Metallogenesis and Tectonics of the Russian Far East, Alaska, and ...

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assemblage is dominant in the upper portion of the dkposit whereas W minerals are dominant at depth. The deposit is of medium
size and has been mined from 1979 to the mid- 1990's.
Sedimentary rocks - shale
with interbedded siltstone
and sandstone
(Early Triassic)
Sandstone with interbedded
srllstone and shale ( kly and
Middle Triassic)
Sn quarh
vein
F&
Figure 97. lultin Sn quartz vein deposit, Chukotka metallogenic belt, Russian Northeast. Schematic geologic map and cross section.
Adapted from Lugov (1986).
Valkumei Sn Silicate-Sulfide Vein Deposk
The Valkumei Sn silicate-sulfide vein deposit (Lugov, h4akeev, and Potapova, 1972; Lugov, 1986) consists of simple and
complex veins, mineralized zones, and less common linear stockworks. The deposit occurs mainly within the wgiital zone of the
Late Cretaceous Pevek pluton, composed of granite, adamelhte, and g~aoodiorite, and to a lesser degree in Cretaceous sandstone
and shale which host the pluton. Mineralization occurs in a north-nofiwest-trending zone alone the contact of the phtan. The ore
bodies commonly consist of a conjugate system of (1) major north-south veins and feathered veinlets; and (2) a zone of
approximately east-west- and northwest-trending veins. Seventy minerals occur in the deposit but the majority of the veins are
composed dominantly of tourmaline, with quartz, chlorite, albite, arsenapynte, cassiterite, pyrrhotite, chalcopyrite, stannite,
sphalerite, stibnite, fluorite, and various carbonates. The ore bodies are vertically extensive. The cassiteritequartz-tourmaline
veins are replaced by sulfide veins at depth. The deposit is large, was discovered in 1935, and has been mined from 1941 to the
mid- 1990's. The average grade is 0.4 to 1.2 % Sn.