Sources of primitive alkaline volcanic rocks from the Central European Volcanic Province (Rhön,Germany) inferred from Hf,Os and Pb isotopes     

S.?JungEmail author  J.?A.?Pf?nder  G.?Brügmann  A.?Stracke 《Contributions to Mineralogy and Petrology》2005,150(5):546-559

Basanites and nephelinites from the Tertiary Rhön area (Germany), which are part of the Central European Volcanic Province (CEVP), have high MgO, Ni and Cr contents and prominent garnet signatures indicating that they represent near-primary magmas formed by melting of a CO₂-bearing peridotitic mantle source at high pressure. The Pb and Hf isotope (and previously published Nd and Sr isotope) ratios of the Rhön lavas are rather uniform, whereas the Os isotope composition is highly variable. For the most primitive basanites, Pb, Os and Hf isotope compositions fall within the range of enriched MORB and some OIB. Other basanites and nephelinites with low Os concentrations have distinctly more radiogenic Os (¹⁸⁷Os/¹⁸⁸Os: 0.160–0.469) isotope compositions, which are inferred to originate from crustal contamination. The samples with the highest Os concentrations have the lowest Os isotope ratios (¹⁸⁷Os/¹⁸⁸Os_(23 Ma): 0.132–0.135), and likely remain unaffected by crustal contamination. Together with their fairly depleted Sr, Nd and Hf isotope ratios, the isotopic composition of the Rhön lavas suggests derivation from an asthenospheric mantle source. Prominent negative K and Rb anomalies, however, argue for melting amphibole or phlogopite-bearing sources, which can only be stable in the cold lithosphere. We therefore propose that asthenospheric melts precipitated at the asthenosphere-lithosphere thermal boundary as veins in the lithospheric mantle and were remelted or incorporated after only short storage times (about 10–100 million years) by ascending asthenospheric melts. Due to the short residence time incorporation of the vein material imposes the prominent phlogopite/amphibole signature of the Rhön alkaline basalts but does not lead to a shift in the isotopic signatures. Melting of the lithospheric mantle cannot strictly be excluded, but has to be subordinate due to the lack of the respective isotope signatures, in good agreement with the fairly thin lithosphere observed in the Rhön area. The fairly radiogenic Pb isotope signatures are expected to originate from melting of enriched, low melting temperature portions incorporated in the depleted upper (asthenospheric) mantle and therefore do not require upwelling of deep-seated mantle sources for the Rhön or many other continental alkaline lavas with similar Pb isotope signatures.  相似文献   

EUV and soft X-ray images of the sun on March 11th, 1971     

H. Bräuninger  H. J. Einighammer  J. V. Feitzinger  H. H. Fink  D. H. Höhn  H. Koops  G. Krämer  U. Mayer  G. Möllenstedt  M. Mozer 《Solar physics》1971,20(1):81-84

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MHD Simulations of Relativistic Jets     

Tobias Leismann  Miguel-Angel Aloy  Ewald Müller 《Astrophysics and Space Science》2004,293(1-2):157-163

In a series of time dependent numerical simulations we have performed a parameter study of magnetised relativistic jets. We have found that the impact of the magnetic field on the morphology of a jet depends strongly on the configuration of the field.  相似文献   

Neue Bücher und Zeitschriften     

v. Bubnoff  E. W.  R. Br. 《International Journal of Earth Sciences》1954,42(2):297-311

Ohne Zusammenfassung  相似文献   

Contents of Volume 48     

Rudolf BráZdil  Christian Pfister  Heinz Wanner  Hans Von Storch  JüRg Luterbacher 《Climatic change》2001,48(4):653-655

Volume Contents

Contents of Volume 48  相似文献   

The parabolic wave equation in local helioseismology     

Brüggen  Marcus 《Solar physics》2000,192(1-2):225-230

In recent years methods of time-distance helioseismology have been used to produce maps of local flows in the surface layers of the Sun. Usually, these studies rely on ray theory to describe the propagation of sound waves. Ray theory, however, is a poor approximation of the acoustic wavefield near the surface of the Sun. In particular, it is inappropriate for the study of scattering and diffraction by inhomogeneities. But an exact solution of the acoustic wave equation in the Sun is not trivial. In this paper I present an approximation to the full wave equation, which transforms it into a parabolic equation. The parabolic equation is commonly used in ocean acoustics and geoseismology because it is much simpler to solve numerically. Here I discuss the parabolic approximation, its limitations and potential applications in helioseismology. Finally, I present some numerical results to demonstrate the capabilities of this method.  相似文献   

Depositional ages of clastic metasediments from Samos and Syros,Greece: results of a detrital zircon study     

Kersten Löwen  Michael Bröcker  Jasper Berndt 《International Journal of Earth Sciences》2015,104(1):205-220

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Evaluation of meteorological controls of reconstructed rockfall activity in the Czech Flysch Carpathians     

Karel Šilhán  Rudolf Brázdil  Tomáš Pánek  Petr Dobrovolný  Lucie Kašičková  Radim Tolasz  Ondřej Turský  Marek Václavek 《地球表面变化过程与地形》2011,36(14):1898-1909

Rockfall is an important process in the final sculpturing of escarpments and scree slopes that originate in bedrock landslides in the Flysch Carpathians. The spatio‐temporal characteristics of rockfall activity were studied at four localities representative of old landslides in the highest part of the Czech Flysch Carpathians (Moravskoslezské Beskydy Mountains). Historical activity, chronology, and spatial context of rockfall activity were reconstructed using dendrogeomorphic techniques and rockfall rate index (RR). A total of 1132 increment cores from 283 trees growing in the rockfall transport and accumulation zones enabled the dating of 989 rockfall events. Reconstruction of a 78‐year‐long RR chronology suggests similar rockfall histories and trends at all study sites, indicating the existence of major common factors driving rockfall dynamics in the region. Temporal analysis and correlation of the RR series obtained with monthly mean temperatures, numbers of days with temperature transitions through 0 °C and monthly precipitation totals show that meteorological characteristics have evident but variable influence on rockfall activity. The most important factor is the effect of freeze–thaw cycles throughout the year, supplemented by low temperatures, especially during autumn. The influence of precipitation totals is of lesser importance. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Reply to Reimer and Mossman. Comment on “Trace-element characteristics of different pyrite types in Mesoarchaean to Palaeoproterozoic placer deposits” by Koglin et al. (<Emphasis Type="Italic">Mineralium Deposita</Emphasis> 42: 259–280, 2010)     

Nikola Koglin  Hartwig E. Frimmel  W. E. Lawrie Minter  Helene Brätz 《Mineralium Deposita》2011,46(7):839-840

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Modelling multiphase chemistry in deliquescent aerosols and clouds using CAPRAM3.0i     

A. Tilgner  P. Bräuer  R. Wolke  H. Herrmann 《Journal of Atmospheric Chemistry》2013,70(3):221-256

Modelling studies were performed with the multiphase mechanism RACM-MIM2ext/CAPRAM 3.0i to investigate the tropospheric multiphase chemistry in deliquesced particles and non-precipitating clouds using the SPACCIM model framework. Simulations using a non-permanent cloud scenario were carried out for two different environmental conditions focusing on the multiphase chemistry of oxidants and other linked chemical subsystems. Model results were analysed by time-resolved reaction flux analyses allowing advanced interpretations. The model shows significant effects of multiphase chemical interactions on the tropospheric budget of gas-phase oxidants and organic compounds. In-cloud gas-phase OH radical concentration reductions of about 90 % and 75 % were modelled for urban and remote conditions, respectively. The reduced in-cloud gas-phase oxidation budget increases the tropospheric residence time of organic trace gases by up to about 30 %. Aqueous-phase oxidations of methylglyoxal and 1,4-butenedial were identified as important OH radical sinks under polluted conditions. The model revealed that the organic C₃ and C₄ chemistry contributes with about 38 %/48 % and 8 %/9 % considerably to the urban and remote cloud / aqueous particle OH sinks. Furthermore, the simulations clearly implicate the potential role of deliquescent particles to operate as a reactive chemical medium due to an efficient TMI/HO_x,y chemical processing including e.g. an effective in-situ formation of OH radicals. Considerable chemical differences between deliquescent particles and cloud droplets, e.g. a circa 2 times more efficient daytime iron processing in the urban deliquescent particles, were identified. The in-cloud oxidation of methylglyoxal and its oxidation products is identified as efficient sink for NO₃ radicals in the aqueous phase.  相似文献