Metallogenesis and Tectonics of the Russian Far East, Alaska, and ...

Eastern Asia-Arctic Metallogenic Belt:
Verkhoyansk-lndigirka (Dulgalak)
Zone of Clastic Sediment-Hosted Hg
and Sb-Au Vein Deposits (Belt EAVI)
Western Part of Russian Northeast
The Verkhoyansk-lndigirka (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 krn long and up
to 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-lndigirka 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 which are crossed by longitudinal and diagonal
faults. The deposits generally are along deep faults which strike subparallel to the strike of the major folds. The Sb-Au vein
deposits generally occur where the Verkhoyansk-lndigirka metallogenic zone overlies Au quartz vein deposits of accretionary
metallogenic belts, such as the Kular metallogenic belt (fig. 1 1). This metallogenic zone contains abundant pre-mineralization
subalkalic basalt dikes of Late Cretaceous and Paleogene age with K-Ar isotopic ages of 90 to 45 Ma. The Verkhoyansk-lndigirka
metallogenic zone is interpreted as possibly forming in the rear (back-arc) portion of the Okhotsk-Chukotka volcanic-plutonic belt
(Nokleberg and others, 1994c, 1997~).
Zagadka Clastic Sediment-Hosted Hg Deposit
The Zagadka clastic sediment-hosted Hg and associated deposits (V.V. Maslennikov, written commun., 1977, 1985)
consists of cinnabar and metacinnabarite which are relatively younger than the Sb-Au vein deposits which consist of stibnite and
berthierite. The Zagadka deposit occurs in Late Permian sandstone and siltstone which is gentle folded and cut by steeply-dipping
faults. The deposit is located along a linear zone about 2.4 km long within one of the faults. The thickness and morphology of the
ore bodies is influenced by shear zones and associated feathered veins and stringers. The ore bodies, mainly cinnabar, range from
0.4 to 3 m thick. Subordinate minerals are galena, sphalerite, stibnite, Pb-sulfosalts, and cassiterite. Gangue minerals are quartz,
dickite, and carbonate minerals. The wall rocks exhibit dickite, quartz and carbonate alteration. Average grades are 0.22-6.2% Hg,
0.8-20% Pb, 2- 10% Zn, 4- 10% Sb, and up to 30 g/t Ag. Estimated resources are 1,7 18 tonnes mercury and 1,000 tonnes antimony.
Kyuchyus Sb-Au-Hg Vein Deposit
The Kyuchyus Sb-Au-Hg vein deposit (Ivensen and others, 1975; lndolev and others, 1980; Konyshev and others, 1993)
occurs in steeply-dipping mineralized reverse shear zones up to 1 m thick and in veins up to 0.5 m thick. The shear zones and
veins contain quartz-stibnite, cinnabar-stibnite-quartz, realgar-quartz and quartz, with various amounts of ankerite, calcite,
kaolinite, dickite, arsenopyrite, pyrite, orpiment, berthierite, sphalerite, galena, bournonite, pyrrhotite, tetrahedrite, native mercury
(up to IS%), and gold. The veins and shear zones crosscut a Middle Triassic (Anisian and Ladinian) sequence of sandstone and
siltstone flysch. Alteration types include argillaceous, silicic, carbonate, and hydromica aureoles which occur near the deposit.
Average grades are 4.5% As, up to 15% Sb, up to 0.6% Hg, and up to 300 g/t Au. The Sb-Au (Hg) vein deposits usually vary
from small to medium in size, and are not economic.
Eastern Asia-Arctic Metallogenic Belt:
Anuyi-Beringovsky Zone of Au-Ag
Epithermal Vein and Disseminated
Au Sulfide Deposits (Belt EAAB)
Northeastern Part of Russian Northeast
The Anuyi-Beringovsky zone of and disseminated Au-sulfide deposits (fig. 102; tables 3,4) occurs in the northeastern
part of the Russian Northeast. The zone extends approximately east-west for more than 1,000 km and ranges from 200 to 250 krn
wide. The zone is hosted in the volcanic rocks of the Okhotsk-Chukotka volcanic-plutonic belt, and in adjacent areas of coeval
granitoid plutons. Most of the deposits in the zone are near-surface, Au-Ag epithermal vein deposits of Late Cretaceous and early
Paleocene age. These Au-Ag epithermal vein deposits occur mainly in volcanic rocks and are spatially related to disseminated Au-
sulfide deposits which occur in clastic rocks of the Chukotka terrane which underlies the Okhotsk-Chukotka volcanic-plutonic
belt. The significant deposits in the zone are (table 4) (Nokleberg and others 1997a, b, 1998): Au-Ag epithermal vein deposits at
Chineyveem, Draznyaschy, Enmyvaam, Gornostai, Maly Peledon, Promezhutochnoe. Shakh, Zhilny, Sopka Rudnaya, Upryamy,
and Valunistoe; a granitoid-related Au deposit at Pelvuntykoinen; and disseminated Au-sulfide deposits at Elveney and Maiskoe.
The depositional environments, ore composition, and ore chemistry of the Anuyi-Beringovsky zone are similar to those of the