|Main commodities||Ag; Au; Bi; Cu|
|Other commodities||Pb; Zn|
|Ore minerals||arsenopyrite; bismuthinite; bornite; chalcopyrite; covellite; enargite; galena; gold; kobellite; loellingite; malachite; pyrite; pyrrhotite; sphalerite; tennantite; ullmannite|
|Gangue minerals||actinolite; allanite; biotite; carbonate; feldspar; quartz; sericite|
|Quadrangle map, 1:250,000-scale||FB|
|Quadrangle map, 1:63,360-scale||A-4|
|Nearby scientific data||Find additional scientific data near this location|
|Location and accuracy||The Liberty Bell mine is located approximately 5.6 miles south-southeast of Rex Dome in the NW1/4 sec. 13, T. 10 S., R. 7 W., of the Fairbanks Meridian. This mine is marked on the Fairbanks A-4 topographic map, and the buildings and workings are prominent in the field. As of 1998, the Liberty Bell property was owned by Columbia Yukon Exploration Inc., and it consisted of five targets over a 10,500-acre claim block (Columbia Yukon Exploration Inc., news release no. 83, June 9, 1998). The mine is locality 40 of Cobb (1972 [MF 410]). This location is probably accurate to within 1000 feet.|
The following geologic summary is taken from Yesilyurt, 1996. The geology of the Liberty Bell gold mine area is dominated by weakly metamorphosed volcaniclastic-sedimentary rocks of the California Creek Member of the Totatlanika Schist, which is of Devonian-Mississippian(?) age. Metamorphosed Mesozoic(?) mafic dikes and unmetamorphosed Late Cretaceous felsic porphyry dikes and plugs are scattered throughout the area. Continental clastic rocks of the Tertiary Nenana Gravel overlie these rocks in angular unconformity. Gold mineralization is associated with sulfide- and sulfosalt-rich lenses, veins, and low-angle shear zones in the Paleozoic phyllitic rocks adjacent to a porphyry intrusion.
Six types of hydrothermal alteration have been differentiated. Carbonate-quartz alteration occurs in a peripheral zone of the metasomatic mineralization at the mine area. An actinolite-pyrrhotite assemblage occurs adjacent to the gold mineralization. Potassium silicate alteration occurs adjacent to the porphyry intrusions; it consists mainly of alkali feldspar, biotite, tourmaline, allanite, and quartz. A chlorite-sericite-carbonate alteration assemblage occurs sporadically in the area. The most widespread type of alteration at Liberty Bell is a quartz-sericite-clay assemblage. Supergene alteration and weathering overprint all of the hydrothermal assemblages. The age of hydrothermal alteration is about 92 Ma, based on two K-Ar radiometric determinations on hydrothermal biotite and sericite.
The principal ore minerals at Liberty Bell are arsenopyrite, pyrite, and pyrrhotite. Also present are chalcopyrite, kobellite, ullmannite, bismuthinite, tennantite, and loellingite, and trace amounts of enargite, covellite, bornite, sphalerite, galena, malachite, and native gold. The ore minerals occur mostly as tabular and stringer replacement bodies, disseminations, cross-cutting veins, and as open space fillings.
The initial discovery was float samples that contained arsenopyrite, bismuth, and bismuthinite. Several shafts and tunnels were driven in 1915 and 1916. By 1930, development included more than 1,000 feet of adits, and several shafts and raises (Moffit, 1933). In 1931 a mill was installed; mining in 1932-33 produced a total of 8,400 ounces of gold from 17,500 tons of ore (Smith, 1933 [B 844-A, p. 19]; Smith, 1937; Toupe and others, 1986). In midsummer of 1936, all work was discontinued and work on the property did not resume until the 1970s (Smith, 1938, p. 35-36). Since 1973, more than 16,000 feet of core has been produced by diamond drilling, and there has been considerable trenching, geologic mapping, geophysical surveys, and several thousand feet of reverse-circulation drilling (see Workings and Exploration field). Recently, five targets have been identified on the 10,500-acre property. The Mine Zone has mineable resources of 1,240,000 tons with an average grade of 0.1 ounce of gold per ton. Drilling has indicated that there is the potential for 250,000 ounces of gold in the Mine Zone and the Northwest Copper Zone (Columbia Yukon Explorations Inc., web site describing 1998 exploration activity).Results from a detailed state airborne geophysical survey completed in 2002 by Alaska Division of Geological and Geophysical Surveys (DGGS) in the Bonnifield Mining District reveal a positive aeromagnetic anomaly at Liberty Bell which suggests an underlying large pluton. This idea is supported by follow-up ground truthing by DGGS in 2005 that noted extensive hornfels and hydrothermal alteration, in addition to granite and granodiorite dikes. The authors suggested from this work that viable exploration targets in the area include replacement/skarn and structurally controlled mineralization, which are both documented at Liberty Bell (Athey and others, 2006).
|Geologic map unit||(-148.847338214213, 64.0515418794899)|
|Mineral deposit model||Many investigators of the property have suggested various types of syngenetic massive sulfide models. Others favor an epigenetic origin, for instance, Yesilyurt (1996, p. 1282), who has done the most thorough modern work on the deposit.|
|Age of mineralization||The age of mineralization has been a source of controversy; the suggestions range from Mesozoic to late Tertiary (Yesilyurt, 1996, p. 1282). Yesilyurt (1996) gives the age of hydrothermal alteration associated with the ore as about 92 Ma, on the basis of two K-Ar radiometric determinations on hydrothermal biotite and sericite that was probably formed contemporaneously with the mineralization.|
|Alteration of deposit||Six types of hydrothermal alteration have been differentiated (Yesilyurt, 1996). Carbonate-quartz alteration occurs in a peripheral zone of the metasomatic minerlization at the mine. An actinolite-pyrrhotite assemblage occurs adjacent to the gold mineralization. Potassium silicate alteration occurs adjacent to the porphyry intrusions and consists mainly of alkali feldspar, biotite, tourmaline, allanite, and quartz. A chlorite-sericite-carbonate alteration assemblage occurs sporadically in the area. The most widespread type of alteration at Liberty Bell is a quartz-sericite-clay assemblage. Supergene alteration and weathering overprint all of the hydrothermal assemblages (Yesilyurt, 1996).|
|Workings or exploration||
By 1918, a tunnel 35 feet long and a shaft 15 feet deep were opened in loose rock (Overbeck, 1918, p. 360). Development work was reported in 1922, 1923, and 1924 (Brooks and Capps, 1924, p. 40; Brooks, 1925, p. 31; Smith, 1926, p. 26). By 1930, developments included more than 1,000 feet of adits and several shafts and raises (Moffit, 1933). In 1931, a mill was constructed by the Fairbanks-based Eva Creek Mining Company (Smith, 1933 [B 844-A, p. 19]). Due to the intense shearing and the degree of decomposition of the schist, much timbering was required to prevent caving (Moffit, 1933). In 1934, very little work was done, and mining was reported to be expensive due to the caving (Smith, 1936, p. 24). In the mid-summer of 1936, all work was discontinued (Smith, 1938, p. 35-36). Interest in the property resumed in the 1970s. In 1973, Alaska Petroleum and Mining and its joint partner Gulf Mineral Company drilled 20 diamond-drill holes totaling 5,839 feet (Yesilyurt, 1996, p. 1282). In 1977, Resource Associates of Alaska (RAA) drilled six diamond-drill holes totaling 4,289 feet (Yesilyurt, 1996, p. 1282). In 1978, the claims were optioned to Cominco Limited, and in 1984 Cominco drilled seven diamond-drill holes totaling 1,578 feet. After the 1984 drilling, RAA acquired the claims under a joint-venture agreement with Cyprus Gold Corporation. A preliminary field study was conducted in 1986, and advanced exploration work began in 1987; it included thirty reverse-circulation drill holes, trenching, and detailed geologic mapping and sampling. In 1989, Nerco Minerals conducted exploration and detailed metallurgical studies at the property (Bundtzen and others, 1990, p. 12). In 1991, some exploration was reported by Amax Gold Inc. (Bundtzen and others, 1991, p. 10). In 1992, Amax Gold completed 5,845 feet of reverse-circulation drilling at the (Nerco-owned) property (Swainbank and others, 1993, p. 9). In 1993, operating on an option from the Liberty Bell Mining Company, Noranda Exploration Inc., funded by Hemlo Gold, mapped and sampled several mineralized zones (Bundtzen and others, 1994, p. 10). In 1994, Noranda Exploration trenched several anomalies that were discovered through geochemistry and geophysics (Swainbank and other, 1995, p. 10). In 1996, lessees of Pacific Northwest Resources Co. conducted a small drilling program (Swainbank and others, 1997, p. 8). In 1997, Liberty Bell Mining conducted a 5,000-foot core-drill program (Swainbank and others, 1998, p. 9).
During 2008, New Gold Inc. completed an exploration program at Liberty Bell consisting of a property-wide geophysical IP-Resistivity survey in combination with surface mapping and geochemical sampling. This work, combined with the results of work completed in 2007, has resulted in the delineation of five separate areas of prospective gold mineralization (New Gold Inc., 2008).
New Gold’s 2009 field program included more geologic mapping, geochemical sampling, and a core drilling program, although no results were announced (Szumigala and others, 2010).
Field work during 2010 by New Gold included geologic mapping, geochemical sampling, and a 9,967-foot core drilling program. Geochemical sampling included whole-rock analysis, U–Pb SHRIMP geochronology, and petrographic analysis. No results were announced. New Gold dropped its option on the Liberty Bell property at year’s end (Szumigala and others, 2011).In 2002, Alaska Department of Natural Resources-Division of Geological and Geophysical Surveys completed a detailed state airborne geophysical survey covering 276 square miles in the Western Bonnifield Mining district, in which lies Liberty Bell. Follow-up geologic ground-truth mapping took place in 2005 and covered 131 square miles. The purpose of the Liberty Bell project was to produce a 1:50,000-scale geologic map to foster a better understanding of the geology and mineral potential of the area (Athey, 2006). This map was published in 2006 (Athey and others, 2006).
|Indication of production||Yes; small|
|Reserve estimates||In 1933, the reserves were estimated at 37,000 tons of ore that had an average assay of $22 in gold per ton (1.06 ounces of gold per ton) (Moffit, 1933). More recent drilling on the Northwest Copper Zone, approximately 2,000 feet from the Mine Zone, indicated an aggregated resource of 2,000,000 tons with a grade of 0.05 ounce of gold per ton (Columbia Yukon Explorations Inc., news release no. 83, June 9, 1998). The Mine Zone has mineable resources of 1,240,000 tons with an average grade of 0.1 ounce of gold per ton. Drilling has indicated that there is the potential for 250,000 ounces of gold in the Mine Zone and the Northwest Copper Zone (Columbia Yukon Explorations Inc., web site describing the 1998 exploration).|
|Production notes||Mining in 1932 and 1933 produced a total of 8,400 ounces of gold from 17,500 tons of ore (Smith, 1937; Toupe and others, 1986).|
Additional commentsOther names associated with Liberty Bell include 'Bearpaw', 'Eva Mining Co.', 'Eva Quartz Mining Co.', 'Irene', 'Johnson, Norberg and Erickson', 'Swanson and Mountaine', 'Short', 'Rose', and 'Wild Goose' (Cobb, 1976 [OFR 76-662 p. 162-167]).
Berg, H.C., and Cobb, E.H., 1967, Metalliferous lode deposits of Alaska: U.S. Geological Survey Bulletin 1246, 254 p.
Bundtzen, T.K., Swainbank, R.C., Deagen, J.R., Moore, J.L., 1990, Alaska's Mineral Industry 1989: Alaska Division of Geological & Geophysical Surveys, Special Report 44, 100 p.
Bundtzen, T. K., Swainbank, R. C., Wood, J. E., and Clough, A. H., 1991, Alaska's mineral industry 1991: Alaska Division of Geological and Geophysical Surveys Special Report 46, 89 p.
Capps, S.R., 1924, Geology and mineral resources of the region traversed by the Alaska Railroad: U.S. Geological Survey Bulletin 755-C, p. 73-150.
Nokleberg, W.J., Bundtzen, T.K., Berg, H.C., Brew, D.A., Grybeck, D.J., Robinson, M.S., Smith, T.E., and Yeend, W., 1987, Significant metalliferous lode deposits and placer districts of Alaska: U.S. Geological Survey Bulletin 1786, 104 p., 2 plates, scale 1:5,000,000.
Smith, P.S., 1933, Mineral industry of Alaska in 1931: U.S. Geological Survey Bulletin 844-A, p. 1-81.
Smith, P.S., 1934, Mineral industry of Alaska in 1932: U.S. Geological Survey Bulletin 857-A, p. 1-91.
Smith, P.S., 1934, Mineral industry of Alaska in 1933: U.S. Geological Survey Bulletin 864-A, p. 1-94.
Smith, P.S., 1936, Mineral industry of Alaska in 1934: U.S. Geological Survey Bulletin 868-A, p. 1-91.
Smith, P.S., 1937, Mineral industry of Alaska in 1935: U.S. Geological Survey Bulletin 880-A, p. 1-95.
Smith, P.S., 1938, Mineral industry of Alaska in 1936: U.S. Geological Survey Bulletin 897-A, p. 1-107.
Szumigala, D.J., Harbo, L.A., and Adleman, J.N., 2011, Alaska's mineral industry 2010: Alaska Division of Geology and Geophysical Surveys Special Report 65, 83 p.
Szumigala, D.J., Harbo, L.A., and Highes, R.A., 2010, Alaska's mineral industry, 2009: Alaska Division of Geological and Geophysical Surveys Special Report 64, 81 p.
|Reporters||J.R. Guidetti Schaefer and C.J. Freeman (Avalon Development Corporation); V.C. Zinno (Alaska Earth Sciences, Inc.)|
|Last report date||2/25/2016|