USGS Professional Paper 1697 - Alaska Resources Library

260 Metallogenesis and Tectonics of the Russian Far East, Alaska, and the Canadian Cordillera
Granisle Porphyry Cu-Au (Mo) Deposit
The Granisle porphyry Cu-Au (Mo) deposit consists of
chalcopyrite, bornite, and pyrite with low grade Au and Ag and
local minor molybdenite that occur in quartz-filled fractures
(Carson and Jambor, 1974; Fahrni and others, 1976; EMR
Canada, 1989; Dawson and others, 1991; Dirom and others,
1995). The deposit is associated with Eocene Babine porphyry
intrusions (with K-Ar isotopic ages of 51.2 Ma) that intrude
volcanic and sedimentary rocks of the Early Jurassic Hazelton
Group. Combined estimated production and reserves re 66.2
million tonnes grading 0.42 percent Cu, 0.12 g/t Au, 1.12 g/t Ag,
and 0.009 g/t Mo. The deposit is centered on the contact between
biotite-feldspar porphyry and an earlier quartz diorite phase.
A central potassic alteration zone is successively rimmed by a
quartz-sericite-carbonate-pyrite alteration zone and by a chloritecarbonate-epidote
alteration zone (Dirom and others, 1995).
Morrison Porphyry Cu-Au (Mo) Deposit
The Morrison Porphyry Cu-Au (Mo) deposit consists of
chalcopyrite and pyrite that occur in a stockwork of veinlets
and fractures, and as disseminations (Carter, 1982; EMR
Canada, 1989; Ogryzlo and others, 1995). Estimated resources
are 86 million tonnes grading 0.42 percent Cu, 0.34 g/t Au, 3.4
g/t Ag, and 0.017 percent Mo. The deposit is hosted in biotitehornblende-plagioclase
porphyry of the Eocene Babine Suite
and in adjacent Jurassic sedimentary rocks. The porphyry,
sedimentary rocks, and deposit are displaced by a fault.
Au-Ag Epithermal Vein Deposits Associated with
Quanchus Plutonic Suite
The Quanchus Plutonic Suite forms an arcuate chain of
large stocks in west-central British Columbia. The plutons in
the suite are similar in composition to plutons in the Nanika
suite to the west but contain more hornblende and biotite;
in addition, the suite contains only minor porphyry Cu-Mo
prospects (Woodsworth and others, 1991). Comagmatic with
the plutons of the Quanchus suite are uplifted and eroded
felsic volcanic centers in the Eocene Ootsa Lake Group in
the Fawnie Range. The significant Au-Ag epithermal vein
prospects are (1) the Holy Cross and Uduk Lake deposits
(Lane and Schroeter, 1995), (2) the Wolf prospect, which
is related to resurgent doming and felsic intrusion within a
caldera (Andrew and others, 1986), (3) the Clisbako prospect,
which is hosted in felsic volcanics of the Eocene Clisbako
formation, and is one of several similar deposits in a caldera
with a diameter of 40 km (Metcalfe and Hickson, 1995), and
(4) the Blackdome mine, which occurs in an Eocene andesiterhyolite-volcaniclastic
sequence that is coeval with the Ootsa
Lake and Clisbako Volcanics to the north, and is controlled by
doming and normal faulting (Vivian and others, 1987).
Origin of and Tectonic Controls for Skeena Metallogenic Belt
The Skeena metallogenic belt of porphyry Cu-Mo,
porphyry Mo; Ag polymetallic vein, and Au-Ag epithermal
vein deposits occurs in central British Columbia (fig. 103)
and is associated with several early Tertiary plutonic suites
in the Intermontane Belt in west-central British Columbia.
The plutonic suites, which consist of the Nanika, Babine,
Quanchus, and Goosly Suites (Woodsworth and others, 1991;
Carter, 1982), are coeval and spatially related to suprajacent
volcanic rocks, indicating that the plutons were the roots of
former volcanic centers. The plutonic suites are commonly
controlled by high-angle faults that caused uplift and blockfaulting
in the Stikinia terrane. The plutonic suites and coeval
volcanic units form part of an extensive continental-margin arc
in the Canadian Cordillera that consisted of the early Tertiary
Kamloops magmatic belt (Plafker and others, 1989; Nokleberg
and others, 1994c, 1997c) and the Late Cretaceous and early
Tertiary Coast-North Cascade plutonic belt (Nokleberg and
others, 1994c, 1997c). These volcanic-plutonic suites in the
southern Intermontane Belt are interpreted as high-level products
of deep-seated plutonism and metamorphism in the Coast Belt
to the west, which formed in a transpressive orogen related to an
extensional stress field (Woodsworth and others, 1991).
Nelson Metallogenic Belt of Ag Polymetallic
Vein, Ag-Pb-Zn Manto, Au-Ag Epithermal Vein,
Porphyry Mo, Paleoplacer U. and Related
Deposits (Belt NS), Southern British Columbia
The Nelson metallogenic belt of Ag polymetallic vein,
Ag-Pb-Zn manto, Au-Ag epithermal vein, porphyry Mo, paleoplacer
U, and related deposits (fig. 103; tables 3, 4) occurs in
southern British Columbia. The belt contains significant Au-
Ag polymetallic vein and manto deposits, which occur in two
settings. Some deposits occur to the east, in or near the Middle
Jurassic Nelson Batholith that is part of the Nelson plutonic
suite (Woodsworth and others, 1991). The significant deposits
in the belt are (table 4) (Nokleberg and others 1997a,b, 1998)
(1) Au-Ag and Ag polymetallic vein deposits at Ainsworth
District, Highland Bell (Beaverdell), Millie Mack, and Silverton
District (Sandon, Silver Ridge), (2) a porphyry Mo deposit
at Carmi Moly, (3) a Zn-Pb-Ag skarn and manto deposit at
Riondel (Blue Bell), and (4) a paleoplacer U deposit at Lassie
Lake area (Blizzard).
Bluebell (Riondel) Zn-Pb-Ag Skarn and Manto Deposit
The Bluebell (Riondel) Zn-Pb-Ag skarn and manto
deposit (fig. 122) consists of sphalerite, galena, pyrrhotite,
pyrite, arsenopyrite, chalcopyrite and knebelite that occur
in replacement bodies and in veins controlled by bedding,
fractures, and open anticlinal culminations (Hoy, 1980, 1982a;
Nelson, 1991; Beaudoin and others, 1992). The manto and
vein deposits occur along bedding or fractures in pre-deformational
breccias and anticlinal culminations in Early Cambrian
limestone of the Badshot Formation, and in quartz-mica
schist of the Mohican Formation. A distinctive skarn mineral
assemblage includes prograde knebelite (Fe-Mn olivine) and