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101.
Miroslav Krs 《Pure and Applied Geophysics》1964,57(1):96-102
Summary The present contribution contains a brief review of palaeomagnetic investigation carried out in Czechoslovak hydrothermal deposits. So far polar wandering has been considered on the basis of palaeomagnetism of lavas and red sediments; to first approximation it agrees with palaeoclimatic data. Since the products of hydrothermal mineralizations have displayed a high stability of the magnetic parameters used in palaeomagnetism, the treatment of a greater amount of statistical material yielded data for deriving the polar wandering path during geological history. By analyzing the curve obtained it is possible to derive some geochronological conclusions concerning the age of the ore-yielding processes in the principal Czechoslovak metallogenic areas. In this way a new dating technique for products of hydrothermal mineralizations is presented based on the study of palaeomagnetic properties. At the same time, these new results are consistent with the geophysical interpretation of the polar wandering curve for Europe. 相似文献
102.
Miroslav Štemprok David Dolejš Axel Müller Reimar Seltmann 《Contributions to Mineralogy and Petrology》2008,155(1):93-109
We report new occurrences of “two-phase” granitic textures from the Western Krušné hory/Erzgebirge pluton (central Europe)
and use crystal-size distribution data and thermodynamic modeling to interpret their crystallization conditions. The two-phase
texture consists of (1) early phenocrysts of quartz, plagioclase, K-feldspar and biotite, (2) medium-grained matrix of the
same phases and (3) interstitial channels and patches of a late-stage, very fine-grained matrix. The porphyritic two-mica
microgranites, which host two-phase textures, occur as minor intrusions in early low-F biotite granites or as marginal parts
of evolved high-F Li-mica granites. Measurements of the crystal-size distribution of quartz revealed three grain populations:
(1) early phenocrysts (0.5–3.0 mm) showing partial resorption by residual melt, (2) a medium-grained population of the equigranular
rock matrix (0.05–0.50 mm) that experienced minor coarsening by subsolidus annealing and (3) a fine-grained population (<0.03 mm)
in the interstitial channels and patches formed during rapid devolatilization; this quartz group shows no or poor grain coarsening.
All samples exhibit similar fraction of the fine-grained population (44–52%) but proportions of phenocrysts to medium-grained
matrix vary significantly. Thermodynamic modeling of liquidus equilibria and experimental data in the hydrous haplogranite
system require: (1) ascent of a granitic suspension (15–25% phenocrysts) under H2O-undersaturated conditions at 25–45 bar/°C and a cooling rate of 40 J/(g kbar) in order to produce partial resorption of
quartz phenocrysts and continued growth of feldspar phenocrysts, followed by (2) emplacement as discrete intrusions or bodies
along pluton roof accompanied by sudden devolatilization. At the onset of matrix nucleation, disequilibrium undercooling of
70–85°C was inferred from the presence of micrographic intergrowths of quartz and K-feldspar. The two-phase granites in the
Western Krušné hory/Erzgebirge pluton and in the Southeast Asian batholith form compositionally narrow groups with high-silica
and moderate volatile enrichments but they differ in peraluminosity and phosphorus concentrations.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
103.
The gravity in the expansive nondecelerative universe originates in the process of permanent constant maximum possible creation of matter . 相似文献
104.
Boris Gurevich Miroslav Brajanovski Robert J. Galvin Tobias M. Müller Julianna Toms-Stewart 《Geophysical Prospecting》2009,57(2):225-237
Natural fractures in hydrocarbon reservoirs can cause significant seismic attenuation and dispersion due to wave induced fluid flow between pores and fractures. We present two theoretical models explicitly based on the solution of Biot's equations of poroelasticity. The first model considers fractures as planes of weakness (or highly compliant and very thin layers) of infinite extent. In the second model fractures are modelled as thin penny-shaped voids of finite radius. In both models attenuation is a result of conversion of the incident compressional wave energy into the diffusive Biot slow wave at the fracture surface and exhibits a typical relaxation peak around a normalized frequency of about 1. This corresponds to a frequency where the fluid diffusion length is of the order of crack spacing for the first model and the crack diameter for the second. This is consistent with an intuitive understanding of the nature of attenuation: when fractures are closely and regularly spaced, the Biot's slow waves produced by cracks interfere with each other, with the interference pattern controlled by the fracture spacing. Conversely, if fractures are of finite length, which is smaller than spacing, then fractures act as independent scatterers and the attenuation resembles the pattern of scattering by isolated cracks. An approximate mathematical approach based on the use of a branching function gives a unified analytical framework for both models. 相似文献
105.
Vladimír Bezák Josef Pek Ján Vozár Miroslav Bielik Jozef Vozár 《Studia Geophysica et Geodaetica》2014,58(3):473-488
Electrical resistivity of the Earth’s crust is sensitive to a wide range of petrological and physical parameters, and it particularly clearly indicates crustal zones that have been tectonically or thermodynamically disturbed. A complex geological structure of the Alpine nappe system, remnants of older Hercynian units and Neogene block tectonics in Western Slovakia has been a target of recent magnetotelluric investigations which made a new and more precise identification of the crustal structural elements of the Western Carpathians possible. A NW-SE magnetotelluric profile, 150 km long, with 30 broad-band and 3 long-period magnetotelluric sites, was deployed, crossing the major regional tectonic elements listed from the north: Brunia (as a part of the European platform), Outer Carpathian Flysch, Klippen Belt, blocks of Penninic or Oravicum crust, Tatricum and Veporicum. Magnetotelluric models were combined with previous seismic and gravimetric results and jointly interpreted in the final integrated geological model. The magnetotelluric models of geoelectrical structures exhibit strong correlation with the geological structures of the crust in this part of the Western Carpathians. The significant resemblance in geoelectrical and crustal geological structures are highlighted in shallow resistive structures of the covering formations represented by mainly Tertiary sediments and volcanics. Also in the deeper parts of the crust highly resistive and conductive structures are shown, which reflect the original building Hercynian crust, with superposition of granitoids or granitised complexes and lower metamorphosed complexes. Another important typical feature in the construction of the Western Carpathians is the existence of young Neogene steep fault zones exhibited by conductive zones within the whole crust. The most significant fault zones separate individual blocks of the Western Carpathians and the Western Carpathians itself from the European Platform. 相似文献
106.
Drifting pulsation structures (DPSs) are considered to be radio signatures of the plasmoids formed during magnetic reconnection in the impulsive phase of solar flares. In the present paper we analyze oscillations and waves in seven examples of drifting pulsation structures, observed by the 800?–?2000 MHz Ond?ejov Radiospectrograph. For their analysis we use a new type of oscillation maps, which give us much more information as regards processes in DPSs than that in previous analyses. Based on these oscillation maps, made from radio spectra by the wavelet technique, we recognized quasi-periodic oscillations with periods ranging from about 1 to 108 s in all studied DPSs. This strongly supports the idea that DPSs are generated during a fragmented magnetic reconnection. Phases of most the oscillations in DPSs, especially for the period around 1 s, are synchronized (“infinite” frequency drift) in the whole frequency range of DPSs. For longer periods in some DPSs we found that the phases of the oscillations drift with the frequency drift in the interval from ?17 to \(+287~\mbox{MHz}\,\mbox{s}^{-1}\). We propose that these drifting phases can be caused (a) by the fast or slow magnetosonic waves generated during the magnetic reconnection and propagating through the plasmoid, (b) by a quasi-periodic structure in the plasma inflowing to the reconnection forming a plasmoid, and (c) by a quasi-periodically varying reconnection rate in the X-point of the reconnection close to the plasmoid. 相似文献
107.
The Lateglacial and Holocene in Central Europe: a multi‐proxy environmental record from the Bohemian Forest,Czech Republic
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Klára Vočadlová Libor Petr Pavla Žáčková Marek Křížek Lenka Křížová Simon M. Hutchinson Miroslav Šobr 《Boreas: An International Journal of Quaternary Research》2015,44(4):769-784
The Hercynian mountain ranges were islands of mountain glaciation and alpine tundra in a Central European ice‐free corridor during the Late Pleistocene. Today they are notable areas of glacial landforms, alpine‐forest free areas, peatlands and woodlands. However, our knowledge of the Lateglacial and early Holocene environmental changes in this region is limited. We present a new multi‐proxy reconstruction of a mid‐altitude environment in the Bohemian Forest spanning this period. A core (5.2 m length) in the ?erné Lake cirque (1028 m a.s.l.) was subjected to lithological, geochemical, pollen and macrofossil analysis supplemented by two optically stimulated luminescence (OSL) and 10 AMS radiocarbon dates. We determined the impact of regional and supraregional climate changes on the environment. The two most significant changes in sedimentation during the Lateglacial (17.6 and 15.8–15.5 cal. ka BP) were synchronous with regional glacial chronostratigraphy. Unlike Central European mountain ranges, in the Bohemian Forest the Younger Dryas was not coincident with glacier re‐advance, but was a dry, cold episode with low lake levels, which prevailed until the early Preboreal. Plant macrofossils indicate local establishment of Betula nana and Betula pendula/pubescens at 15.4–13.4 cal. ka BP. Comparison with Holocene records from Central Europe shows a similar immigration history of vegetation at mid and higher altitudes. The tree line exceeded an altitude of ~1000 m a.s.l. around 10.5 cal. ka BP and coincided with rapid geochemical changes in the sediment. The 8.2 ka BP event did not have any response in the sedimentary record, but corresponded to stabilization of the Picea abies population and expansion of Fagus. Fagus colonized the Bohemian Forest earlier than other Hercynian mid‐mountains, but never predominated in the composition of the forest at higher elevations. Abies alba was the last tree species that immigrated to the study area. 相似文献
108.
Miroslav Trnka Josef Eitzinger Daniela Semer��dov�� Petr Hlavinka Jan Balek Martin Dubrovsky Gerhard Kubu Petr ?t��p��nek Sabina Thaler Martin Mo?ny Zden��k ?alud 《Climatic change》2011,108(1-2):261-289
During the past few decades, the basic assumption of agroclimatic zoning, i.e., that agroclimatic conditions remain relatively stable, has been shattered by ongoing climate change. The first aim of this study was to develop a tool that would allow for effective analysis of various agroclimatic indicators and their dynamics under climate change conditions for a particular region. The results of this effort were summarized in the AgriClim software package, which provides users with a wide range of parameters essential for the evaluation of climate-related stress factors in agricultural crop production. The software was then tested over an area of 114,000 km2 in Central Europe. We have found that by 2020, the combination of increased air temperature and changes in the amount and distribution of precipitation will lead to a prolonged growing season and significant shifts in the agroclimatic zones in Central Europe; in particular, the areas that are currently most productive will be reduced and replaced by warmer but drier conditions in the same time the higher elevations will most likely experience improvement in their agroclimatic conditions. This positive effect might be short-lived, as by 2050, even these areas might experience much drier conditions than observed currently. Both the rate and the scale of the shift are amazing as by 2020 (assuming upper range of the climate change projections) only 20?C38% of agriculture land in the evaluated region will remain in the same agroclimatic and by 2050 it might be less than 2%. On the other hand farmers will be able to take advantage of an earlier start to the growing season, at least in the lowland areas, as the proportion of days suitable for sowing increases. As all of these changes might occur within less than four decades, these issues could pose serious adaptation challenges for farmers and governmental policies. The presented results also suggest that the rate of change might be so rapid that the concept of static agroclimatic zoning itself might lose relevance due to perpetual change. 相似文献
109.
Miroslav Boboň Alfred A. Christy Daniel Kluvanec L’udmila Illášová 《Physics and Chemistry of Minerals》2011,38(10):809-818
Recently, near infrared spectroscopy in combination with double derivative technique has been effectively used by Christy
(Vib Spectrosc 54:42–49, 2010) to study and differentiate between free and hydrogen bonded silanol groups on silica gel surface. The method has given some
insight into the type of functionalities, their location in silica gel samples, and the way the water molecules bind onto
the silanol groups. The important information in this respect comes from the overtones of the OH groups of water molecules
hydrogen-bonded to free silanol groups, and hydrogen-bonded silanol groups absorbing in the region 5,500–5,100 cm−1. Chemically, opal minerals are hydrated silica and the same approach was adapted to study the state of water molecules, silanol
functionalities, and their locations in opal samples from Slovakia. Twenty opal samples classified into CT and A classes and
one quartz sample were used in this work. The samples were crushed using a hydraulic press and powderized. Each sample was
then subjected to evacuation process to remove surface-adsorbed water at 200°C, and the near infrared spectrum of each sample
was measured using a Perkin Elmer NTS FT-NIR spectrometer equipped with a transflectance accessory and a DTGS detector. The
samples were also heated to 750°C to remove the hydrogen-bonded silanol groups on the surface to reveal their locality. Second
derivative profiles of the near infrared reflectance spectra were obtained using the instrument’s software and used in the
detailed analysis of the samples. The analysis of the near infrared spectra and their second derivative profiles had the aim
in finding relationships between the surface chemical structure and the classification of opal samples. The dry opal samples
were also tested for their surface adsorption effectivity toward water molecules. The results indicate that the opal samples
contain (1) surface-adsorbed water, (2) free and hydrogen-bonded silanol groups on the surface, (3) trapped water molecules
in the bulk, and (4) free and hydrogen-bonded silanol groups in the cavity surfaces in the bulk. A part of the water molecules
in the bulk of opal minerals are found as free molecules and the rest are found in hydrogen-bonded state to either free or
vicinal or geminal silanol groups. 相似文献
110.