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.