Orbital evolution of Uranus’s new outer satellites

Data on three recently discovered satellites of Uranus are used to determine basic evolutional parameters of their orbits: the extreme eccentricities and inclinations, as well as the circulation periods of the pericenter arguments and of the longitudes of the ascending nodes. The evolution is mainly investigated by analytically solving Hill’s double-averaged problem for the Uranus-Sun-satellite system, in which Uranus’s orbital eccentricity e _U and inclination i _U to the ecliptic are assumed to be zero. For the real model of Uranus’s evolving orbit with e _U≠0 and i _U≠0, we refine the evolutional parameters of the satellite orbits by numerically integrating the averaged system. Having analyzed the configuration and dynamics of the orbits of Uranus’s five outer satellites, we have revealed the possibility of their mutual crossings and obtained approximate temporal estimates.     

Numerical modeling of the cross-section structure of the subarctic/subtropical boundary in the North Pacific

A simple variational model of the zonal region between waters has been developed with a specified density gradient and a convergence zone. An approximate analytical solution has been constructed. The boundary between waters is shown to divide into two fronts, a convergence front and a density front. The density front should be shifted equatorward relative to the convergence axis. Such a structure corresponds to the subarctic/subtropical boundary in the Pacific Ocean: the subarctic front and the Kuroshio Extension front that goes into the North Pacific Current.     

Lessons learned from two case histories of seismic microzonation in Italy

The prediction of the variability of the seismic ground motion in a given built-up area is considered an effective tool to plan appropriate urban development, to undertake actions on seismic risk mitigation and to understand the damage pattern caused by a strong-motion event. The procedures for studying the seismic response and the seismic microzonation of an urban area are well established; nevertheless, some controversial points still exists and are discussed here. In this paper, the selection of a reference input motion, the construction of a subsoil model and the seismic response analysis procedures are discussed in detail, based on the authors’ experience in two Italian case histories: the seismic microzonation of the city of Benevento, which was a predictive study, and the simulation of seismic response and damage distribution in the village of San Giuliano di Puglia, which was a retrospective analysis.     

Scientific problems addressed by the Spektr-UV space project (world space Observatory—Ultraviolet)

The article presents a review of scientific problems and methods of ultraviolet astronomy, focusing on perspective scientific problems (directions) whose solution requires UV space observatories. These include reionization and the history of star formation in the Universe, searches for dark baryonic matter, physical and chemical processes in the interstellar medium and protoplanetary disks, the physics of accretion and outflows in astrophysical objects, from Active Galactic Nuclei to close binary stars, stellar activity (for both low-mass and high-mass stars), and processes occurring in the atmospheres of both planets in the solar system and exoplanets. Technological progress in UV astronomy achieved in recent years is also considered. The well advanced, international, Russian-led Spektr-UV (World Space Observatory—Ultraviolet) project is described in more detail. This project is directed at creating a major space observatory operational in the ultraviolet (115–310 nm). This observatory will provide an effective, and possibly the only, powerful means of observing in this spectral range over the next ten years, and will be an powerful tool for resolving many topical scientific problems.     

Macroseismic attenuation in the Campanian area, southern Italy

The main objective of the present study is to evaluate seismic attenuation relationships for the Campanian area (southern Italy) using the felt intensity report data obtained from comprehensive historical databases (DOM 4.1). We focused our attention on the Campania region because it is characterized by a high seismic hazard and risk, particularly in the Naples area and its suburbs. In order to derive an attenuation relationship for the area, we fitted the observed data by using several functions. We found that a linear plus logarithmic model gives the best fits for the data in the Campanian region. Most of the attenuation relationships proposed up to now for the Italian Peninsula have an isotropic behavior and do not always properly describe the macroseismic attenuation. Therefore, in order to check the possible dependence of the attenuation on the azimuth of the seismic rays, we divided our data set in octants and performed for each of them the same analysis we carried out for the whole data set. The obtained results differ from octant to octant and the differences, besides being associated with the source effects, could be interpreted as probably due to the existence of lateral variations in the lithological and physical features of the crust at different depths, which could affect the patterns of attenuation.     

Phlogopite and phlogopite–amphibole parageneses in the lithospheric mantle of the Birekte terrane (Siberian craton)

Mantle xenoliths containing phlogopite and phlogopite–amphibole mineralization from kimberlites of the Kuoika field have been studied. Such xenoliths were found in two series of rocks: magnesian (Mg) pyroxenite–peridotite and Fe-type phlogopite–ilmenite hyperbasite. The ⁴⁰Ar/³⁹Ar phlogopite age (1600–1800 Ma) and Re–Os and oxygen isotope data in rocks and minerals of the first series of rocks allow us to suggest that Phl–Amph metasomatism of the lithospheric mantle under the Birekte block and its accretion to the Siberian craton occurred in the subduction zone. The second series of rocks is comagmatic to potassium ultramafites and mafites, finding in the Siberian Platform. The phlogopite ages (870–850 Ma) from Phl–Ilm ultramafites corresponds to the beginning of the breakup of the supercontinent Rodinia and is close to ancient age datings of the alkaline ultramafic-carbonatite Tomtor massif. Phlogopite from xenoliths with garnet is much younger in age (500–600 Ma).

     

Fluid composition and origin in the hydrothermal system of the Nezhdaninsky gold deposit,Sakha (Yakutia), Russia

Petrochemical characteristics of igneous, sedimentary, and metasomatic rocks; chemical and isotopic compositions of minerals and fluids; and PT parameters of mineral formation at the Nezhdaninsky deposit are reported. A model of hydrothermal system formation is developed on this basis. In addition to decreasing Ba/Rb and Li/Mg ratios in the course of the hydrothermal process, resulting in the formation of ore-bearing metasomatic rocks, increasing K/Ba and diminishing K/Cs ratios indicate the probable participation of magmatic fluid in the ore deposition. The agreement of the K/Rb and K/Ba ratios with the values typical of the main trend of igneous rocks (MT) implies that the K, Rb, and Ba contents were distributed in the ore-forming hydrothermal fluid according to the ratios in the source magmatic chamber. The K/Rb ratios in metasomatic rocks correspond to the MT and approach the pegmatitic-hydrothermal trend and the composition of orthomagmatic fluid of Mo-W greisen. Similar REE patterns of igneous and terrigenous rocks do not allow the REE source to be constrained unequivocally. The lithological control of lithophile element distribution testifies to the supply of host rock components to the hydrothermal system. All studied rocks and minerals are enriched in LREE. The REE total and the contribution of HREE decrease from preore to synore metasomatic rocks, from preore to regenerated carbonates, and from older to younger scheelite. A similar tendency is noted in granitoids of the Kurum pluton. The δ¹⁸O values of quartz range from +10.3 to +12.6‰ in Au-Mo-W zones, from +15.9 to +16.4‰ in metasomatic rocks, from +14.8 to +16.6‰ in gold-ore veins, and from +13.5 to +16.9‰ in silver-base-metal ore mineralization. The estimates of \(\delta ^{18} O_{H_2 O} \) suggest that water was supplied from a magmatic source (δ¹⁸O = +(5.5?9.0‰)) and as a product of sedimentary rock dehydration. High-temperature (up to 390°C) and highly concentrated (up to 31 wt % NaCl equiv) fluids participated in the mineral formation. The phase separation of the fluid into H₂O-CO₂ liquid and predominantly carbon dioxide gas was combined with mixing of a high-temperature and relatively highly concentrated chloride solution with a low-temperature and poorly mineralized fluid. The redox conditions varied from equilibrium with CH₄-bearing fluid at the gold-molybdenum-tungsten stage to equilibrium with CO₂-bearing fluid during the gold-ore stage.     

Hydrocarbons and other volatile components in alkaline rocks from the Ukrainian shield and Kola Peninsula

Gas chromatography and other analytical techniques (EMR, PMR, and IR spectroscopy) were used to examine volatile components (CH₄, C₂-C₃, CO₂, CO, H₂, H₂O, and others) in alkaline rocks and minerals from the Ukrainian Shield (eight massifs and dikes of grorudites) and from the Khibina and Lovozero massifs in the Baltic Shield. The alkaline rocks from the Ukrainian Shield are mostly of Proterozoic (1.7–2.1 Ga) age. The alkaline rocks from the Kola Peninsula were confirmed to be rich in methane (21 ± 14 μl/g on average) and other hydrocarbons, whereas the analogous rocks from the Ukrainian Shield are poor in methane (2.1 ± 1.6 μl/g on average at a maximum of 14 μl/g). The latter rocks are richer in CO₂, which is one of the major volatile components of alkaline rocks, including agpaitic nepheline syenites from the Kola Peninsula. The rocks from the Ukrainian Shield often have elevated contents of nitrogen (up to 20 μl/g). The reasons for the differences in the composition of volatile components of rocks from the Kola Peninsula and Ukrainian Shield are as follows: the agpaitic crystallization trends of large massifs in the Kola Peninsula and much less clearly pronounced agpaitic trends in the small massifs in the Ukrainian Shield, the affiliation of these rocks with different complexes, the deeper erosion levels of the Ukrainian alkaline massifs, different ages of these rocks, etc.