Volume 24, 6, 2005
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Volume 24, 6, 2005 |
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A.K. Basharin, S.Yu. Belyaev, A.V.
Khomenko
North Asian craton and Siberian Platform: modern structure
The geological content and the relation of the fundamental concepts ?craton? and ?ancient platform? are considered. The principles of restriction of these elements are formulated with reference to the North Asian craton and the Siberian Platform. Three structural levels are identified and confirmed in the North Asian craton. These are the pre-Neogaean basement, and the Neogaean and epi-Neogaean (Mesozoic-Cenozoic) covers. Three structural stages are distinguished in the present-day structure of the Neogaean cover: rift, plate, and orogenic. The block structure of the craton and platform as well as the peculiarities of restriction of the identified blocks is shown.
B. F.
Shevchenko and V. B. Kaplun
Deep structure and kinematics of the Eurasian and Amur lithospheric plates
junction area (Mongol-Okhotsk segment)
The main features of the deep structure of the junction area of two lithospheric
plates, Eurasian and Amur, are recognized on the basis of geothermal,
seismotomographic, seismic, geoelectrical, gravimetric and magnetometric data
interpretation. The complex geological-geophysical model of the lithosphere of
the area under study was constructed. It is characterized by the layered-block
structure of a variable thickness of 100 to 170 km. Four subhorizontal layers of
possible intraplate displacements are distinguished. The depth model makes it
possible to perform one of the stages of geodynamic interpretation - the
development of the kinematic scheme of the operating forces within the
lithospheric layer.
L.I. Popeko, G.V.
Kotlyar, A.V. Kurilenko
The Permian stage of the geologic history of the Transbaikal region
The position of Permian assemblages in the structures of the Transbaikal segment
of the Mongol-Okhotsk orogenic belt and its framing is analyzed. The geodynamic
settings of their formation are reconstructed. The volume of the regional
stratigraphic units of the Permian in the Transbaikal region - horizons, is
specified, and their paleontological characteristics are supplemented.
Correlation is made between the horizons and the stages of the modified General
stratigraphic chart of the Permian system of the Boreal realm, which implies the
3-member division of the system into series. Correlation is also made between
the horizons and the stages of the Global stratigraphic chart. Biostratigraphic
units are distinguished in the rank of layers with fauna.
A.I.
Malinovsky, V.V. Golozoubov, V.P. Simanenko, A.N. Mitrokhin
Kema terrane (East Sikhote-Alin Range) - a fragment of the Early Cretaceous
island-arc system of the East Asian margin
The paper deals with the structure, composition and depositional environment of
the Barremian (?)-Albian volcanogenic-sedimentary assemblages of the Kema
terrane (East Sikhote-Alin), which are interpreted as deposits of the back-arc
basin of the Moneron-Samarga island-arc system. The compositional features of
the different-type deposits indicate a near-slope depositional environment
influenced by volcanic processes. The study of slump folds orientation testifies
to the gravitational sliding of accumulated material from southeast to northwest.
Judging by compositional peculiarities of terrigenous rocks, an ensialic
volcanic island arc was the major source for detrital material. Petrochemical
characteristics of basaltic rocks indicate that the formations studied were
confined to the rear part of the arc.
B.I. Pavlyutkin, T.I. Petrenko,
I.Yu. Chekryzhov
The problems of the stratigraphy of the Pavlovka coal-field Tertiary deposits,
Primorye
The stratigraphical position of the Pavlovka Suite (Lower-Middle Miocene, by the
official standpoint) on the basis of the new geological and paleobotanical data
is revised. According to the analyzed data of micro- and macroflora, the age of
the Pavlovka Suite falls in the range from Late Eocene through Late Oligocene.
Long stratigraphical hiatuses in the Tertiary deposits of the Pavlovka general
Cenozoic section is confirmed; the Pavlovka Suite is validated; and its typical
section (lectostratotype) is characterized.
V.G. Gonevchuk, G.A. Gonevchuk,
A.M. Kokorin, V.A. Lebedev, A.A. Orekhov
New isotope-geochronological data, and some genesis problems of tin
mineralization of Kavalerovo district (Primorye, Russia)
The probable period of formation (72.5-61.6 million years) of the Iskra tin
deposit in the Kavalerovo ore district is determined for the first time based on
the results of isotope-geochronological (K-Ar) investigation. New datings for
magmatic complexes were obtained, which are presumably related to mineralization
of the district. The results of the investigation together with the
mineralogical and geochemical features of the ores and rocks of the dike complex
closely connected with ore formation, which were earlier recognized by the
authors, allow us to suggest the formation of the deposit from the interaction
of different-composition magmatic chambers. The granitoid chamber is the most
significant in this process. The change of the general geodynamic regime in the
region under study is assumed to strongly influence ore formation.
I.A.
Alexandrov
High pressure metamorphism of amphibolite facies rocks of the
Dzhugdzhur-Stanovoy block (Eastern Siberia)
Geothermobarometry of amphibolite facies rocks of the Dzhugdzhur-Stanovoy block
(Eastern Siberia) was carried out on the basis of the new microprobe analysis.
It is established that metamorphism of the Zeya and Stanovoy rocks occurred in a
temperatures range of 600 to 700°C. Lithostatic pressure evaluations for the
Stanovoy complex rocks range in between 6.5 and 9 kbar; whereas the values for
metamorphic rocks of the Zeya complex are from 9 to 13-14 kbar. Metamorphism of
the Dzhugdzhur-Stanovoy block is related to widespread reworking of the
Aldan-Stanovoy shield in the Late paleo-Proterozoic (~1.9 Ga). In terms of
geodynamics, the cause of the reworking could be subduction (or partial
underthrust during continental collision) of the Stanovoy plate beneath the
southern edge of the Aldan shield.
V.A.
Guryanov, M.V. Goroshko
The main features of the Precambrian metallogeny of the Ulkan region
The paper gives a review of ore mineralization occurrences in the Ulkan trough,
most part of which was detected during the last 20 years. Judging by the
predicted resources, many of the occurrences correspond to large, medium-size
and small deposits. It is shown that the metallogenic characteristics of the
trough are determined by beryllium, tantalum, niobium, yttrium and cerium group
rare earths, uranium, gold and lithium. The central part of the trough is the
Ulkan massif of granitoids. The segments of the trough adjacent to the massif,
which are characterized by a large accumulation of ore objects comprising these
metals, are regarded as a new potential tantalum-, uranium,- and gold-bearing
rare earth-rare metal ore district. The peculiarity of its metallogeny is
determined by the coincidence in plan of two different metallogenic epochs: the
Late Karelian (1720-1670 Ma) rare earth-rare metal epoch, spatially and
genetically related to Ulkan alkaline-granitic magmatism, and the Middle Riphean
(1300-1150 Ma) uranium and gold ore epoch, which was manifested in metasomatites
of the zones of tectonic weakness; the zones being of cross-cutting type with
respect to the structure of the Ulkan trough. Commercially attractive genetic
types are distinguished. Patterns of distribution of mineral resources are
considered, and the prospects of the distinguished ore fields and of the region
in general are defined. The role of localization factors of different genetic
type mineralizations is reflected, among which the main types are tectonic,
lithological, structural, geochemical and mineralogical-petrographical.