USGS Professional Paper 1697 - Alaska Resources Library

202 Metallogenesis and Tectonics of the Russian Far East, Alaska, and the Canadian Cordillera
Kandychan Sn Polymetallic Vein Deposit
Sn polymetallic vein deposits, as at Kandychan and
Kheta, are hosted mainly in Late Cretaceous subvolcanic and
flow rocks of moderately felsic to felsic composition. The
Kandychan deposit (Firsov, 1972; Lugov and others, 1974a,b;
N.E. Savva, written commun., 1980) consists of groups of
veins and veinlets that occur in a generally north-south-trending
band more than 2 km long and from 500 to 600 m wide.
The host volcanic rocks are propylitized, silicified, and argillized.
The ore bodies consist of quartz-chlorite-cassiterite-sulfide
veins with various carbonates (calcite, siderite, dolomite),
sericite, hydromica, kaolinite, dickite, pyrophyllite, fluorite,
and tourmaline. The sulfide minerals are mainly stannite, pyrargyrite,
hessite, and argentite and lesser pyrite, chalcopyrite,
arsenopyrite, marcasite, pyrrhotite, sphalerite, galena,bornite,
and covellite. The deposit is characterized by high Ag, Bi,
Co, and Au. The sulfide veins with colloform cassiterite near
the surface change with depth to low-sulfide chlorite-quartz
veins with crystalline cassiterite. The deposit is small, is partly
mined, and has produced 2,000 tonnes Sn.
Suvorov Rhyolite-Hosted Sn Deposit
Rhyolite-hosted Sn deposits, as at Suvorov, and Sn
polymetallic vein and Sn greisen deposits, as at Dneprovskoe
and Khenikandja, are associated with small Cretaceous granitoid
plutons. The Suvorov rhyolite-hosted Sn deposit (Lugov
and others, 1974a,b; Flerov, 1974) consists of colloform cassiterite
nodules (wood tin) that occur in intensely silicified and
kaolinized, fluidal rhyolite, agglomerate vitric tuff flows, and
tuff and lavabreccia. The host Late Cretaceous volcanic rocks
form various volcanic vent facies. Cassiterite is associated
with fine-grained quartz, hematite, chlorite, kaolinite, pyrite,
and arsenopyrite. The ore is characterized by high Fe and In.
The deposit is small.
Shkolnoe Granitoid-Related Au and Au Quartz Vein Deposit
The Shkolnoe granitoid-related Au and Au quartz vein
deposit (fig. 95) (Orlov and Epifanova, 1988; S.V. Voroshin
and others, written commun., 1990; Palymsky and Palymskaya,
1990; V.A. Banin, written commun., 1993; Goncharov,
1995; Goryachev, 1998, 2003) consists of an en echelon system
of quartz veins that trend generally east-west. The veins
occur in a multiphase granitoid stock about 4 km 2 composed
mainly of granodiorite and adamellite. The stock is intruded
by dikes of granite-porphyry, rhyolite, pegmatite, aplite, and
lamprophyre. The quartz veins are surrounded by zones of
beresitic and argillic alteration, and skarn and greisen alteration
also locally is present. The deposit occurred in two stages
separated by intrusion of lamprophyre dikes (Goryachev,
1998) (1) an older granitoid-related Au vein deposit containing
molybdenite, arsenopyrite, löellingite, native bismuth, Bi-tellurides,
and native gold (herein interpreted as part of the Yana-
Kolyma metallogenic belt), and (2) the most economically
important stage, a Au quartz vein deposit containing arseno-
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Felsic dike (Late Cretaceous)
Mafic dike (Late Cretaceous)
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Quartz diorite (Late Jurassic and
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Granitoid-related Au veins and pods
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Figure 95. Shkolnoe granitoid-related Au deposit,
Verkhne Kolyma zone, eastern Asia-Arctic metallogenic
belt, Russian Northeast. Schematic geologic
map and cross section. Adapted from Sidorov and
Goryachev (1994) and Sidorov and Eremin (1995).
See figure 79 and table 4 for location.
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