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

(Goryachev, 1998, 2003). The deposits are hosted in Carboniferous and Permian clastic rocks of the North Asian Craton Margin
(Verkhoyansk fold belt, unit NSV; Nokleberg and others, 1994c, 1997~). The Vostochno-Verkhoyansk metallogenic belt is the
loci of old mining which started in the 18th century. The belt contains newly-discovered deposits which are currently being
developed for mining. The significant deposits in the belt are Ag polymetallic vein deposits at Altaiskoe, Bezymyannoe,
Kuolanda, Mangazeika, Prognoz, and Verkhnee Menkeche, and a Sn polymetallic vein deposit at lmtachan (table 4) (Nokleberg
and others 1997a, b, 1998). Ag polymetallic vein deposits and occurrences, as at Altaiskoe, Mangazeika, and Menkeche, occur in
longitudinal and diagonal faults which crosscut the hinges of major folds.
The age of mineralization for the Vostochno-Verkhoyansk metallogenic belt is interpreted as Late Cretaceous to
Paleogene because the deposits formed prior to the development of the clastic sediment-hosted Hg deposits of the Verkhoyansk-
Indigirka metallogenic belt in the same region (Indolev, 1979; Goryachev, 1998). The Vostochno-Verkhoyansk metallogenic zone
is interpreted as forming in the rear (back-arc) part of the Cretaceous and early Tertiary Okhotsk-Chukotka volcanic-plutonic belt
(fig. 79).
Mangazeika Ag Polymetallic Vein Deposit
The Mangazeika deposit (N.A. Tseidler, written commun., 1985; Goryachev, 1998) consists of polymetallic veins which
occur in Early Permian argillite and sandstone which occur in gently-plunging tight folds. The veins fill fissures between argillite
and sandstone layers and are conformable to bedding. The veins range from 50 to 1,300 m long, and from 3 cm to 1 m thick. The
main ore minerals are galena and sphalerite; minor minerals are pyrite, arsenopyrite, chalcopyrite, owyheeite, freibergite,
diaphorite, boulangerite, pyrargyrite, miargyrite, cassiterite, stamite, and native gold, native silver, and argentite. Gangue minerals
are manganosiderite, quartz, ankerite, sericite, chlorite, and tourmaline. This and similar deposits do not contain significant
amounts of sulfide minerals; silver amalgam is locally present. Other deposits, as at Menkeche and Bezymyannoe, are associated
with Early and Late Cretaceous basaltic dikes and associated Sn polymetallic vein deposits. Wallrock alteration, including
carbonization and silicification, is not significant. Estimated reserves are 62,375 tonnes Pb, 2,900 tonnes Zn, and 324 tonnes Ag.
Estimated total resources are more than 1,000 tonnes Ag. Average grades are 75% Pb; 0.3-5% An; 500-3,938 g/t Ag; and 0.1-0.5
g/t Au. Silver was mined from 19 15- 1922.
Eastern Asia-Arctic Metallogenic Belt:
Adycha-Taryn Zone of Au-Ag Epithermal Vein,
AgSb Polymetallic Vein, and Clastic
Sediment-Hosted Sb-Au Deposits (Belt AT)
Western Part of Russian Northeast
The Adycha-Taryn metallogenic zone forms a linear array of clastic sediment-hosted Sb-Au, Au-Ag epithermal vein, and
Ag-Sb polymetallic vein associated deposits (fig. 79; tables 3,4) which occur adjacent to the Adycha-Taryn fault in the western
part of the Russian Northeast (Goryachev, 1998). The Adycha-Taryn fault is a major collisional suture zone between the Kular-
Nera accretionary-wedge terrane of the Kolyma-Omolon terrane to the northeast and the North Asian Craton Margin
(Verkhoyansk fold belt, unit NSV) to the southwest (Nokleberg and others, 1994c, 1997~). The metallogenic belt is about 750 km
long and 5 to 10 km wide. Several groups of deposits occur in the metallogenic belt (table 4) (Nokleberg and others 1997a, b,
1998): (1) small Au-Ag epithermal vein deposits, as at Ak-Altyn; (2) small Ag-Sb polymetallic vein occurrences; and (3) highgrade
clastic-sediment-hosted Au-Sb deposits, as at Billyakh, Sarylakh, Sentachan, and Uzlovoe. Many of the clastic-sedimenthosted
Au-Sb deposits, as at Sarylakh, are partly mined out.
The age and genesis of the Adycha-Taryn zone is more complex than previously interpreted because some of the
deposits: (1) are not evidently magmatism-related; (2) are relatively younger than Au quartz vein and Sn-W vein deposits which
occur in the same area; and (3) locally crosscut homfels near granite intrusions which exhibit K-Ar isotopic ages of 110 to 90 Ma.
Three possible origins are suggested for the genesis of the Au-Sb deposits in the Adycha-Taryn metallogenic belt. (1) A deep and
possible mantle origin may be indicated by the local occurrence of native metals in the Au-Sb deposits (Anisimova and others,
1983). (2) The clastic-sediment-hosted Au-Sb deposits, which occur in and near the major Adycha-Taryn fault, may have formed
in an accretionary environment and are related to metamorphism which occurred immediately after collision and accretion of the
Kolyma-Omolon superterrane to the North Asian Craton Margin (Verkhoyansk fold belt, unit NSV, fig. 79) along the Adycha-
Taryn fault (Berger, 1978, 1993; Nokleberg and others, 2000). And (or; 3) the Au-Sb epithermal deposits and the polymetallic
vein deposits may have formed in a post-accretional environment and are related to younger, Cretaceous and Paleogene basaltic
magmatism in the region (Indolev and others, 1980). Alternatively, the clastic-sediment-hosted Au-Sb deposits may be part of a
suite of quartz vein deposits and are part of the Yana-Kolyma metallogenic belt (Berger, 1978, 1993). The epithermal and
polymetallic vein deposits of the Adycha-Taryn metallogenic zone are herein interpreted as forming in the rear and transverse part
of the Cretaceous to early Tertiary Okhotsk-Chukotka volcanic-plutonic belt (fig. 79) which forms a major, post-accretionary
continental-margin arcs in the Russian Northeast (Nokleberg and others, 1994c, 1997c; 2000).