McCarty Mine, Fairbanks Mining District, Fairbanks North Star Borough, Alaska, USAi

Regional Level Types
McCarty Mine	Mine
Fairbanks Mining District	Mining District
Fairbanks North Star Borough	Borough
Alaska	State
USA	Country

Location: Cobb (1972, MF-413), loc. 46; NW1/4NE1/4 sec. 28, T. 3 N., R. 2 E., of the Fairbanks Meridian. The McCarty Mine is labeled on the Livengood A-1 quadrangle. Ore was brought to this mill from a group of six claims at the head of Fairbanks Creek.
Geology: The McCarty mine milled ore from the Henry Ford group of claims which included ore from both the McCarty vein (ARDF no. LG150), the Henry Ford vein (ARDF no. LG153) and the American Eagle vein, which is located closest to the mill. This mine is located at the head of Fairbanks Creek and has been one of the largest lode-gold producers in the Fairbanks Creek area, second only to the Hi-Yu mine (ARDF no. LG182). Country rock in the area is generally quartz-mica schist, but quartzite schist and calcareous schist are also present. Sericitization is said to characterize the wall rock near the vein (Joesting, 1941). Most ore milled came from the nearby American Eagle vein, which is from one to three feet thick, strikes N 60 W, dips 55 to 60 SW; it consists of coarsely crystalline quartz with free gold and small proportions of jamesonite, stibnite, arsenopyrite and sphalerite (Joesting, 1941, p. 3). Occasional large kidneys of high-grade stibnite, with up to 60.66% antimony, are associated with the vein (Joesting, 1941, p. 3). The McCarty group of veins at the head of Fairbanks creek were mined sporadically from 1911 to 1917 and almost continously from 1927 to 1942, with production estimates ranging from 26,800 ounces from 16,750 tons of ore grading 1.6 ounces of gold per ton (Porterfield and Croff, 1986), to an estimated 60,000 ounces of gold (Metz and others,1987). There is no record of work on the property from 1942 until 1984, when Placid Oil Company drilled 6,137 feet in 23 diamond core holes. Preliminary ore reserves from this work were calculated at 15,000 tons grading 0.80 ounces of gold per ton. In 1987 and 1988, Fairbanks Exploration, Inc. conducted geochemical sampling of stamp sand tailings and waste dumps of the McCarty mine. Stamp sands yielded gold values of 0.314 and 1.028 ounces of gold per ton with highly anomalous silver, antimony and arsenic (Fairbanks Exploration Inc., unpublished report, 1986). Geochemical samples collected during the 1987 field program were designed to test the precious metal content of the McCarty mine tailings dumps. This site contains stamp sands with interbeds of sulfide rich material in which fine gold occurs in its native form and as inclusions in arsenopyrite and pyrite. The McCarty mine tailings ponds exhibit distinct sulfide and gold rich lenses from 1 to 4 inches thick separated by 1 to 2 feet of virtually clean quartz sand. The average gold grades from the McCarty mine waste dumps range from 0.132 to 0.158 ounces of gold per ton (Fairbanks Exploration Inc., unpublished report, 1988).
Workings: The McCarty mine, also known as the American Eagle mine, was one of the most productive gold mines in the district. The American Eagle shear zone was accessed through the American Eagle adit and American Eagle shaft. Although the old stamp mill and head-frame of the American Eagle shaft are still standing, the underground workings of the mine are inaccessible (Freeman, 1992). During the winter of 1914-1915, a 450 foot adit was driven on the American Eagle claim and significant amounts of ore were extracted during the summer of 1915 (Stewart, 1915). The American Eagle shaft had been sunk to a depth of 107 feet by 1915 (Brooks, 1915). In 1936, United States Smelting Refining and Mining Company (USSR&M) began drifting along the 135-foot level through the American Eagle shaft (Smith, 1939; B 910). Extensive development continued in 1938 but the results of bulk sampling were not encouraging (Smith, 1939; B 917). USSR&M sank 120 feet of shaft in the American Eagle shaft, put in 625 feet of raise and drove 1,816 feet of drift, cross-cuts and adit in 1938 (Reed, 1939). Mining continued in 1939 when USSR&M completed 465 feet of drifts and crosscuts and nearly 400 feet of raising. The ore was treated in a 2 stamp Nissen mill and the tailings were impounded for later up-grading (Smith, 1941). Mining continued in 1940 during which 639 feet of drifts and crosscuts were driven as well as 545 feet of raises. The American Eagle shaft was deepened to 250 feet giving access to over a mile of drifts and 1,750 feet of raises on the 28, 135 and 235 foot levels (Smith, 1942). Mining continued in 1941 when USSR&M sank a 65 foot winze from the east end of the 235 level. USSR&M maintained the properties until 1958 but no further mining was reported from the mine (Porterfield and Croff, 1986). In 1984, Placid Oil Company drilled 6,137 feet in 23 diamond core holes. During this period Alaska Mineral Services constructed a small carbon-in-pulp leach plant (the Haskins mill) at the McCarty mine site to treat stamp mill sands from the McCarty mine and the Hi Yu mine. The open pits, mine waste dumps and stamp sand tailings of the McCarty mine were examined and sampled in 1986 (Fairbanks Exploration Inc., unpublished report, 1986).
Alteration: Seritization.
Production: Total production from the American Eagle shear through 1917 was approximately 967 ounces of gold with an average grade of about one ounce of gold per ton (J. McCarty, unpublished report, 1932). Milling of development material in 1929 and 1930 produced 1,274 ounces of gold from 1,225 tons of ore averaging 1.04 ounces of gold per ton (J. McCarty, unpublished report, 1932; Hill, 1931). During 1931, approximately 34 ounces of gold averaging 1.25 ounces of gold per ton was recovered from 27 tons of material excavated from a surface cut on the American Eagle shear zone (J. McCarty, unpublished report, 1932). Smith (1933; B 844) reported that the McCarty mine was the largest producer in the Fairbanks Creek basin in 1931. A total of 600 tons of ore from the American Eagle workings was milled in 1938 at a rate of 240 tons per month (Reed, 1939). The McCarty mine ceased operations in 1942 due to War Production Board Limitation Order L208. However, about 15 tons of high grade stibnite ore was shipped from the prospect in 1942. This ore graded 60.66% antimony (Joesting, 1942; ATDM Pamph. 1). In addition, about 5 tons of stibnite ore grading 45% antimony was also shipped from the American Eagle mine in 1942 (Joesting, 1943; Killeen and Mertie, 1943). Total production from the McCarty mine workings (American Eagle, Henry Ford and McCarty shear zones) is estimated at 26,800 ounces from 16,750 tons of ore grading 1.6 ounces of gold per ton (Porterfield and Croff, 1986). However, Metz and others (1987) estimate production from the McCarty mine was approximately 60,000 ounces of gold.
Reserves: In 1984 Placid Oil Company drilled 6,137 feet in 23 diamond core holes. Preliminary ore reserves from this work were calculated at 15,000 tons grading 0.80 ounces of gold per ton. In 1988, Fairbanks Exploration Inc. conducted bulk sampling of the American Eagle mine tailings and waste dump. Based on the results of this sampling, ore grade and tonnage estimates were calculated. These reserve estimates do not reflect mining conducted by Tri-Con Mining after mid-August 1988. The average gold grades from the American Eagle mine tailings range from 0.091 to 0.168 ounces of gold per ton. However, a portion of the samples were taken from stamp sands which had been re-treated in a cyanide mill erected on the prospect for this purpose in the early 1980's. Therefore, composite sample results are not an accurate estimate of gold grades for the bulk of the American Eagle mine stamp sands. Channel sampling of American Eagle mine tailings conducted in 1987 indicated average grades of 0.123 ounces of gold per ton and 0.74 ounces of silver per ton (Fairbanks Exploration Inc., unpublished report, 1987). Estimated tonnage of stamp sands at the American Eagle mine is 3,000 tons. The average gold grades from the American Eagle mine waste dumps range from 0.132 to 0.158 ounces of gold per ton (Fairbanks Exploration Inc., unpublished report, 1988).

Commodities (Major) - Au; (Minor) - Sb, Zn
Development Status: Yes; small
Deposit Model: Polymetallic vein (Cox and Singer, 1986; model 22c).

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Link to USGS - Alaska:	LG152

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References