Home – Home – Jornals – Russian Geology and Geophysics 2002 number 11

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

The picrite-dolerite ore association 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 sulphide-silicate liquation in an intermediate chamber to fractional crystallization of a sulphide 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, enriching the residual sulphide melt. The fact that Au dominates over Pd in the Kuolotong ores suggests considerably advanced fractionation of sulphide liquid during their formation, which corresponds to experimental data for these metals in sulphide systems. The isotope composition of sulphur in the ores is close to the meteorite standard, slightly deviating toward the heavy isotope. Halogen-bearing fluids little contribute to migration and concentration of noble metals. The petrologic 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.

At the initial stage of genesis of precious opal from concentrated suspensions of mono-disperse silica spheres, supra-molecular gel crystals with solid silica particles form. The latter are localized at the lattice sites and are separated by liquid partings

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 re-efogenic ones, can be subdivided into zones with different degrees of catagenetic transformation and different reservoir properties.

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

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.

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