USGS Professional Paper 1697 - Alaska Resources Library

during hypogene and supergene alteration that was associated
with karst formation. The U-Pb zircon isotopic age of baddeleyite
is approximately 100 Ma (J.N. Aleinikoff, written
commun., 1992). The origin of the stratiform Zr deposits is
interpreted as related to alkalic igneous rocks, possibly including
carbonatite, which were associated with the late stage
intrusion of the zoned mafic-ultramafic rocks, possibly part
of the same belt of Late Jurassic to mid-Cretaceous intrusives
at Kondyor. With this interpretation, the Algama belt formed
during intrusion of alkali igneous rock associated with maficultramafic
plutons that intruded along major continentalmargin
transform faults during subduction of terranes along
Mongol-Okhotsk fault system.
Kondyor Metallogenic Belt of Zoned
Mafic-Ultramafic Cr-PGE Deposits (Belt KO)
Northern Part of Russian Southeast
The Kondyor metallogenic belt of zoned mafic-ultramafic
PGE-Cr deposits (fig 61; tables 3, 4) occurs in several
zoned linear intrusions (Kondyor, Chad, Ingagli, Sy-Bakn,
Usmun-Dara, Arbarastakh) across the Khabarovsk province
for about 850 km (Zalishchak and others, 1993). The deposits
are interpreted as occurring along a northwest-trending,
deep-seated, buried fault that cuts the southeastern part of the
Stanovoy block of the North Asian Craton (unit NSS). This
area is in the northern part of the Khabarovsk province of
the Russian Southeast. The belt contains a single large zoned
mafic-ultramafic Cr-PGE deposit at Kondyor and Chad (table
4) (Nokleberg and others 1997a,b, 1998). In a generalized plan
view, the zoned complexes consist of circular-shaped plutonic
bodies of dunite that are successively rimmed by pyroxenite,
0 1 km
Early Cretaceous Metallogenic Belts (144 to 120 Ma; figs. 61, 62) 143
peridotite, gabbro, ojolite, and nepheline syenite (Marakushev
and others, 1990).
Kondyor Zoned Mafic-Ultramafic Cr-PGE Deposit
The productive Kondyor (fig. 65) (Marakushev and
others, 1990) and Chad PGE-Cr deposits contain two types
of lode deposits—(1) semi-massive to massive lenses of
chromite, which range from 2 to 50 m thick, and (2) ovalshaped,
roughly equadimensional metasomatic deposits,
which range from 200 to 300 m thick. The first type consists
of PGE minerals that occur as intergrowths with chromite
and olivine, and as small inclusions. Isoferroplatinum is the
major PGE mineral. The second type consists of PGE minerals
that form intergrowths with magnetite, pyroxene, and rarely
with metasomatic phlogopite, chrome diopside, and magnetite.
This deposit is cut by veins and dikes of alkalic igneous
rocks, including nepheline syenite, lujavrite, ijolite, and urtite.
In addition to isoferroplatinum and tetraferroplatinum, this
type of deposit commonly contains as much as 5 to 8 percent
sulfide and arsenide minerals. At Kondyor approximately 13.5
tonnes PGE were produced from 1984-1993 (Bundtzen and
Sidorov, 1998). Annual production has averaged about 2.5 to
3.0 tonnes PGE since 1993. In 1999, approximately 2.9 tonnes
PGE were produced (Bakulin and others, 1999). Beginning in
1999, PGE production was started at the Chad zoned complex
(Bakulin and others, 1999; N.I. Lysyuk and N.P. Romanovsky,
written commun., 2000). By-product gold, which is also
recovered from the Kondyor deposit, contains as much as 10
percent Pd and 40 percent Cu (Zalishchak and others, 1993; V.
Molchanov and V. Sapin, written commun., 1993). All production
is from placer deposits, not lode deposits. The Kondyor
placer deposits have produced 3.1 and 2.2 kg platinum nuggets
Granodiorite and granite
Monzodiorite
Dunite
Pyroxenite
Skarn
Hornfels, calciphyre, and
marble
Riphean sandstone and
mudstone
Fault
Contact
Figure 65. Kondyor zoned mafic-ultramafic PGE-Cr deposit, Kondyor metallogenic belt, Russian Southeast.
Adapted from Nekrasov and others (1994). See figure 61 and table 4 for location.