Mogul Bluff

Prospect, Active?

Commodities and mineralogy

Main commodities Ag; Au
Other commodities As; Hg; Sb
Ore minerals gold

Geographic location

Quadrangle map, 1:250,000-scale EA
Quadrangle map, 1:63,360-scale D-2
Latitude 64.9013
Longitude -141.7468
Nearby scientific data Find additional scientific data near this location
Location and accuracy The Mogul Bluff gold prospect is located on a bluff on the west side of Mogul Creek about 2 miles southeast of its mouth. The coordinates are located at the approximate center of drillhole-collar locations, in section 24, T. 4 N., R. 29 E., of the Fairbanks Meridian; the location is accurate. Mogul Creek is locality 27 of Cobb (1972 [MF-393]) and locality 40 of Eberlein and others (1977). The Mogul Bluff prospect is located within Doyon, Ltd. selected or conveyed land.

Geologic setting

Geologic description

The Mogul Bluff epithermal gold prospect is located in the middle of a linear trend of gold prospects informally known as the Crooked Creek trend (Rogers and Bradley, 1998). This trend of sediment-hosted epithermal gold prospects also includes the Ptarmigan Hill (EA028) prospect and the Ruby and Hudson Coulee gold anomalies defined by soil sampling. Late Cretaceous to Pliocene, terrigenous sedimentary rocks crop out in the Mogul Bluff area (Foster, 1976). Conglomerate at Mogul Bluff contains well-rounded quartz and chert clasts and thin interbeds of sandstone, siltstone, and shale (WGM Inc., 1998 [DLR 98-19]). Tertiary felsic volcanic and hypabyssal intrusive rocks, including quartz-eye rhyolite and quartz-feldspar porphyry, are nearby along regional high-angle faults. Small serpentinite bodies are juxtaposed with the conglomerate by splays of the Tintina Fault. Detrital muscovite from silicified, gold-bearing conglomeratic sandstone at the Ptarmigan Hill prospect (EA028) gives an average 40Ar/39Ar reset age of 54 Ma; this is interpreted as the time of silicification and gold mineralization (Newberry and others, 1996). The Mogul Bluff prospect is similar and may be of the same age.
The gold potential is highest in the conglomerate units, but volcanic rocks in the area also show significant gold potential (Rogers and Bradley, 1998). Soil sampling on a detailed grid indicates that the Mogul Bluff prospect is associated with an approximately 200-foot-wide by 800-foot-long soil anomaly in gold, with several values in excess of 3,000 ppb gold (WGM Inc., 1998 [DLR 98-19]). Strong mercury, arsenic, and antimony anomalies are coincident with, or more extensive than the gold anomaly. The anomaly may be truncated on the east by a north-trending fault that offsets mineralization to the south. Scarce placer cinnabar was found in Mogul Creek (Joesting, 1942). Drill holes at Mogul Bluff intersected gold mineralization within silicified conglomerate, including 81.2 feet with 0.055 ounce of gold per ton (WGM Inc., 1998 [DLR 98-19]). Gold (as much as 35 ppb) is present in soils about 1 mile to the south of Mogul Bluff. The Ptarmigan Hill (EA028) and Mogul Bluff prospects are characterized by distinct resistivity highs due to silicification of the clastic sedimentary rocks. Areas of high resistivity between Mogul Bluff and the Hudson Coulee soil geochemical anomaly to the east correlate with high gold values in panned heavy-mineral concentrate and soil samples.
In 1987 and 1988, the Crooked Creek trend was explored by American Copper and Nickel Company (Rogers and Bradley, 1998). They drilled 2,410 feet in nine holes to test a gold anomaly and conducted EM and magnetic surveys. In 1996, WGM Inc. conducted soil sampling on widely separated lines to the southeast of Mogul Bluff and reconnaissance soil sampling of ridges throughout the area (WGM Inc., 1998 [DLR 98-19]). An airborne EM-magnetic survey was flown over the Flume, Deep Creek, and Crooked Creek gold trends of the Seventymile gold belt in 1997.
Geologic map unit (-141.749127566287, 64.9009910986875)
Mineral deposit model Possibly Comstock epithermal veins (Cox and Singer, 1986; model 25c?).
Mineral deposit model number 25c?
Age of mineralization Detrital muscovite from silicified, gold-bearing conglomeratic sandstone at the Ptarmigan Hill (EA028) prospect gives an average 40Ar/39Ar reset age of 54 Ma, interpreted as the time of silicification and gold deposition (Newberry and others, 1996). Similarities to Ptarmigan Hill suggest the Mogul Bluff prospect may be of the same age.
Alteration of deposit There is silicification of conglomerates (WGM Inc., 1998 [DLR 98-19]).

Production and reserves

Workings or exploration In 1987 and 1988, the Crooked Creek trend was explored by American Copper and Nickel Company (Rogers and Bradley, 1998). They drilled 2,410 feet in 9 holes to test a gold anomaly and conducted EM and magnetic surveys. In 1996, WGM Inc. conducted soil sampling on lines to the southeast of Mogul Bluff and reconnaissance soil sampling of ridges throughout the area (WGM Inc., 1998 [DLR 98-19]). An airborne EM-magnetic survey was flown over the Flume, Deep Creek, and Crooked Creek gold trends of the Seventymile gold belt in 1997.
Indication of production None

Additional comments

The Mogul Bluff prospect is located within Doyon, Ltd. selected or conveyed land. For more information contact Doyon, Ltd., Fairbanks, Alaska.

References

References

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., 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.
Reporters M.B. Werdon; R.L. Flynn
Last report date 5/1/2002