Metallogenesis and Tectonics of the Russian Far East, Alaska, and ...

Keno HSldGaiene Hill Disbkt of
Ag PoJymetallic Vein Deposits
The Keno Hill-Galena Hill dishict of Ag polymetallic vein deposits (fig. 77) consists of argentiferous galena, fieibergite,
and pyrargyrite with minor polybasite, stepbanire, argentite and native silver whch occur in fault veins, breccias and sheeted
zones (Watson, 1986; Lynch, 1989; Murphy and Roots, 1992; Yukon Minfile, 1992). The deposit is hosted predominantly within
the Keno Hill Quartzite of the Early Mississippian Upper Earn Group which fonns part of a Devonian and Mississippian clastIc
wedge in the North American Cvatan Margin. Two stages of veining occur: an earlier stage of quartz-pyrite-arsenopyrite-
sulpbosalts and trace Au which formed prior to movement on fault veins; and a post-fault set of siderite-galena-sphaltrite~yrile-
fiiiebergite-pyrargyrite. A K-Ar isotopic age of 90 Ma age, which is interpreted as age of deposif may be related to granitoid
intrusioos of similar age to the north and south of Keno Hill. Between I92 I and 1988, estimated production was 6769 t of Ag, half
of which cstme from the Elsa, Keno No. 9, Lucky Queen, Silver King, Sadie-Ladue, and Husky Mines. Total production was 4.87
million tomes of ore of average gra& 1412 g/t Ag, 6.8% Pb, 4.6% Zn and 0.02 g/t Au (Yukon Minfite, 1992). More than 65 ore
deposits and prospects occur in the district. The Keno Hill-Galena Hill district is the second largest silver producer in Caaada.
Similar Ag po1yrneta)lic vem districts occur to the west and northwest of Keno Hill at Nadaleen Mountain, Rusty Mountain,
Kathleen Lakes, and McKay Hill.
Figure 77. Keno Hill (Galena HAI) Ag polymetallic vein deposit, Tombstone metallogenic be#. Canadian Cordillera. Schematic
regional geobgic map shewing locations of major deposits. Adapted from Watson (1986).
Bmwery Creek Sb-Au Vein Deposit
The Sb-Au vein deposits at Brewery Creek (Loki Gold) are hosted by sheared clastic rocks of the Earn Group and
adjacent porphyry sib (Bmer, 1990). Eight separate deposits occur over a strike length of 5.5 km elong a shear zone between a
sill of quartz momonite, syenite and latite of the Todstone suite, and graphitic argillite, chert, sandstone, coaglomeratc and
bedded barite. The deposits consist of gold which occurs in fine-grained chalcedony-pyrite-arsenopyrire stockworks. About 90%
of the deposit is oxidized at dews of 10-1 10 m. Narrow quartz-stibnite veins post-date the Au veins. An open pit, heap-leach
mine started m tho dqmsit ia 1995 with estimated pre-production reserves of 19.2 million tomes grading 1.53 glt Au (Brernner,
1990; Loki Gold Corp., News Release, January 1 1, 1994). Other Au-Sb (W-Pb-Ag) veins in the region are at Antimony Mountain,
West Ridge, and Spotted Fawn.
Eagle (Dublin Gulch) Perphyry Au-W Deposit
The Eagle (Dublin Gulch) porphyry Au-W deposit consists of granitoid-related Au vein stockworks which are similar to
the Fort Knox deposits near Fairbanks, Alaska (Mortensen and others, 1994; Hitchins and Orssich, 1995). The Late Cretaceous
Dublin Gulch biotite granodioritc stock, with a K-Ar isotopic age of 95-87 Ma, contains: (1) sheeted Au-As-Cu-Bi-W quartz veins