USGS Professional Paper 1697 - Alaska Resources Library

154 Metallogenesis and Tectonics of the Russian Far East, Alaska, and the Canadian Cordillera
by relatively high CaO and low alkali content, have some predominance
of K over Na, and have initial Sr rations of 0.7057
to 0.7087. Accessory minerals are ilmenite, garnet, zircon and
sulfide minerals (Gamyanin and others, 1991). Associated
with these plutons are Au lode and W vein deposits.
Also part of the Yana-Kolyma metallogenic belt are suite
of Sn quartz vein and greisen, W vein, Sb-Au and clasticsediment-hosted
Hg occurrences (fig. 61). Notable examples
are Sn quartz vein and greisen deposits at Alaskitovoye and
Burgavli, the Krokhalin Sb-Au vein occurrence, and the clastic-sediment-hosted
Hg at Kuzmichan. Most of the Sn deposits
are small, except for Alaskitovoye.
Natalka Au Quartz Vein Deposit
The Natalka Au quartz vein deposit (fig. 68) (Firsov,
1957a; Shilo, 1960; Voroshin and others, 1989; Goncharov,
1995; Eremin and others, 1994) consists of zones of subparallel
and reticulate quartz veinlets that can be grouped into
two or three systems that converge locally along strike into
podiform and platy veins. The ore minerals cement schistose,
brecciated, cataclastic, and graphite-altered Late Permian
tuffaceous sedimentary rocks. The deposit occurs along the
Tenka strike-slip fault. The ore deposit is deformed with synclines
and anticlines that occur near the fault zone. The deposit
is intruded locally by abundant pre-ore and post-ore dikes of
A
A
Cross section
B
B 1,000 m
400 m
0
felsic to intermediate composition. The zone of mineralized
veinlets is approximately 300 m wide; individual ore bodies
occur in zones ranging from 50 to 300 m long and from 1 to
15 m thick. The gangue in the veinlets are composed mainly
of quartz (90 to 95 percent), albite, anorthoclase, carbonate,
chlorite, and sericite, with lesser kaolinite, barite, apatite, and
graphite. The ore minerals are dominated by fine-grained disseminated
arsenopyrite intergrown with pyrite in wall rocks.
Subordinate and rare minerals include galena, sphalerite,
chalcopyrite, pyrrhotite, bournonite, boulangerite, tetrahedritetennantite,
scheelite, rutile, ilmenite, and stibnite. Fine-grained
and microscopic, low-grade Au is commonly associated with
arsenopyrite and galena in the veins and veinlets. A considerable
proportion of the gold is intergrown in arsenopyrite in the
wall rock adjacent to the veins. The Natalka deposit is large
with total reserves of 450 tonnes Au. From 1945 to 1994, the
Natalka mine has produced 75 tonnes Au and 22 tonnes Ag.
The annual production is 8 tonnes Au and 4 tonnes Ag. The
lower grade ores average 4 g/t. More recent production data
are not available.
Svetloe and Kholodnoe Au Quartz Vein Deposits
The Svetloe Au quartz vein deposit (fig. 70) (P.I.
Skornyakov, written commun., 1953; Fedotov, 1960b, 1967,
Goryachev, 1998, 2003) consists of subparallel quartz veins
Upper Nerychin
Formation
Lower Nerychin
Formation
Atkan Formation
Tasskaya
Formation
Porphyry dike
Lamprophyre dike
Quartz vein
Fault
Contact
1
2 km
Permian
Figure 69. Natalka Au quartz vein
deposit, Yana-Kolyma metallogenic
belt, Russian Northeast. Schematic
geologic map and cross section.
Adapted from Eremin (1995). See
figure 61 and table 4 for location.