Geology and Geophysics, 2004, V 45, N 4, April.
TECTONICS AND GEODYNAMICS
Cenozoic continental-margin volcanism in the Pacific and Bering Sea
sectors of Kamchatka: geodynamic implications.
N.A. Bogdanov and V.D. Chekhovich
391
Late Quaternary geodynamics and tectonic activity within the Kan
fault system
(southwestern Siberian Platform).
S.G. Arzhannikov, A.S. Gladkov, and R.M. Semenov..
399
Fault pattern in continental zones of lithospheric extension.
K.Zh. Seminsky
411
Recent vertical crustal movements in the region of Yenisei Ridge.
P.P. Kolmogorova and V.G. Kolmogorov
421
STRATIGRAPHY
The Vendian of the Baikal-Patom Upland, Siberia. V.V. Khomentovsky,
A.A. Postnikov, G.A. Karlova, B.B. Kochnev, M.S. Yakshin, and
V.A. Ponomarchuk
430
Calcareous algae and lower boundary of Cambrian in the western
Altai-Sayan Folded Area.
A.A. Terleev, V.A. Luchinina, O.V. Sosnovskaya, and G.N. Bagmet
449
PETROLOGY, GEOCHEMISTRY AND MINERALOGY
Estimation of the conditions of formation of REE-carbonatites in
Western Transbaikalia.
A.G. Doroshkevich and G.S. Ripp
456
Reconstruction of the thermal history of metamorphic rocks from the
exchange-diffusion zoning of minerals. V.N. Korolyuk, G.G. Lepezin,
and A.V. Korsakov
464
Sedimentation of monodisperse silica spheres and their
coagulation-related aggregation at high temperatures.
D.V. Kalinin and V.V. Serdobintseva
476
BRIEF COMMUNICATIONS
The age and geodynamic setting of formation of high-temperature
metamorphic complexes in the South Mongolian Belt.
I.K. Kozakov, E.B. Sal'nikova, A.N. Didenko, V.P. Kovach,
A.M. Fedoseenko, and S.Z. Yakovleva
482
The Filippovka buried depression near Novosibirsk: a possible impact
crater of Triassic -
Early Jurassic age. S.A. Vishnevsky and V.A. Bogdashev
488
PERSONALIA
George V. Chilingarian (in honor of the 75th
birthday)
494
CENOZOIC CONTINENTAL-MARGIN VOLCANISM IN THE PACIFIC AND BERING
SEA SECTORS OF KAMCHATKA: GEODYNAMIC IMPLICATIONS
N.A. Bogdanov and V.D. Chekhovich
Institute of the Lithosphere of Marginal and Intracontinental Seas,
Russian Academy of Sciences, 22 per. Staromonetnyi,
Moscow, 109180, Russia
The tectonic position and ages of suprasubduction
continental-margin volcanoplutonic belts controlled by their
Cenozoic geodynamic environments are notably different in the
Pacific and Bering Sea sectors of Kamchatka and southern Koryakia.
In pre-Cenozoic time the two sectors were separated by a
long-existing transform fault whose western segment now coincides
with the Komandor strike-slip fault and the eastern segment is
clearly traceable by satellite gravity data on the Pacific floor
southeastwards on the continuation of the Komandor fault.
Continental-margin volcanic belts, subduction, collision,
transform faults, Kamchatka
LATE QUATERNARY GEODYNAMICS AND TECTONIC ACTIVITY
WITHIN THE KAN FAULT SYSTEM (southwestern Siberian Platform)
S.G. Arzhannikov, A.S. Gladkov, and R.M. Semenov
Institute of the Earth's Crust, Siberian Branch of the RAS, 128 ul.
Lermontova, Irkutsk, 664033, Russia
Late Quaternary tectonic activity in the southwestern Siberian
Platform was investigated in the Kan fault system. Geodynamic
analysis indicates an inherited style of faulting, mostly of oblique
geometry, at the junction of the East Sayan Ridge and the Rybnaya
basin. Motions on NW faults dramatically restructured the surface
topography and produced horst anticlines and horsts. Aerial and
satellite imagery of the Kiyai-Arbai fault zone in the Kan system
detects traces of earthquake rupture along 100 km of the fault from
the Anzha to the upper Kungus River. A 9 km long segment of the
fault scarp was excavated near Malinovka Village between 55.09° N,
94.44° E and 55.07° N and 94.46° E. Trenching of the NW striking
scarp produced mainly by a reverse slip on a plane dipping to the
northeast at 45° to 65° exposed Devonian basement sandstones thrust
on Quaternary lacustrine clays. The maximum offset varies from 6.6
to 7.8 m as a function of the fault plane strike and dip. The
causative earthquake may have reached a magnitude of M = 7.9-8.
Faults, prehistoric earthquakes, earthquake rupture, thrusts,
reverse faults, fractures
FAULT PATTERN IN CONTINENTAL ZONES OF LITHOSPHERIC EXTENSION
K.Zh. Seminsky
Institute of the Earth's Crust, Siberian Branch of the RAS, 128 ul.
Lermontova, Irkutsk, 664033, Russia
A typical pattern common to second-order faults in extended
lithosphere was revealed based on field geological and structural
data from the Obruchev fault in the Baikal rift and published
evidence of rift-related faulting worldwide. The typical fault
family is dominated by rift-parallel synthetic and antithetic normal
faults and includes transverse faults of normal and strike-slip
geometry, strike-slip faults oblique to the rift strike, and
rift-parallel reverse faults and thrusts. The coexistence of faults
of various types within first-order extension zones is accounted for
by accommodation of shear strain and by the kinematics of large
basin-parallel normal faults. The suggested typical pattern can be
used for reference in interpretation of faulting histories in rifted
continental lithosphere.
Faults, faulting pattern, Baikal rift, zones of extension
RECENT VERTICAL CRUSTAL MOVEMENTS IN THE REGION OF YENISEI RIDGE
P.P. Kolmogorova and V.G. Kolmogorov*
Institute of Geophysics, Siberian Branch of the RAS, 3 prosp. Akad.
Koptyuga, Novosibirsk, 630090, Russia
* Siberian State Geodetic Academy, 10 ul. Plakhotnogo, Novosibirsk,
630108, Russia
Distribution of recent crustal uplift at the junction of the
West Siberian Plate and the Siberian craton was inferred from
repeated leveling geodetic data. The new results have been applied
to compile a map model of recent vertical crustal movements in the
Yenisei Ridge, to correlate their rates with the modern surface
topography, and to detect fault zones. Uplift rate anomalies, which
represent four types of deformation, were estimated from
differential rates of land uplift measured in active faults
traversed by releveling profiles. The Yenisei Ridge is generally a
non-deformable solid block tilted to the west towards the West
Siberian Plate.
Recent land uplift, map model, correlation analysis, Yenisei
Ridge
THE VENDIAN OF THE BAIKAL-PATOM UPLAND, SIBERIA
V.V. Khomentovsky, A.A. Postnikov, G.A. Karlova, B.B. Kochnev, M.S.
Yakshin, and V.A. Ponomarchuk
Institute of Petroleum Geology, Siberian Branch of the RAS, 3 prosp.
Akad. Koptyuga,
Novosibirsk, 630090, Russia
A large gap is documented in the Patom Upland, at the base of
the Zherba Formation. The closely connected Tirbes Formation is now
considered as its completing member. The Tinnaya Formation is
separated from the Zherba and the overlying Nokhtuisk Formations by
gaps. Small shelly fossils found there for the first time gave
grounds for substantiation the lower boundary of the Cambrian at the
bottom of the Nokhtuisk Formation and for referring the Tinnaya
Formation to the Nemakit-Daldyn Stage of the Vendian. The more
precise isotope chemostratigraphy of the Vendian-Cambrian deposits
has shown that here, as in the other sections of the Siberian
Platform, a negative marking excursion of Δ13C matches the
paleontologically substantiated lower boundary of the Cambrian. The
adjacent peaks helps to draw the boundaries of the regularis and
lenaicus Zones and permit two conclusions. First, fossils of the
trisulcatus Zone in the Siberian sections occur below the base of
the Manykai Formation, whereas some representatives of the Ediacaran
fauna penetrate there from below. Therefore, the Manykai Stage
recognized on basis of this formation has no biostratigraphic sense
and its lower boundary cannot be used for supporting the
Vendian-Cambrian border. Second, the Zherba Formation corresponds to
the Ediacaran Stage of the Khorbusuonka section of the Olenek
uplift. The Lower Vendian deposits in the region were preserved only
in paleodepressions. Their most complete section is known in the
Bodaibo-Baikal pericratonic trough. The Lower Vendian is linked
there, through gradual transitions, to the host rocks. Glacial
formations and cap-dolomites are absent from it and, therefore,
cannot be used as the bottom of the terminal Neoproterozoic of the
International Scale. Quite promising for this purpose are
pre-Vendian and intra-Vendian tectonic rearrangements whose ages
reliably suggest that the Lower Vendian of the region formed in the
interval from 650 to 612-620
Ma. Thus, the section of the Upper Vendian of the Baikal-Patom
Upland is well substantiated by direct data at the Neoproterozoic
III of the International Scale.
Vendian, paleontology, stages, zones, chemostratigraphy,
zoning, correlation, International Scale, Patom Upland, Siberia
CALCAREOUS ALGAE AND LOWER BOUNDARY OF CAMBRIAN IN THE WESTERN
ALTAI-SAYAN FOLDED AREA
A.A. Terleev, V.A. Luchinina, O.V. Sosnovskaya*, and G.N. Bagmet**
Institute of Petroleum Geology, Siberian Branch of the RAS, 3 prosp.
Akad. Koptyuga, Novosibirsk, 630090, Russia
* Krasnoyarskgeols'emka Enterprise, 3 ul. Berezina, Krasnoyarsk,
660020, Russia
** West Siberian Testing Center, Zapsibgeologiya Ltd., 7 prosp.
Pionersky, Novokuznetsk, 654027, Russia
New data are reported on occurrences of calcareous algae and
other concurrent groups of fossils in the transient Vendian-Cambrian
deposits of the western Altai-Sayan Folded Area (East Sayans,
Gornaya Shoria, Kuznetsk Alatau, and Gorny Altai). There are two
successive algal complexes: lower - with Korilophyton, Gemma,
Razumovskia, Girvanella, Proaulopora, and Renalcis; upper - the
same, supplemented with abundant species of the genus Epiphyton and
with the genera Batinevia, Tubophyllum, and Subtifloria. These
complexes are compared with the Nemakit-Daldyn (Upper Vendian) and
Tommotian (Lower Cambrian) associations of algae of the Siberian
Platform. A conclusion is made that the lower boundary of the
Cambrian in the Altai-Sayan Folded Area can be tentatively drawn
where the lower complex is replaced by the upper one. These
inferences receive support from rare findings of small shelly
fossils.
Vendian, Cambrian, calcareous algae, small shelly fossils,
Altai-Sayan Folded Area
ESTIMATION OF THE CONDITIONS OF FORMATION OF REE-CARBONATITES IN
WESTERN TRANSBAIKALIA
A.G. Doroshkevich and G.S. Ripp
Geological Institute, Siberian Branch of the RAS, 6a ul.
Sakh'yanovoi, Ulan Ude, 671000, Russia
Results of thermobarogeochemical study of bastnaesite and
fluorite from the Yuzhnoe and Arshan REE deposits in western
Transbaikalia are presented. The minerals have been found to bear
solid, primary and secondary multiphase, and gas-liquid inclusions.
The studies showed that homogenization of primary gas-liquid
inclusions in fluorite from carbonatites proceeded in the
temperature range 370-400°C. Bastnaesite formed at T >> 520°C. We
failed to detect homogenization of multiphase salt inclusions
because of the thermal decomposition of bastnaesite in the air at
480-520°C. The salt inclusions are Na, K, and Ca sulfates, iron
oxides, and unidentified fluoride complexes. The presence of
sulfates and hematite evidences that the carbonatites formed in the
oxidizing conditions, and the high contents of SO3 and F are a
specific feature of the parental melt. The presence of alkalies in
the form of soluble sulfates and their removal from the carbonatite
melt favored alkaline metasomatism, which resulted in biotitization
at the Yuzhnoe deposit and albitization and biotitization at the
Arshan one.
REE-carbonatites, bastnaesite, multiphase salt inclusions,
gas-liquid inclusions
RECONSTRUCTION OF THE THERMAL HISTORY OF METAMORPHIC ROCKS
FROM THE EXCHANGE-DIFFUSION ZONING OF MINERALS
V.N. Korolyuk, G.G. Lepezin, and A.V. Korsakov
United Institute of Geology, Geophysics and Mineralogy, Siberian
Branch of the RAS, 3 prosp. Koptyuga,
Novosibirsk, 630090, Russia
We mathematically justified a model for the formation of
chemical zoning in minerals involved in exchange-diffusion reactions
of the type FeOl+MgOpx=FeOpx+MgOl. We constructed FeO concentration
profiles for garnet crystals of different sizes, using a
garnet-pyroxene thermobarometer and diffusivities, and estimated the
rates of burial and exhumation of low-temperature granulite facies
rocks and eclogites.
Chemical zoning, exchange-diffusion reactions, partition
coefficients, diffusion, rates of burial and exhumation, duration
SEDIMENTATION OF MONODISPERSE SILICA SPHERES AND THEIR
COAGULATION-RELATED AGGREGATION AT HIGH TEMPERATURES
D.V. Kalinin and V.V. Serdobintseva
Institute of Mineralogy and Petrography, Siberian Branch of the RAS,
3 prosp. Akad. Koptyuga,
Novosibirsk, 630090, Russia
The effect of high temperatures on the sedimentation of
suspensions of monodisperse silica spheres (MSS) is considered. The
MSS suspensions chosen as a model for our research, with ethanol as
a dispersion medium, are stable to a particular temperature. The
results obtained made us to study MSS suspensions in aqueous medium
at much higher temperatures. With increasing temperature, the rate
of sedimentation of MSS suspensions is much higher than it is on
decreasing dispersion medium viscosity. This is due to the particle
coagulation caused by a change in the electrolyte dissociation in
the dispersion medium. With increasing temperature, the degrees of
dissociation of acids and alkalies in the precritical state of
solution change in the opposite manner. With decreasing temperature,
the coagulation and sedimentation stabilities of positively and
negatively charged particles in the dispersion media of hydrothermal
solutions also show opposite tendencies. This difference must be
taken into account in study of hydrothermal mineral formation
involving disperse systems.
Disperse systems, sedimentation rate, temperature dependence,
aggregation, supramolecular crystallization, hydrothermal conditions
THE AGE AND GEODYNAMIC SETTING OF FORMATION OF HIGH-TEMPERATURE
METAMORPHIC COMPLEXES IN THE SOUTH MONGOLIAN BELT
I.K. Kozakov, E.B. Sal'nikova, A.N. Didenko*, V.P. Kovach, A.M.
Fedoseenko,
and S.Z. Yakovleva
Institute of Geology and Geochronology of the Precambrian, Russian
Academy of Sciences, 2 nab. Makarova,
Saint Petersburg, 199034, Russia
* Gamburtsev Institute of the Earth's Physics, Russian Academy of
Sciences, 10 ul. Bol'shaya Gruzinskaya,
Moscow, 123810, Russia
Based on the first isotope-geochronological data obtained, the
age of metamorphic processes in Hercynian crystalline complexes in
southeastern Mongolia has been estimated. The average 207Pb/235U age
of monazite from synmetamorphic granites is 224 +- 1 Ma. The Sm-Nd
age for the bulk rock and its mineral inclusions is 219.2 +- 6.2 Ma.
We have established that highly metamorphosed rocks of Early and
Late Hercynian (Indo-Sinian) folded structures in the South
Mongolian belt cannot be fragments of the Caledonian (or more
ancient) ensialic basement. They resulted from the development of
deep segments in the Earth's crust during the closure of the South
Mongolian and the Inner Mongolian ocean basins.
Tectonics, metamorphism, geochronology, Hercynides,
Indo-Sinides
THE FILIPPOVKA BURIED DEPRESSION NEAR NOVOSIBIRSK: A POSSIBLE IMPACT
CRATER OF TRIASSIC-EARLY JURASSIC AGE
S.A. Vishnevsky and V.A. Bogdashev*
Institute of Mineralogy and Petrography, Siberian Branch of the RAS,
3 prosp. Akad. Koptyuga,
Novosibisrk, 630090, Russia
* Novosibirskgeologiya Enterprise, 28 ul. Romanova, Novosibisrk,
630099, Russia
Owing to its crater-like morphology as well as to geophysical
(negative gravity) and geological (superimposed setting) features,
the Filippovka (Philippe) buried depression near Novo<->sibirsk,
Siberia, can be considered as a possible deeply eroded impact crater
of Triassic-Early Jurassic age, with an initial diameter of ~20 km.
Filippovka buried depression, impact crater (astrobleme)