On the Study of the Spatial Variability of the Composition of the Lunar Material in Experiments on Gamma Spectroscopy Onboard a Mobile Spacecraft Using the Tagged-Cosmic-Rays Method

Solar System Research - The article proposes a “tagged cosmic particle” method that uses the natural flux of high-energy particles of Galactic Cosmic Rays to study the composition of...     

The axial zone of avoidance in the globular cluster system and the distance to the galactic center

We have checked the existence of a zone of avoidance oriented along the Galactic rotation axis in the globular cluster (GC) system of the Galaxy and performed a parametrization of this zone in the axisymmetric approximation. The possibility of the presence of such a structure in the shape of a double cone has previously been discussed in the literature. We show that an unambiguous conclusion about the existence of an axial zone of avoidance and its parameters cannot be reached based on the maximization of the formal cone of avoidance due to the discreteness of the GC system. The ambiguity allows the construction of the representation of voids in the GC system by a set of largest-radius meridional cylindrical voids to be overcome. As a result of our structural study of this set for northern and southern GCs independently, we have managed to identify ordered, vertically connected axial zones of avoidance with similar characteristics. Our mapping of the combined axial zone of avoidance in the separate and joint analyses of the northern and southern voids shows that this structure is traceable at |Z| ? 1 kpc, it is similar in shape to a double cone whose axis crosses the region of greatest GC number density, and the southern cavity of the zone has a less regular shape than the northern one. By modeling the distribution ofGalactocentric latitudes forGCs, we have determined the half-angle of the cone of avoidance α₀ = 15?. 0_{?4?. 1} ^{+2?. 1} and the distance to the Galactic center R ₀ = 7.3 ± 0.5 kpc (in the scale of the Harris (1996) catalog, the 2010 version) as the distance from the Sun to the point of intersection of the cone axis with the center–anticenter line. A correction to the calibration of the GC distance scale obtained in the same version of the Harris catalog from Galactic objects leads to an estimate of R ₀ = 7.2±0.5|_stat ±0.3|_calib kpc. The systematic error in R ₀ due to the observational incompleteness of GCs for this method is insignificant. The probability that the zone of avoidance at the characteristics found is random in nature is ≤2%. We have revealed evidence for the elongation of the zone of avoidance in the direction orthogonal to the center–anticenter axis, which, just as the north–south difference in this zone, may be attributable to the influence of the Magellanic Clouds. The detectability of similar zones of avoidance in the GC systems of external galaxies is discussed.     

Composition,sources, and mechanisms of origin of rare-metal granitoids in the Late Paleozoic Eastern Sayan zone of alkaline magmatism: A case study of the Ulaan Tolgoi massif

The Ulaan Tolgoi massif of rare-metal (Ta, Nb, and Zr) granites was formed at approximately 300Ma in the Eastern Sayan zone of rare-metal alkaline magmatism. The massif consists of alkaline salic rocks of various composition (listed in chronologic order of their emplacement): alkaline syenite → alkaline syenite pegmatite → pantellerite → alkaline granite, including ore-bearing alkaline granite, whose Ta and Nb concentrations reach significant values. The evolution of the massif ended with the emplacement of trachybasaltic andesite. The rocks of the massif show systematic enrichment in incompatible elements in the final differentiation products of the alkaline salic magmas. The differentiation processes during the early evolution of the massif occurred in an open system, with influx of melts that contained various proportions of incompatible elements. The magma system was closed during the origin of the ore-bearing granites. Rare-metal granitoids in the Eastern Sayan zone were produced by magmas formed by interaction between mantle melts (which formed the mafic dikes) with crustal material. The mantle melts likely affected the lower parts of the crust and either induced its melting, with later mixing the anatectic and mantle magmas, or assimilated crustal material and generated melts with crustal–mantle characteristics. The origin of the Eastern Sayan zone of rare-metal alkaline magmatism was related to rifting, which was triggered by interaction between the Tarim and Barguzin mantle plumes. The Eastern Sayan zone was formed in the marginal part of the Barguzin magmatic province, and rare-metal magmas in it were likely generated in relation with the activity of the Barguzin plume.     

Vertical fault systems in the tectonosphere geoelectrical section in petroliferous domains of Sakhalin Island (Russia) and Gulf of Tonkin (Vietnam): Evidence from magnetotelluric sounding

The transverse current anomalies evident from magnetotelluric sounding (MTS) data in the transition zone from the Asian continent to the Pacific Ocean and a geoelectrical model suitable for explaining these effects are discussed. Using simulation results and new MTS data on Sakhalin and northern Vietnam, ultra-deep fluid–fault system (UDFFS) models are constructed, comprising steeply dipping low-resistivity and high-resistivity linear bodies which penetrate through the whole section of the lithosphere, continuing deep into the asthenosphere. The structure of these systems reflects the development of deep and ultra-deep fault zones, along which mantle-originated fluids may migrate through sediments to reach the surface. This allows the anisotropic–conductive fractured structures adjacent to these faults to be considered as being most favorable for hydrocarbon accumulations.     

Sedimentary Waves of the Southeastern Barents Sea Shelf (Kanin Peninsula–Cheshskaya Bay)

Oceanology - Sedimentary waves are represented by a series of wavelike accumulative features with various degrees of morphological expression. These morphological forms are superimposed on the...     

Bastnaesite: a promising U-Pb geochronological tool

Doklady Earth Sciences -     

Resolution of the observed dispersion of the radial velocities of a galactic subsystem into components

Possible approaches are considered to the problem of resolving the observed dispersion in the radial velocities of objects of a given kind in the Galaxy into the system’s true dispersion and the contribution of random errors in heliocentric distances r. Of the methods that have been constructed, only the joint estimation of the true dispersion and the relative mean error in r can yield satisfactory results. This method is used for the subsystem of CO clouds with an observed dispersion of 8.7 ± 0.4 km/sec to obtain the true dispersion of 8.0 ± 0.6 km/sec and the mean error of 0^m.25 ± 0^m.085 in their distance moduli. Translated from Astrofizika, Vol. 43, No. 3, pp. 443-450, July–September, 2000.