USGS Professional Paper 1697 - Alaska Resources Library

186 Metallogenesis and Tectonics of the Russian Far East, Alaska, and the Canadian Cordillera
0 200 400 600 m
.
Basalt and gabbro
(Early Cenozoic)
Ignimbrite tuff and
hypabyssal rhyolite
(Early Paleocene)
Sandstone
(Early Cretaceous)
Sedimentary breccia
(Olistrastrome)
grades are 62 g/t Ag, 1.5 to 8.7 percent Pb, and, 1.36 to 10.5
percent Zn. The deposit has been mined from 1970’s to present.
The main shaft is about 500 m deep.
Partizanskoe Pb-Zn Skarn Deposit
The Partizanskoe Pb-Zn skarn deposit (fig. 87) (Ratkin,
Simanenko, and Logvenchev, 1991) consists of numerous
small steeply dipping ore bodies that occur at the contact of a
Triassic limestone olistolith surrounded by Early Cretaceous
clastic rocks. The ore bodies merge and form a single skarn
deposit about 400 m below the surface and pinch out at a depth
of approximately 600 m. The ore and skarn assemblages are
vertically zoned; higher temperature assemblages occur deeper.
Massive, densely disseminated Ag-Pb-Zn ore (Pb/Zn ratio of
about 1.0) occurs above a quartz-calcite aggregate in the upper
part of the deposit; massive, densely disseminated Pb-Zn ore
(Pb/Zn ratio of about 0.8) is associated with Mn-hedenbergite
skarn and occurs at the middle part of the deposit; and disseminated
Zn ore (Pb/Zn ratio of about 0.5) occurs in ilvaite-garnet-hedenbergite
skarn in the lower part of the deposit. Galena
and sphalerite are the dominant ore minerals; chalcopyrite
and arsenopyrite are common; minor magnetite, pyrrhotite,
and marcasite also occur. Silver-bearing minerals are Ag- and
Sb-sulfosalts in the upper part of the deposit and galena in the
lower part. Galena contains Ag as a solid solution of matildite.
The age of mineralization is bracketed between 60 and 70 Ma
by basalt dikes, with K-Ar isotopic ages of 60 to 70 Ma, which
cut the deposit at the contact of olistolith, and by the lower part
of the overlying volcanic strata, with K-Ar ages of 70 to 80 Ma,
Tr
Limestone (Triassic)
Skarn
Fault
Contact
Figure 86. Nikolaevskoe Pb-Zn skarn deposit, Taukha metallogenic
belt, Russian Southeast. Schematic cross section adapted
from Ratkin (1995). See figure 79 and table 4 for location.
which are cut by ore body. The deposit consists of four or more
related ore bodies that occur over about 5 km strike length,
including the Soviet 2, Partizansk East, Partizansk West, and
Svetlotvod ore bodies. The underground workings for the ore
bodies follow contacts and have a total length of about 11 km.
The deposit is of medium size. Average grades are 67.6 g/t Ag,
1.5 to 3 percent Pb, and 0.6- to 4 percent Zn . The deposit has
been mined from the 1950’s to present.
Krasnogorskoe Pb-Zn Polymetallic Vein Deposit
The Krasnogorskoe Pb-Zn polymetallic vein deposit
(fig. 88) (Ratkin and others, 1990) consists of steeply dipping
quartz-sulfide veins, as much as several hundred m
length along strike and from 0.2 to 1.5 m thick, that cut a
sequence of Late Cretaceous (Cenomanian to Turonian) ash
flow tuff. Sphalerite and galena are the dominant ore minerals;
the flanks of veins contain pyrite-marcasite-pyrrhotite
with lesser Sb-Ag-sulfosalts. At the deeper levels of the ore
bodies, galena contains as much as several percent Ag and Bi
in matildite. The volcanic rocks adjacent to the polymetallic
veins are altered to quartz and chlorite. In the core of the
veins, chlorite, Mn-calcite, rhodochrosite, rhodonite, and
spessartine occur with quartz gangue. The veins occur near
an Late Cretaceous-Paleocene (Maastrichtian to Danian)
volcanic vent. The vent breccia also contains disseminated
sphalerite, galena, and cassiterite. The veins formed immediately
after mineralization of vent breccia, which were
dated as approximately 65 Ma by K-Ar isotopic studies. The
deposit is of medium size. Average grades are 62 g/t Ag, 5
percent Pb, 0.26 percent Sn, and 6.77 percent Zn.
0 200 400 600 m
Basalt dike (Early
Cenozoic to
Paleocene)
Sandstone (Early
Cretaceous)
Siltstone (Early
Cretaceous)
Sedimentary
breccia
(Olistostrome)
. .
.
.
.
.
.
.
. .
.
. .
. .
Limestone
(Triassic)
Skarn (Early
Cretaceous)
Fault
Contact
Figure 87. Partizanskoe Pb-Zn skarn deposit, Taukha metallogenic
belt, Russian Southeast. Schematic cross section adapted
from Ratkin (1995). See figure 79 and table 4 for location.