USGS Professional Paper 1697 - Alaska Resources Library

206 Metallogenesis and Tectonics of the Russian Far East, Alaska, and the Canadian Cordillera
a concealed cupola of the Omsukchan granite. This deposit
differs from similar precious metal epithermal deposits by a
predominance of Ag and multistage formation from the Early
Cretaceous through the early Paleogene. This rich vein deposit
is interpreted as forming during partial Ag remobilization of
the disseminated sulfide minerals, which were deposited during
Early Cretaceous Askoldin magmatism (Milov and others,
1990). This mining district has potential for additional, undiscovered
deposits, similar to Dukat, with bulk-mineable lowgrade
Ag deposits similar to Waterloo and other Ag pipe-like
deposits in Mexico (Natalenko and Kalinin, 1991).
Eastern Asia-Arctic Metallogenic Belt:
Chokurdak Zone of Granitoid-Related Sn Greisen,
Sn-Polymetallic Vein, Sn Greisen, and Au-Ag
Epithermal Vein Deposits (Belt EACD), Northern
Part of Russian Northeast
The Chokurdak metallogenic zone of granitoid-related Sn
greisen, Sn polymetallic vein, and Au-Ag epithermal deposits
(fig. 79; tables 3, 4) occurs in the northern part of the Russian
Northeast. The deposits are closely related to mid-Cretaceous
felsic volcanic rocks and associated Late Cretaceous leucocratic
granite dikes and plutons with K-Ar isotopic ages of 90
to 105 Ma (Nokleberg and others, 1994c, 1997c). The significant
deposits in the zone are Sn silicate-sulfide vein deposits at
Chokurdakh, Churpunnya, and Sigilyakh; Sn polymetallic vein
and Sn greisen deposits at Pavel-Chokhchurskoe, Deputatskoe,
Djaktardakh, Khomustak, Odinokoe, and Ukachilkan; and Sn
and Au-Ag polymetallic vein deposits at Polevaya, Primorskoe,
and Yuzhnoe (table 4) (Nokleberg and others 1997a,b, 1998).
The Chokurdak metallogenic belt is hosted in one of the rear,
mid- to Late Cretaceous parts of the Okhotsk-Chukotka volcanic-plutonic
belt (Nokleberg and others, 1994c, 1997c).
The Sn polymetallic vein deposits, as at Primorskoe,
Deputatskoe, and Dyaktardak, are associated with small
intrusions of moderately felsic granite and quartz monzonite
with K-Ar isotopic ages of 110 to 100 Ma and with subalkalic
mafic and intermediate dikes with K-Ar isotopic ages of 100
to 70 Ma. These granitoid rocks constitute one of the rear parts
of the Okhotsk-Chukotka volcanic-plutonic belt. Sn greisen
deposits, as at Khomustak and Odinakoe, occur in the apical
portions of granitic intrusions or in subvolcanic rhyolite
bodies, as at Churpunya and Odinokoe. Economic Sn deposits
occur at Deputatskoe and Churpunnya. The Sn deposits are the
sources for commercial cassiterite place deposits in the region,
including a coastal belt of Sn placer deposits.
Deputatskoe Sn Polymetallic Vein(?) Deposit
The Deputatskoe Sn polymetallic vein(?) deposit (Flerov,
1974) includes about 150 separate ore bodies that occur in
shear zones, veins, and linear stockwork zones. The main
ore bodies occur in mineralized zones, which are explored
to depths of more than 350 m with adits and drillholes. The
deposit ranges as much as 18 m thick and as much as 1,400 m
long. Major and minor minerals are quartz, tourmaline, chlorite,
axinite, fluorite, pyrrhotite, cassiterite, chalcopyrite, pyrite,
siderite, ankerite, sphalerite, galena, marcasite, wolframite,
stannite, franckeite, boulangerite, bismuth, bismuthine, topaz,
apatite, scheelite, and sulfosalts. The wallrocks altered to silica,
tourmaline, chlorite, and less common greisen and sulfides.
The deposit is large with an average grade of 0.3 to 0.7 percent
Sn, and local high-grade zones with as much as 10 percent Sn.
The deposit is hosted in contact metamorphosed Middle Jurassic
shale and in an unexposed granite stock, which is penetrated
by drilling at 377 m depth. The stock exhibits a K-Ar isotopic
age of 108 to 104 Ma. Predeposit, coeval and post-deposit
dikes of mafic, intermediate, and felsic intrusive rocks are
widespread. Many of the polymetallic veins occur in felsic and
intermediate dikes. The Deputatskoe deposit has been the largest
producer of Sn in the Russian Far East.
Churpunnya Sn Silicate-Sulfide Vein Deposit
The Churpunnya Sn silicate-sulfide vein deposit (Nekrasov
and Pokrovsky, 1973; Flerov and Shur, 1986; A.I. Kholmogorov,
written commun., 1987) consists of shear zones,
stringers, and veins with tourmaline and quartz-tourmaline,
cassiterite (as much as 10 percent), sericite, marcasite, and 1
to 2 percent arsenopyrite, bismuth, bismuthine, wolframite,
pyrrhotite, chalcopyrite, stannite, valleriite, siderite. The ore
zones range from 0.1 to 0.7 m thick, are about one hundred
meters long, and are drilled to a depth of 150 to 200 m. The
deposit is small and locally contains as much as 10 percent Sn.
The deposit hosted in intensely tourmalinized and silicified
rhyolite-dacite volcanic rocks and in a related Early Cretaceous
granitoid stock. (Layer and others, 1999.)
Eastern Asia-Arctic Metallogenic Belt: Chaun Zone
of Granitic-Magmatism-Related Deposits (Belt
EACN), Northeastern Part of Russian Northeast
The Chaun zone of felsic-magmatism-related deposits
(fig. 79; tables 3, 4) occurs in the northeastern part of the
Russian Northeast (Goryachev, 1998, 2003; this study). The
principal deposit types in the Chaun zone are Sn silicate-sulfide
vein, Sn greisen, Sn skarn, porphyry Sn, Sn and Sn-Ag
polymetallic vein, and granitoid-related Au deposits. The zone
occurs in the rear of the Okhotsk-Chukotka volcanic-plutonic
belt and adjacent areas (Nokleberg and others, 1994c, 1997c),
and extends approximately east-west for about 1,300 km from
the mouth of the Kolyma River to Uelen. The Chaun zone is
correlated across the Bering Straits with the Seward Peninsula
metallogenic belt in northwestern Alaska, which contains similar
deposits (fig. 80). The significant deposits in the zone are
(table 4) (Nokleberg and others 1997a,b, 1998) (1) Sn silicatesulfide
vein and Sn polymetallic vein deposits at Dioritovoe,
Elmaun, Erulen, Eruttin, Ichatkin, Kekur, Kukenei, Lunnoe,
Mramornoe, Mymlerennet, Telekai, Valkumei, and Vodor-