodities (Major) - Hg; (Minor) - Ag, As, Au
Development Status: None
Deposit Model: Polymetallic vein (Cox and Singer, 1986; model 22c).
3 entries listed. 3 valid minerals.
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Bundtzen, T.K., and Laird, G.M., 1983, Geologic map of the Iditarod D-1 quadrangle, Alaska: Alaska Division of Geological and Geophysical Surveys Professional Report 78, scale 1:63,360. Cobb, E.H., 1972, Metallic mineral resources map of the Iditarod quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-363, 1 sheet, scale 1:250,000. Malone, Kevin, 1962, Mercury occurrences in Alaska: U.S. Bureau of Mines Circular 8131, 57 p. Miller, M.L., Bundtzen, T.K., and Gray, J.E., 2005, Mineral resource assessment of the Iditarod quadrangle, west-central Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-2219-B, scale 1:250,000, pamphlet. Sainsbury, C.L., and MacKevett, E.M., Jr., 1965, Quicksilver deposits of southwestern Alaska: U.S. Geological Survey Bulletin 1187, 89 p.