Aurora

The Aurora is a zinc mine located in Alaska.

About the MRDS Data:

All mine locations were obtained from the USGS Mineral Resources Data System. The locations and other information in this database have not been verified for accuracy. It should be assumed that all mines are on private property.

Mine Info

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Site Name

Primary: Aurora

Commodity

Primary: Zinc
Secondary: Arsenic
Secondary: Antimony
Secondary: Fluorine-Fluorite
Secondary: Copper
Secondary: Lead
Secondary: Gold
Secondary: Silver

Location

State: Alaska
District: Nome

Land Status

Not available

Holdings

Not available

Workings

Not available

Ownership

Not available

Production

Not available

Deposit

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

Physiography

Not available

Mineral Deposit Model

Model Name: Massive sulfide, kuroko

Orebody

Not available

Structure

Not available

Alterations

Alteration Type: L
Alteration Text: Remobilization of metallic minerals and carbonates during Cretaceous metamorphism.

Rocks

Not available

Analytical Data

Not available

Materials

Ore: Arsenopyrite
Ore: Tennantite
Ore: Stibnite
Ore: Sphalerite
Ore: Pyrite
Ore: Gold
Ore: Galena
Ore: Fluorite
Ore: Chalcopyrite
Ore: Barite
Gangue: Ankerite
Gangue: Dolomite
Gangue: Quartz
Gangue: Muscovite

Comments

Comment (Geology): Age = Syngenetic in early Paleozoic (Devonian) sedimentary and marine volcanic rocks with remobilization during mid-Cretaceous deformation and metamorphism. Mineralization along crosscutting structures is mid-Cretaceous or younger.

Comment (Exploration): Status = Inactive

Comment (Reference): Primary Reference = This report

Comment (Deposit): Model Name = Metamorphosed volcanogenic massive sulfide (Cox and Singer, 1986; model 28a [Kuroko massive sulfide]).

Comment (Geology): Geologic Description = The Aurora zinc (lead) deposit was discovered in 1966 as the result of followup of a geochemical survey using the cold extraction-dithizone method (Herreid, 1968). Prospecting fairly quickly found boulders of disseminated to semi-massive sulfides, especially sphalerite, scattered along a north-northwest trend bisected by Aurora Creek. The occurrence was located and initial work was done by Resource Associates of Alaska. Herreid (1970) also conducted more work in the area; he defined a soil anomaly along the deposit at least 7,000 feet long. In 1976 and 1977, Cominco mapped, explored, and drilled a series of 22 holes in the deposit. In general, mineralized intervals were too thin to be significant, but drillhole 76-17 found an interval more than 100 feet thick that contained about 5 percent zinc and some gold. In 1990, Kennecott Exploration Company began to explore the deposit, partly to evaluate a volcanic exhalative hypothesis for the origin of the deposit. Kennecott conducted new soil surveys, excavated a series of trenches by tracked backhoe, and completed some new drilling. The extent of mineralization was similar to that found by Cominco, and the prospect, leased from Bering Straits Regional Corporation, was allowed to lapse. The work suggests that the origin of Aurora is very complex; early mineralization was probably syngenetic and related to rhyolitic volcanism. Remoblization of mineralization probably took place during Cretaceous metamorphism of the deposit. Gold was possibly introduced along northeast-striking faults during waning stages of Cretaceous tectonism.? Where the deposit crosses Aurora Creek, disseminated and semi-massive sulfide deposits grade into a nearly white quartz-sericite schist which contains knots of purple fluorite. This unit is part of the felsic, muscovite-bearing, metavolcanic schist mapped by Bundtzen and others (1994). The unit has at least three distinct facies; (1) zircon-rich muscovite quartz schist, (2) feldspar-rich porphyroblastic schist, and (3) tourmaline-bearing muscovite-quartz-feldspar schist. Ankerite and dolomite are commonly present and locally abundant. Whole-rock analyses obtained by Kennecott Exploration Company on samples of the nearly white quartz-muscovite schist indicated from 69 to 82 percent silica, 9.5 to 15.3 percent alumina, very low calcium, magnesium, and sodium, and 2.2 to 4.8 percent potassium (C.C. Hawley, Cindy Buxton, and D.L. Olson, written communication, 1992). Iron (reported as ferric iron) ranged from 1.9 to 6.6 percent, suggesting some ferrophengitic mica is present. Fluorine exceeded 1 percent in all four rock samples; all had high background zinc (hundreds of parts per million) and one sample contained 700 ppm lead. Except for their low content of sodium, the analyses are fairly typical of felsic igneous rocks. The white quartz sericite schist, believed to be a metarhyolite, stratigraphically overlies graphitic quartz schist.? the geology of a section through Cominco drillhole 76-17 is consistent with thickening of the mineralized section by folding. This drill hole also contains about 0.1 ounce of gold per ton. This part of the deposit is also cut by a strong northeast-trending fault. The fault displaces the zinc-rich layer and possibly was the conduit for late gold mineralization. Other parts of the Aurora prospect are carbonate hosted. Locally, there are zones that are mostly barite accompanied by fine-grained pyrite. Antimony and arsenic are the characteristic trace elements in the deposit. There is some arsenopyrite, but the antimony and arsenic may also be in a sulfosalt, such as tennantite. Pyrite exceeds arsenopyrite, and chalcopyrite is locally present. In almost all samples, sphalerite is the dominant sulfide; it is commonly light orange to brown, suggesting a low iron content.

Comment (Workings): Workings / Exploration = Soil surveys conducted by Alaska Division of Geological and Geophysical Surveys (Herreid, 1970); shallow diamond drilling by Cominco in 1976-77; soil surveys, trenching, and drilling by Kennecott Exploration in 1991-93.

References

Reference (Deposit): Bundtzen, T.K., Reger, R.D., Laird, G.M., Pinney, D.S., Clautice, K.H., Liss, S.A., and Cruse, G.R., 1994, Progress report on the geology and mineral resources of the Nome mining district: Alaska Division of Geological and Geophysical Surveys, Public Data-File 94-39, 21 p., 2 sheets, scale 1:63,360.

Reference (Deposit): Cobb, E.H., 1978, Summary of references to mineral occurrences (other than mineral fuels and construction materials) in the Nome quadrangle, Alaska: U.S. Geological Survey Open-File report 78-93, 213 p.

Reference (Deposit): Herreid, G.H., 1970, Geology and geochemistry of the Sinuk area, Seward Peninsula, Alaska: Alaska Division of Mines and Minerals Geologic Report 36, 61 p., 3 sheets, scale 1:42,000.

Reference (Deposit): Cobb, E.H., 1972, Metallic mineral resources map of the Nome quadrangle, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-463, 2 sheets, scale 1:250,000.

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