USGS Professional Paper 1697 - Alaska Resources Library

220 Metallogenesis and Tectonics of the Russian Far East, Alaska, and the Canadian Cordillera
and 0.2 to 0.4 g/t Au in disseminated and veinlet ore and as
much as 0.8 g/t Au in oxidized ore. The Iruneiskiy terrane is
interpreted as part the Olyutorka-Kamchatka island-arc terrane
that was accreted in the early Tertiary onto the North Asian
continental margin (Nokleberg and others, 2000).
Metallogenic Belts Formed in Late Mesozoic
and Early Cenozoic Part of Okhotsk-Chukotka
Continental-Margin Arc, Russian Northeast and
Western Alaska
Eastern Asia-Arctic Metallogenic Belt: Verkhne-
Yudomsky (Yuzhno-Verkhoyansk) Zone of Sn and
Ag Polymetallic Vein (Southern Bolivian type)
Deposits (Belt VY), West-Central Part of Russian
Northeast
The Verkhne-Yudomsky (Yuzhno-Verkhoyansk) metallogenic
zone of Sn and Ag polymetallic vein (Southern Bolivian
type) deposits (fig. 102; tables 3, 4) extends north-south for
400 km with a maximum width of 100 km. The belt occurs in
the west-central part of the Russian northeast and is hosted by
either the clastic sedimentary rocks of the North Asian Craton
Margin (Verkhoyansk fold belt), the Okhotsk cratonal terrane,
or the volcanic rocks of the Okhotsk-Chukotka volcanicplutonic
belt. The significant deposits in the zone are (table
4) (Nokleberg and others 1997a,b, 1998): Sn polymetallic
vein deposits at Balaakkalakh, Diring-Yuryak, Khaardak, and
Khoron, and various types of polymetallic vein deposits at
Dzhaton, Kutinskoe, Nivandzha, and Zarnitsa.
The metallogenic zone is associated with major hypabyssal
Early and Late Cretaceous felsic intrusions that occur in
the landward part of the Cretaceous to early Tertiary Okhotsk-
Chukotka volcanic-plutonic belt (unit ok, fig. 102) (Nokleberg
and others, 1994c, 1997c). The deposits generally consist of
quartz-chlorite-sulfide veins with cassiterite, hematite, sericite,
fluorite, arsenopyrite, pyrite, chalcopyrite, galena, sphalerite,
stannite, tetrahedrite, and gold that occur in steeply dipping
shear zones to 20 m thick and in elongate (stringer) masses in
dacite, rhyolite, and granite porphyry. Wallrocks are generally
altered to chlorite and sericite. Also associated with the Sn and
Ag polymetallic vein deposits are small Sn (Bi, W) greisen
deposits, generally small and uneconomic, which are related
to Late Cretaceous leucocratic granitoid plutons. The major Sn
and Ag polymetallic vein deposit is at Zarnitsa-Kutinskoe. The
Verkhne-Yudomsky metallogenic zone is interpreted as forming
in the rear of the perivolcanic zone of the Cretaceous to early
Tertiary Okhotsk-Chukotka volcanic-plutonic belt (fig. 102).
Zarnitsa-Kutinskoe Pb-Zn-Ag Polymetallic Vein Deposit
The Zarnitsa-Kutinskoe Pb-Zn-Ag polymetallic vein
deposit (V.I. Korostolev, written commun., 1963) consists
of two polymetallic quartz-sulfide veins that contain galena,
sphalerite, pyrite, chalcopyrite, and silver minerals. The larger
vein is as much as 500 m long and 6 m thick. The veins cut
Late Cretaceous granite-porphyry and rhyolite and have a
fringe of disseminated sulfides as much as 20 m thick. The
Kutinskoe deposit consists of one vein about 3 m thick and
400 m long that is composed of quartz, pyrite, galena, sphalerite,
and pyrrhotite. The Kutinskoe vein cuts contact-metamorphosed
Late Permian sandstone and shale. The deposit is
medium size with average grades of 4.86 to 7.75 percent Pb,
4.1 to 5 percent Zn, and 44 to 3,268 g/t Ag.
Eastern Asia-Arctic Metallogenic Belt: Verkhoyansk-Indigirka
(Dulgalak) Zone of Clastic Sediment-Hosted
Hg and Sb-Au Vein Deposits (Belt
EAVI), Western Part of Russian Northeast
The Verkhoyansk-Indigirka (Dulgalak) metallogenic zone
of clastic sediment-hosted Hg, and Sb-Au vein deposits (fig.
102; tables 3, 4) occurs in a narrow arc in the western part of
the Russian Northeast. The zone is more than 1,200 km long
and as much as 50 km wide. The zone mostly occurs within
the North Asian Craton Margin (Verkhoyansk fold belt, unit
NSV), to a lesser amount in the Kular-Nera accretionary-wedge
terrane of the Kolyma-Omolon superterrane. The significant
deposits in the belt are (table 4) (Nokleberg and others 1997a,b,
1998) clastic sediment-hosted Hg deposits at Erel, Iserdek,
Kholbolok, Seikimyan, Singyami, Zagadka, and Zvezdochka,
and Sb, Sb-As, Sb-Au, and Sb-Au-Hg vein deposits at Baidakh,
Betyugen, Imnekan, Kyuchyuss, Selerikan, Senduchen, and
Stibnitovoe. The one is locally extensively overlain by unconsolidated
Cenozoic sedimentary deposits of the Primorskaya
lowland. The Verkhoyansk-Indigirka metallogenic belt may be
a portion of a greater Verkhoyansk-Chukchi mercury belt. The
major clastic sediment-hosted Hg deposits are at Zagadka and
Zvezdochka, and the major Sb-Au vein deposit is at Kyuchyuss
(fig. 105). The clastic sediment-hosted Hg, and Sb-Au vein
deposits are hosted mainly in clastic sandstone and shale and
generally occur along the hinges of anticlines that are crossed
by longitudinal and diagonal faults. The deposits generally
are along deep faults that strike subparallel to the strike of the
major folds. The Sb-Au vein deposits generally occur where
the Verkhoyansk-Indigirka metallogenic zone overlies Au
quartz vein deposits of accretionary metallogenic belts, such as
the Kular metallogenic belt (fig. 61). This metallogenic zone
contains abundant premineralization subalkalic basalt dikes of
Late Cretaceous and Paleogene age with K-Ar isotopic ages of
90 to 45 Ma. The Verkhoyansk-Indigirka metallogenic zone is
interpreted as possibly forming in the rear (back-arc) portion of
the Okhotsk-Chukotka volcanic-plutonic belt (Nokleberg and
others, 1994c, 1997c).
Zagadka Clastic Sediment-Hosted Hg Deposit
The Zagadka clastic sediment-hosted Hg and associated
deposits (V.V. Maslennikov, written commun., 1977, 1985) con-