Siberian flood basalt magmatism and Mongolia-Okhotsk slab dehydration

Experimental data combined with numerical calculations suggest that fast subducting slabs are cold enough to carry into the deep mantle a significant portion of the water in antigorite, which transforms with increasing depth to phase A and then to phase E and/or wadsleyite by solid-solid phase transition. Clathrate hydrates and ice VII are also stable at PT conditions of cold slabs and represent other potential phases for water transport into the deep mantle. Some cold slabs are expected to deflect while crossing the 410 km and stagnate in transition zone being unable to penetrate through 660 km discontinuity. In this way slabs can move a long way beneath continents after long-lived subduction. With time, the stagnant slabs are heated to the temperature of the ambient transition zone and release free H~2~O-bearing fluid. Combining with transition zone water filter model this may cause voluminous melting of overlying upper mantle rocks. If such process operates in nature, magmas geochemically similar to island-arc magmas are expected to appear in places relatively remote from active arcs at the time of their emplacement. Dolerites of the south-eastern margin of the Siberian flood basalt province, located about 700 km from suggested trench, were probably associated with fast subduction of the Mongolia-Okhotsk slab and originated by dehydration of the stagnant slab in the transition zone. We show that influence of the subduction-related deep water cycle on Siberian flood basalt magmatism gradually reduced with increasing distance from the subduction zone

Triplets of galaxies: Their dynamics, evolution, and the origin of chaos in them

Recently Karachentsev's group at The Smithsonian Astrophysical Observatory (SAO) (6-meter Telescope Observatory) published a list of 84 triple systems of galaxies with their distances, radial (line of sight) velocities, and angular sizes (Karachentseva et al., 1988). This gives a new ground for studies of the dark matter problem which fills the gap between the large cosmic scales (White, 1987; Dekel and Rees, 1987, and Einasto et al., 1977) and the scale of individual galaxies (Erickson et al., 1987). The data on the typical velocity dispersions and linear dimension of the triplets indicate that they contain considerable amounts of dark matter (see also earlier work of Karachentseva et al., 1979). Numerical simulations show that the statistical characteristics of the Karachentsev triplets can be imitated by model ensembles of triple systems with dark matter masses M sub d = (1-3 x 10(exp 12) M sub O, which is almost ten times greater than the typical mass of stellar galaxies estimated by the standard mass-to-luminosity ration (Kiseleva and Chernin, 1988). Here, the authors report that important information can be drawn from the data on the visible configurations of these systems. The statistics of configurations provide an independent evidence for dark matter in the triplets; moreover, it enables one to argue that dark matter seems to be distributed over the whole volume of the typical triplet forming its common corona rather than concentrated within individual coronae (or haloes) of the member galaxies

Dynamics and configurations of galaxy triplets

The purpose is to infer the probable dynamical states of galaxy triplets by the observed data on their configurations. Two methods are proposed for describing the distributions of the triplet configuration parameters characterizing a tendency to alignment and hierarchy: (1) obtaining a representative sample of configurations and determining its statistical parameters (moments and percentages); and (2) dividing the region of possible configurations of triple systems (Agekian and Anosova, 1967) into a set of segments and finding the probabilities for the configurations to find themselves in each of them. Both these methods allow representation of the data by numerical simulations as well as observations. The effect of projection was studied. It rather overestimates the alignment and hierarchy of the triple systems. Among the parameters of interest there are found some parameters that are least sensitive to projection effects. The samples consist of simulated galaxy triplets (with hidden mass) as well as of 46 probably physical triple galaxies (Karachentseva et al., 1979). The observed triples as well as numerical models show a tendency to alignment. The triple galaxies do not show any tendency to hierarchy (formation of the temporary binaries), but this tendency may be present for simulated triplets without significant dark matter. The significant hidden mass (of order ten times the total mass of a triplet) decreases the probability of forming a binary and so weakens the hierarchy. Small galaxy groups consisting of 3 to 7 members are probably the most prevalent types of galaxy aggregate (Gorbatsky, 1987). Galaxy triplets are the simplest groups, but dynamically nontrivial ones

ГЛУБИННАЯ ГЕОДИНАМИКА: ГРАНИЦЫ ПРОЦЕССА ПО ГЕОХИМИЧЕСКИМ И ПЕТРОЛОГИЧЕСКИМ ДАННЫМ

Geochemical features for volcanic rocks and petrologic data for deep-seated inclusions, which can be used to infer mass transfer between different geospheres, are reviewed. It is typically believed that slabs can subduct as deep as the core-mantle boundary with the following recycling by plumes coming up to the sublithospheric regions of magma generation. However, the petrologic evidence of the deepest accessible material is limited by the depth of the uppermost lower mantle (~650–700km), i.e. by the depth of the deepest earthquakes. Ferropericlase inclusions in some diamonds do not exclude involvement of deeper mantle horizons, yet do not unambiguously support it. No unambiguous confirmation of involvement of the lower mantle into magma generation underneath volcanically active regions is obtained from geochemical data either, while the geochemical data suggest complete chemical isolation of the Earth’s core from the upper mantle processes.Проведен анализ геохимических характеристик вулканических пород и петрологических данных по глубинным включениям, которые могут быть использованы для оценки обмена веществом между различными геосферами Земли. Несмотря на то, что обычно рассматривается возможность субдуцирования слэбов вплоть до границы ядро–мантия и последующего возвращения материала в область подлитосферной магмогенерации в форме мантийных плюмов, петрологические доказательства самого глубокого поступления вещества на поверхность ограничиваются верхними горизонтами нижней мантии (~650–700 км), т.е. глубиной самых глубоких землетрясений. Включения ферропериклаза в некоторых алмазах не опровергают вовлечение и более глубоких горизонтов мантии, однако не дают этому однозначного подтверждения. Геохимические данные также не дают однозначного подтверждения вовлечения вещества нижней мантии в процессы магмогенерации под вулканически активными районами. В то же время они свидетельствуют о полной вещественной изоляции ядра от верхнемантийных процессов

ВЗАИМОДЕЙСТВИЕ МАНТИЙНЫХ РАСПЛАВОВ С КОРОЙ ПРИ ИХ ПОДЪЕМЕ К ПОВЕРХНОСТИ: ПРИЧИНА И СЛЕДСТВИЯ

The work considers the mechanism of upwelling of the basaltic melt to the surface and the reason of its stoppage in the crust. The process of stoppage, probably, is controlled by ratio between density of the basaltic melt and density of the crust. If density of the basaltic melt is lower it goes up to the surface without significant stoppage, if the opposite it stays in the crust. Because the melt density decreases with increase of its alkalinity and/ or fluid content, it explains why highly alkaline melts are characterized by low degree of crustal contamination compared to normal alkaline dry melts.В работе рассматривается механизм подъема базальтовых магм к поверхности и причина их возможной задержки в коре. Процесс задержки магм, по-видимому, контролируется соотношением плотности базальтового расплава и плотности верхней коры. Если плотность базальтового расплава оказывается ниже, то он поднимается к поверхности без существенной задержки, если выше – застревает. Поскольку плотность расплава падает с ростом его щелочности и/или флюидонасыщенности, это объясняет, почему высокощелочные расплавы характеризуются меньшей степенью контаминированности в сравнении с сухими расплавами нормальной щелочности

Displacement effect in strong-field atomic ionization by an XUV pulse

We study strong-field atomic ionization driven by an XUV pulse with a non\-zero displacement, the quantity defined as the integral of the pulse vector potential taken over the pulse duration. We demonstrate that the use of such pulses may lead to an extreme sensitivity of the ionization process to subtle changes of the parameters of a driving XUV pulse, in particular, the ramp-on/off profile and the carrier envelope phase. We illustrate this sensitivity for atomic hydrogen and lithium driven by few-femto\-second XUV pulses with intensity in the $\rm 10^{14}~W/cm^2$ range. We argue that the observed effect is general and should modify strong-field ionization of any atom, provided the ionization rate is sufficiently high.Comment: 5 pages, 7 figure

LVCSR System on a Hybrid GPU-CPU Embedded Platform for Real-Time Dialog Applications

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Primary Sequences of Protein-Like Copolymers: Levy Flight Type Long Range Correlations

We consider the statistical properties of primary sequences of two-letter HP copolymers (H for hydrophobic and P for polar) designed to have water soluble globular conformations with H monomers shielded from water inside the shell of P monomers. We show, both by computer simulations and by exact analytical calculation, that for large globules and flexible polymers such sequences exhibit long-range correlations which can be described by Levy-flight statistics.Comment: 4 pages, including 2 figures; several references added, some formulations improve