Rare-metal granitoids of the Ulug-Tanzek deposit (Eastern Tyva): Age and tectonic setting

Doklady Earth Sciences -     

Structure of the transition zone from the barents sea shelf to the Knipovich Ridge Northward from Medvezhii Island (Preliminary results of the 26th cruis of R/V Akademik Nikolaj Strakhov)

Doklady Earth Sciences -     

The appearance of a radio-pulsar magnetosphere from a vacuum with a strong magnetic field. Motion of charged particles

The motion of electrons and positrons in the vacuum magnetosphere of a neutron star with a surface magnetic field of B ≈ 10¹² G is considered. Particles created in the magnetosphere or falling into it from outside are virtually instantaneously accelerated to Lorentz factors γ ≈ 10⁸. After crossing the force-free surface, where the projection of the electric field onto the magnetic field vanishes, a particle begins to undergo ultra-relativistic oscillations. The particle experiences a regular drift along the force-free surface simultaneous with this oscillatory motion.     

Stratigraphic chart of Cambrian deposits in the Turukhansk–Irkutsk–Olekma region,Siberian Platform

The former stratigraphic chart of the Cambrian in the Turukhansk–Irkutsk–Olekma region of the Siberian Platform was compiled in 1986 and approved in 1988. Large amounts of data were obtained from new wells drilled in the western and northern parts of the region during the preceding 20 years. Modifications necessitated by new data entail an indefinitely continuous series of revised facies zonation, recognition of new facies areas, regions and zone, as well as definition of a regional early Mayan stratigraphic hiatus. A new local stratigraphic division is the Olenchima Member (base of the Evenk Formation) underlain by a hiatus. The term Kochumdek Formation is no longer used in the Bakhta region and its lithologically distinct subformations (Yasenga, Moktakon, Mara, and Abakun) were raised to formation rank. The Olenchima Formation is no longer used in the Baikit zone; but instead, the Litvintsevo Formation was established here by correlation.     

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.     

Geological structure of the oil-and-gas plays and oil-and-gas potential of the southern Siberian Platform

The paper discusses modern views of the structure of the main producing plays in the southern Siberian Platform: Riphean, Vendian, and Lower Cambrian. The major zones of oil and gas accumulation have been distinguished. Forecast resources have undergone differentiated expert evaluation, and methods for their development have been recommended.     

First results of U-Pb geochronological studies of the Precambrian granitoids of the Batomga block of the Aldan shield

This paper reports the first U-Pb geochronological data on the Precambrian granitoids of the Batomga block (Aldan shield). It was established that the amphibole diorites of this block have an age of 2062 ± 14 Ma, while biotite granites are dated at 2055 ± 7 Ma. These granitoids were subjected to epidote-amphibolie facies metamorphism 1920 ± 8 Ma ago.