USGS Professional Paper 1697 - Alaska Resources Library

sists of a mineralized fracture zone in Late Cretaceous sandstone
and mudstone. The fracture zone is cemented by quartz
and dolomite with subordinate kaolinite and calcite. Disseminated
cinnabar occurs in the vein or coats breccia clasts as thin
rims. Stibnite and pyrite are minor. The ore minerals range
from disseminated to massive and occur in breccia, veinlets,
and banded disseminations. The ore bodies vary in size from
0.1 to 4.2 m in width by 110 m to 420 m in length. The most
promising ore bodies occur in faults that trend northeast,
parallel to major fold axes. The Lyapganai deposit is similar to
many other clastic sediment-hosted Hg deposits in the Koryak
upland. The deposit is of medium size and contains an estimated
1,400 tonnes of ore grading from 0.5 to 2.4 percent Hg.
Both volcanic-hosted Hg and Sn deposits occur in a major,
northwest-trending transverse lineament along the northeastern
flank of the belt. The host rocks are rhyolite, andesite, basalt, clastic,
and siliceous-volcanogenic rocks and ophiolite allochthons.
The significant deposits are the volcanic-hosted Hg deposit at
Lamut and a major silica-carbonate Hg and W deposit at Tamvatney.
Some Hg deposits are similar to hot-spring Hg deposits.
Lamut Volcanic-Hosted Hg Deposit
The small volcanic-hosted Hg Lamut deposit (Babkin,
Drabkin, and Kim, 1967; Rozenblyum, Zincevich, and Nevretdinov,
1975) consists of lenticular occurrences and masses
of quartz, opal, chalcedony, dolomite, dickite, and cinnabar.
Early to Middle Tertiary Metallogenic Belts (52 to 23 Ma; figs. 102, 103) 267
Subordinate ore minerals are metacinnabar, realgar, stibnite,
and pyrite. The deposit occurs in intensely silicified, kaolinized,
carbonatized, and chloritized late Paleogene rhyolite, and
less commonly in basalt and tuff. The deposit occurs along
northeast-trending fracture zones.
Tamvatney Silica-Carbonate Hg Deposit
The major Tamvatney silica-carbonate Hg deposit
(Rozenblum and others, 1973; Babkin, 1975; Voevodin and
others 1979, 1980) consists of cinnabar, tungstenite, wolframite,
and Fe and As sulfides that occur in altered serpentinite,
serpentinized peridotite, conglomerate, coarse-grained
sandstone, and argillite. The serpentinite is deformed into
mylonite and displays carbonate, silica, and argillic alteration.
The main ore minerals are cinnabar, tungstenite, wolframite,
huebnerite, scheelite, marcasite and pyrite. Minor minerals
are metacinnabar, stibnite, realgar, orpiment, arsenopyrite,
sphalerite, chalcopyrite, millerite, bravoite, chalcocite, pyrrhotite,
and hematite. Relic ilmenite, chromite, magnetite,
niccolite, and pentlandite occur in serpentinite and silica-carbonate
alteration. The vein gangue minerals mainly quartz,
chalcedony, magnesite, dolomite, kaolinite, dickite associated
with peculiar hard and liquid bitumens, and native sulfur. The
middle part of the deposit consists of stockworks, masses of
ore minerals, veins, and a dense network of sulfide veinlets.
The zone of mineralization extends for about 20 km with an
Unconsolidated deposits
(Quaternary)
Dacite porphyry
(Oligocene)
Diorite porphyry
(Oligocene)
Two-pyroxene andesite
(Oligocene)
Dacitic andesite
(Oligocene)
Dacite (Oligocene)
Quartz vein
Tuff (Oligocene)
Fault
Contact
0 200 400 600 m
Figure 124. Ametistovoe Au-Ag epithermal vein deposit, Central Koryak metallogenic belt, Russian Northeast.
Schematic geologic map. Adapted from Khvorostov (1983). See figure 102 and table 4 for location.