Disturbance of ionosphere during American high-altitude nuclear explosion of 9. 7. 1962 indicated by atmospherics in central Europe     

Ladislav Křivský 《Studia Geophysica et Geodaetica》1963,7(3):296-298

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Geochemistry and Evolution of Subcontinental Lithospheric Mantle in Central Europe: Evidence from Peridotite Xenoliths of the Kozakov Volcano, Czech Republic     

Ackerman  Lukas; Mahlen  Nancy; JelInek  Emil; Medaris  Gordon  Jr; Ulrych  Jaromir; Strnad  Ladislav; MihaljeviC  Martin 《Journal of Petrology》2007,48(12):2235-2260

Neogene basanite lavas of Kozákov volcano, located alongthe Lusatian fault in the northeastern Czech Republic, containabundant anhydrous spinel lherzolite xenoliths that providean exceptionally continuous sampling of the upper two-thirdsof central European lithospheric mantle. The xenoliths yielda range of two-pyroxene equilibration temperatures from 680°Cto 1070°C, and are estimated to originate from depths of32–70 km, based on a tectonothermal model for basalticunderplating associated with Neogene rifting. The sub-Kozákovmantle is layered, consisting of an equigranular upper layer(32–43 km), a protogranular intermediate layer that containsspinel–pyroxene symplectites after garnet (43–67km), and an equigranular lower layer (67–70 km). Negativecorrelations of wt % TiO₂, Al₂O₃, and CaO with MgO and clinopyroxenemode with Cr-number in the lherzolites record the effects ofpartial fusion and melt extraction; Y and Yb contents of clinopyroxeneand the Cr-number in spinel indicate 5 to 15% partial melting.Subsequent metasomatism of a depleted lherzolite protolith,probably by a silicate melt, produced enrichments in the largeion lithophile elements, light rare earth elements and highfield strength elements, and positive anomalies in primitivemantle normalized trace element patterns for P, Zr, and Hf.Although there are slight geochemical discontinuities at theboundaries between the three textural layers of mantle, theretends to be an overall decrease in the degree of depletion withdepth, accompanied by a decrease in the magnitude of metasomatism.Clinopyroxene separates from the intermediate protogranularlayer and the lower equigranular layer yield ¹⁴³Nd/¹⁴⁴Nd valuesof 0·51287–0·51307 (_Nd = +4·6 to+8·4) and ⁸⁷Sr/⁸⁶Sr values of 0·70328–0·70339.Such values are intermediate with respect to the Nd–Srisotopic array defined by anhydrous spinel peridotite xenolithsfrom central Europe and are similar to those associated withthe present-day low-velocity anomaly in the upper mantle beneathEurope. The geochemical characteristics of the central Europeanlithospheric mantle reflect a complex evolution related to Devonianto Early Carboniferous plate convergence, accretion, and crustalthickening, Late Carboniferous to Permian extension and gravitationalcollapse, and Neogene rifting, lithospheric thinning, and magmatism. KEY WORDS: xenoliths; lithospheric mantle; REE–LILE–HFSE; Sr–Nd isotopes; Bohemian Massif  相似文献   

Methodology of flood risk assessment from flash floods based on hazard and vulnerability of the river basin   总被引：1，自引：1，他引：0  

Martina Zeleňáková  Lenka Gaňová  Pavol Purcz  Ladislav Satrapa 《Natural Hazards》2015,79(3):2055-2071

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Lead Isotopic Composition in Biogenic Certified Reference Materials Determined by Different ICP‐based Mass Spectrometric Techniques          下载免费PDF全文

Jana Ďurišová  Lukáš Ackerman  Ladislav Strnad  Vladislav Chrastný  Jan Borovička 《Geostandards and Geoanalytical Research》2015,39(2):209-220

This work presents data for the radiogenic Pb isotopic ratios (²⁰⁶Pb/²⁰⁷Pb and ²⁰⁸Pb/²⁰⁶Pb) in nine biogenic certified reference materials (NIST SRM 1515, 1566b, 1570a, 1573a, 1575a; BCR 100, BCR 101, BCR 670 and IAEA 359), which are suitable for analytical quality control in environmental research. The results were obtained using three different types of ICP‐based mass spectrometer (quadrupole‐based/magnetic sector field single‐collector ICP‐MS instruments and a multi‐collector ICP‐MS) and applying different mass bias correction procedures (calibrator‐sample bracketing and external Tl normalisation) with and without Pb separation from the matrix using ion exchange chromatography. In the majority of the samples, the measurements from all three of the ICP‐MS instruments were in agreement within ± 0.1%, despite the lower analytical precision of the single‐collector ICP‐MS instruments. We demonstrate that the presence of the sample matrix did not significantly influence the Pb isotopic ratios measured by magnetic sector field ICP‐MS, whereas the use of the two different mass bias corrections resulted in a systematic difference of 0.09% for the ²⁰⁸Pb/²⁰⁶Pb ratio.  相似文献   

Early Pragian conodont‐based correlations between the Barrandian area and the Spanish Central Pyrenees     

Ladislav Slavík  Jos Ignacio Valenzuela‐Ríos  Jind&#x;ich Hladil  Peter Carls 《Geological Journal》2007,42(5):499-512

Occurrences and distribution of extremely scarce eognathodontids do not facilitate reliable correlation across the European regions. The correlation of the traditional early Pragian of the Prague Synform (a part of the classical Barrandian area) and the Spanish Central Pyrenees (section Segre 1) is based on conodont taxa of the Icriodus steinachensis and the Pelekysgnathus serratus stocks. This correlation has the potential to be extended to other peri‐Gondwanan regions where this scarcity of eognathodontid faunas exists as well. Application of the morphotype subdivision in I. steinachensis enables approximation of the beginning of the Pragian in the Pyrenees. It is based on the entry of I. steinachensis beta morphotype; it enters together with early eognathodontid taxa in the Barrandian sections. These correlations show that routine application of certain zonal concepts can lead to misleading conclusions. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

The Problem of Viscoelastic Relaxation of the Earth Solved by a Matrix Eigenvalue Approach Based on Discretization in Grid Space     

Ladislav Hanyk  Ctirad Matyska  David A. Yuen 《Visual Geosciences》2000,5(4):1-11

Viscoelasticity is a geophysical process which operates over intermediate timescales between a few years to millions of years, depending on the ambient thermal conditions of the self-gravitating spherical planet. Topography undulations with time represent geological signatures to both the internal and external loading processes, such as post-glacial rebound, volcanic eruptions, sedimentary loading, meteoritic impacts and mountain building. The span of relaxation timescales or relaxation spectrum in a viscoelastic spherical body has traditionally been determined by employing the Laplacian transform method and the correspondence principle relating the elastic solution to its viscoelastic counterpart.We have devised a novel approach based on the method of lines in which the equations at each angular order in the spherical harmonic expansion are discretized in the radial co-ordinate. The finite-dimensional space spanned by the discretized points in the radial direction of the planetary model then forms the basis of a matrix Eigenvalue problem. The Eigenvalues can be computed very fast because of the availability of public domain software. We can, for instance, compute the entire range of viscoelastic relaxation with computational times from 0.05 to 50 sec using only 30 to 300 radial grid points. The models can have both realistic density and elastic parameter profiles, derived from seismology. We show results here for complicated viscosity profiles with an asthenosphere in the upper mantle and a viscosity hill in the middle portion of the lower mantle. Because of the rapidity of the code, we may use this new method for exploring non-linear inversion problems by parameter sweeping.  相似文献   

Climate change scenarios of precipitation extremes in Central Europe from ENSEMBLES regional climate models     

Jan Kyselý  Ladislav Gaál  Romana Beranová  Eva Plavcová 《Theoretical and Applied Climatology》2011,104(3-4):529-542

The study examines future scenarios of precipitation extremes over Central Europe in an ensemble of 12 regional climate model (RCM) simulations with the 25-km resolution, carried out within the European project ENSEMBLES. We apply the region-of-influence method as a pooling scheme when estimating distributions of extremes, which consists in incorporating data from a ‘region’ (set of gridboxes) when fitting an extreme value distribution in any single gridbox. The method reduces random variations in the estimates of parameters of the extreme value distribution that result from large spatial variability of heavy precipitation. Although spatial patterns differ among the models, most RCMs simulate increases in high quantiles of precipitation amounts when averaged over the area for the late-twenty-first century (2070–2099) climate in both winter and summer. The sign as well as the magnitude of the projected change vary only little for individual parts of the distribution of daily precipitation in winter. In summer, on the other hand, the projected changes increase with the quantile of the distribution in all RCMs, and they are negative (positive) for parts of the distribution below (above) the 98% quantile if averaged over the RCMs. The increases in precipitation extremes in summer are projected in spite of a pronounced drying in most RCMs. Although a rather general qualitative agreement of the models concerning the projected changes of precipitation extremes is found in both winter and summer, the uncertainties in climate change scenarios remain large and would likely further increase considerably if a more complete ensemble of RCM simulations driven by a larger suite of global models and with a range of possible scenarios of the radiative forcing is available.  相似文献   

Geochemistry of the Drahotín and Mutěnín intrusions, West Bohemian shear zone, Bohemian massif: contrasting evolution of mantle-derived melts     

Lukáš Ackerman  Martina Krňanská  Wolfgang Siebel  Ladislav Strnad 《Mineralogy and Petrology》2010,99(3-4):185-199

In western Bohemia, the Drahotín (gabbro-diorite) and Mutěnín (gabbronorite-diorite-syenite) intrusions show different origins and patterns of geochemical evolution. Parental magmas of the Drahotín intrusion were derived predominantly from enriched mantle sources, and the melts have undergone a significant degree of assimilation-fractional crystallization (AFC) during their ascent and/or emplacement into the crust. In contrast, the compositional variation of the complex Mutěnín intrusion cannot be explained by simple AFC processes, but more likely reflects the involvement of several parental magmas. The gabbronorite was derived from a depleted mantle source, whereas the diorite/syenite stem from a mixed mantle-crust reservoir. The contrasting evolution of the Drahotín and Mutěnín intrusions may be due to their melt derivation and magma emplacement under different tectonothermal regimes at different times.  相似文献   

Ccd Photometry of Neglected Eclipsing Binaries – Kz Dra, Lr Cam and Im Vul     

Ondřej Pejcha  David Motl  Miloslav Zejda  Karel Koss  Jitka KudrnÁčovÁ  Petr HÁjek  Ladislav Šmelcer  Pavol A. Dubovský  Eva ŠafÁřovÁ  Marek Wolf 《Astrophysics and Space Science》2005,296(1-4):285-288

We present ephemerides and solutions of one Algol-type (KZ Dra) and two overcontact systems (LR Cam and IM Vul) based on V(RI)_C CCD observations obtained in the project Prosper (network of amateur observers).  相似文献   

Cloud coverage aspects of the albedo effect     

David Vokrouhlický  Ladislav Sehnal 《Celestial Mechanics and Dynamical Astronomy》1993,57(3):493-508

We discuss some details of the cloud coverage aspects of the albedo effect — the pressure of the radiation reflected by the Earth — on the motion of an artificial satellite. We focus on modeling of the Earth's surface reflection and propagation of the radiation through the atmosphere. We adopt analytical models of these phenomena from radiative transfer theory, in contrast to earlier approaches, based on the fitting of satellite photometry data. We perform several computations based on the accepted models for the ERS-1 and MACEK satellites to test the hierarchy of importance of the effects investigated. In the case of the MACEK mission (which carried a precision accelerometer on board) this information might be essential when interpreting the data.  相似文献