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Ductile extensional movements along the steeply inclined Hoher-Bogen shear zone caused the juxtaposition of Teplá-Barrandian
amphibolites, granulites, and metaperidotites against Moldanubian mica schists and paragneisses. Garnet pyriclasites are well
preserved within low-strain domains of this shear zone. Their degree of metamorphism is significantly higher than that of
the surrounding rocks. Microstructural and mineral chemical data suggest in situ formation of the garnet pyriclasite by dehydration
of pyroxene amphibolite at T>750–840°C and P<10–13 kbar including recrystallization-accommodated grain-size reduction of plagioclase
and clinopyroxene, nucleation of garnet, and breakdown of amphibole into garnet+clinopyroxene+rutile. Subsequent decompression
and retrograde extensional shearing led to the formation of mylonitic epidote amphibolite. The presence of lower crustal and
mantle-derived slices within the Hoher-Bogen shear zone supports the view that (a) in Upper Devonian times the Teplá-Barrandian
unit was thrust over Moldanubian rocks as a complete crustal unit, and (b) that during the subsequent Lower Carboniferous
orogenic collapse, the garnet pyriclasite and metaperidotite were scraped off from the basal parts of the Teplá-Barrandian
unit being dragged into the Hoher-Bogen shear zone due to dramatic and large-scale elevator-style movements.
Received: 23 March 1999 / Accepted: 25 August 1999 相似文献
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Photometry and spectrophotometry of the proper motion star G 82-23 are presented. A comparison with subdwarfs and white dwarfs in the same range of temperature shows only partial agreement. If the parallax is taken into account, the best explanation of this object seems to be a binary structure with a K-subdwarf and a DC-white dwarf.Communication presented at the International Conference on Astrometric Binaries, held on 13–15 June, 1984, at the Remeis-Sternwarte Bamberg, Germany, to commemorate the 200th anniversary of the birth of Friedrich Wilhelm Bessel (1784–1846). 相似文献
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The behaviour and estimation of pollutant transport with water in an aquifer are based on the determination of displacement parameters (velocity field, dispersion tensor, kinematic porosity, etc.). We consider the one-dimensional and isothermal displacement of two miscible fluids through an isotropic and homogeneous porous medium in mechanical dispersion. An in situ measurement technique coupled with an impulse response method is used to verify the theoretical solution in the error function (trace case). With viscosity and density gradients, experimental and numerical (application of instability criterion) results are in good agreement. For a quasi-stable displacement, we have shown an asymptotic dispersion regime. The localization of a pollutant front in the studied configuration, is discussed.
Abstract
Le transfert d'un polluant par l'eau dans un milieu naturel repose sur la détermination des paramètres de déplacement (champ des vitesses tenseur de dispersion, porosité cinematique, ...). On considère un écoulement unidimensionnel et isotherme de deux fluides miscibles dans un milieu poreux homogène et isotrope en régime de dispersion mécanique. Une technique de mesure in situ couplée avec une méthode de réponse impulsionnelle a permis de vérifier la solution analytique en fonction erreur (cas du traceur). Dans le cas d'un déplacement avec contrastes de densité et de viscosité, les résultats expérimentaux et numériques (application d'un critère d'instabilité) concordent. Pour un déplacement quasi-stable, nous avons mis en évidence un régime de dispersion asymptotique. Nous analysons, ensuite, la localisation d'un front de pollution dans la configuration étudiée. 相似文献
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The West Bohemian shear zone (WBSZ) forms a steep collapse structure along which east-side-down normal movements led to the juxtaposition of the relatively cold Cadomian basement of the Tepla-Barrandian unit against high grade Moldanubian rocks. Synkinematic plutons straddle the WBSZ. The Mut3nin pluton intruded into Moldanubian crust at a depth of 23dž km as derived by using Al-in-hornblende barometry. The Tepla-Barrandian Babylon pluton intruded at <12 km depth as indicated by phengite barometry and petrogenetic considerations. Both emplacement depths, together with mineral cooling ages, result in a minimum vertical displacement of 10 km between 340 and 320 Ma. This large throw could be explained by over-thickened crust that was weakened from below. The alkaline signature of the Mut3nin diorite indicates that mantle melting was important to thermally weaken the crust at 340 Ma. The cold Tepla-Barrandian upper crust sank into its weak, partly molten Moldanubian substratum, resulting in elevator-style movements, not only along the WBSZ, but also along the Hoher Bogen and Central Bohemian shear zone. All these ductile normal shear zones were active simultaneously during the Lower Carboniferous and dip steeply towards the Tepla-Barrandian unit that probably formed a highly elevated plateau at this time. 相似文献
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I. Bues 《Astrophysics and Space Science》1987,130(1-2):75-79
During a photometric and spectrophotometric survey of 200 white dwarf candidates with mpg<15m.0 in a field around the South Galactic Pole two new cataclysmic variables have been identified and new observations of one already known object have been accumulated. Observations in the visible and UV-region show variability and differences in spectral type. If compared to the numbers of cataclysmic variables/white dwarfs as computed by Ritter and Burkert (1985) there is a shortage of a factor of 5.Paper presented at the IAU Colloquium No. 93 on Cataclysmic Variables. Recent Multi-Frequency Observations and Theoretical Developments, held at Dr. Remeis-Sternwarte Bamberg, F.R.G., 16–19 June, 1986. 相似文献
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The igneous complex of Neukirchen–Kdyn
is located in the southwestern part of the Teplá–Barrandian unit (TBU) in the Bohemian Massif. The TBU forms the most extensive surface exposure of Cadomian basement in central Europe. Cambrian plutons show significant changes in composition, emplacement depth, isotopic cooling ages, and tectonometamorphic overprint from NE to SW. In the NE, the V
epadly granodiorite and the Smr
ovice diorite intruded at shallow crustal levels (<ca. 7 km depth) as was indicated by geobarometric data. K–Ar age data yield 547±7 and 549±7 for hornblende and 495±6 Ma for biotite of the Smr
ovice diorite, suggesting that this pluton has remained at shallow crustal levels (T<ca. 350 °C) since its Cambrian emplacement. A similar history is indicated for the V
epadly granodiorite and the Stod granite. In the SW, intermediate to mafic plutons of the Neukirchen–Kdyn
massif (V
eruby and Neukirchen gabbro, Hoher–Bogen metagabbro), which yield Cambrian ages, either intruded or were metamorphosed at considerably deeper structural levels (>20 km). The Teufelsberg (
ert
v kámen) diorite, on the other hand, forms an unusual intrusion dated at 359±2 Ma (concordant U–Pb zircon age). K–Ar dating of biotite of the Teufelsberg diorite yields 342±4 Ma. These ages, together with published cooling ages of hornblende and mica in adjacent plutons, are compatible with widespread medium to high-grade metamorphism and strong deformation fabrics, suggesting a strong Variscan impact under elevated temperatures at deeper structural levels. The plutons of the Neukirchen area are cut by the steeply NE dipping Hoher–Bogen shear zone (HBSZ), which forms the boundary with the adjacent Moldanubian unit. The HBSZ is characterized by top-to-the-NE normal movements, which were particularly active during the Lower Carboniferous. A geodynamic model is presented that explains the lateral gradients in Cambrian pluton composition and emplacement depth by differential uplift and exhumation, the latter being probably related to long-lasting movements along the HBSZ as a consequence of Lower Carboniferous orogenic collapse. 相似文献
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