USGS Professional Paper 1697 - Alaska Resources Library

10 percent Cu, as much as 0.92 percent WO 3, and as much as
0.3 percent Mo.
Eastern Asia-Arctic Metallogenic Belt:
Korkodon-Nayakhan Zone of Porphyry Mo and
Granitoid-Related Au Deposits (Belt EAKN),
East-Central Part of Russian Northeast
The Korkodon-Nayakhan zone of porphyry Mo and
granitoid-related Au deposits (fig. 79; tables 3, 4) occurs in
two parts in the east-central part of the Russian Northeast.
Each part is about 200 km long. The zone contains a small
porphyry Mo deposit at Orlinoe, a granitoid-related Au
deposit at Khetagchan, a Fe skarn deposit at Skarn, a Au-Ag
polymetallic vein deposit at Verkhny-Koargychan, and a Fe-
Pb-Cu-Ag-Au skarn deposit at Sedoi (table 4) (Nokleberg and
others 1997a,b, 1998). Both types of deposits are related to
subalkalic felsic and intermediate composition intrusions of
granite and granosyenite. The deposits generally occur either
in the apical parts of the intrusive rocks or in the adjacent wall
rocks. The granitoid-related Au deposits are characterized by
Ag tellurides. The deposits are generally small. Most of the
lode deposits in the zone consist of sulfides disseminations
and stringers. The granitoid rocks hosting the Korkodon-Nayakhan
zone form a belt that is transverse or orthogonal to the
Okhotsk-Chukotka volcanic-plutonic belt. The relation of the
origin of the granitoid rocks to the Okhotsk-Chukotka volcanic-plutonic
belt is unclear.
Orlinoe Porphyry Mo Deposit
The Orlinoe porphyry Mo deposit (V.N. Okhotnikov,
written commun., 1957) consists of a steeply dipping stockwork
that extends for tens of meters. The stockwork consists
of thin quartz veins and veinlets with disseminations and
masses of molybdenite. Subordinate minerals are pyrite, chalcopyrite,
wolframite, powellite, muscovite, fluorite, calcite,
chlorite, and garnet. The deposit occurs in contact-metamorphosed,
Late Triassic sedimentary rocks and in Late Cretaceous
granite that intrudes the sedimentary rocks. The deposit
is small and averages 0.01 to 0.03 percent Mo, but locally is as
much as 8.5 percent Mo.
Khetagchan Porphyry Granitoid-Related Au Deposit
The Khetagchan porphyry granitoid-related Au deposit
(V.A. Sidorov, written commun., 1990) consists of zones of
sulfide-quartz and sulfide-chlorite-quartz veins and veinlets as
much as 150 m long and 10 to 15 m thick. The veins and veinlets
occur along the contacts of a Late Cretaceous granodiorite,
both within and adjacent to the intrusion. The ore minerals are
galena, sphalerite, chalcopyrite, wolframite, pyrite, arsenopyrite,
bismuthinite, native bismuth, gold, electrum, tetrahedritetennantite,
Ag-sulfosalts, and argentite. The deposit is judged
as small and contains as much as 20 g/t Au and as much as 50
to 60 g/t Ag.
Early Late Cretaceous Metallogenic Belts (100 to 84 Ma; figs. 79, 80) 201
Eastern Asia-Arctic Metallogenic Belt: Verkhne-
Kolyma Zone of Sn-Ag Polymetallic Vein, Southern
Bolivian type), Sn Polymetallic Vein, Rhyolite-
Hosted Sn, and Granitoid-Related Au Deposits (Belt
EAVK), Southeastern Part of Russian Northeast
The Verkhne-Kolyma zone of Sn polymetallic vein (Southern
Bolivian type), Sn-Ag polymetallic vein, rhyolite-hosted Sn
deposits, and granitoid-related Au deposits (fig. 79; tables 3, 4)
occurs in the southeast part of the Russian Northeast. The belt
trends mainly northwest-southeast, extends for about 700 km
and is as much as 100 km wide. The metallogenic belt is associated
with Cretaceous plutonic rocks that intrude the North Asian
Craton Margin (Verkhoyansk fold belt, unit NSV) and the Viliga
passive continental-margin terrane (Nokleberg and others,
1994c, 1997c). These plutonic rocks form an orthogonal branch
of the Okhotsk-Chukotka volcanic plutonic belt. Sn polymetallic
vein (Southern Bolivian type) and Sn-Ag polymetallic vein
deposits are hosted mainly in Late Cretaceous dacite and rhyolite
subvolcanic dikes and stocks. The significant deposits in
the zone are (table 4) (Nokleberg and others 1997a,b, 1998) (1)
Sn silicate-sulfide and Sn polymetallic vein deposits at Baryllyelakh-Tsentralny,
Bogatyr, Dneprov, Kandychan, Kharan,
Khenikandja, Kheta, Khuren, Kuranakh-Sala, Kyurbelykh,
Porozhistoe, Svetloe, and Tigrets-Industriya, (2) a Sn greisen
deposit at Ossolony, (3) a rhyolite-hosted Sn deposit at Suvorov,
(4) Au-Ag epithermal vein deposits at Aida and Zerkalnoe, (5)
Pb-Zn-Ag vein or skarn deposits at Bulunga and Tektonicheskoe,
(6) granitoid-related Au deposits at Netchen-Khaya, Shkolnoe,
(7) a porphyry Mo deposit at Tankist, and (8) a Co-Bi-As
vein deposit at Verkhne-Seimkan. The Co and Bi deposits, as
at Verkhny Seimkan, are associated with Cretaceous granitoid
plutons of the Okhotsk-Chukotka volcanic-plutonic belt. The
deposits are generally small and exhausted, partly mined, or
starting to be mined, as at Shkolnoe. Local Sn deposits with Ag,
Pb, and Zn, may be of future economic interest.
Tigrets-Industriya Sn Polymetallic Vein Deposit
The small Tigrets-Industriya Sn polymetallic vein deposit
(Lychagin, 1967; Plyashkevich, 1990) consists of quartz-carbonate-sulfide,
quartz-sulfide, and sulfide-quartz veins and
lenticular bodies and zones of veinlets that occur in weakly
metamorphosed Late Permian sedimentary rocks intruded by a
Late Cretaceous granite porphyry. The ore bodies occur along
northeast-trending fractures, are 100 to 200 m long, and range
from 0.1 to 0.8 m thick. Late Cretaceous siliceous lava flows
occur peripheral to the mineralized area. Several Sn and Ag
mineral assemblages occur in the deposit. A period of deformation
separated early and late stages. The early assemblage
consists of quartz-cassiterite and polysulfide containing cassiterite,
arsenopyrite, pyrite, chalcopyrite, sphalerite, galena,
canfieldite, Fe-freibergite, stannite, and pyrargyrite. The late
seleno-canfieldite-quartz assemblage contains quartz, pyrite,
sphalerite, galena, stannite, selenocanfieldite, and Mn-calcite.