Big Denver

Prospect, Active?

Commodities and mineralogy

Main commodities Au
Other commodities Ag; As; Bi; Cu; Sb
Ore minerals gold; tetradymite
Gangue minerals calcite

Geographic location

Quadrangle map, 1:250,000-scale TN
Quadrangle map, 1:63,360-scale A-2
Latitude 65.02059
Longitude -150.78614
Nearby scientific data Find additional scientific data near this location
Location and accuracy The site of the Big Denver lode prospect is at the 1855-foot summit of a western spur of Bean Ridge, in the northwest quarter of section 10, T. 2 N., R. 16 W., of the Fairbanks Meridian. The site represents an area of prospecting that stretches for several miles along an east-northeast trend.

Geologic setting

Geologic description

The country rocks in the area of the Big Denver prospect consist of the Tertiary Manley Hot Springs granite; Cretaceous graywacke, sandstone, quartzite, siltstone, slate, argillite, and rare conglomerate; and a zone of contact metamorphosed sedimentary rocks (hornfels) peripheral to the granite (Chapman and others, 1982; Reifenstuhl and others, 1998). The hornfels is described by Reifenstuhl and others (1998) as dark gray to black, very fine grained, and hard, with randomly oriented crystals or rosettes of muscovite, biotite, and andalusite.
Several drill targets have been identified by North Star Exploration, Inc., in calcareous sedimentary strata just beyond the hornfels zone (North Star Exploration, Inc., 1999 [Report 99-34]; North Star Exploration, Inc., 2000 [Reduced calcic gold skarns]). Aeromagnetic surveys flown by the Alaska Division of Geological and Geophysical Surveys (Staff and others, 1996) indicate deep magnetic lows over the hornfels zones, moderate to low values over the granite, and strong highs over several elliptical bodies interpreted by North Star Exploration, Inc. as skarn targets. Magnetic highs are coincident with EM (electromagnetic) conductors. North Star Exploration, Inc., reports that sediments from streams that drain this area contain gold, arsenic, antimony, copper, and bismuth. Native gold and tetradymite have also been found in placer concentrates.
The area of interest includes Big Denver Creek (TN095), and the Hot Springs Dome (TN103) and Big Denver (TN089) lode deposits. Mertie (1934) reports gold- and silver-bearing calcite veins in a shear zone that appears to strike N75E. The mineralized shear zone reportedly could be traced for 3,000 feet from Big Denver Creek to Blowback Creek, but Mertie's location is poorly constrained, and there may be more than one system of veins.
Geologic map unit (-150.788607287561, 65.0200961437099)
Mineral deposit model Au-Cu skarn (after Cox and Singer, 1986; model 18b).
Mineral deposit model number 18b
Age of mineralization If present, mineralization presumably is Tertiary (62 +/- 3 Ma), the age of the Manley Hot Springs granitic body (Chapman and others, 1982).
Alteration of deposit Contact metamorphism.

Production and reserves

Workings or exploration North Star Exploration, Inc., identified the Big Denver prospect as a priority target in the late 1990s, based on compilation and interpretation of regional and detailed geological, geophysical, geochemical, and Landsat data. Included in this compilation are proprietary and public domain, helicopter-borne magnetic/resistivity/EM (electromagnetic) geophysical surveys. North Star is using these data to identify skarn targets (North Star Exploration, Inc., 2000 [Reduced calcic gold skarns]).
Indication of production None

Additional comments

This site is on land selected by or conveyed to Doyon, Ltd. For further information, contact Doyon, Ltd., at 210 1st Avenue, Fairbanks, Alaska, 99701.

References