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Broken Shovel Prospect, Iditarod District, Yukon-Koyukuk Borough, Alaska, USA

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Location: The Broken Shovel prospect is about 0.3 mile southeast of hill 2225 and 1.2 mile northwest of the Moore Creek placer mine (ID084). It is at an elevation of about 1,700 feet, about 0.3 mile southwest of the center of section 9, T. 29 N., R. 42 W., of the Seward Meridian. The location is accurate. Work in 2007 nearby identified nearby mineralization in the Spring and Troy Zones.
Geology: The Broken Shovel prospect is a N20E-trending, steeply dipping quartz-dolomite-sulfide vein in medium-grained monzonite of the Upper Cretaceous, Moore Creek pluton (Bundtzen, Laird, and Lockwood, 1988; Miller, Bundtzen, and Gray, in press). The pluton has been dated at 68.9 Ma (Miller, Bundtzen, and Gray, 2005) The Broken Shovel vein, as defined in prospect trenches and rubble, is about 5 feet thick and can be traced along strike for about 650 feet. Both walls of the vein are sericitized and a pocket of tourmaline is exposed near the its southwest end (Bundtzen, Laird, and Lockwood, 1988). Grab and chip-channel samples contained up to 555 parts per million (ppm) silver, 1,600 parts per billion (ppb) gold, 4,860 ppm copper, 1,430 ppm lead, 760 ppm zinc, 5,500 ppm arsenic, and 2,400 ppm antimony (Bundtzen, Laird, and Lockwood, 1988; McGimsey and others, 1988). Arsenopyrite, scheelite, visible gold, and lead-antimony sulfosalts have been identified in both hand specimen and by microprobe analysis; gold and tungsten values may be understated in the chemical analyses of the samples. The Broken Shovel prospect has been investigated intermittently since the 1930s by placer miners from Moore Creek, notably Elmer Keturi and Jules Stuver, who prospected the lode in the 1940s and 1950s (Don Harris, oral communication, 1983). When the prospect was examined in 1983 by the Alaska Division of Geological and Geophysical Surveys, it had been explored both by modern bulldozer cuts and much older hand-dug prospect pits (Bundtzen, Laird, and Lockwood, 1988). On the basis of numerous chip-channel surface samples, Bundtzen, Laird, and Lockwood, (1988) estimated that the Broken Shovel prospect contains an inferred resource of about 16,000 tons of material that contained about 150.0 ppm silver, and about 1.0 percent combined base metals. The average gold grade was not determined. In early 2008, Full Metals and Highbury Projects, Inc. were jointly exploring the area under a letter of agreement (Full Metal Minerals, 2008, Moore Creek; 2008, Trenching) . They dug numerous trenches and identified three zones with multiple types of mineralization. In the Spring Zone, sheeted quartz-tourmaline veins contain coarse gold and disseminated sulfides. Several notable samples across widths of from 4.0 to 11.0 meters contained 2.17 to 8.86 grams of gold per ton. The mineralization in the Troy Zone consists of gold-quartz veins in a wider zone of lower grade gold mineralization. Notable samples of the veins included 0.2 meters with 88.5 grams of gold per ton and 0.2 meters with 36.0 grams of gold per ton; these occur within a 3.0-meter-long channel sample that averaged 7.6 grams of gold per ton. The Broken Shovel zone is a steeply dipping quartz vein; twelve samples contained from a trace to 3.84 grams of gold per ton and 2.0 to 1,105 grams of silver per ton, along with anomalous bismuth, arsenic, and mercury.
Workings: The Broken Shovel prospect has been investigated intermittently since the 1930s by placer miners from Moore Creek, notably Elmer Keturi and Jules Stuver, who prospected the lode in the 1940s and 1950s (Don Harris, oral communication, 1983). When the prospect was examined in 1983 by the Alaska Division of Geological and Geophysical Surveys, it had been explored both by modern bulldozer cuts and by much older hand-dug prospect pits (Bundtzen, Laird, and Lockwood, 1988). The U.S. Geological Survey also investigated the prospect in 1985 ( McGimsey and others, 1988). In early 2008, Full Metals and Highbury Projects, Inc. were jointly exploring the area under a letter of agreement (Full Metal Minerals, 2008, Moore Creek; 2008, Trenching). They dug numerous trenches and identified three zones with multiple types of mineralization: the Spring, Troy, and Broken Shovel zones.
Age: Unknown; the Moore Creek pluton that hosts some of the mineralization is 68.9 Ma (Bundtzen, Laird, and Lockwood, 1988).
Alteration: The rocks adjacent to the vein have been altered to sericite, dolomite, and tourmaline.
Reserves: Based on numerous chip-channel surface samples, Bundtzen, Laird, and Lockwood, (1988) estimated that the Broken Shovel prospect contains an inferred resource of about 16,000 tons of material with about 150.0 ppm silver, and about 1.0 percent combined base metals. The average gold grade was not determined.

Commodities (Major) - Ag, Au; (Minor) - As, Cu, Pb, Sb, Zn
Development Status: None
Deposit Model: Gold--silver-quartz veins with sulfides.

Mineral List



7 entries listed. 6 valid minerals.

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References

Bundtzen, T.K., Laird, G.M., and Lockwood, M.S., 1988, Geologic map of the Iditarod C-3 quadrangle, Alaska: Alaska Division of Geological and Geophysical Surveys Professional Report 96, 13 p., 1 sheet, scale 1:63,360. Full Metal Minerals, 2008 (Moore Creek): http://www.fullmetalminerals.com/s/moorecreek.asp (as of March 4, 2008). Full Metal Minerals, 2008 (Trenching), Moore Creek Project, 2007 trenching program: http://www.fullmetalminerals.com/i/common/featurepics/August-2007-Trenching-Map.jpg (as of March 4, 2008). McGimsey, R.G., Miller, M.L., and Arbogast, B.F., 1988, Paper version of analytical results, and sample locality map for rock samples from the Iditarod quadrangle, Alaska: U.S. Geological Survey Open-File Report 88-421-A, 110 p., 1 sheet, scale 1:250,000. Miller, M.L., and Bundtzen, T.K., 1994, Generalized geologic map of the Iditarod quadrangle, Alaska showing potassium-argon, major oxide, trace element, fossil, paleocurrent, and archeological sample localities: U.S. Geological Survey Miscellaneous Field Studies Map MF-2219-A, 48 pages; 1 sheet, scale 1:250,000. 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.

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