Syenite Porphyry Prospect, Iditarod Mining District, Yukon-Koyukuk Census Area, Alaska, USAi

Regional Level Types
Syenite Porphyry Prospect	Prospect
Iditarod Mining District	Mining District
Yukon-Koyukuk Census Area	Census Area
Alaska	State
USA	Country

Location: This prospect is on peak 3957 at the head of Windy Creek in the western Beaver Mountains. It is at an elevation of about 3,950 feet in the SW1/4 SW1/4, section 33, T. 33 N., R. 41 W., of the Seward Meridian. The location is accurate.
Geology: The Syenite Porphyry prospect consists of fine-grained cinnabar and stibnite along fracture surfaces in an altered iron-stained roof pendant and intrusive rocks of the 70.3 Ma, Beaver Mountain stock (Bundtzen and Laird, 1982). The roof pendant is a mudstone that has been altered to a hard, dark-gray hornfels. The underlying intrusion is a potassically altered, syenite-porphyry phase of the Beaver Mountains intrusion. The sulfide-bearing fractures contain amethyst, and smokey and chalcedonic quartz (Szumigala, 1993). Grab samples of mineralization collected by the U.S. Geological Survey contained more than 10 parts per million (ppm) mercury and 200 ppm zinc (McGimsey and others, 1988, Miller, Bundtzen, and Gray, 2005). Grab samples collected by Battle Mountain Mining Company contain up to 1,960 parts per billion (ppb) gold, 3.9 parts per million silver, 896 ppm arsenic, 1,896 ppm antimony, and more than 50 ppm mercury. Six of of the nine samples contained greater than 50 ppm mercury (Szumigala, 1993).
Workings: The Alaska Division of Geological and Geophysical Surveys examined the Syenite Porphyry prospect in 1979 (Bundtzen and Laird, 1980 and 1982). Noranda Exploration looked at the occurrence in 1983 (John Dunbier, oral communication, 1983). Surface sampling was conducted by the U.S. Geological Survey in 1984 and 1985 (McGimsey and others, 1988). Battle Mountain Mining Company investigated the Syenite Porphyry prospect in 1990 (Szumigala, 1993).
Age: Undated; may be related to emplacement of the Beaver Mountains stock that has been dated at 70.3. Ma (Bundtzen and Laird, 1982).
Alteration: Iron staining; potassic alteration.

Commodities (Major) - Au, Hg, Sb; (Minor) - Ag, As, Zn
Development Status: None
Deposit Model: Hot springs Au-Ag (Cox and Singer, 1986; model 25a).

Other Databases

Link to USGS - Alaska:	ID004

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References