USGS Professional Paper 1697 - Alaska Resources Library

54 Metallogenesis and Tectonics of the Russian Far East, Alaska, and the Canadian Cordillera
son, 1991; Dawson and others, 1991; Hoy, 1991; George Cross
Newsletter no. 30, February 12, 1993; Pearson, 1993). The
deposits contain an estimated combined production and reserves
of 30.3 million tonnes grading 2.23g/t Au, 54.5g/t Ag, 2.12 percent
Cu, and 7.1 percent Zn. The deposit is hosted within felsic
volcanics of the Late Devonian Myra Formation in the Sicker
Group. The deposits occur at two stratigraphic levels—the H-W
horizon, at the base of the Myra Formation and the Lynx-Myra-
Price horizon, in the central portion of the Myra Formation.
Under the H-W deposit, the stratigraphic footwall consists of
greater than 300 m of basaltic andesite of the Price Formation
that is intensely altered to to quartz-sericite-pyrite.
Origin of and Tectonic Controls for Mount Sicker
Metallogenic Belt
The kuroko volcanogenic massive sulfide Zn-Cu-Pb-
Au-Ag deposits in the Mount Sicker metallogenic belt occurs
mainly in fragmental basaltic andesite, lesser dacite and
andesite, intermediate pillow lava, and epiclastic volcanic
rock. The host rock and deposit distribution are defined by
three fault-bounded uplifts. The volcanic rocks are 310 to 440
m thick and exhibit an U-Pb zircon isotopic age of 370 Ma
(Juras, 1987 ). Underlying pillow basaltic flows of the Price
Formation formed during a nonexplosive effusive event that
was succeeded by rifting, felsic volcanism, and formation
of massive sulfide deposits. The volcanic rocks are overlain
by Carboniferous sedimentary rocks that contain bioclastic
crinoidal limestone in the Buttle Lake Formation. Significant
kuroko massive sulfide deposits occur in felsic volcanics of
the upper part of the Sicker Group in domal culminations.
The calc-alkaline volcanic rocks hosting the Mount Sicker
metallogenic belt are interpreted as part of the minor, middle
Paleozoic Sicker island arc, which forms the oldest part of the
Alexander sequence of the Wrangellia superterrane (Monger
and Nokleberg, 1996; Nokleberg and others, 1994c, 1997c). In
this paper, following Nokleberg and others (1994c, 2000), the
Wrangellia superterrane is subdivided into three sequences,
from west to east to southeast, the Peninsular, Wrangellia,
and Alexander sequences. These sequences are interpreted as
forming the once continuous core of the superterrane and have
been subsequently tectonically dismembered.
Kootenay-Shuswap Metallogenic Belt of Volcanogenic
Zn-Pb-Cu-Ag-Au Massive Sulfide
Deposits(Belt KS) Southern British Columbia
The Kootenay-Shuswap metallogenic belt of volcanogenic
Zn-Pb-Cu-Ag-Au massive sulfide deposits (fig. 17;
tables 3, 4) occurs in Southern British Columbia. The belt is
hosted in is a discontinuous assemblage of metamorphosed
and intensely deformed siliceous clastic, carbonate, volcanic,
and plutonic rocks of the Kootenay terrane in the Shuswap
region. This metamorphosed continental margin terrane occurs
between the North America Craton Margin to the east, and
the accreted island arc Quesnellia terrane to the west (fig. 17).
The belt contains Kuroko, Besshi, Cyprus, SEDEX Zn-Pb,
Southeast Missouri, and bedded barite deposits (table 4) (Nokleberg
and others (1997a,b). Four types of volcanogenic massive
sulfide deposits are recognized by Preto and Schiarriza
(1985).The significant deposits in the metallogenic belt are
the Cyprus-type Chu Chua and Harper Creek Cyprus massive
sulfide deposits, the kuroko-type Homestake and Rea (Hilton)
kuroko sulfide deposits, the Goldstream Besshi massive
sulfide deposit, the Adams Plateau Zn-Pb-Ag SEDEX deposits
(Spar, Lucky Coon, King Tutt, Mosquito King), and the Rexspar
(Birch Island) felsic plutonic U-REE deposit (Nokleberg
and others 1997a,b, 1998).
Homestake and Rea Gold Kuroko Zn-Pb-Cu-Au-Ag Deposits
The Homestake kuroko Zn-Pb-Cu-Au-Ag deposit
consists of two tabular sulfide-barite horizons that occur in
intensely quartz-sericite-pyrite altered sericite schist derived
from felsic to mafic tuffaceous units of the Devonian Eagle
Bay Assemblage (Dawson and others, 1991; Høy, 1991).
Sulfide minerals are tetrahedrite, galena, sphalerite, pyrite, and
chalcopyrite. Estimated reserves are 919,420 tonnes grading
248 g/t Ag, 2.5 percent Pb, 4 percent Zn, 0.55 percent Cu, and
275,500 tonnes grading 36.7 percent Ba. The deposit is overlain
by intermediate to felsic volcanics of Eagle Bay Assemblage.
The Rea Gold volcanogenic sulfide deposit occurs
about 4 km to the norwest, and contains contains mining
reserves of 376,385 tonnes grading 2.2 percent Pb, 2.3 percent
Zn, 6.1 g/t Au, and 76 g/t Ag.
Goldstream Besshi Cu-Zn-Ag Deposit
The Goldstream Besshi Cu-Zn-Ag volcanogenic massive
sulfide deposit occurs in the eastern part of the Kootenay
terrane and consists of massive pyrrhotite, chalcopyrite and
sphalerite often exhibiting gneissic texture with subrounded
quartz, phyllite and carbonate inclusions (Høy, 1991; MIN-
FILE, 2002). The deposit occurs as a thin, conformable sheet
(400 x 1500 x 1-3m thick) and as several other horizons in
sericite quartzite and calcareous and chloritic phyllite in the
lower Index Formation of the Cambrian Lardeau Group. The
host metavolcanic-phyllite unit consists of mafic tholeiitic
volcanic rocks, massive greenstone, chloritic phyllite, ultramafic
pods and dark calcareous to pelitic schist. In 1983 and
1984, 427,886 tonnes were mined averaging 8.9 g/t Au, 4.43
percent Cu, and 0.12 percent Zn. Production restarted in 1992;
estimated reserves are 3.2 million tonnes grading 4.5 percent
Cu, 3.1 percent Zn, and 20 g/t Ag.
Harper Creek and Chu Chua Cu-Zn-Ag-Au Deposits
The Harper Creek Cu-Ag-Au volcanogenic massive sulfide
deposit consists of disseminated pyrite, pyrrhotite and chalcopyrite
with minor molybdenite, galena, sphalerite, and tetrahedrite
that occur in tabular zones in mafic metavolcanic rocks and
quartz-sericite phyllite of the Devonian Eagle Bay Formation