USGS Professional Paper 1697 - Alaska Resources Library

and quartz monzodiorite stock and sill that intrude sedimentary
and volcanic rocks of the Triassic Stuhini Group and
the Early and Middle Jurassic Hazelton Group. Estimated
resources at Red Mountain are 2.5 million tonnes of 12.8 g/t
Au and 38.1 g/t Ag (Rhys and others, 1995).
The Silbak Premier Au-Ag-Pb-Zn epithermal vein deposit
is hosted by volcanic and volcaniclastic rocks of the Hazelton
Assemblage. The deposit consists of argentite and electrum that
occur both in low-sulfide and base-metal sulfide ore. The veins
are related to subvolcanic, quartz-K-feldspar porphyry dikes
that form part of the Texas Creek plutonic suite. Between 1918
and 1987, about 56.1 tonnes of Au and 1,270 tonnes of Ag were
produced. Estimated reserves are 6.1 million tonnes grading
2.33 g/t Au and 90.5 g/t Ag (Alldrick and others, 1987).
Polaris Au Quartz Vein Deposit
The Polaris Au quartz vein deposit consists of native gold
associated with arsenopyrite and stibnite in quartz-ankerite
veins (Marriott, 1992; Mihalynuk and Marriott, 1992). The
deposit has produced approximately 231,000 oz Au from
760,000 tons of ore, with a recovered grade of 0.30 oz Au/t.
The deposit contains estimated resources of 2.196 million
tonnes grading 14.74 g/t Au. The deposit is underlain by late
Paleozoic to Triassic Stuhini Group volcanic and sedimentary
rocks. The volcanic rocks composed of andesite and basalt
flows and pyroclastic rocks host gold in an assemblage of
arsenopyrite, ankerite, sericite, pyrite, fuchsite, and stibnite.
The structures hosting the deposit are splays of the Tulsequah
River shear zone.
Muddy Lake Au Quartz Vein Deposit
The Muddy Lake (Golden Bear, Totem) Au quartz vein
deposit consists of disseminations and fracture-fillings of
extremely fine-grained pyrite that occur along fault contacts
of tuffite and limestone (Melis and Clifford, 1987; Osatenko
and Britton, 1987; Schroeter, 1987; Dawson and others, 1991;
North American Metals Corp, news release, February 1995).
The deposit contains estimated reserves of 720,000 tonnes
grading 5.75 g/t Au. The deposit has been interpreted as a
mesothermal Au-quartz veins hosted by silicified limestone,
dolostone, and tuff of the Permian Asitka Assemblage, and
mineralization is probably related to an unexposed pluton of
the Texas Creek suite. The deposit occurs in a north-trending,
20-km-long fault zone. Four deposits occur on the property at
Bear, Fleece, Totem, and Kodiak. Recent studies interpret the
deposit as a Carlin-type deposit (Poulsen, 1996; Lefebure and
others, 1999) that contains both oxidized and primary ore.
Origin of and Tectonic Controls for Texas Creek
Metallogenic Belt
The Texas Creek metallogenic belt occurs in a suite of
dominantly calc-alkaline granitoid, but in part gabbroic and
alkalic, plutons that intruded mainly in the Early Jurassic as
part of the Stikinia arc and the flanking Cache Creek subduc-
Early Jurassic Metallogenic Belts (208 to 193 Ma; fig. 42) 97
tion-zone terrane, prior to accretion to North America in the
Middle Jurassic (Dawson and others, 1991; Kirkham and
Margolis, 1995; Mihalynuk and others, 1994; Monger and
Nokleberg, 1996; Nokleberg and others, 2000). The Stikinia
island-arc terrane is interpreted as forming on the deformed
continental-margin strata of Yukon-Tanana terrane, which is
interpreted as a rifted fragment of the North American Craton
Margin (Gehrels and others, 1990; Monger and Nokleberg,
1996; Nokleberg and others, 1994c, 1997c; 2000). Several
metallogenic belts formed during granitic magmatism associated
with formation of the Stikinia and Quesnellia island arcs.
The metallogenic belts, which formed in conjunction with the
Stikinia island arc are the Copper Mountain (North), Galore
Creek, Guichon, Klotassin, Texas Creek, and Toodoggone
belts. The Copper Mountain (South) and Guichon metallogenic
belts formed in conjunction with the Quesnellia island arc.
Early Jurassic Metallogenic Belts (208
to 193 Ma; fig. 42)
Overview
The major Early Jurassic metallogenic belts in Alaska and
the Canadian Cordillera are summarized in table 3 and portrayed
on figure 40. No major Early Jurassic metallogenic belts existed
in the Russian Far East. The major belts in Alaska and the Canadian
Cordillera are as follows: (1) Three belts are hosted in the
Wrangellia island-arc superterrane. These belts are the Talkeetna
Mountains-Alaska Range belt (TM), which contains kuroko
massive sulfide deposits, the Alaska Peninsula (AP) belt, which
contains granitic magmatism deposits, and the Island Porphyry
(IP) belt, which contains granitic-magmatism-related deposits.
These belts are interpreted as forming in the Talkeetna-Bonzana
arc preserved in the Wrangellia superterrane. (2) In the Canadian
Cordillera, continuing on from the Late Triassic and commencing
in the Early Jurassic were the Coast Mountains (CM),
Copper Mountain (North; CMN), Copper Mountain (South;
CMS), Galore (GL), Guichon (GU), Klotassin (KL), and Texas
Creek (TC), and Toodoggone (TO) belts, which contain granitic
magmatism-related deposits and are interpreted as forming in the
axial parts of the Stikinia-Quesnellia island arc. In the followiung
descriptions of metallogenic belts, a few of the noteable signficant
lode deposits (table 4) are described for each belt.
Metallogenic-Tectonic Model for Early Jurassic
(208 to 193 Ma; fig. 43)
During the Early Jurassic (Hettangian to Pleinsbachian—208
to 193 Ma), the major metallogenic-tectonic
events were (fig. 43; table 3) (1) continuation of continentalmargin
arcs and associated subduction near the North Asian
Craton in the Russian Far East, (2) beginning of assembly
of previously rifted cratonal, passive continental-margin and