Duval Creek Prospect, Fortymile District, Southeast Fairbanks Borough, Alaska, USA
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Location: The Duval Creek prospect covers about 6 square miles in upper Duval Creek, a small west tributary of the Middle Fork of the Fortymile River, in about the middle of the southwest portion of the Eagle B-5 quadrangle. Duval Creek is not named on the U.S. Geological Survey topographic map of the quadrangle. The coordinates are the approximate center of the prospect, on the bpundary between sections 8 and 9, T. 7 S., R. 22 E., of the Fairbanks Meridian; the location is accurate within 1 mile. The Duval Creek prospect is located within Doyon, Ltd. selected or conveyed land.
Geology: The rocks in the Duval Creek area consist of hornfelsed Paleozoic gneiss, schist, quartzite, amphibolite, and augen gneiss (Foster, 1976). These rocks have been intruded by a large undifferentiated granitic plutonic body of Tertiary to Mesozoic age and various kinds of shallow felsic intrusive rocks. The intrusive rocks are mostly quartz diorite to granodiorite. The metamorphic country rocks occur as roof pendants in the central and southern part of the Duval Creek prospect (Dashevsky and others, 1986). Rhyodacite(?) caps the ridges in the southeastern portion of the prospect and forms a north-south-trending dike swarm in the southwest part. A major fault in the upper part of the Duval Creek valley cuts both the Paleozoic metamorphic rocks and Mesozoic intrusive rocks (Dashevsky and others, 1986). In the Duval Creek area, tungsten occurs in skarn in roof pendants and along intrusive contacts; mineralization may be related to other tungsten and molybdenum occurrences in the Mount Harper area (for example, the Airplane Ridge prospect, EA093), about 20 km to the southwest (WGM Inc., 1998 [DLR 98-10]). Float of calcareous actinolite schist contains 0.026 percent WO3, and pyritic felsic intrusive rocks contain 0.2 percent tungsten (Dashevsky and others, 1986). These two samples were found in an area associated with several tungsten anomalies of as much as 385 ppm in panned heavy-mineral concentrates. Scheelite occurs as disseminated, coarse grains in calc-silicate schist. Scheelite was not observed in some of the tungsten-rich concentrate samples, suggesting that wolframite(?) may also be a source of tungsten anomalies in the area. Quartz-fluorite veinlets and small quartz-filled breccias with trace scheelite occur locally in the central part of the prospect. Anomalous tungsten was discovered in stream-sediment and heavy-mineral concentrates in Duval Creek during reconnaissance sampling by WGM Inc. in 1978. This work was followed up in 1979 by additional reconnaissance rock, soil, and pan-concentrate sampling, mapping, and minor prospecting with an ultraviolet lamp (Dashevsky and others, 1986; WGM Inc., 1998 [DLR 98-10]). In 1981, Arctic Resources Inc. conducted 10 miles of traverses in the vicinity of the Duval Creek prospect; only four samples were collected, and no significant tactite (skarn) was observed (Dashevsky and others, 1986). In 1991, Central Alaska Gold Company conducted stream-sediment, and rock,and soil sampling in the Duval Creek prospect area (Central Alaska Gold Co., 1992 [DLR 92-72]).
Workings: Anomalous tungsten was discovered in stream-sediment and heavy-mineral concentrates in Duval Creek during reconnaissance sampling by WGM Inc. in 1978. This work was followed up in 1979 by additional reconnaissance rock, soil, and pan-concentrate sampling, mapping, and minor prospecting with an ultraviolet lamp (Dashevsky and others, 1986; WGM Inc., 1998 [DLR 98-10]). In 1981, Arctic Resources Inc. conducted 10 miles of traverses in the vicinity of the Duval Creek prospect; only four samples were collected,and no significant tactite (skarn) was observed (Dashevsky and others, 1986). In 1991, Central Alaska Gold Company conducted stream-sediment and rock and soil sampling in the Duval Creek prospect area (Central Alaska Gold Co., 1992 [DLR 92-72]).
Age: The tungsten is probably related to Mesozoic or Tertiary intrusive rocks.
Commodities (Major) - W; (Minor) - F
Development Status: None
Deposit Model: W skarn (Cox and Singer, 1986; model 14a).
Mineral List
4 entries listed. 3 valid minerals.
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References
Burleigh, R.E., and Lear, K.G., 1994, Compilation of data for Phase I of the mineral resource evaluation of the Bureau of Land Management Black River and Fortymile subunits: U.S. Bureau of Mines Open-File Report 48-94, 116 p. Carter, C.H., 1981, Doyon exploration program, Blocks 4, 5, 8, and 22: Doyon, Ltd. Report 81-27. (Report held by Doyon, Ltd., Fairbanks, Alaska). Central Alaska Gold Co., 1992, Central Alaska Gold Co. annual report, Alaska field operations - Doyon option, volume 1: Doyon, Ltd. Report 92-70, 156 p. (Report held by Doyon, Ltd., Fairbanks, Alaska). Central Alaska Gold Co., 1992, Central Alaska Gold Co. annual report, Alaska field operations plates 13-24, Wiseman north, Fortymile south, Fortymile central, Manley Hot Springs, volume 3: Doyon, Ltd. Report 92-72, 12 p. (Report held by Doyon, Ltd., Fairbanks, Alaska). Dashevsky, S.S., Nicol, D.L., and Bond, J., 1986, Mines, prospects, and geochemical anomalies on Doyon Limited regional overselection lands, Alaska, Blocks 1-8: Doyon, Ltd. Report 86-01a, 300 p. (Report held by Doyon, Ltd., Fairbanks, Alaska). Foster, H.L., 1976, Geologic map of the Eagle quadrangle, Alaska: U.S. Geological Survey Miscellaneous Investigations Series, Map 922, 1 sheet, scale 1:250,000. Lessman, J., 1979, 1978 annual progress report, Doyon Project, South Block 8, tungsten and gold anomalies: Doyon, Ltd. Report 79-13. (Report held by Doyon, Ltd., Fairbanks, Alaska). WGM Inc., 1979, Summary of information on Carrie Creek, Duval Creek, Little Whiteman Creek, and Granite Creek, 1979: Doyon, Ltd. Report 79-03. (Report held by Doyon, Ltd., Fairbanks, Alaska). WGM Inc., 1998, Veta property, 1997 annual report, volume 1: Doyon, Ltd. Report 98-10, 227 p. (Report held by Doyon, Ltd., Fairbanks, Alaska).
