The Paleoproterozoic Kolvitsa Anorthosite Massif: New Data on the U–Pb Age (ID TIMS) and Geochemical Features of Zircon

Doklady Earth Sciences - The rocks and minerals of the Kolvitsa massif are studied by complex isotopic–geochronological and geochemical (U–Pb, Sm–Nd, REE contents of zircons)...     

Mineral Composition and Structure of the Sverdlovsk Meteorite (H4-5)

A fragment of the Sverdlovsk Meteorite, which was found in 1985 in the Central Urals, is studied by modern analytical methods. It belongs to H chondrites of petrologic type 4–5; shock stage of meteorite is S1-2, terrestrial weathering is W1. The composition of minerals of the meteorite is studied. It is found for the first time that the metal and sulfides are concentrated in fine veinlets of the recrystallized matrix of the chondrite and are accompanied by segregations of metal and troilite inside these veinlets. The distribution of trace elements of the metal phase of the meteorite is studied.

     

Ya.B. Zeldovich and Foundation of the Accretion Theory

This brief review is dedicated to academician Yakov Borisovich Zeldovich, the science of his epoch and the creation of modern accretion theory.     

Dynamics of Natural Satellites of Planets Based on Observations

There is wide interest in the results of studies of the dynamics of satellites of planets. Such data are needed to determine the physical properties of celestial bodies, and they may be able to provide information about the origins and evolution of the solar system. The general approach to studying the dynamics of satellites involves developing models for the motion and ephemerides based on observational data. Ephemerides are required to prepare and launch space missions to other planets and help discover new celestial bodies. High-precision astrometric coordinates of the principal satellites of Jupiter, Saturn, and Uranus are derived from photometric observations of occultations and eclipses of these satellites. To this end, worldwide observing campaigns have been organized. Enhancement in the precision of ephemerides can be obtained not only by increasing the accuracy of observations, but also by expanding the time interval covered by the observations. Many new, distant satellites of the major planets were discovered in the early 21st century. However, observations of these satellites are scarce and were obtained over short time intervals; as a result, some of these satellites were lost. To date, 179 natural satellites are known. This paper is based on a presentation made at the conference “Modern Astrometry 2017,” dedicated to the memory of K.V. Kuimov (Sternberg Astronomical Institute, Moscow State University, October 23–25, 2017).

     

Cosmology and Astrometry

Astronomy Reports - It has recently become clear that the potential role of astrometry in cosmological studies has been underestimated. Some areas of cosmology that should be investigated using...     

Evolution and Spectrum of the Radio Emission of Tycho’s Supernova Remnant

The radio spectrum of Tycho’s Supernova Remnant is constructed at frequencies 12.6–143 000 MHz for epoch 2010.3, taking into account the secular decrease in the radio flux density of the remnant at the rate d = ?(0.46 ± 0.03)%/year:

$$S_\nu ^{3C10} (t = 2010.3) = (43.1 \pm 1.8 Jy)(\nu [GHz])^{ - (0.592 \pm 0.019) + (0.041 \pm 0.012)\log (\nu [GHz])} .$$

The spectrum has positive curvature. The presence of a low-frequency turnover in the spectrum of the radio source 3C10 with its maximum at 7.7 MHz is predicted, due to absorption in the interstellar medium in the direction toward the source.

     

Results of magnetotelluric surveyon reference geophysical profiles of the Karaton-Sarkamys block in Kazakhstan

A digital geoelectric model of the Karaton-Sarkamys block located in the southern (Kazakhstan) part of the Caspian Depression has been developed on the basis of processing and interpretation of magnetotelluric sounding data. Geoelectric sections and structural maps of geoelectric layers have been constructed. It has been shown that magnetotelluric sounding combined with seismic and GIS data can be efficiently used to obtain additional information on the lithologic and reservoir properties of petroleum plays.     

A Polychronous Locality of Megafauna on the Northwestern Coast of Lake Baikal

Doklady Earth Sciences - Based on geochronological data, it is shown that the formation of sediments of a 50–80 m terrace of Lake Baikal occurred during the Middle Pleistocene and its top...     

Climatic Changes in the Dynamic Topography and Geostrophic Circulation of the Arctic Ocean

Doklady Earth Sciences - According to historical oceanographic data, anomalies in the dynamic topography during the winter period were calculated and two climatic stages of dynamic condition of the...     

Magnetic measurements in electrical prospecting by resistivity methods

The electrical resistivity and induced polarization (IP) methods are widely used in geological mapping, prospecting and exploration of mineral deposits, engineering geology, hydrogeology, archaeology, and geotechnical and environmental applications. Historically, these methods have formed the basis of the electrical prospecting technique. In these methods, a DC or low-frequency AC electrical current is introduced into the earth through a grounded transmitter line. The measured quantity is the electric field. However, if the earth’s resistivity or chargeability changes horizontally, this change gives rise to an anomalous magnetic field, which is studied by the magnetometric resistivity (MMR) and magnetic induced polarization (MIP) methods, respectively. Along with advantages, some shortcomings are inherent in the MMR and MIP techniques. Apparently, the main drawback of these methods is that the magnetic fields of both the transmitter line wire and ground electrodes on the surface are several orders of magnitude greater than the anomalous magnetic field response. This introduces a significant “noise” to magnetic-resistivity data. We investigate the potential of using a circular electric dipole (CED) in magnetometric resistivity techniques. It has been found that the application of a CED, instead of a conventional transmitter line, dramatically enhances the signal-to-noise ratio.