USGS Professional Paper 1697 - Alaska Resources Library

146 Metallogenesis and Tectonics of the Russian Far East, Alaska, and the Canadian Cordillera
Lowland. The deposits of the Kular belt occur in or near Early
Cretaceous collisional (anatectic) granitoid rocks of the Verkhoyansk
collisional granite belt (unit vk), which intrude Late
Permian and Triassic sandstone and shale of the Verkhoyansk
complex within the Kular-Nera terrane of the Kolyma-Omolon
superterrane (Nokleberg and others, 1994c, 1997c). Most
of the deposits occur adjacent to or in granite and adamellite
of the informally-named Kular batholith (Ivensen and others,
1975). The significant deposits in the belt are the Burguat and
Dzhuotuk Au quartz vein deposits, the Novoe and Solur granitoid-related
Au deposits, and the Tirekhtyak district (Nagornoe,
Podgornoe, Poputnoe) with Sn quartz vein deposits
(table 4) (Nokleberg and others 1997a,b, 1998).
The major Au quartz vein deposits, as at Burguat and
Dzhuotuk, typically consist of lenticular veins of quartz and
carbonate-quartz with gold and scarce (1 to 2 percent) sulfide
minerals, including pyrite, galena, sphalerite, and chalcopyrite.
Minor granitoid-related Au deposits, as at Solur and Novoe,
typically consist of quartz and white mica-quartz veins. The
veins and mineralized shear zones occur in Late Permian clastic
rocks adjacent to an Early Cretaceous granitic intrusion.
Also in this area are associated placer Au deposits in the Kular
district. Small, non-economic occurrences of Sn and W occur
in Sn quartz vein deposits, as at Nagornoe and Poputnoe in the
Tirekhtyak district, and are also associated with Early Cretaceous
granitoid plutons.
The lode deposits of the Kular metallogenic belt are
related mainly to the Early Cretaceous collisional (anatectic)
granitoid rocks of the Verkhoyansk collisional granite belt
(fig. 61) (Nokleberg and others, 1994c, 1997c). The Verkhoyansk
belt, of Late Jurassic and Early Cretaceous age consists
chiefly of two major belts, the Main granite belt of Late
Jurassic to early Neocomian age, and the Northern granite belt
of Neocomian age. The Northern granite belt, which hosts
the Kular metallogenic belt, extends for about 600 km along
northwestern margin of the Kolyma-Omolon superterrane.
The Northern belt consists of inclined sheet-like plutons, as
much as 200 km long, which are generally conformable with
major folds. Major lithologies are tonalite, granodiorite, and,
less commonly, two mica leucogranite. These granitoid rocks
are interpreted as forming immediately after the Late Jurassic
accretion of the Kolyma-Omolon superterrane to the North
Asian Craton (Nokleberg and others, 2000).
Allakh-Yun Metallogenic Belt of Au Quartz Vein
Deposits, and Associated W-Sn Quartz Vein
Deposits (Belt AY), Southern Part of Russian
Northeast
The Allakh-Yun metallogenic belt Au of quartz vein
deposits, W and Sn quartz vein deposits (fig. 61; tables 3,
4) occurs in the southern part of the Russian Northeast.
The deposits are hosted in late Paleozoic to early Mesozoic
carbonate and clastic rocks of the North Asian Craton Margin
(Verkhoyansk fold belt, unit NSV; Nokleberg and others,
1994c, 1997c; Goryachev, 1998, 2003). The sedimentary rocks
are regionally metamorphosed to greenschist facies, locally to
staurolite grade along major fault zones (Simanovich, 1978).
Regional metamorphism is interpreted as occurring prior to
the development of Au quartz vein deposits. Sparse intermediate-composition
granitic dikes and major granodiorite plutons,
with K-Ar ages of 140-110 Ma, occur in the region (Nenashev,
1979). The Au-quartz vein deposits occur along a linear trend
along the western boundary of the belt of granitoid plutons
and dikes. The significant deposits in the belt are the Bular,
Duet, Malyutka, Nezhdaninka, Novinka, Onello (Lider),
Svetly, Voskhod, Yur, and Zaderzhnoe Au quartz vein deposits,
the Dies and Muromets Cu-Mo skarn deposits, the Burgali
porphyry-Mo (W) deposit, the Levo-Dybin granitoid-related
Au deposit, and the It-Yuryak W vein and Sn (W)-quartz vein
deposit (table 4) (Nokleberg and others 1997a,b, 1998).
The Au quartz vein deposits consist of three types: (1)
Concordant deposits, as at Bular, Yur, and Duet, are interpreted
as metamorphic and have K-Ar isotopic ages of 170
to 140 Ma (Nenashev, 1979; Goryachev, 1998, 2003). (2)
Crosscuttting, postmetamorphic Au-quartz veins and mineralized
shear zones, as at Voskhod, Novinka, Zaderzhnoe,
and Nezhdanin, are closely related to the early stage granitic
dikes and are interpreted as igneous (Ivensen, Levin, 1975;
Gamyanin and others, 1985; Goryachev, 1998, 2003). (3)
Quartz granitioid-related Au deposits, as at Levo-Dybin, and
W-Sn quartz vein deposits, as at Yt-Yuryak, are associated
with and interpreted as related to late-stage granitoid rocks.
The deposit sizes range from small to large. Related placer
Au deposits are widespread in the southern portion of the
metallogenic belt.
Nezhdanin Au Quartz Vein Deposit
The major Nezhdanin Au quartz vein (shear zone Au)
deposit (fig. 66) (V.I. Korostolev, written commun., 1963;
Silichev and Skobelev, 1970; Grinberg and others, 1970;
Gamyanin and others, 1985; G.N. Gamyanin and others, written
commun., 1990, Goryachev, 1995, 1998, 2003) consists of
disseminated gold in (1) steeply dipping shear zones as much
as 40 m thick and 5.4 km long, (2) related tension-gash quartz
veins as much as 200 m long and 1.2 m thick, and (3) quartz
lenses within the shear zones. Vein minerals include quartz,
carbonate, arsenopyrite, galena, sphalerite, scheelite, sericite,
albite, chalcopyrite, tetrahedrite, lead and copper sulfosalts,
stibnite, and gold. Wallrock alteration includes silicification,
sulfidization, and sericitization. Quartz-silver-polymetallic ore
bodies both cross-cut and post-date the feathered quartz-vein
mineralization. The ore bodies are located along a deep fault
that cuts the core of a doubly plunging anticline in Late Carboniferous
to Early Permian sandstone and shale. The deposit
extends more than 1,000 m vertically. Workings include
boreholes and seven levels of adits. The deposit is major with
proven reserves of 475 tonnes Au and an estimated additional
resource of more than 500 tonnes Au. The average minimum
grade is 5 g/t Au with as much as 6,748 g/t Au, and as much as
8,300 g/t Ag in veins.