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

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118. Adanac-Adera porphyry Mo deposit, Surprise Lake metaYogenic bell, Canadian Cordillera. Gemraked cross %&ion ffmugh
high-grade zone. Adapted from Pinsent and Christopher (1995).
Red Mountain Porphyry Mo Deposit
The Red Mountain porphyry Mo deposit consists of disseminated molybdenite which occurs in a quartz stockwork (EMR
Canada, 1989; Dawson, and others, 1991 ; Yukon Minfile, 1992; Sinclair, 1986). Estimated resemes are 187 million tames
grading 0.167% MoS2 (with a 0.1% cul-off), and 2 1.3 million tomes grading 0.293% MoS2 with a 0.25% cut-off. Tbe deposit
occurs in an altered Late Cretaceous quartz rnonzonite stock of the Surprise Lake Suite, with a K-Ar isotopic age of 87.3 Ma, and
in adjacent contact-metamorphosed argillite of tbe early Paleozoic Nasina Assemblage of the Yukon-Tanana Wane. The stock is
complex, exhibits a classical alteration pattern, and is intruded by barren quartz diorite.
Surprise Lake Polymetallic and
Epithermal Au-Ag Veins.
Ag-Pb polymetallic vein deposits are associated with an Late Cretaceous pluton at Boswell River, Yukon Tenitory (Lea,
1936), and near the Red Mountain porphyry Mo deposit. Several Au-Ag polymetallic vein mines at Venus, Montana Mormtain,
and Wheaton River are hosted in or near the Late Cretaceous Carcross plulon which occurs south of Whitehorse, Yukon Territoty
(Hart, 1994). Au veins at the Engineer Mine, southwest of Atlin, B.C., are probably related to Eocene magmatism which formed
both the volcanic rocks and late stocks (Mihalynuk, 1990). The deposit at the Fhqheer Mine are cut by the major Lewellyn Fault.
The Au epithermal veins at the Engineer mine are transitional between mesothermal and epithermal, low-sulphidaiton type.
Origin of and Tectonic Controls for
Surprise Lake Metallogenic Belt
The Surprise Lake metallogenic belt is associated with the Surprise Lake Plutonic Suite which consists of stocks and
batholiths, comprising mainly felsic, high-level, Si- and lithophile tlement-rich rocks, and has K-Ar isotopic ages of 84 Ma
(Woodsworth and others, 1991). Plutons in the suite intrude the Cassiar, Stikine, Yukon-Tanam, and Cache Creek terranes. The
major plutonic units are the Surprise Lake batholith, near Atlin, B.C., and the Needlepoint Pluton, near Cassiar, B.C.
(Woodsworth and others, 1991). The Surprise Lake Plutonic Suite is part of the extensive Late Cretaceous and early Tertiary
Coast-North Cascade plutonic belt which occurs along the western and central parts of the Canadian Cordillera and into East-
Central Alaska (fig. 103) (Noklehg and others, 1994c, 1997c; Monger and Nokleberg, 1996). Probable coeval, extrusive
equivalents for the Surprise Lake Plutonic suite are the Windy-Table Volcanics to the east and west (Mihalynuk, 1999; Mihalynuk
and others, 1992), and the Carmacks Assemblage to the north (Grond and others, 1984) and ulnamned tuBaceous units in the
Sustut Basin to the south (Woodsworth and others, 1991). The Coast-North Cascade plutonic belt forms the major part of the
Coast continental-margin arc m the region.