Alder Creek Prospect (lode in Eagle D-3 quadrangle), Eagle District, Southeast Fairbanks Borough, Alaska, USA

The Alder Creek Lode prospect is located within Doyon, Ltd. selected or conveyed land. For more information contact Doyon, Ltd., Fairbanks, Alaska.
Location: The Alder Creek prospect covers about one-third of a square mile along lower Alder Creek, a small south tributary of the Seventymile River. The coordinates are the approximate center of the prospect area, in section 30, T. 2 N., R. 27 E., of the Fairbanks Meridian; the location is accurate. There is another Alder Creek lode prospect (EA069) in the Eagle B-2 quadrangle. The Alder Creek lode prospect is located within Doyon, Ltd. selected or conveyed land.
Geology: The Alder Creek prospect is one of a northwest-trending set of ophiolite-hosted gold prospects informally referred to as the Flume trend. Other lode gold prospects within the Flume trend include Flume Creek (EA009), Bonanza Creek (EA010), and Flanders (EA015). One-half mile to the south, subparallel to the Flume trend, the Deep Creek trend of volcanic-hosted lode gold prospects includes the Deep Creek (EA017) and Kill Zone 2 (EA016) prospects and the Jay Creek and Kill Zone 3 gold anomalies that are defined by soil sampling. There is also a placer gold mine on Alder Creek (EA011), just downstream from the Alder Creek lode prospect. The Flume trend prospects are in weakly metamorphosed ultramafic, mafic, and oceanic sedimentary rocks of the Seventymile terrane (Foster and others, 1985). Rocks of the Seventymile terrane are deformed and cut by internal thrust faults. These rocks are juxtaposed with Paleozoic metamorphic rocks to the north and south along northwest-trending strands of the Tintina strike-slip fault. Bimodal Tertiary(?) dikes, including porphyritic rhyolite and diorite-gabbro, intrude all older rocks. The host rocks for the Alder Creek prospect are mixed layers or units of folded Paleozoic greenstone, pillow basalt, crystal-lithic tuff, and argillite. These units are cut by a set of sub-parallel quartz-carbonate zones associated with the gold mineralization; these are cut by a set of later high-angle faults. Gold predominantly occurs in propylitically altered basalt on the south limb of a northwest-trending anticline (WGM Inc., 1998 [DLR 98-19]). Numerous zones of quartz-carbonate alteration as much as 60 feet thick contain gold-bearing quartz veins. The veins are mostly in stockworks and gash structures with ribbon veins, breccia in-fills, and comb-texture veins. Arsenopyrite and pyrite are common in the veins and adjacent quartz-carbonate alteration zones. Hydrothermal white mica from wall rocks adjacent to a gold-bearing quartz-arsenopyrite vein at the nearby Flume Creek prospect (EA009) gives a 40Ar/39Ar plateau age of 100 +/- 3 Ma, interpreted to be the age of gold mineralization (Newberry and others, 1996). Geologic similarities suggest the Alder Creek gold mineralizing event may be of the same age. The prospects along the Flume trend form a semi-continuous 4-mile-long soil anomaly with greater than 10 ppb gold and elevated arsenic. The Alder Creek prospect is defined by an 1,800-foot-wide gold anomaly in soils (WGM Inc., 1998 [DLR 98-19]). Soils contain as much as 2,340 ppb gold; bedrock float exposed in placer tailings assay as much as 0.16 ounce of gold per ton. Four holes have been drilled, all of which are located east of the creek and the main gold-in-soil anomaly. Significant drill intercepts reported by Central Alaska Gold Co. include 22 feet with 0.084 ounce of gold per ton and 18 feet with 0.052 ounce of gold per ton. The Alder Creek drilling and trenching are south of the anticlinal crest believed to be the center of fracturing, alteration, and gold mineralization. On the basis of data from four drill holes on a single north-south line and one trench, there is an inferred resource of 71,000 tons of material that contains 0.06 ounce of gold per ton (WGM Inc., 1998 [DLR 98-19]). Reconnaissance exploration by WGM Inc. in the mid-1970's located several gold targets in the Seventymile region (WGM Inc., 1998 [DLR 98-19]). In 1989 and 1990, Central Alaska Gold Co. explored the Flume Creek (EA009) and Deep Creek (EA017) areas. In 1996, WGM Inc. expanded their soil sampling grids at the Flanders (EA015) and Deep Creek (EA017) prospects; conducted ridgetop sampling along a 13-mile-long segment between the Crooked Creek trend and Flume and Deep Creek trends; and had an airborne geophysical survey flown over the Flume, Deep Creek, and Crooked Creek trends.
Workings: Reconnaissance exploration by WGM Inc. in the mid-1970's located several gold targets in the Seventymile region (WGM Inc., 1998 [DLR 98-19]). In 1989 and 1990, Central Alaska Gold Co. explored the Flume Creek (EA009) and Deep Creek (EA017) areas. In 1996, WGM Inc. expanded their soil sampling grids at the Flanders (EA015) and Deep Creek (EA017) prospects; conducted ridgetop sampling along a 13-mile-long segment between the Crooked Creek trend and Flume and Deep Creek trends; and had an airborne geophysical survey flown over the Flume, Deep Creek, and Crooked Creek trends. The prospects along the Flume trend form a semicontinuous 4-mile-long soil anomaly with greater than 10 ppb gold, and elevated arsenic. The Alder Creek prospect is defined by an 1,800-foot-wide gold anomaly in soils (WGM Inc., 1998 [DLR 98-19]). Soils contain as much as 2,340 ppb gold; bedrock float exposed in placer tailings assay as much as 0.16 ounce of gold per ton. Four holes have been drilled, all of which are located east of the creek and the main gold-in-soil anomaly. Significant drill intercepts reported by Central Alaska Gold Co. include 22 feet with 0.084 ounce of gold per ton and 18 feet with 0.052 ounce of gold per ton.
Age: Hydrothermal white mica from wall rocks adjacent to a gold-bearing quartz-arsenopyrite vein at the nearby Flume Creek prospect (EA009) gives a 40Ar/39Ar plateau age of 100 +/- 3 Ma, interpreted to be the age of gold mineralization (Newberry and others, 1996). Geologic similarities suggest the Alder Creek prospect may be of the same age.
Alteration: Gold mineralization at the Alder Creek prospect occurs within propylitically altered basalt. Quartz-carbonate alteration accompanies the gold mineralization and is a favorable indicator for gold at prospects along the Flume trend (WGM Inc., 1998 [DLR 98-19]).
Reserves: On the basis of data from four drill holes on a single north-south line and one trench, there is an inferred resource of 71,000 tons of material that contains 0.06 ounce of gold per ton (WGM Inc., 1998 [DLR 98-19]).

Commodities (Major) - Au
Development Status: None
Deposit Model: Listwaenite (altered ophiolite) Au (Newberry and others, 1998).

References:
Clark, S.H.B., and Foster, H.L., 1971, Geochemical and geological reconnaissance in the Seventymile River area, Alaska: U.S. Geological Survey Bulletin 1315, 21 p. Dashevsky, S.S., 1983, Doyon exploration program, Block 8 - Fortymile, 1982: Doyon, Ltd. Report 83-01. (Report held by Doyon, Ltd., Fairbanks, Alaska). Dashevsky, S.S., and Nicol, D.L., 1985, Geologic field examinations in Doyon, Ltd. Regional Selection Blocks 1,6, 8, 9, 10, 12, 13, 18, 19, 20, 21, and Hughs and MTNT Village Lands, 1984: Doyon, Ltd. Report 85-07. (Report held by Doyon, Ltd., Fairbanks, Alaska). Foster, H.L., Cushing, G. W., Keith, T. E. C., and Laird, J., 1985, Early Mesozoic tectonic history of the Boundary area, east-central Alaska: Geophysical Research Letters, v. 12, p. 553-556. Keith, T.E., Foster, H.L., Foster, R.L., Post, E.V., and Lehmbeck, W.L., 1981, Geology of an alpine-type peridotite in the Mt. Sorenson area, east-central Alaska: U.S. Geological Survey Professional Paper 1170-A, p. A1-A9. Lessman, J., and Rishel, J., 1978, 1977 annual progress report, Doyon Project, Volume 25, Blocks 7 and 8: Other prospects: Doyon, Ltd. Report 78-19. (Report held by Doyon, Ltd., Fairbanks, Alaska). Newberry, R.J., Layer, P.W., Burleigh, R.E., and Solie, D.N., 1996, New 40Ar/39Ar dates for intrusions and mineral prospects in the eastern Yukon-Tanana terrane, Alaska - Regional patterns and significance, in Gray, J.E., and Riehle, J.R., eds., Geological Studies in Alaska by the U.S. Geological Survey, 1996: U.S. Geological Survey Professional Paper 1595, p. 131-159. Rogers, Bob, and Bradley, Laura, 1998, Gold deposits of the Seventymile Belt: Extended Abstracts of the 16th Biennial Conference on Alaskan Mining, Second Rush of 98; Alaska Miners Association meeting March 2-7, 1998, Fairbanks, Alaska, p. 22. WGM Inc., 1977, Doyon Project, 1976 annual progress report, volume 1a, Blocks 1, 4, 5, 7, 8: Doyon, Ltd. Report 77-02a. (Report held by Doyon, Ltd., Fairbanks, Alaska). WGM Inc., 1998, Ventures Resource Alaska projects, 1997 progress report, Seventymile property exploration, volume 1: Doyon, Ltd. Report 98-19. (Report held by Doyon, Ltd., Fairbanks, Alaska). WGM Inc., 2000, Seventymile property summary, in Ventures Resource Alaska project overview and properties summary: Ventures Resource Corporation report.