Organic and inorganic geochemistry of Ljubija siderite deposits,NW Bosnia and Herzegovina     

Sabina Strmić Palinkaš  Jorge E. Spangenberg  Ladislav A. Palinkaš 《Mineralium Deposita》2009,44(8):893-913

The Ljubija siderite deposits, hosted by a Carboniferous sedimentary complex within the Inner Dinarides, occur as stratabound replacement-type ore bodies in limestone blocks and as siderite–sulfides veins in shale. Three principal types of ore textures have been recognized including massive dark siderite and ankerite, siderite with zebra texture, and siderite veins. The ore and host rocks have been investigated by a combination of inorganic (major, trace, and rare earth element concentrations), organic (characterization of hydrocarbons including biomarkers), and stable isotope geochemical methods (isotope ratios of carbonates, sulfides, sulfates, kerogen, and individual hydrocarbons). New results indicate a marine origin of the host carbonates and a hydrothermal–metasomatic origin of the Fe mineralization. The differences in ore textures (e.g., massive siderite, zebra siderite) are attributed to physicochemical variations (e.g., changes in acidity, temperature, and/or salinity) of the mineralizing fluids and to the succession and intensity of replacement of host limestone. Vein siderite was formed by precipitation from hydrothermal fluids in the late stage of mineralization. The equilibrium fractionation of stable isotopes reveals higher formation temperatures for zebra siderites (around 245°C) then for siderite vein (around 185°C). Sulfur isotope ratios suggest Permian seawater or Permian evaporites as the main sulfur source. Fluid inclusion composition confirms a contribution of the Permian seawater to the mineralizing fluids and accord with a Permian mineralization age. Organic geochemistry data reflect mixing of hydrocarbons at the ore site and support the hydrothermal–metasomatic origin of the Ljubija iron deposits.  相似文献   

Moldavites from the Cheb Basin, Czech Republic     

Roman Skála  Ladislav Strnad  Miroslav ?ada 《Geochimica et cosmochimica acta》2009,73(4):1145-2158

Between 1993 and 2007, an estimated 2500-3000 individual moldavite pieces have been found in the Tertiary Cheb Basin, Western Bohemia. This identifies the area as the third most prominent source of Central European tektites, next to the South Bohemian and West Moravian strewn subfields. Basic macroscopic physical properties (weight, shape, color and sculpture) were evaluated for over 350 individual finds of tektites from 4 different localities in the Cheb Basin. All these properties are similar to those observed for the South Bohemian moldavites, particularly with respect of color and weight distribution. In total, 24 tektites from the Cheb Basin have been characterized chemically using electron microprobe. For comparison, a set of 17 moldavites from the South-Bohemian and Moravian strewn subfields was measured as well. Contents of major elements overlap between the two sample sets; the largest variation was observed for iron. The trends observed in the Harker plots, however, seem to differentiate several partial subgroups, some of them characteristic for Cheb tektites only. These results are also substantiated by cluster analysis, which reveals a tight group for most of the tektites from the Cheb Basin, forming two partial clusters. The rest of the Cheb moldavites cluster with the South Bohemian samples. Minor and trace elements were measured with an LA-ICP-MS technique; CI-normalized REE patterns compare well with those for other moldavites. Many tektites, both from Cheb and South Bohemia or Moravia, display considerable heterogeneity: they frequently show schlieren and fluidal fabric. Two samples of this kind from the Cheb Basin showed considerable enrichment in volatile elements (e.g., Zn and Cu), which is typical for Muong Nong-type Australasian tektites. Mössbauer spectroscopy confirmed the highly reducing character of 5 studied moldavites. Discovery of a new moldavite strewn subfield around Cheb substantiates the theory that moldavites were ejected from the Ries impact structure in a fan-shaped jet, although it is not clear yet if it was continuous or composed of individual rays. In addition, the chemistry of the Cheb moldavites indicates significant precursor material heterogeneity.  相似文献   

Correlation between Loess profiles on the basis of mineralogical,malacological, and anthropogenic indicators: A case study from Moravany-Lopata,western Slovakia     

Maciej Pawlikowski  Witold P. Alexandrowicz  Ladislav Banesz  Josef Hromada  Janusz K. Kozlowski  Krzysztof Sobczyk  Barbara Kazior 《Geoarchaeology》1998,13(6):565-594

Moravany-Lopata, located in the complex of sites in the middle Vah basin, dates to the period immediately preceding the LGM. The authors use this site to demonstrate the usefulness of mineralogical, sedimentological, palaeomalacological, and anthropogenic criteria for the correlation of loess profiles. This analysis is especially concerned with sites in loess territories where the loess layers covering archaeological levels are not thick. Such sites occur frequently on the plateaus of the northern part of Central Europe, though they appear most notably in the areas in which the last loess cover, corresponding to the period after the last Pleniglacial and/or Late Glacial postloess sediments, is absent. The archaeological levels dated to before or directly after the LGM occur in the upper portion of the loess, overlain by the Holocene soil. The investigations at the Moravany-Lopata site have confirmed the usefulness of the anthropogenic indicators in the 0.1–1.0 mm fraction for the identification of occupation levels extending even beyond the area of occurrence of macrofinds and evident type structures. On this basis, a relationship could be established between two occupational levels and two ice-wedge generations in the period from 21.4 to 20 ky. Gravettian settlement in western Slovakia seems to have persisted up to the maximum of the LGM. Population groups representing the end of the shouldered points horizon (pointes à cran) appeared in western Slovakia in the intervals between the formation of large networks of ice wedges. The next settlement phase in that territory falls at about 18–17 ky B.P. This is the Epigravettian settlement, which is culturally unrelated to the shouldered points horizon. © 1998 John Wiley & Sons, Inc.  相似文献   

On some aspects of the albedo effect application to the ERS-1 satellite     

David Vokrouhlický  Ladislav Sehnal 《Celestial Mechanics and Dynamical Astronomy》1993,56(3):471-490

Some aspects of the perturbative influence of radiation reflected by the Earth's surface on the motion of an artificial satellite are discussed. We concentrate on consequences of the extreme models with anisotropic reflection on the Earth's surface (specular reflection, clouds with anisotropic phase function). The possible effects of Lála's modification of the Earth's albedo nominal value are investigated. The role of the satellite surface optical properties is pointed out in the context of the albedo effect. All mentioned models are purely numerical. The whole message of the paper can be summarized in the following items

-It is very doubtful that the 10^?8 ÷ 10^?9 m s^?2 level is reached when determining the perturbing accelerations caused by the albedo effect in the case of the ERS-1 satellite due to poorly defined optical characteristics of the Earth's atmosphere, the Earth and the satellite's surface.

-In the general case this albedo effect uncertainty level is about 50% with respect to the averaged values, and probably as high as 100% with respect to the instantaneous values of the perturbing accelerations.

  相似文献   

On the possibility of generating gravitational radiation by the sun     

Ladislav Křivský  Tomáš Zeithamer 《Astrophysics and Space Science》1982,85(1-2):309-313

In the present paper the gravitational radiation emitted from large solar energetic flares and from the Sun as a whole in the course of the generation shock waves and quadrupole oscillations of the solar body are studied. The expected densities of the energy fluxes of the gravitational radiation at the distance of the Earth are calculated.  相似文献   

Proton flares in the variation of the auroral electrojet in solar cycle no 21     

Ladislav Křivský  František Zloch 《Studia Geophysica et Geodaetica》1992,36(3):293-295

Summary The effects of the solar proton flare product on ionospheric circumpolar currents (Auroral Electrojet Index) for the interval 1978–1986 (solar cycle No 21) are investigated. A significant increase of the AE two days after the zero-day of appearance of the proton flare was displayed.  相似文献   

Correlation of Triassic advanced rifting-related Neotethyan submarine basaltic volcanism of the Darnó Unit (NE-Hungary) with some Dinaridic and Hellenidic occurrences on the basis of volcanological, fluid–rock interaction, and geochemical characteristics     

Gabriella Kiss  Ferenc Molnár  Ladislav A. Palinka?  Sándor Kovács  Hazim Horvatovi? 《International Journal of Earth Sciences》2012,101(6):1503-1521

Comparative volcanological, mineralogical, petrological, and geochemical studies of blocks of Triassic submarine basalt occurrences hosted by the Jurassic mélange have been carried out. The studied localities are located in displaced parts of the Dinarides in NE-Hungary (Darnó Unit), in the Dinarides (Kalnik Mts., Croatia and Vare?-Smreka, Bosnia and Herzegovina), and in the Hellenides (Stragopetra, Greece). The common characteristic of the studied occurrences is the well observable result of the lava–water-saturated sediment mingling, i.e., the presence of the so-called carbonate peperitic facies. Mixing of the basaltic lava with pelagic lime mud (representing the unconsolidated stage of the red, micritic limestone), as well as fluid inclusion and chlorite thermometry data support that the carbonate peperite was formed above CCD and at the Bosnian locality, a shallower water, about 1.4?km depth is proven. The igneous rocks show mainly within-plate basalt geochemical characteristics; MORB signatures are not common. Low temperature (<200°C) hydrothermal alteration is characteristic to the pillow basalt blocks with peperitic facies. The similarities in the volcanological, geochemical, and textural characteristics observed at the different localities support a strong genetic connection among them. The results of this study suggest to the advanced rifting stage origin of the Triassic basaltic suits and their distinction from the true oceanic basalt pillow units of the Dinarides can be based on the occurrences of the peperite facies.  相似文献   

Tests of the 2011 Tohoku earthquake source models using free-oscillation data from GOPE     

Eli?ka Zábranová  Ctirad Matyska  Ladislav Hanyk 《Studia Geophysica et Geodaetica》2012,56(2):585-594

Data from a superconducting gravimeter were obtained from the Geodetic Observatory Pecny (GOPE), Czech Republic, and compared with acceleration data from a broadband seismometer at the same location. We calculated synthetic seismograms for several point- and finite-source fast solutions of the 2011 Tohoku earthquake obtained from surface waves and tested them only against the observed gravity data because of high-noise levels in the low-frequency seismic data. We have obtained a good fit of the synthetic amplitude spectrum with the data up to 1.7 mHz without an additional increase of the moment magnitude M_w. In this aspect, the 2011 Tohoku earthquake was similar to the 2010 Maule earthquake and different from the 2004 Sumatra-Andaman earthquake, where the free-oscillations studies resulted in an increase of the early M_w values. The degree-one mode ₃S{ia1} dominates the ₃S_1?C2S_2?C1S₃ triplet at the GOPE station.  相似文献   

Motion of dust in mean motion resonances with planets     

Pavol Pástor  Jozef Klačka  Ladislav Kómar 《Celestial Mechanics and Dynamical Astronomy》2009,103(4):343-364

Effect of stellar electromagnetic radiation on the motion of spherical dust particle in mean motion orbital resonances with a planet is investigated. Planar circular restricted three-body problem with the Poynting–Robertson (P–R) effect yields monotonic secular evolution of eccentricity when the particle is trapped in the resonance. Planar elliptic restricted three-body problem with the P–R effect enables nonmonotonous secular evolution of eccentricity and the evolution of eccentricity is qualitatively consistent with the published results for the complicated case of interaction of electromagnetic radiation with nonspherical dust grain. Thus, it is sufficient to allow either nonzero eccentricity of the planet or nonsphericity of the grain and the orbital evolutions in the resonances are qualitatively equal for the two cases. This holds both for exterior and interior mean motion orbital resonances. Evolutions of argument of perihelion in the planar circular and elliptical restricted three-body problems are shown. Numerical integrations show that an analytic expression for the secular time derivative of the particle’s argument of perihelion does not exist, if only dependence on semimajor axis, eccentricity and argument of perihelion is admitted. Connection between the shift of perihelion and oscillations in secular eccentricity is presented for the planar elliptic restricted three-body problem with the P–R effect. Period of the oscillations corresponds to the period of one revolution of perihelion. Change of optical properties of the spherical grain with the heliocentric distance is also considered. The change of the optical properties: (i) does not have any significant influence on the secular evolution of eccentricity, (ii) causes that the shift of perihelion is mainly in the same direction/orientation as the particle motion around the Sun. The statements hold both for circular and noncircular planetary orbits.  相似文献   

Phantom midge-based models for inferring past fish abundances     

Kimmo?T.?TolonenEmail author  Klaus?P.?Brodersen  Tanya?A.?Kleisborg  Kerstin?Holmgren  Magnus?Dahlberg  Ladislav?Hamerlik  Heikki?H?m?l?inen 《Journal of Paleolimnology》2012,47(4):531-547

We sampled living and subfossil phantom midge (Diptera: Chaoboridae) larvae from surface sediments of 21 small lakes in Southern Sweden to examine the influence of fish and selected abiotic variables on the abundance and species composition of chaoborid assemblages. We expected total Chaoborus abundance to be inversely correlated with fish abundance and Chaoborus species most sensitive to fish predation to be found only in fishless lakes. We aimed to use the observed relationships to develop models to reconstruct past fish abundances from chaoborid remains and the abiotic environment. C. flavicans occurred in almost every lake, whereas subfossil C. obscuripes were found in the surface sediments of only one fishless lake. The density of living C. flavicans larvae correlated negatively with fish abundance, lake order and size. The concentration of C. flavicans subfossils was negatively associated with pH, lake size, water transparency and fish abundance. Regression models that included lake morphometry and landscape position as additional predictors of fish abundance performed better than models that used only Chaoborus predictors. The explained variance in fish abundance varied from 52 to 86%. Leave-one-out cross-validation indicated moderate performance of the two best models. These models explained 51 and 56% of the observed untransformed fish density and biomass, respectively. In addition, all Chaoborus models were unbiased in closely following the 1:1 reference line in plots of observed versus predicted values. These results are a promising step in developing midge-based paleolimnological reconstructions of past fish abundance, and the approach might be improved by including chironomid remains in the models.  相似文献