USGS Professional Paper 1697 - Alaska Resources Library

256 Metallogenesis and Tectonics of the Russian Far East, Alaska, and the Canadian Cordillera
pendant of Jurassic to Cretaceous metasedimentary and metavolcanic
rocks of the Cretaceous Gambier Group. The plutonic
rocks are part of the Coast Plutonic Complex. Poorly estimated
reserves are 272,000 tonnes grading 9 percent Zn with variable
Ag (MINFILE, 2002). Local high-grade zones contain as much
as 68.6 g/t Ag and as much as 20 percent Zn. The deposit age is
interpreted as Late Cretaceous to early Tertiary.
Origin of and Tectonic Controls for Gambier
Metallogenic Belt
The Gambier metallogenic belt is defined by the distribution
of a suite of small, early Tertiary granitoid bodies that
constitute the younger part of the Coast Plutonic Complex,
which is part of the Coast-North Cascade plutonic belt; this
belt forms a major granitoid plutonic belt of Late Cretaceous
and early Tertiary age that extends the length of the Canadian
Cordillera and into East-Central Alaska (fig. 103). The belt
consists chiefly of quartz diorite, granodiorite, and locally
more mafic or felsic plutons (Rubin and others, 1991; Gehrels
and others, 1990; Wheeler and McFeeley, 1991; van der
Heyden, 1992; Woodsworth and others, 1992; Journeay and
Friedman, 1993).
Catface Metallogenic Belt of Porphyry Cu-Mo-
Au and Au-Ag Polymetallic Vein Deposits (Belt
CF), Vancouver Island
The Catface metallogenic belt of porphyry Cu-Mo-Au
and Au-Ag polymetallic vein deposits (fig. 103; tables 3, 4)
occurs on Vancouver Island in the southern Canadian Cordillera
and is associated with the middle to late Eocene Catface
plutonic suite, which consists of numerous, small irregular
stocks, dikes, and sills (Carson, 1973) that form a broad belt
extending from near Nanaimo west to Ucluelet and north to
Zeballos on Vancouver Island. The 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 for several thousand km (Nokleberg
and others, 1994c, 1997c; Monger and Nokleberg, 1996).
The significant deposits in the belt are at Catface, Domineer-
Lakeview, and Privateer (table 4) (Nokleberg and others
1997a,b, 1998).
Porphyry Cu-Mo and Polymetallic Vein Deposits
The Catface porphyry Cu (Au-Mo) deposit consists
of chalcopyrite, bornite, chalcocite, pyrite, pyrrhotite and
molybdenite that occur in a stockwork of fractures and quartz
veinlets (Dawson and others, 1991; Mining Review, 1992;
Enns and McDougall, 1995; MINFILE, 2002). The stockwork
is accompanied by biotite alteration. Estimated resources for
the Cliff Zone are 188 million tonnes grading 0.42 percent Cu,
0.014 percent Mo and 308 million tonnes grading 0.37 percent
Cu and 0.12 percent Mo; potential for additional resources
exists at depth (McDougall, 1976; Enns and McDougall,
1995).The deposit is hosted in an apophysis of Eocene porphyritic
quartz diorite of the Catface plutonic suite and has a K-Ar
isotope age of 48 Ma. The diorite intrudes relatively older
quartz monzonite and metabasalt of the Late Triassic Karmutsen
Formation of Wrangellia.
The Domineer-Lakeview Au-Ag polymetallic vein zone
occurs at Mount Washington, near Comox, and consists of a
silicified vein-shear zone that cuts basaltic volcanic rocks of
the Late Triassic Karmutsen Formation, sedimentary rocks of
the Late Cretaceous Nanaimo Group, and sills of the Catface
Plutonic Suite. The Au-Ag polymetallic vein zone is interpreted
as a shallow-dipping, post intrusion body. The shear
zone is intensely altered to kaolinite and contains tabular
zones that are silicified and cut by Au veins with quartz,
pyrite, and arsenopyrite. The deposit is associated with a
small, previously producing porphyry Cu-Mo deposit, and
several mineralized breccia pipes. Estimated reserves are
550,298 tonnes grading 6.75 g/t Au and 32.2 g/t Ag (Muller
and Carson, 1969; MINFILE, 2002).
The Privateer Au polymetallic vein deposit consists of
a set of thin, ribbon quartz veins that cut contact-metamorphosed
volcanic rocks of the Middle Jurassic Bonanza Group,
as well as the Zeballos stock of the Catface Plutonic Suite. The
Privateer is the largest and most productive of a group of small
mines in and adjacent to the stock. The major ore minerals are
abundant pyrite and arsenopyrite, sphalerite, less abundant
chalcopyrite, galena, and pyrrhotite, and rare free gold. Estimated
production is 280,000 tonnes of ore containing 18.8 g/t
Au along with Ag, Pb, and Zn (Stevenson, 1950; Dawson and
others, 1991).
Origin of and Tectonic Controls for Catface
Metallogenic Belt
The Middle to Late Eocene intrusions of the Catface
Plutonic Suite are mainly calc-alkaline, tonalite and quartz
diorite and minor granodiorite and granite, and commonly
porphyritic. The plutons are roughly synchronous with
Paleogene plutons in the southern Coast and Intermontane
belts, were emplaced at high levels as indicated by associated
breccias and diatremes, and intrude rocks as young as the Late
Cretaceous Nanaimo Group (Woodsworth and others, 1991).
The Catface Plutonic Suite is the southern part of the extensive
Late Cretaceous and early Tertiary Coast-North Cascade
plutonic belt that formed a major continental-margin arc in
mainly the western Canadian Cordillera (Nokleberg and others,
1994c, 1997c; Monger and Nokleberg, 1996).
Metallogenic Belts Formed in Back-arc Part of
Early Tertiary Coast Continental-Margin Arc,
Southern Canadian Cordillera
The Skeena (SK) and Nelson (NS) constitute two major
metallogenic belts of granitic-magmatism-related deposits in
the southern Canadian Cordillera (fig. 103; tables 3, 4) that
are interpreted as forming during granitic plutonism occurring