USGS Professional Paper 1697 - Alaska Resources Library

26 Metallogenesis and Tectonics of the Russian Far East, Alaska, and the Canadian Cordillera
belt contains a group of significant deposits at South Khingan
(table 4) (Nokleberg and others 1997a,b, 1998).
The South Khingan deposit (fig. 9) consists of Fe- and
Mn-bearing beds that are composed of magnetite-, hematite-,
and magnetite-hematite-bearing quartzite in beds from 18 to
26 m thick that are interlayered with chlorite-dolomite breccia
(Kazansky, 1972). Underlying sedimentary rocks contain
braunite-haussmanite-rhodochrosite layers between 2 and
9 m thick. The Fe- and Mn-bearing layers are overlain by a
dolomite sequence that is overlain in turn by shale, limestone,
and dolomite that all occur in the lower portion of the Early
Cambrian Khingan series. The deposit has not been developed
because of the difficulties with ore concentration and
steeply dipping beds. The largest deposits at Kimkanskoe,
Kastenginskoe, and South Khingan are estimated as containing
approximately 3 billion tonnes of Fe and Mn minerals.
Mineralogic and geochemical studies suggest an sedimentaryexhalative
origin. The Early Cambrian Khingan series is part
of the Bureya superterrane, which is interpreted as a fragment
of a continental-margin arc that was accreted to Sino-Korean
Craton during the Paleozoic (Nokleberg and others, 1994c,
1997c). The superterrane contains Late Proterozoic and
Devonian granitoid rocks, with K-Ar isotopic ages of 604 and
301 Ma that locally form extensive plutons and batholiths.
The metallogenic belt is interpreted as forming in volcanic and
sedimentation basin along an unstable protocontinental margin
or in a fragment of Archean craton that was incorporated into
an accretionary wedge terrane.
Gar Metallogenic Belts of Volcanogenic Fe
Deposits and Stratiform Cu and Pb-Zn Deposits
(Belt GR), Western Part of Russian Southeast
Two Gar metallogenic belts of volcanogenic Fe and
stratiform Cu and Pb-Zn deposits (fig. 2; tables 3, 4) occur in
the northwestern part of the Russian Southeast. The belts are
hosted in the Mamyn continental-margin arc terrane (unit MM,
fig. 2) (Nokleberg and others, 1994c, 1997c). The Fe deposits
generally consist of lenses and beds of magnetite that is
spatially associated with basalt and limestone. A large deposit
occurs at Gar; coincidental with the Gar of volcanogenic Fe
deposits is a metallogenic belt of Cu and Pb-Zn stratiform sulfide
deposits (Nokleberg and others 1997a,b, 1998). The belt
also contains (table 4) (1) small massive Cu sulfide deposits,
as at Kamenushinskoe, which occur in rhyolite that underlies a
sequence of magnetite-bearing basalt; and (2) a small stratiform
Pb-Zn vein deposit at Chagoyan.
Gar Volcanogenic Fe Deposit
The large Gar volcanogenic Fe deposit (Zimin, 1985;
Zimin and Konoplev, 1989) consists of sheeted iron ore bodies
that occur in metamorphosed, Early Cambrian(?) felsic
and mafic volcanogenic rocks with limestone lenses part of
the Gar terrane. The iron ore beds occur chiefly in the upper
Early Cambrian(?) section composed mainly of mafic volcanic
rocks. The ore occurs within a section 220 to 250 m thick, but
most of the ore, about 75 percent, occurs within an interval
ranging from 156 to 184 m thick. The ore horizon occurs for
4 km along strike. The deposit has estimated reserves of 389.1
million tonnes grading 41.7 percent Fe. Total inferred reserves
in the metallogenic belt are 4 billion tonnes (Zimin and Konoplev,
1989). The Gar deposit has not been mined. The deposit
is intruded by early Paleozoic gabbro, diabase, and plagiogranite
and is locally metamorphosed to skarn. Magnetite is
the dominant ore mineral. Similar volcanogenic iron deposits
occur north of the Gar deposit and need further exploration.
Kamenushinskoe Cu Massive Sulfide Deposit
The small Kamenushinskoe Cu massive sulfide deposit
(P.N. Radchevsky, written commun., 1956; V.V. Ratkin, this
Schist (Cambrian)
Limestone (Cambrian)
Ironstone (Cambrian)
Manganese ore (Cambrian)
Dolomite sedimentary breccia
(Cambrian)
Fault
Contact
0 1 2 3 km
Figure 9. South Khingan ironstone deposit, South Khingan metallogenic belt, Russian Southeast. Schematic
geologic map and cross section. Adapted from Korostelev and others (1990). See figure 2 and table 4
for location.