Geology and Geophysics, 2002, V 43, N 11, November.

PETROLOGY, GEOCHEMISTRY, AND MINERALOGY

ISOTOPE GEOCHRONOLOGY OF PALEOZOIC GRANITOIDS OF THE SELENGA-STANOVOY 
MOUNTAINOUS AREA 
M. E. Kazimirovskii, G. P. Sandimirova, and E. V. Bankovskaya
973
     We have considered the problems of dating Paleozoic granitoids of the 
Selenga-Stanovoy mountainous area (SSMA) and reviewed and compared the available 
dates. New Rb-Sr isotope dates for four objects of the West Stanovoy structure-
formational zone (SFZ) are presented, which confirm the existence of 
Carboniferous (360-290 Ma) magmatic stage not only in the west but also in the 
center of the SFZ and refine the age of Early Paleozoic batholiths of the Olekma 
complex (480-430 Ma). This indicates that they are coeval with batholiths of the 
Malkhan complex in the neighboring Khilok-Vitim SFZ. Moreover, as all studied 
granitoids are of crustal (palyngenetic) origin, we proposed a model for Sr-
isotope evolution of this crustal segment.
     Mongolo-Okhotsk belt, Transbaikalia, Paleozoic granitoids, isotope dates, 
Sr-isotope evolution of the crust

PETROLOGY OF THE KUOLOTONG SULFIDE COPPER-NICKEL DEPOSIT IN
NORTHWESTERN CHINA 
A. I. Glotov, A. P. Krivenko, G. V. Polyakov, and E. A. Uvarova
990
     The picrite-dolerite ore associaton was well expressed at the orogenic 
stage of development of the Hercynides of the Zaisan-Gobi fold belt, separate 
parts of which are associated with Cu-Ni ore occurrences and deposits. 
Exemplified by the Kuolotong deposit (North Xinjiang, China), the main stages of 
its formation as a single ore-magmatic system have been shown: from sulfide-
silicate liquation in an intermediate chamber to fractional crystallization of a 
sulfide melt in the ore-hosting intrusion. The fractional crystallization played 
a leading role in the formation of ores of varying composition (Ni-Fe, Fe-Cu, 
and abnormally cupriferous). Additional evidence is distribution in them of Pt, 
Pd, Au, and Ag, enrinching the residual sulfide melt. The fact that Au dominates 
over Pd in the Kuolotong ores suggests considerably advanced fractionation of 
sulfide liquid during their formation, which corresponds to experimental data 
for these metals in sulfide systems. The isotope composition of sulfur in the 
ores is close to the meteorite standard, slightly deviating toward the heavy 
isotope. Galogen-bearing fluids little contribute to migration and concentration 
of noble metals. The petrological and geochemical characteristics of the 
Kuolotong deposits, in combination with mineralogical and geochemical signatures 
of other ore-bearing intrusions of picrite-dolerite ore association, may be used 
for estimating the unclear ore potential of such intrusions.
     Picrite-dolerite rock association, Cu-Ni ores, sulfide liquid, fractional 
crystallization, platinum group elements, fluids, Xinjiang, China

THIXOTROPY IN SUPRAMOLECULAR CRYSTALLIZATION AND GENESIS OF
MACROSTRUCTURES OF PRECIOUS OPAL 
D. V. Kalinin, V. V. Serdobintseva, and Ya. V. Kuznetsova
1002
     At the initial stage of genesis of precious opal from concentrated 
suspensions of monodisperse silica spheres, supramolecular gel crystals with 
solid silica particles form. The latter are localized at the lattice sites and 
are separated by liquid partings - ionic atmospheres around the particles. These 
crystals with weak bonds between their structural units form and exist under the 
balance of the forces of electrostatic repulsion of counter-ionic atmospheres, 
on the one hand, and the total forces of molecular attraction and gravitational 
compression of the particles, on the other. Under mechanical action, the balance 
is disturbed, and reversible thixotropic destruction (liquescency) of the 
structure into particles and microblocks (clusters) takes place, thus producing 
suspension. This suspension recrystallizes, the growth of secondary crystals 
being contributed by the clusters. Secondary thixotropic crystallization 
produces nests and veinlets in the initial structure of precious opal and 
accounts for a considearble diversity of macrostructural patterns of natural 
precious opal.
     Precious opal, genesis, supramolecular crystallization, thixotropic recrystallization

RECOGNITION OF ZONES OF CATAGENETIC CEMENTATION IN CARBONATE ROCKS
OF THE KARACHAGANAK HYDROCARBON DEPOSIT FROM DEFECTS OF CRYSTALLINE
STRUCTURE OF CALCITE 
A. V. Peskov and V. V. Gusev
1009
     Study was given to the lithology of carbonate reservoirs of the 
Karachaganak oil and gas-condensate deposit (KOGCD). The calcites from the KOGCD 
limestones were explored to reveal crystal structure imperfections (CSI), whose 
parameters were estimated to a different degree of catagenetic transformation. 
Using the X-ray structural analysis, we can determine the amount of catagenetic 
calcite. Using the X-ray approximation, we have established zones of catagenetic 
cementation in the limestones of the Karachaganak hydrocarbon deposit. According 
to CSI parameters, the compositionally uniform carbonate formations, especially 
reefogenic ones, can be subdivided into zones with different degrees of 
catagenetic transformation and different reservoir properties.
     Limestone calcites, catagenesis, hydrocarbons, crystal structure, carbonate 
reservoirs, Karachaganak deposit

STRATIGRAPHY AND PALEONTOLOGY PALYNOSTRATIGRAPHY OF PALEOGENE AND NEOGENE 
DEPOSITS OF THE BARABA-KULUNDA FACIES ZONE OF WEST SIBERIA 
V. S. Volkova, I. A. Kul'kova, and O. B. Kuz'mina
1017
     New data are reported to give stratigraphic support for the age of 
Paleogene marine and Paleogene-Neogene continental deposits exposed in three 
wells drilled on the Irtysh River near the town of Omsk, West Siberia. According 
to dinoflagellates and SPA, two formations, Lyulinvor and Tavda, have been 
recognized as part of the marine Paleogene. On the basis of dinocysts, two zones 
are established in the Lyulinvor Formation, named after the index species: 
Dracodinium varielongitudum+D. simile Zone and Charlesdowniea coleopthrypta 
rotundata+Ch. coelothrypta Zone, corresponding to nannoplankton zones 11-14. The 
sediments date from the Lower Eocene+early Middle Eocene (Yprian+lower Lutetian 
Stages).
     The marine Tavda Formation also comprises two zones of dinocysts: 
Rhombodinium draco+Areosphaeridium dictyoplocus, comparable with nannoplankton 
zones 16-19. The age of the formation is constrained by the late Middle and Late 
Eocene (upper Lutetian+Bartonian+Priabonian Stages).
     The Paleogene and Neogene continental deposits are characterized by eight 
palynocomplexes, providing support for recognition in wells of the Zhuravka, 
Abrosimov, Beshcheul', and Tavolga Formations. The development of vegetation is 
subdivided into three steps: tropical, Turgai, and post-Turgai.
Dinoflagellates, spores, pollen, formations: Lyulinvor, Tavda, Zhuravka, 
Abrosimov, Beshcheul', Tavolga; vegetation, West Siberia

GEOPHYSICS

THE 1992 SUUSAMYR EARTHQUAKE AND THE AFTERSHOCK STRAIN FIELD 
O. A. Kuchai, A. M. Muraliev, K. E. Abrdakhmatov, D. Delvaux, and A. D. Duchkov
1038
     Analysis of breakage and seismic strain associated with the aftershocks of 
the 19 August 1992 M=7.3 Suusamyr earthquake shows that the surface rupture 
occurs in the region of highest homogeneous strain. Reorientation of stress axes 
on the tips of the rupture is accompanied by rift-type aftershocks. The nearly 
horizontal N-S orientation of the principal P axis remained invariable and that 
of the T axis changed 25 years before the main shock, during the aftershock 
activity, and later, which is consistent with the direction of maximum 
compression in the region.
     Aftershocks, seismic strain, large earthquake

HEAT FLOW IN THE REGION OF THE BARENTS AND KARA SEAS 
L. A. Tsibulya and L. S. Sokolova
1049
     The paper presents a heat flow map of the region of the Barents and Kara 
Seas which is a synthesis of geothermal data from the West Arctic shelf 
collected since the 1980s. The heat flow distribution is strongly uneven and 
reflects complex geology and geodynamic environment of the territory. Heat flows 
are notably lower in the continental part of the region than in the ocean (40-60 
mW/m2 against an average of 100-120 mW/m2 in submerged ridges and 70-80 mW/m2 
elsewhere), with about an order of magnitude difference between the lower and 
upper limits (20 mW/m2 on the Precambrian Baltic shield against 200 mW/m2 and 
higher in the rift of the submerged Knipovich Ridge). The generally elevated 
mantle heat flow on the Barents and Kara sea shelves is evidence of hot 
anomalous mantle apparently associated with recent ocean opening.
     Heat flow, Arctic shelf, Barents and Kara Seas