USGS Professional Paper 1697 - Alaska Resources Library

120 Metallogenesis and Tectonics of the Russian Far East, Alaska, and the Canadian Cordillera
quartz, calcite, and rhodochrosite with subordinate adularia,
dolomite, celestite, and gypsum. Au:Ag ratio varies from 1:5
to 1:30. The deposit occurs mainly in propylitically altered
trachyandesite that is part of an Late Jurassic volcaniclastic
sequence that is intruded by hypabyssal bodies and dikes of
gabbro rocks, syenite, granodiorite porphyry, and andesitedacite,
all of Late Jurassic to Late Cretaceous age. The deposit
is of medium size and grade ranges from 0.1 to 48 g/t Au and
as much as 300 g/t Ag.
Origin of and Tectonic Controls for Oloy Metallogenic Belt
The age of mineralization age for the Oloy metallogenic
belt is interpreted as Late Jurassic (Gulevich, 1974). However,
some K-Ar isotopic data indicate an Early Cretaceous age for
some of the associated intrusions, and some deposits occur in
Early Cretaceous wall rocks (Gorodinsky and others, 1978).
Some, still younger porphyry and epithermal vein deposits
may be related to remobilization during postaccretionary
magmatism in the Late Cretaceous. The porphyry deposits in
the Oloy metallogenic belt contain characteristic, widespread
magnetite, Co, and PGE minerals that are interpreted as being
derived from hosting oceanic terranes into which igneous
rocks of the Oloy volcanic-plutonic belt intruded.
The Oloy metallogenic belt is hosted in the younger (Neocomian)
part of Late Jurassic-Neocomian Oloy-Svyatoy Nos
volcanic belt (Nokleberg and others, 1994c, 1997c). This igne-
0 4km
ous belt occurs along the northeastern margin of the Kolyma-
Omolon superterrane and is part of the Indigirka-Oloy sedimentary-volcanic-plutonic
assemblage. The volcanic belt occurs
along the northeastern margin of the Kolyma-Omolon superterrane
and consists of shallow-marine and nonmarine mafic,
intermediate, and siliceous volcanic rocks and tuff, associated
sedimentary rocks, and small plutons of granite, granodiorite,
and monzogranite (Shul’gina and others, 1990; Natapov and
Shul’gina, 1991). The volcanic belt also contains small bodies
of granite, granodiorite, and monzogranite. The Oloy volcanic
belt is interpreted as forming the upper part of the Oloy island
arc during a short-lived period of Early Cretaceous subduction
of part of the South Anyui terrane beneath the northeastern margin
of the Kolyma-Omolon superterrane after accretion of the
Kolyma-Omolon superterrane to the North Asian Craton Margin
(Nokleberg and others, 1994c, 1997c, 2000).
Pekulney Metallogenic Belt of Basaltic Cu
Deposits (Belt PK), Eastern Part of Russian
Northeast
The Pekulney metallogenic belt of basaltic Cu deposits
occurs in a north-east-trending belt that extends along the
Pekulney Range in the eastern part of the Russian Northeast
(fig. 48; tables 3, 4) (Nokleberg and others, 1997b, 1998). The
belt extends for about 170 km and is as much as 20 km wide.
Surficial rock (Quaternary)
Andesite and dacite
(Late Cretaceous)
Continental sedimentary rocks:
sandstone & siltstone with
interlayered gritstone,
conglomerate, and coal (Early
Cretaceous)
Marine sedimentary rocks:
siltstone, mudstone,
sandstone, conglomerate,
tuff, and lava (Late
Jurassic)
Late Jurassic-Early Cretaceous
Subvolcanic and Intrusive rock
Trachydacite, trachyrhyolite,
trachyandesite
Quartz syenite, granosyeniteporphyry,
quartz monzonite,
monozonite-porphyry
Gabbro, monzodiorite,
gabbro-monzonite
Contact
Fault
Cu-Mo ore
Au-Ag ore
Figure 53. Peschanka porphyry Cu deposit, Oloy metallogenic belt, Russian Northeast. Schematic
geologic map. Adapted from Migachev and others (1984) using materials of V.V. Gulevich and E.F.
Dylevsky. See figure 48 and table 4 for location.