USGS Professional Paper 1697 - Alaska Resources Library

sian Northeast. The belt is hosted in a zone of metamorphic
rocks in Paleozoic and older rocks in the western part of the
Shamanikha subterrane of the passive continental-margin
Prikolyma terrane of the Kolyma-Omolon superterrane (fig.
61). The zone of metamorphic rocks and vein deposits is
adjacent to the Late Jurassic volcanic and plutonic rocks of the
Indigirka-Oloy overlap assemblage (unit io; Nokleberg and
others, 1994c, 1997c). The major deposits in the belt are the
Glukhariny and Kopach Au quartz vein deposits, and the Opyt
Cu-Ag quartz vein deposit (table 4) (Nokleberg and others
1997a,b, 1998). The metallogenic belt extends north-south for
about 350 km and varies in width from 5 to 50 km.
Au Quartz Vein Deposits
The Au quartz vein deposits generally occur as thin quartz
veins in late Proterozoic sedimentary rocks metamorphosed to
greenschist facies. The significant Au quartz vein deposits are
at Glukhariny and Kopach. The Glukhariny occurrence (E. Ya.
Lutskin, written commun., 1964; V.A. Semenov, written commun.,
1974) consists of gold in quartz veins in Late Proterozoic
quartz-chlorite-epidote schist, quartzite, and metarhyolite and
in quartz-cemented breccias in these rocks. The wall rocks are
metamorphosed to upper greenschist facies. The ore minerals
are native gold, galena, chalcopyrite, arsenopyrite, and hematite.
The deposit occurs in three east-west trending zones that
are as much as 1,200 to 4,000 m long and vary from 400 to 900
m wide. The deposit is small. Grab samples contain as much as
25 g/t Au and as much as 50 g/t Ag.
Cu-Ag quartz Vein Deposits
The Cu-Ag quartz vein deposits occur in Late Proterozoic
Cu-bearing sandstone metamorphosed to greenschist facies.
The significant deposit at Opyt (E. Ya. Lyaski, written commun.,
1937; V.A. Erzin, written commun., 1946; A.N. Ruchkin
and S.L. Tsykarev, written commun., 1984) occurs as veins
and zones of massive, disseminated, and brecciated veinlets.
The ore minerals are pyrite, chalcopyrite, bornite, galena,
sphalerite, cuprite, native copper, chalcocite, arsenopyrite, and
electrum. The gangue minerals are quartz, calcite, dolomite,
graphite, and chlorite. The veins are hosted in Late Proterozoic,
Cu-bearing, graphite-sericite-chlorite-quartz schist, and
also in Late Jurassic siltstone and sandstone. The deposit is
located at the intersection of a Late Jurassic depression and a
block of old metamorphic rocks near a barely eroded granite
body. The main ore body is about 2 km long; the entire
deposit trends northwest-southeast for about 3 km. The deposit
contains a probable resource of 14 million tonnes of reserves
grading 1.5 percent Cu, 1.2 percent Pb, 0.5 percent Zn, 180 g/t
Ag, and as much as 1 g/t Au. The Cu-Ag quartz vein deposits
of the Shamanikha metallogenic belt occur adjacent to
the Late Jurassic Uyandin-Yassachny volcanic-plutonic belt,
which forms the southwestern part of the Indigirka-Oloy sedimentary
and igneous assemblage (unit io, fig. 61). The Cu-Ag
quartz vein deposits exhibit a more diverse mineral composition
compared to the Au quartz vein deposits in the same belt.
Early Cretaceous Metallogenic Belts (144 to 120 Ma; figs. 61, 62) 151
Origin of and Tectonic Controls for Shamanikha
Metallogenic Belt
Because the metamorphic vein deposits of the Shamanikha
metallogenic belt occur partly in Late Jurassic sedimentary
rock, the veins are interpreted in forming in the latest Jurassic
or Early Cretaceous (Nokleberg and others, 2000; this study).
The metamorphism, associated deformation, and formation
of the Au and Cu-Ag quartz vein deposits are interpreted as
occurring during one of two major tectonic events (Nokleberg
and others, 2000)—(1) the latest Jurassic and Early Cretaceous
accretion of the Kolyma-Omolon superterrane, including accretion
of the Prikolyma passive-continental-margin terrane, to the
North Asian Craton margin (unit NSV, fig. 61), or (2) the Early
to mid-Cretaceous accretion of the Chukotka superterrane
against the South Anyui and Velmay subduction-zone terranes
and the Nutesyn island-arc terrane that were in turn colliding
with the Kolyma-Omolon superterrane to the southwest.
Herein, the first interpretation is favored.
Verkhoyansk Metallogenic Belt of Au Quartz
Vein, Au-Sn Polymetallic Vein Deposits (Belt VK),
Western Part of Russian Northeast
The Verkhoyansk metallogenic belt of Au quartz vein and
Au polymetallic vein and Sn vein deposits (fig. 61; tables 3, 4)
occurs in the western part of the Russian Northeast (Goryachev,
1998, 2003). The deposits are hosted in the North Asian Craton
Margin (Verkhoyansk fold belt, unit NSV) (Nokleberg and others,
1994c, 1997c). The belt extends for about 1,000 km from
the Tompo River Basin to the Arctic Ocean in a narrow band
that occurs in the axial portion of the Verkhoyansk meganticlinorium.
The major Au quartz vein deposits are at Anna-
Emeskhin, Enichan-Tolono, Galochka, Nikolaevskoe, Otkrytoe,
Syncha-I and II, and Syugyunyakh-Kende, and the major Au-Sn
polymetallic vein deposits are at Balbuk, Bochiyskoe, Chochimbal,
Dyabkhanya, and Imtandzha (table 4) (Nokleberg and others
1997a,b, 1998). A Pb polymetallic vein deposit is at Balbuk.
The Au quartz vein deposits are interpreted as synmetamorphic
and formed relatively earlier than the nearly coeval
Au-polymetallic vein deposits (Goryachev, 1998, 2003). The
Au quartz vein deposits are controlled by diagonal and longitudinal
faults and anticlinal domes (Amuzinsky, 1975) and occur
both as sheeted ore bodies and sometimes as stockworks.
An example of an Au polymetallic vein deposit is at
Chochimbal. An example of a Sn polymetallic vein deposits
is at Imtandzha. The polymetallic vein deposits occur in the
southern half of the metallogenic belt and are closely associated
with Cretaceous granitoid rocks. The Au-Sn polymetallic
vein deposits are relatively older than associated granitoid
rocks (Ivensen and others, 1975; Goryachev, 1998, 2003).
Nikolaevskoe and Otkrytoe Au Quartz Vein Deposits
The Au quartz vein deposits at Nikolaevskoe and Otkrytoe
(Abel and Slezko, 1988) consist of conformable and cross-