Model of Formation of the Sedimentary System of the Eurasian Basin,the Arctic Ocean,as a Basis for Reconstructing Its Tectonic Evolution

Geotectonics - For the first time tectonic reconstructions was carried out along the entire seismic dataset, including both Russian and international seismic lines. Based on the analysis of the...     

Rb-Sr geochronology of Vendian shales,the Staraya Rechka Formation,Anabar Massif,northern Siberia

Fine-grained clayey subfractions (SF) with particle sizes of 1–2, 0.6–1.0, 0.3–0.6, 0.2–0.3, 0.1–0.2, and <0.1 μm were extracted from shales of the Vendian Staraya Rechka Formation in the Anabar Massif and studied by XRD and Rb-Sr methods. All the clayey subfractions are represented by illite with high crystallinity indices, which are characteristic of the low-temperature diagenesis/catagenesis zone and grow with the decrease of the particle size. The Rb-Sr systematics in clayey subfractions combined with mineralogical data provide grounds for the conclusion that illite from clayey rocks of the Staraya Rechka Formation was forming during two periods: approximately 560 and 391–413 Ma ago. The first illite generation was likely formed in the course of lithostatic subsidence of the Staraya Rechka sediments and the second one, during the Devonian lithogenesis stage. It is assumed that age of the first generation (∼560 Ma) is close to that of the Staraya Rechka Formation. This inference is consistent with biostratigraphic, chemostratigraphic, and geochronological data obtained for both rocks of the Anabar Massif and Vendian sediments from other regions of Siberia.     

Origin of carbonatites of eastern taimyr deduced from an isotopic and geochemical study of zircons

Injection carbonatites of volcanic-plutonic origin with Au-bearing base-metal sulfide mineralization were established in 2006–2007 along the southern slope of the Byrranga Range in the Russian continental sector of the Arctic. According to thermobarogeochemical data, carbonatites were formed at a temperature not lower than 380–410°C from boiling gas-liquid H₂O-CO₂-salt fluids under decompression. The REE concentrations and patterns of sedimentary and magmatic carbonates are sharply distinct. Carbonatites are enriched in REE as compared to carbonates from limestone and are characterized by an REE distribution close to MORB. The geochronological and isotopic geochemical study of zircons has shown that carbonatite bodies (lavas?) were formed 238–219 Ma ago (Middle-Late Triassic); zircon crystallized at a high temperature. Detrital zircons from the Lower Carboniferous crinoid limestone are not younger than 594 Ma. The absolute predominance of Precambrian zircons, which are variable in age, indicates that they were captured from the crust, when carbonatitic magma ascended from subcrustal depths.     

Star burst activity in high surface brightness galaxies

High surface brightness galaxies are also galaxies with high star-forming activity. About a half of them omit, on the average, twice as much energy in the IR than in the blue. The rates of star formation are 10–30 times higher than those in normal galaxies. On average 100–300 solar masses gas are converted into stars every year and 10–30 are massive stars.     

Moho imbrication in the Middle Urals

New processing of part of the Europrobe's Seismic Reflection Profiling in the Urals (ESRU) reflection seismic data in the Middle Urals shows a southwest‐dipping Moho imbrication and crustal underthrusting that was not previously imaged. The area of thickening associated with it roughly coincides with a deepening of the Moho imaged by the GRANIT refraction data. This feature does not fit with the currently known Palaeozoic crustal architecture of the Uralides or with its geodynamic history. Geological data suggest that it is not related to a relict southwest‐dipping subduction zone. Based on its lower crustal and Moho reflection seismic character it is presently interpreted to be a post‐Uralide feature, possibly related to Mesozoic intraplate shortening in the area. Its coincidence with a locus of mild earthquake activity further suggests that it might be active today.     

The luminosity excess of OB stars in quasi-stationary X-ray binaries

We have found a mass—luminosity relation for the OB components of massive X-ray binaries that is a good estimator of the masses of these evolutionarily important binaries. Analysis of this relation showed a systematic luminosity excess of ≈1^m for the OB components in these systems. No such excess was discovered for the evolutionarily related WR + O binaries, which also undergo mass exchange between their components and are the immediate precursors of X-ray binaries. A study of possible origins of the luminosity excess suggests that the most likely explanation is an X-ray luminosity related selection effect for massive X-ray binaries. Estimates show that the probability of detecting X-ray binary increases due to the enhancement of the stellar wind, which increases the efficiency of accretion by the relativistic companion while the optical component evolves along the main sequence. This can explain the magnitude of the observed luminosity excess and the position of the optical components of X-ray binaries in the luminosity—radius plane.     

The clayey—carbonate sedimentation cycle and carbonate platform formation: evidence from the linok formation, the middle riphean of the turukhansk uplift, siberia

Using the Linok Formation as an example, spatiotemporal relationships between siliciclastic and carbonate systems in the epeirogenic-type basin and an initial stage of the carbonate platform development are considered. Clayey-carbonate rocks of the Linok Formation correspond to the middle part of the upper Middle Riphean, up to 1.4 km thick terrigenous-carbonate cycle occurring at the base of the Turukhansk Uplift section. The formation is subdivided into the lower clayey-calcareous (18–43 m), middle, mainly argillite (40–75 m), and upper carbonate (120–220 m) subformations. The analysis of facies associations revealed that the formation was deposited as a symmetrical transgressive-regressive rock succession representing a common stratigraphic sequence. Rocks from the lower and middle subformations correspond to the agradational development of the distal and relatively deep part of the basin with mixed clayey-calcareous sedimentation, whereas the upper subformation reflects the processes of formation and expansion of the carbonate platform. It is shown that the platform development initiated in the external area of the basin, from where fine-grained sediments expanded to the internal deep-water zones. It is assumed that progradation of the platform at the initial stage of its development was characterized by diffused patterns