USGS Professional Paper 1697 - Alaska Resources Library

262 Metallogenesis and Tectonics of the Russian Far East, Alaska, and the Canadian Cordillera
suite (Woodsworth and others, 1991). Other deposits occur to
the west in the Okanagan Valley in or near the Eocene alkaline
Coryell Plutonic Suite, which is interpreted as forming during
regional extension. The Coryell Suite is interpreted as the rear
or back-arc part of the Coast-North Cascade plutonic belt. The
vein and manto deposits that occur in or around the Middle
Jurassic Nelson Batholith, including those in the Silverton,
Ainsworth, Slocan, and Sandon districts, were originally
interpreted as forming during the Middle Jurassic intrusion of
the batholith and associated granitoid dikes (Cairnes, 1934;
Hedley 1947, 1952). However, recent isotopic studies suggest
(1) an Eocene age for mineralization for deposits in the district
(Beaudoin and others, 1992), including the large Bluebell
(Riondel) skarn and manto, and (2) that the deposits formed
during intrusion of (Eocene) mafic and lamprophyric dikes.
To the west in the Okanagan Valley several other Au-
Ag epithermal vein deposits are hosted by Eocene trachyte
volcanic rocks of the Marron Formation, which is genetically
related to the alkalic Coryell Plutonic Suite (Woodsworth
and others, 1991; Church, 1973). The Au-Ag epithermal
vein deposits include the Vault (Panteleyev, 1991) and
Dusty Mac (Zhang and others, 1989) deposits. The igneous
rocks and associated deposits are interpreted as forming during
Eocene regional extension associated with the low-angle
Okanagan shear zone (Tempelman-Kluit and Parkinson,
1986; Parrish and others, 1991).
Early to Middle Tertiary Metallogenic
Belts (52 to 23 Ma; figs. 102, 103)
Overview
The major early Tertiary metallogenic belts in the Russian
Far East and the Canadian Cordillera are summarized
in table 3 and portrayed on figures 102 and 103. The major
belts are as follows: (1) In the Russian Southeast, the Central
Sakhalin (CS) belt, which contains Au quartz vein and talc
deposits, is hosted in deformed units of the Aniva subductionzone
terrane and is interpreted as forming in collisional event
during the early Tertiary(?) accretion of outboard terranes to
the east. (2) On the southern Kamchatka Peninsula in the Russian
Northeast, the Sredinny metallogenic belt of Au quartz
vein and metamorphic REE vein(?) deposits is hosted in the
Sredinny-Kamchatka terrane and is interpreted as forming
during accretion of the outboard outboard Olyutorka arc and
generation of hydrothermal fluids. (3) Also on the southern
Kamchatka Peninsula in the Russian Northeast, the Kvinumsky
metallogenic belt of hornblende peridotite Cu-Ni and
gabbroic Ni-Cu deposits is hosted in cortlandite-norite-diorite
intrusions that intrude the older metamorphic and granitoid
rocks of the Sredinny-Kamchatka metamorphic terrane. The
belt is interpreted as forming during back-arc intrusion related
to subduction beneath the Kamchatka Peninsula part of North-
east Asia continental-margin arc. (4) In the Russian Northeast,
the Central Koryak (CKY) belt, which contains granitic-magmatism-related
deposits, is hosted in the Kamchatkak-Koryak
volcanic-plutonic belt, and is interpreted as forming along a
transform continental-margin arc. (5) In the Russian Northeast,
the Olyutor (OT) belt, which contains granitic-magmatism-related
and clastic sediment-hosted Hg deposits, is hosted
in the East Kamchatka Volcanic and Sedimentary Basin and
is interpreted as forming during subduction-related granitic
plutonism that formed the Kamchatka Peninsula part of
Northeast Asia continental margin. (6) In the central Canadian
Cordillera, the Pinchi Lake belt, which contains Hg epithermal
vein, Sb-Au vein, silica-carbonate Hg deposits hosted in or near
shear zones, is interpreted as forming during transcurrent faulting
along Cascade volcanic-plutonic belt. (7) In the southern
Canadian Cordillera, the Owl Creek (OC) belt, which also
contains granitic-magmatism-related deposits, is hosted in the
Cascade volcanic-plutonic belt and is interpreted as forming
during subduction-related granitic plutonism that formed the
Cascade continental-margin arc. In the below descriptions of
metallogenic belts, a few of the noteable or signficant lode
deposits (table 4) are described for each belt.
Metallogenic-Tectonic Model for Early to Middle
Tertiary (52 to23 Ma; fig. 123)
During the early to middle Tertiary (middle Eocene to the
early Miocene—42 to 23 Ma), the major metallogenic-tectonic
events were (fig. 123; table 3) (1) accretion of the Olyutorka
island arc, (2) continuation of a series of continental-margin
arcs, associated metallogenic belts, and companion subduction-zone
assemblages around the Circum-North Pacific, (3)
continuation of sea-floor spreading in the Arctic and eastern
Pacific Oceans, (4) establishment of a new continental margin
in the northern and eastern parts of the Circum-North Pacific
as the result of the disappearance of the Kula oceanic plate and
inception of subduction of the leading edge of the Pacific oceanic
plate, (5) continuation of dextral transpression between
the Pacific oceanic plate (PAC) and the North American continental
margin in the eastern part of the Circum-North Pacific,
and (6) a change to orthogonal transpression between the
Pacific oceanic plate and the southern Alaska continental margin
because of counterclockwise rotation of western Alaska.
At about 50 Ma (Vogt and others, 1979), the Gakkel
Ridge (GK; northern extension of the Atlantic mid-Ocean
Ridge) was initiated and sea-floor spreading extended into the
Eurasia Basin (eb) in the Arctic ocean, thereby resulting in the
North American–Eurasia plate boundary in the Russian Northeast.
The exact location of the Euler pole changed throughout
the Cenozoic, thereby resulting in regional changes in the
stress regime (Savostin and others, 1984; Harbert and others,
1990). Analysis of marine magnetic anomalies in the Eurasia
Basin suggests that the region underwent extension from about
56 to 36 Ma (Savostin and Drachev, 1988a,b; Harbert and others,
1990; Fujita and others, 1997).