Crystal fractionation in the petrogenesis of an alkali monzodiorite–syenite series: the Oshurkovo plutonic sheeted complex, Transbaikalia, Russia     

Boris A. Litvinovsky  Bor-ming Jahn  Ada N. Zanvilevich  Michael G. Shadaev 《Lithos》2002,64(3-4):97-130

The Oshurkovo Complex is a plutonic sheeted complex which represents numerous successive magmatic injections into an expanding system of subparallel and subvertical fractures. It comprises a wide range of rock types including alkali monzodiorite, monzonite, plagioclase-bearing and alkali-feldspar syenites, in the proportion of about 70% mafic rocks to 30% syenite. We suggest that the variation within the complex originated mainly by fractional crystallization of a tephrite magma.

The mafic rocks are considered as plutonic equivalents of lamprophyres. They exhibit a high abundance of ternary feldspar and apatite, the latter may attain 7–8 vol.% in monzodiorite. Ternary feldspar is also abundant in the syenites. The entire rock series is characterized by high Ba and Sr concentrations in the bulk rock samples (3000–7000 ppm) and in feldspars (up to 1 wt.%). The mafic magma had amphibole at the liquidus at 1010–1030 °C based on amphibole geothermometer. Temperatures as low as this were due to high H₂O and P₂O₅ contents in the melt (up to 4–6 and 2 wt.%, respectively). Crystallization of the syenitic magmas began at about 850 °C (based on ternary feldspar thermometry). The series was formed at an oxygen fugacity from the NNO to HM buffer, or even higher.

The evolution of the alkali monzodiorite–syenite series by fractional crystallization of a tephritic magma is established on the basis of geological, mineralogical, geochemical and Sm–Nd and Rb–Sr isotope data. The geochemical modeling suggests that fractionation of amphibole with subordinate apatite from the tephrite magma leaves about 73 wt.% of the residual monzonite melt. Further extraction of amphibole and plagioclase with minor apatite and Fe–Ti oxides could bring to formation of a syenite residuum. Rb–Sr isotopic analyses of biotite, apatite and whole-rock samples constrain the minimum age of basic intrusions at ca. 130 Ma and that of cross-cutting granite pegmatites at ca. 120 Ma. Hence the entire evolution took place in an interval of ≤10 My. Initial ⁸⁷Sr/⁸⁶Sr ratios for the mafic rocks range from 0.70511 to 0.70514, and for syenites from 0.70525 to 0.70542. Initial _Nd (130 Ma) values for mafic rocks vary from −1.9 to −2.4, and for syenites from −2.9 to −3.5. In a _Nd(T) vs. (⁸⁷Sr/⁸⁶Sr)_i diagram, all rock types of the complex fall in the enriched portion of the Mantle Array, suggesting their derivation from a metasomatized mantle source. However, the small but distinguishable difference in Sr and Nd isotopic compositions between mafic rocks and syenites probably resulted from mild (10–20%) crustal contamination during differentiation. Large negative Nb anomalies are interpreted as a characteristic feature of the source region produced by Precambrian fluid metasomatism above a subduction zone rather than by crustal contamination.  相似文献   

Probabilistic yielding and cyclic behavior of geomaterials     

Kallol Sett  Boris Jeremić 《国际地质力学数值与分析法杂志》2010,34(15):1541-1559

In this paper, the novel concept of probabilistic yielding is used for 1‐D cyclic simulation of the constitutive behavior of geomaterials. Fokker–Planck–Kolmogorov equation‐based probabilistic elastic–plastic constitutive framework is applied for obtaining the complete probabilistic (probability density function) material response. Both perfectly plastic and hardening‐type material models are considered. It is shown that when uncertainties in material parameters are taken into consideration, even the simple, elastic‐perfectly plastic model captures some of the important features of geomaterial behavior, for example, modulus reduction with cyclic strain, which, deterministically, is only possible with more advanced constitutive models. Furthermore, it is also shown that the use of isotropic and kinematic hardening rules does not significantly improve the probabilistic material response. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Potential forest fire danger over Northern Eurasia: Changes during the 20th century   总被引：4，自引：1，他引：3  

Pavel Ya. Groisman  Boris G. Sherstyukov  Vyacheslav N. Razuvaev  Richard W. Knight  Jesse G. Enloe  Nina S. Stroumentova  Paul H. Whitfield  Eirik Frland  Inger Hannsen-Bauer  Heikki Tuomenvirta  Hans Aleksandersson  Anna V. Mescherskaya  Thomas R. Karl 《Global and Planetary Change》2007,56(3-4):371

Significant climatic changes over Northern Eurasia during the 20th century have been reflected in numerous variables of economic, social, and ecological interest, including the natural frequency of forest fires. For the former USSR, we are now using the Global Daily Climatology Network and a new Global Synoptic Data Network archive, GSDN, created jointly by U.S. National Climatic Data Center and Russian Research Institute for Hydrometeorological Information. Data from these archives (approximately 1500 of them having sufficiently long meteorological time series suitable for participation in our analyses) are employed to estimate systematic changes in indices used in the United States and Russia to assess potential forest fire danger. We use four indices: (1) Keetch–Byram Drought Index, (KBDI; this index was developed and widely used in the United States); (2) Nesterov, (3) Modified Nesterov, and (4) Zhdanko Indices (these indices were developed and widely used in Russia). Analyses show that after calibration, time series of the days with increased potential forest fire danger constructed using each of these three indices (a) are well correlated and (b) deliver similar conclusions about systematic changes in the weather conditions conducive to forest fires. Specifically, over the Eastern half of Northern Eurasia (Siberia and the Russian Far East) statistically significant increases in indices that characterize the weather conditions conducive to forest fires were found. These areas coincide with the areas of most significant warming during the past several decades south of the Arctic Circle. West of the Ural Mountains, the same indices show a steady decrease in the frequency of “dry weather summer days” during the past 60 yr. This study is corroborated with available statistics of forest fires and with observed changes in drought statistics in agricultural regions of Northern Eurasia.  相似文献   

Detecting short-term evolution of Etnean scoria cones: a LIDAR-based approach   总被引：1，自引：1，他引：0  

Alessandro Fornaciai  Boris Behncke  Massimiliano Favalli  Marco Neri  Simone Tarquini  Enzo Boschi 《Bulletin of Volcanology》2010,72(10):1209-1222

The 2001 and 2002–2003 flank eruptions on Mount Etna (Italy) were characterized by intense explosive activity which led to the formation of two large monogenetic scoria cones (one from each eruption) on the upper southern flank of the volcano. Continuous monitoring of Etna, especially during flank eruptions, has provided detailed information on the growth of these cones. They differ in genesis, shape, and size. A set of high resolution (1 m) digital elevation models (DEMs) derived from light detection and ranging (LIDAR) data collected during four different surveys (2004, 2005, 2006, and 2007) has been used to map morphology and to extract the morphometric parameters of the scoria cones. By comparing LIDAR-derived DEMs with a pre-eruption (1998) 10 m DEM, the volume of the two scoria cones was calculated for the first time. Comparison of the LIDAR-derived DEMs revealed in unprecedented detail morphological changes during scoria cone degradation. In particular, the morphologically more exposed and structurally weaker 2002–2003 cone was eroded rapidly during the first few years after its emplacement mainly due to gravitational instability of slopes and wind erosion.  相似文献   

Tides in marginal seasA special issue in memory of Professor Alexei V. Nekrasov     

Alexander B. Rabinovich  Michael G.G. Foreman  Boris A. Kagan  Josef Y. Cherniawsky 《Continental Shelf Research》2010

  相似文献   

Alexei Vsevolodovich Nekrasov (1933–2008)     

Lev N. Karlin  Nikolai L. Plink  Boris A. Kagan 《Continental Shelf Research》2010

  相似文献   

Fuzzy-probabilistic calculations of water-balance uncertainty   总被引：1，自引：0，他引：1  

Boris Faybishenko 《Stochastic Environmental Research and Risk Assessment (SERRA)》2010,24(6):939-952

Hydrogeological systems are often characterized by imprecise, vague, inconsistent, incomplete, or subjective information, which may limit the application of conventional stochastic methods in predicting hydrogeologic conditions and associated uncertainty. Instead, predictions and uncertainty analysis can be made using uncertain input parameters expressed as probability boxes, intervals, and fuzzy numbers. The objective of this paper is to present the theory for, and a case study as an application of, the fuzzy-probabilistic approach, combining probability and possibility theory for simulating soil water balance and assessing associated uncertainty in the components of a simple water-balance equation. The application of this approach is demonstrated using calculations with the RAMAS Risk Calc code, to assess the propagation of uncertainty in calculating potential evapotranspiration, actual evapotranspiration, and infiltration—in a case study at the Hanford site, Washington, USA. Propagation of uncertainty into the results of water-balance calculations was evaluated by changing the types of models of uncertainty incorporated into various input parameters. The results of these fuzzy-probabilistic calculations are compared to the conventional Monte Carlo simulation approach and estimates from field observations at the Hanford site.  相似文献   

Geophysical flows with anisotropic turbulence and dispersive waves: flows with a β-effect     

Boris Galperin  Semion Sukoriansky  Nadejda Dikovskaya 《Ocean Dynamics》2010,60(2):427-441

Geostrophic turbulence is a key paradigm in the current understanding of the large-scale planetary circulations. It implies that a flow is turbulent, rotating, stably stratified, and in near-geostrophic balance. When a small-scale forcing is present, geostrophic turbulence features an inverse energy cascade. When the meridional variation of the Coriolis parameter (or a β-effect) is included, the horizontal flow symmetry breaks down giving rise to the emergence of jet flows. The presence of a large-scale drag ensures that the flow attains a steady state. Dependent on the governing parameters, four steady-state flow regimes are possible, two of which are considered in this study. In one of these regimes, a flow is dominated by the drag while in the other one, the recently discovered regime of zonostrophic turbulence, a flow becomes strongly anisotropic and features slowly evolving systems of alternating zonal jets. Zonostrophic turbulence is distinguished by anisotropic inverse energy cascade and emergence of a new class of nonlinear waves known as zonons. In addition, meridional scalar diffusion is strongly modified in this regime. This paper provides an overview of various regimes of turbulence with a β-effect, elaborates main characteristics of friction-dominated and zonostrophic turbulence, elucidates the physical nature of the zonons, discusses the meridional diffusion processes in different regimes, and relates these results to oceanic observations.  相似文献   

Midges of the genus Pseudodiamesa Goetghebuer (Diptera, Chironomidae): current knowledge and palaeoecological perspective     

Boris P. Ilyashuk  Elena A. Ilyashuk  Eugeny A. Makarchenko  Oliver Heiri 《Journal of Paleolimnology》2010,44(2):667-676

Larvae of the genus Pseudodiamesa Goetghebuer, which includes 12 described valid species and is divided by Makarchenko and Makarchenko (1999) into two species groups, Pseudodiamesa branickii group and Pseudodiamesa nivosa group, are widespread in lakes and running waters of cold, high-latitude and high-altitude areas of the Northern Hemisphere. Larval remains of the genus are often found in subfossil assemblages from these cold regions, but intra-genus morphotypes usually are not distinguished by palaeoecologists. Current knowledge of the ecology of the species indicates that the Pseudodiamesa nivosa group is more cold-adapted than the Pseudodiamesa branickii group and, therefore, these two intra-genus morphotypes cannot be amalgamated into a larger taxonomic unit without losing substantial information. Here we present the morphological characters of head capsules of Pseudodiamesa larvae attributed to the different species-group morphotypes, which are clearly visible in subfossil specimens. The information summarized in this paper will help provide more reliable chironomid-based palaeoclimatic inferences from lake sediment records covering colder phases through the late Quaternary in the Northern Hemisphere.  相似文献   

Regularization in the Ideal Resonance Problem     

Boris Garfinkel 《Celestial Mechanics and Dynamical Astronomy》1972,5(2):189-203

The Ideal Resonance Problem, defined by the HamiltonianF=B(y)+2A (y) sin² x, 1, has been solved in Garfinkelet al. (1971). There the solution has beenregularized by means of a special function _j , introduced into the new HamiltonianF, under the tacit assumption thatA anB¨' are of order unity.This assumption, violated in some applications of the theory, is replaced here by the weaker assumption ofnormality, which admits zeros ofA andB inshallow resonance. It is shown here that these zeros generate singularities, which can be suppressed if _j is suitably redefined.With the modified _j , and with the assumption of normality, the solution is regularized for all values ofB, B¨', andA. As in the previous paper, the solution isglobal, including asymptotically the classical limit withB as a divisor of O(1).A regularized first-order aloorithm is constructed here as an illustration and a check.Presented at the XXII International Congress of I.A.F., Brussels, Belgium, Sept. 20, 1971.  相似文献