USGS Professional Paper 1697 - Alaska Resources Library

in a island arc that was tectonically linked to the Alkatvaam
accretionary-wedge terrane (Nokleberg and others, 2000).
Svyatoy-Nos Metallogenic Belt of Au-Ag
Epithermal Vein Deposits (Belt SVN), Northern
Part of Russian Northeast
The Svyatoy-Nos metallogenic belt of Au-Ag epithermal
vein deposits (fig. 48; tables 3, 4) occurs in the northern part
of the Russian Northeast. The deposits are closely related to
intermediate and felsic dikes with K-Ar isotopic ages of 149
Ma that are part of Late Jurassic Svyatoy Nos volcanic belt
(Bakharev and others, 1998). The epithermal Au-Ag deposits in
the metallogenic belt, as at Polevaya, are associated with dikes
and small bodies of Early Cretaceous subvolcanic rhyolite,
monzonite, and quartz syenite-porphyry (Nokleberg and others
1997a,b, 1998). The Svyatoy-Nos metallogenic belt is partly
overlain by Cenozoic sedimentary rocks of the Primorskaya
lowland. The sole significant deposit is at Polevaya (table 4).
Polevaya Au-Ag Polymetallic Vein Deposit
The Polevaya Au-Ag polymetallic vein deposit (Nekrasov,
1962; Bakharev and others, 1988) consists of two thin,
subparallel zones of intensely silicified and sericitized granodiorite
and quartz diorite. The zones range from 1 to 2 m thick
and to as much as 500 m long. The zones occur along and
near the contact of an Early Cretaceous pluton that forms the
core of a complex, Late Jurassic to Late Cretaceous volcanicplutonic
structure. The major minerals are chalcedony-like
cryptocrystalline quartz, calcite, pyrite, galena, sphalerite,
chalcopyrite, and gold. The sulfide content is about 2-3 percent.
The deposit contains as much as 10 g/t Au, 10 g/t Ag,
0.020-1 percent Pb, 0.050-1 percent Zn, 0.005-0.3 percent Cu,
and 0.5 percent Sn.
Origin of and Tectonic Controls for Svyatoy-Nos
Metallogenic Belt
The Svyatoy-Nos metallogenic belt is hosted in the
younger (Neocomian) part of Late Jurassic and Early Cretaceous
Oloy-Svyatoy Nos volcanic belt (Nokleberg and others,
1994c, 1997c). This igneous belt occurs along the northeastern
margin of the Kolyma-Omolon superterrane and is part of the
Indigirka-Oloy sedimentary-volcanic-plutonic assemblage. The
belt contains mainly andesite, rhyolite, and tuff with interlayered
shallow-marine sandstone, conglomerate, and siltstone
(Parfenov, 1995a,b). The Oloy-Svyatoy Nos volcanic belt
occurs adjacent to and southwest of the South Anyui terrane
(fig. 48) and consists of mainly shallow-marine, rarely nonmarine
basalt, andesite, rhyolite, and tuff with interlayered sandstone,
conglomerate, siltstone, and shale. The volcanic belt also
contains small bodies of granite, granodiorite, and monzogranite.
The belt is interpreted as possibly related to a short-lived
period of Late Jurassic Early Cretaceous subduction of the part
of the South Anyui oceanic terrane beneath the northeastern
Late Jurassic Metallogenic Belts (163 to 144 Ma; figs. 48, 49) 123
margin of the Kolyma-Omolon superterrane, after accretion of
the Kolyma-Omolon superterrane to the North Asian Craton
Margin (Nokleberg and others, 1994c, 1997c, 2000).
Kuyul Metallogenic Belt of Podiform Cr, PGE and
Associated Deposits (Belt KUY), East-Central
Part of Russian Northeast
The Kuyul metallogenic belt of podiform Cr and associated
PGE deposits (fig. 48; tables 3, 4) occurs in the southern
part of the major nappe and thrust belt of the Koryak Highlands
in the east-central part of the Russian Northeast. The belt
extends for more than 900 km from the Taigonoss Peninsula
to the northern spurs of the Pekulney Range. The metallogenic
belt is hosted in the Kuyul ophiolite, part of the Gankuvayam
and Elistratov units of the Kuyul subterrane (unit TLK) of the
Talovskiy subduction-zone and oceanic terrane (Nokleberg
and others, 1994c, 1997c). The Kuyul ophiolite contains about
20 poorly-prospected Cr deposits in serpentinized peridotites
that occur in about 50 mainly small, discontinuously exposed
ultramafic bodies. The significant deposits in the belt are
at Talov and Tikhorechen (table 4) (Nokleberg and others
1997a,b, 1998). These deposits consist of chromite and accessory
chromium spinel that occur with PGE minerals in dunite
and associated ultramafic rocks. PGE minerals, in association
with gold, are hosted in serpentinite and rodingite adjacent to
peridotite and dunite. Local Cu-Zn-Co-Ag sulfide minerals
occur in carbonate breccias (Gorelova, 1990).
Origin of and Tectonic Controls for Kuyul Metallogenic Belt
The Kuyul subterrane of the Talovskiy terrane consists
chiefly of tectonic sheets composed of (Nokleberg and others,
1994c, 1997c) (1) serpentinite mélange with blocks of: (a)
ultramafic rock, gabbro, plagiogranite, dike suites of oceanic
and subduction zone origin, and amphibolite,, (b) island
arc volcanic and sedimentary deposits composed mainly of
andesite, dacite, tuff; and glaucophane schist, and (c) fore-arc
tuff and sedimentary rocks, (2) Kuyul ophiolite composed
of harzburgite, gabbro, troctolite, wehrlite, plagiogranite,
sheeted dikes, and pillow lava of Bathonian and Tithonian
age (Chekov, 1982; Markov and others, 1982), (3) Kingiveem
complex composed of oceanic volcanic, siliceous, and carbonate
rocks of Permian, Middle and Late Triassic, and Middle
Jurassic age, and (4) the Kuyul subduction-zone mélange composed
of Late Jurassic and Early Cretaceous turbidite deposits,
which contain Buchia and Middle Jurassic radiolarian chert.
The Kulul ophiolite assemblage that hosts the Kuyul
metallogenic belt is interpreted as forming either (1) during
spreading of a marginal-sea basin during the early stages of
island-arc formation; or (2) adjacent to a transform fault along
the margin of an ocean basin (Palandzhyan and Dmitrenko,
1990). The Talovskiy subduction-zone terrane is tectonically
linked to the mainly Late Jurassic and Early Cretaceous Koni-
Murgal island-arc terrane (Nokleberg and others, 2000).