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101.
Ocean Dynamics - Long-lived and large-scale anticyclonic Aleutian eddies (AEs), detaching from the Alaskan Stream to the west of 180∘ and propagating southwestward or almost zonally in the... 相似文献
102.
M. V. Portnyagin V. B. Naumov N. L. Mironov I. A. Belousov N. N. Kononkova 《Geochemistry International》2011,49(11):1085-1110
The powerful eruption in the Akademii Nauk caldera on January 2, 1996, marked a new activity phase of Karymsky volcano and
became a noticeable event in the history of modern volcanism in Kamchatka. The paper reports data obtained by studying more
than 200 glassy melt inclusions in phenocrysts of olivine (Fo
82-72), plagioclase (An
92-73), and clinopyroxene (Mg#83-70) in basalts of the 1996 eruption. The data were utilized to estimate the composition of the parental melt and the physicochemical
parameters of the magma evolution. According to our data, the parental melt corresponded to low magnesian, highly aluminous
basalt (SiO2 = 50.2 wt %, MgO = 5.6 wt %, Al2O3 = 17 wt %) of the mildly potassic type (K2O = 0.56 wt %) and contained much dissolved volatile components (H2O = 2.8 wt %, S = 0.17 wt %, and Cl = 0.11 wt %). Melt inclusions in the minerals are similar in chemical composition, a fact
testifying that the minerals crystallized simultaneously with one another. Their crystallization started at a pressure of
approximately 1.5 kbar, proceeded within a narrow temperature range of 1040 ± 20°C, and continued until a near-surface pressure
of approximately 100 bar was reached. The degree of crystallization of the parental melt during its eruption was close to
55%. Massive crystallization was triggered by H2O degassing under a pressure of less than 1 kbar. Magma degassing in an open system resulted in the escape of 82% H2O, 93% S, and 24% Cl (of their initial contents in the parental melt) to the fluid phase. The release of volatile compounds
to the atmosphere during the eruption that lasted for 18 h was estimated at 1.7 × 106 t H2O, 1.4 × 105 t S, and 1.5 × 104 t Cl. The concentrations of most incompatible trace elements in the melt inclusions are close to those in the rocks and to
the expected fractional differentiation trend. Melt inclusions in the plagioclase were found to be selectively enriched in
Li. The Li-enriched plagioclase with melt inclusions thought to originate from cumulate layers in the feeding system beneath
Karymsky volcano, in which plagioclase interacted with Li-rich melts/brines and was subsequently entrapped and entrained by
the magma during the 1996 eruption. 相似文献
103.
Yu. I. Portnyagin E. G. Merzlyakov T. V. Solov’eva A. I. Pogorel’tsev E. V. Suvorova P. Mukhtarov D. Pancheva 《Izvestiya Atmospheric and Oceanic Physics》2011,47(1):108-118
The height-latitude distributions of parameters of the vertical wind component of the semidiurnal tide were calculated for the mesosphere and lower thermosphere (MLT) region (80–100 km) on the basis of empirical height-latitude distributions of the monthly mean parameters of variations in the horizontal wind component of the migrating semidiurnal tide. The constructed distributions are compared with the results of a numerical modeling of the migrating semidiurnal tide with the aid of a model of global circulation in the middle and upper atmosphere, as well as with the parameters of semidiurnal temperature variations obtained from the data of satellite measurements. It is shown that different models yield the distributions of parameters of semidiurnal variations, which agree within the errors of their values. The presence of high-latitude regions of local maximal amplitudes is a specific feature of the distributions of parameters of semidiurnal variations in the vertical wind constructed in the course of this work. On the whole, at heights of about 90 km and higher, semidiurnal variations in the vertical wind exceed the prevailing vertical wind in amplitude. 相似文献
104.
Vera Ponomareva Maxim Portnyagin Alexander Derkachev I. Florin Pendea Joanne Bourgeois Paula J. Reimer Dieter Garbe-Schönberg Stepan Krasheninnikov Dirk Nürnberg 《International Journal of Earth Sciences》2013,102(6):1673-1699
We report tephrochronological and geochemical data on early Holocene activity from Plosky volcanic massif in the Kliuchevskoi volcanic group, Kamchatka Peninsula. Explosive activity of this volcano lasted for ~1.5 kyr, produced a series of widely dispersed tephra layers, and was followed by profuse low-viscosity lava flows. This eruptive episode started a major reorganization of the volcanic structures in the western part of the Kliuchevskoi volcanic group. An explosive eruption from Plosky (M~6), previously unstudied, produced tephra (coded PL2) of a volume of 10–12 km3 (11–13 Gt), being one of the largest Holocene explosive eruptions in Kamchatka. Characteristic diagnostic features of the PL2 tephra are predominantly vitric sponge-shaped fragments with rare phenocrysts and microlites of plagioclase, olivine and pyroxenes, medium- to high-K basaltic andesitic bulk composition, high-K, high-Al and high-P trachyandesitic glass composition with SiO2 = 57.5–59.5 wt%, K2O = 2.3–2.7 wt%, Al2O3 = 15.8–16.5 wt%, and P2O5 = 0.5–0.7 wt%. Other diagnostic features include a typical subduction-related pattern of incompatible elements, high concentrations of all REE (>10× mantle values), moderate enrichment in LREE (La/Yb ~ 5.3), and non-fractionated mantle-like pattern of LILE. Geochemical fingerprinting of the PL2 tephra with the help of EMP and LA-ICP-MS analyses allowed us to map its occurrence in terrestrial sections across Kamchatka and to identify this layer in Bering Sea sediment cores at a distance of >600 km from the source. New high-precision 14C dates suggest that the PL2 eruption occurred ~10,200 cal BP, which makes it a valuable isochrone for early Holocene climate fluctuations and permits direct links between terrestrial and marine paleoenvironmental records. The terrestrial and marine 14C dates related to the PL2 tephra have allowed us to estimate an early Holocene reservoir age for the western Bering Sea at 1,410 ± 64 14C years. Another important tephra from the early Holocene eruptive episode of Plosky volcano, coded PL1, was dated at 11,650 cal BP. This marker is the oldest geochemically characterized and dated tephra marker layer in Kamchatka to date and is an important local marker for the Younger Dryas—early Holocene transition. One more tephra from Plosky, coded PL3, can be used as a marker northeast of the source at a distance of ~110 km. 相似文献
105.
S. A. Silantyev A. A. Novoselov E. A. Krasnova M. V. Portnyagin F. Hauff R. Werner 《Petrology》2012,20(1):21-39
During cruise SO201-1b of the joint Russian-German expedition on the R/V Sonne in 2009, mantle peridotites affected by varying secondary alteration were dredged on the eastern slope of the northwestern
segment of the Stalemate transverse ridge adjacent to the eponymous fracture zone. The collection discussed in this paper
included four samples of silicified serpentinites after dunites and 11 lherzolite samples serpentinized to a varying degree.
The abundance of amorphous silica and quartz, very high SiO2 content (up to 88.7 wt %), and unusually low MgO (up to 1.4 wt %) in the serpentinized dunites strongly distinguish these
rocks from the known products of hydrothermal alteration and low-temperature (seafloor) weathering of peridotites in the oceanic
crust. In order to determine the conditions and processes resulting in the silicification of peridotites at the Stalemate
Fracture Zone, thermodynamic modeling accounting for the kinetics of mineral dissolution implemented in the GEOCHEQ program
package was used in this study. The results of modeling allowed us to suppose that the geochemical and mineralogical effects
observed in the silicified serpentinized dunites of the Stalemate Fracture Zone are consequences of low-temperature deserpentinization
of oceanic materials under subaerial conditions. 相似文献
106.
Maxim V. Nyrtsov Maria E. Fleis Michael M. Borisov Philip J. Stooke 《The Cartographic journal》2013,50(2):114-124
Many small solar system bodies such as asteroids or small satellites have irregular shapes, often approximated by the reference surface of a triaxial ellipsoid. Map projections for the triaxial ellipsoid are needed to present the incoming data in the form of maps. In this paper the formulae of equal-area cylindrical and azimuthal projections of the triaxial ellipsoid were derived and practically implemented for the first time using as an example the asteroid 253 Mathilde. This paper is the final in a series of papers devoted to all main classes of projections of the triaxial ellipsoid. Before this, the authors obtained equidistant along meridians projection and Jacobi conformal projection for the triaxial ellipsoid. 相似文献
107.
Maxim Shoshany Asaf Even‐Paz Shlomo Bekhor 《International journal of geographical information science》2013,27(7):777-797
Recent developments in sensing and tracking technologies have enabled large geographical databases to be established that represent spatial dynamics of ‘behavioral entities’. Within this type of dynamics there are several levels and modes of organization that need to be revealed. Clusters are high‐level groupings of entities, where change in their location and form, including split and merge events, represents self‐organization and functioning patterns. Such information may contribute for better understanding spatially complex dynamic patterns. The main objective of this article is to develop an adaptable methodology that facilitates exploration of spatial order and processes in point pattern dynamics. The approach presented here utilizes data‐clustering at each snapshot of the moving pattern, and then involves pairwise linking between the clusters identified at each snapshot and those identified in the following snapshot. Such linking is based on a new methodology that defines well globally optimized solutions for numerous possible linking combinations based on Linear Programming. A preliminary assessment of the approach was conducted with an existing Ants' simulation tool, capable of creating data sets covering in detail a substantial portion of the nest's life cycle. 相似文献
108.
Brad M. S. Hansen † Maxim Lyutikov† 《Monthly notices of the Royal Astronomical Society》2001,322(4):695-701
We describe the possible electromagnetic signals expected from the magnetospheric interactions of a neutron star binary prior to merger. We find that both radio and X-ray signals of detectable strength are possible. We discuss possible links with the phenomenon of gamma-ray bursts (GRBs) and describe the prospects for direct detection of these signals in searches for radio and X-ray transients. 相似文献
109.
110.
Heavy mineral associations from tephra layers in the Quaternary deposits of the Sea of Okhotsk and their chemical characteristics were studied by various techniques. It was shown that such investigations may have a bearing on the problems of tephrostratigraphic correlation. We assessed the possibility of application of the mineral composition of distal tephra for identification and, in particular, estimation of the relation of tephras to the explosive volcanism of back-arc and frontal zones of island arcs. The investigation of the compositions of minerals and use of mineral geothermometers and geobarometers (two-pyroxene, magnetite–ilmenite, and amphibole) provided evidence on the physicochemical parameters of melt crystallization during the explosive volcanic eruptions that produced the distal tephra layers. It was established that the pyroclastic material of some tephra layers was supplied during explosive eruptions not only from shallow magma chambers but also from deeper and higher temperature reservoirs. Together with the geochemical signatures of volcanic glasses, the obtained results on mineral associations and the geochemistry of mineral inclusions are applicable for the comparative analysis and correlation of tephras from marine and continental sequences, as well as for the identification of explosive volcanic products in adjacent land areas. 相似文献