Golden Zone

Site Name

Primary: Golden Zone

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Commodity

Primary: Silver
Primary: Gold
Secondary: Copper
Secondary: Zinc
Secondary: Lead

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Location

State: Alaska
District: Valdez Creek

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Land Status

Not available

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Holdings

Not available

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Workings

Not available

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Ownership

Not available

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Production

Not available

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Deposit

Record Type: Site
Operation Category: Producer
Operation Type: Unknown
Years of Production:
Organization:
Significant:

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Physiography

Not available

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Mineral Deposit Model

Model Name: Polymetallic veins

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Orebody

Not available

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Structure

Not available

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Alterations

Alteration Text: Alteration and mineral zonation is present around the Golden Zone pipe. A distal lead and zinc halo is reported up to 2 miles from the pipe; the gold/silver ratios in arsenopyrite and chalcopyrite show a systematic variation; and red-bed sediments show widespread bleaching (C.C. Hawley, oral communication, 1999). Propylitic haloes consisting of epidote-carbonate-chlorite are present at the margin of the quartz diorite stock, and hornfels-skarn zones are in carbonate-rich country rock. Sericite is the dominant alteration mineral in the breccias, and argillic overprinting (?), quartz flooding and Fe-carbonates are also reported, but their paragenesis is as yet unclear.

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Rocks

Not available

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Analytical Data

Not available

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Materials

Ore: Arsenopyrite
Ore: Chalcopyrite
Ore: Galena
Ore: Pyrite
Ore: Sphalerite
Ore: Tetrahedrite
Gangue: Calcite
Gangue: Quartz
Gangue: Sericite

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Comments

Comment (Reference): Primary Reference = Hawley and others, 1978

Comment (Workings): Workings / Exploration = There are both surface and underground workings at the Golden Zone mine. Exploration between 1936 and 1996 included 54,326 feet of drilling in 137 drill holes (102 core and 35 reverse circulation holes). Numerous trenches and geochemistry samples have been collected. 1,900 feet of underground development has accumulated on the 100, 200 and 500 foot levels. Close-spaced helicopter aeromagnetic and EM geophysical surveys have been flown over the mine, along with some ground-based IP work (unpublished report by Addwest Minerals International Ltd., 1997). The State of Alaska sponsored an aeromagnetic survey in 1996 that included the mine site in 1996 (Burns, 1997). Sulfide-dominated events have overprinted the earlier, relatively barren, quartz-dominated brecciation, producing breccias containing over 10% sulfides. These younger breccias can be subdivided into arsenic-rich zones (earliest) and copper-rich zones (late); the former contains better gold grades - in places up to 5 ounces of gold per ton.

Comment (Deposit): Model Name = Polymetallic vein and Au-Ag breccia pipe or Cu-Au porphyry (Cox and Singer, 1986; models 22c, 20c)

Comment (Reserve-Resource): Reserves = The proven and probable reserves of the breccia pipe and surrounding prospect are 8 million tons containing 0.1 ounce of gold per ton (at a cutoff of 0.02 ounce of gold per ton), or about 800,000 ounces of gold.

Comment (Geology): Geologic Description = The country rocks in the area of the Golden Zone mine include Devonian to Triassic clastic, carbonate, volcanic, and volcaniclastic strata, which are intruded by an Upper Cretaceous (70-65 Ma) biotite-quartz diorite porphyry plug (Swainbank and others, 1977). The Golden Zone is the most significant deposit in the southwest portion of the Healy quadrangle. The deposit consists mostly of a single breccia pipe that measures 250 by 300 feet at the surface and thins downward. The contacts are steeply dipping except on the northern side where the dips appear to flatten to the north. Drilling has confirmed that the pipe reaches a depth of 650 feet and possibly as deep as 1,500 feet. The pipe is almost entirely contained within a biotite-quartz diorite porphyry plug measuring 600 by 1,000 feet. The breccia pipe was produced by magmatic devolatilization either from the diorite porphyry or from a related intrusion at depth. Both the breccia and the porphyry have been dated at 65-70 Ma (Swainbank and others, 1977). Major faults in the area trend northeast-southwest and have imparted a strong northeast trending fabric to the host rocks. Differential motion along these faults has localized the subsequent emplacement of the biotite-quartz diorite porphyry and mineralizing fluids. Postmineral northwest-trending faults cut the breccia (unpublished report by Addwest Minerals International, Ltd, 1997). Early brecciation produced angular clasts cemented by vuggy, pale-gray quartz and minor amounts of arsenopyrite, pyrite, pyrrhotite, chalcopyrite and sphalerite. Several younger, sulfide-dominated events have overprinted the earlier, relatively barren, quartz-dominated brecciation, producing breccias containing over 10% sulfides. These younger breccias can be subdivided into arsenic-rich zones (earliest) and copper-rich zones (late); the former contains better gold grades - in places up to 5 ounces of gold per ton.

Comment (Production): Production Notes = The mine produced 49,169 grams of gold, 267,990 grams of silver, and 19 tonnes of copper between 1941 and 1942 (Hawley and Clark, 1974).

Comment (Exploration): Status = Active

Comment (Geology): Age = The Golden Zone is a magma-driven breccia pipe. Both the intrusion and the breccia minerals are Late Cretaceous (70-65 Ma) in age (Swainbank and others, 1977).

Comment (Deposit): Model Number = 22c, 20c

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References

Reference (Deposit): Clark, A.L., and Cobb, E.H., 1972, Metallic mineral resources map of the Healy quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-394, 1 sheet, scale 1:250,000.

Reference (Deposit): Hawley, C.C., Meier, A.L., and Miller, R.L., 1968, Geochemical investigations at Antimony Creek antimony prospect, northern Talkeetna Mountains, Alaska: U.S. Geological Survey Open-File Report 337, 9 p.

Reference (Deposit): Balen, M.D., 1990, Geochemical sampling results from the Bureau of Mines investigations in the Valdez Creek mining district, Alaska: U.S. Bureau of Mines Open-File Report 34-90, 218 p., 2 plates, scale 1:250,000.

Reference (Deposit): Burns, L.E., 1997, Portfolio of aeromagnetic and resistivity maps of the Chulitna mining district: Alaska Division of Geological and Geophysical Surveys Public-Data File 97-7, 13 p.

Reference (Deposit): Cobb, E.H., 1978, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Healy quadrangle, Alaska: U.S. Geological Survey Open-File Report 78-1062, 113 p.

Reference (Deposit): Kurtak, J.M., Southworth, D.D., Balen, M.D., and Clautice, K.H., 1992, Mineral investigations in the Valdez Creek mining district, south-central Alaska: U.S. Bureau of Mines Open-File Report 1-92, 659 p., 2 plates, scale 1:250,000.

Reference (Deposit): Nokleberg, W.J., and 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: Boulder, Colorado, Geological Society of America: The Geology of North America, v. G1, p. 855-904 and v. G1, Plate 11, scale 1:2,500,000.

Reference (Deposit): Hawley, C.C., and others, 1978, Mineral appraisal of lands adjacent to Mt. McKinley National Park, Alaska. Contract No. JO166107: U.S. Bureau of Mines Open-File Report 24-78, 274 p., 12 sheets.

Reference (Deposit): Hawley, C.C., and Clark, A.L., 1974, Geology and mineral deposits of the upper Chulitna district, Alaska: U.S. Geological Survey Professional Paper 758-B, p. 1-47, 2 sheets, scale 1:12,000 and 1:48,000.

Reference (Deposit): Swainbank, R.C., Smith, T.E., and Turner, D.L., 1977, Geology and K-Ar age of mineralized intrusive rocks from the Chulitna mining district, central Alaska, in Short notes on Alaskan geology-1977: Alaska Division of Geological and Geophysical Surveys, Geologic Report 55, p. 23-28.

Reference (Deposit): Balen, M.D., 1990, Geochemical sampling results from the Bureau of Mines Investigations in the Valdez Creek mining district, Alaska: U.S. Bureau of Mines Open-File Report 34-90, 218 p., 2 plates, scale 1:250,000.

Reference (Deposit): Balen, M.D., 1990, The feasibility of mining in the Valdez Creek mining district, Alaska: U.S. Bureau of Mines Open-File Report 40-90, 58 p.

Reference (Deposit): 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.

Reference (Deposit): Hawley, C.C., and Clark, A.L., 1968, Occurence of gold and other metals in the upper Chulitna district, Alaska: U.S. Geological Survey Circular 564, 21 p.

Reference (Deposit): Eakins, G.R., Bundtzen, T.K., Lueck, L.L. Green, C.B., Gallagher, J.L., and Robinson, M.S., 1985, Alaska mineral industry, 1984: Alaska Division of Geological and Geophysical Surveys Special Report 38, 57p.

Reference (Deposit): Mulligan, J.J., Warfield, R.S., and Wells, R.R., 1967, Sampling a gold-copper deposit, Golden Zone Mine, south-central Alaska: U.S. Bureau of Mines Open-File Report 9-67, 59 p.

Reference (Deposit): Berg, H.C., and Cobb, E.H., 1967, Metalliferous Lode Deposits of Alaska. U.S. Geological Survey Bulletin 1246, 254 p.

Reference (Deposit): Ross, C.P., 1933, The Valdez Creek mining district, Alaska: U.S. Geological Survey Bulletin 849, p. 289-467.

Reference (Deposit): Wells, R.R., 1956, Laboratory concentration of various Alaska copper ores: U.S. Bureau of Mines Report of Investigations 5245, 9 p.

Reference (Deposit): 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.

Reference (Deposit): Capps, S.R., 1933, The eastern portion of Mount McKinley National Park: U.S. Geological Survey Bulletin 836, p. 219-300.

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