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Gábor Dobosi Pamela D. Kempton Hilary Downes Antal Embey-Isztin Matthew Thirlwall Peter Greenwood 《Contributions to Mineralogy and Petrology》2003,144(6):671-683
Mafic granulite xenoliths from the lower crust of the Pannonian Basin are dominated by LREE-depleted bulk-rock compositions. Many of these have MORB-like 143Nd/144Nd but 87Sr/86Sr is elevated relative to most MORBs. Their '18O values cover a wide range from +3.8 to +9.5. A group of LREE-enriched mafic granulites have higher 87Sr/86Sr (0.704-0.708) and lower 143Nd/144Nd (0.5128-0.5124), with higher '18O values on average (+7.8 to +10.6) than the LREE-depleted granulites. The LREE-enriched granulites are, however, isotopically similar to newly discovered metasedimentary granulite xenoliths. A sublinear correlation in )Hf-)Nd isotope space has a shallower slope than the crust-mantle array, with the metasedimentary rocks forming the low )Hf end member; the radiogenic end is restricted to the LREE-depleted granulites and these overlap the field of MORB. Pb isotopes for the LREE-depleted samples are less radiogenic on average than those of the LREE-enriched and metasedimentary xenoliths, and metasedimentary granulites have consistently higher 208Pb/204Pb. The wide range in '18O over a restricted range in Nd and Sr isotope values, in combination with the predominance of LREE-depleted trace-element compositions, is consistent with an origin as a package of hydrothermally altered oceanic crust. The existence of '18O values lower than average MORB and/or mantle peridotite requires that at least some of these rocks were hydrothermally altered at high temperature, presumably in the oceanic lower crust. The low 143Nd/144Nd of the LREE-enriched mafic granulites cannot be explained by simple mixing between a LREE-depleted melt and an enriched component, represented by the recovered metasediments. Instead, we interpret these rocks as the metamorphic equivalent of the shallowest levels of the ocean crust where pillow basalts are intimately intercalated with oceanic sediments. A possible model is accretion of oceanic crustal slices during subduction and convergence, followed by high-grade metamorphism during the Alpine orogeny. 相似文献
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Antal?Embey-IsztinEmail author Gábor?Dobosi Jean-Louis?Bodinier Delphine?Bosch G.?A.?Jenner Simone?Pourtales Olivier?Bruguier 《Contributions to Mineralogy and Petrology》2014,168(3):1054
Peridotite xenoliths erupted by alkali basaltic volcanoes in the western Pannonian Basin can be divided into two fundamentally contrasting groups. Geochemical characteristics of the abundant protogranular, porphyroclastic and equigranular nodules suggest that these samples originate from an old consolidated and moderately depleted lithospheric mantle domain. In contrast, the geochemical features of the worldwide rare, but in the Pannonian Basin relatively abundant, poikilitic xenoliths attest to a more complex evolution. It has been argued that the origin of the peculiar texture and chemistry may be intimately linked to melt/rock reactions at successively decreasing liquid volumes in a porous melt flow system. The most likely site where such reactions can take place is the asthenosphere–lithosphere boundary. In this context, poikilitic xenoliths may provide petrological and geochemical evidence for reactions between magmatic liquids issued from the uprising asthenosphere and the solid mantle rocks of the lithosphere. These reactions are important agents of the thermal erosion of the lithosphere; thus, they could have considerably contributed to the thinning of the lithosphere in the Pannonian region. We suggest that in the Pannonian Basin, there could be a strong relation between the unusual abundance of poikilitic mantle xenoliths and the strongly eroded lithosphere. 相似文献
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Vladimir Yu. Semenov Josef Pek Antal Ádám Waldemar Jóźwiak Boris Ladanyvskyy Igor M. Logvinov Pavel Pushkarev Jan Vozar 《Acta Geophysica》2008,56(4):957-981
In the years 2001–2003, we accomplished the experimental phase of the project CEMES by collecting long-period magnetotelluric
data at positions of eleven permanent geomagnetic observatories situated within few hundreds kilometers along the south-west
margin of the East European Craton. Five teams were engaged in estimating independently the magnetotelluric responses by using
different data processing procedures. The conductance distributions at the depths of the upper mantle have been derived individually
beneath each observatory. By averaging the individual cross-sections, we have designed the final model of the geoelectrical
structure of the upper mantle beneath the CEMES region. The results indicate systematic trends in the deep electrical structure
of the two European tectonic plates and give evidence that the electrical structure of the upper mantle differs between the
East European Craton and the Phanerozoic plate of west Europe, with a separating transition zone that generally coincides
with the Trans-European Suture Zone. 相似文献
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Dr. Ing. Antal Ádám Dipl. Geophys. András Erkel Lászlò Szabadváry 《Pure and Applied Geophysics》1962,52(1):127-138
Zusammenfassung Die Einleitung gibt einige Gesichtspunkte der heutigen geoelektrischen Instrumentenentwicklung in Ungarn. Dann werden zwei neue ungarische geoelektrische Instrumente u.z.w.: 1) ein den spezifischen Widerstand unmittelbar lieferndes Instrument und 2) ein isolationsfehlerloses geophysikalisches Fotoregistrier-instrument mit ihren theoretischen Grundlagen behandelt. Am Ende des Artikels werden einige technische Daten der Instrumenten mitgeteilt.
Summary The introduction deals with the general aspects of the development of modern geoelectrical instruments in Hungary. Then two hungarian geoelectrical instruments: 1) an instrument giving directly the value of the resistivity and 2) a geophysical recording instrument free from isolation errors are discussed from the point of view of the theoretical problems of the instrument-constructions. Finally some technical data of the instruments are presented.相似文献
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Antal Embey-Isztin Gabriella Noske-Fazekas 《Contributions to Mineralogy and Petrology》1981,77(4):325-331
Large phenocrysts of clinopyroxene, amphibole in the Godóvár tuff show normal zoning with mg-values decreasing from the center towards the border zones. Clinopyroxenes exhibit a primitive Cr-diopsidic (Mg48Fe7Ca45) core which with a sudden change in the composition is surrounded by an augitic rim (Mg44Fe14Ca42). No such abrupt change can be observed in amphibole crystals which are typical pargasites and only the outermost zones may pass into the magnesio-hastingsite field. It is argued that the Cr-diopside may have separated from a basaltic liquid at depths greater than about 18 km, while the other pyroxene zones with the pargasite and plagioclase crystals accumulated in a storage chamber at a depth of about 12–15 km. 相似文献
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Paz Garcia-Martinez Antal K.D. Hajos David R. Livingstone Gary W. Winston 《Marine environmental research》1992,34(1-4)
The modulation of the mutagenicity of 4-nitroquinoline N-oxide (4-NQO) by M. edulis digestive gland cytosolic and microsomal fractions was studied by monitoring the induction of the umu operon by 4-NQO in Salmonella typhimurium 1535/pSK1002. The mutagenicity of 4-NQO was increased by M. edulis cytosol and microsomes in dose-dependent manner with respect to protein and toxicant concentration. The mutagenic enhancement reflected increased NAD(P)H-dependent oxygen consumption by microsomes in the presence of 4-NQO and enhanced nitroreductase activity in cytosol. The former was stimulated by azide, indicating 4-NQO-enhanced oxyradical production by microsomes, and the latter was inhibitable by dicoumarol, indicating involvement of DT-diaphorase in nitroreduction by M. edulis cytosol. Neither dicoumarol nor allopurinol (inhibitors of DT-diaphorase and xanthine oxidase, respectively) affected the enhanced mutagenic expression of 4-NQO by cytosol. The results support the possibility of oxidative stress as a pollution-mediated mechanism of toxicity. 相似文献
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The feasibility of green growth is studied in the context of climate change. As carbon emissions are easier to quantify than many other types of environmental pressure, it will be possible to reach a more definite conclusion about the likelihood of green growth than has been possible in the long-standing historical debate on growth versus the environment. We calculate the rate of decoupling between gross domestic product (GDP) and GHG emissions needed to achieve internationally agreed climate targets. Next, eight arguments are considered that together suggest that fast decoupling will be very difficult. Subsequently, we examine the main lines of research used by proponents of green growth to support their viewpoint, including theoretical arguments, exercises with integrated assessment models, and studies of the environmental Kuznets curve hypothesis. It will be concluded that decoupling as a main or single strategy to combine economic and environmental aims should be judged as taking a very large risk with our common future. To minimize this risk we need to seriously consider reducing our dependence on growth. This requires a fundamental change of focus in both economic research and policy.
Policy relevance
Currently, green growth is the only strategy of mainstream economists and policy makers to address climate change. This article demonstrates that such an exclusive focus is very risky due to the scale of the challenge and the existence of various barriers to the fast decoupling of GHG emissions from economic output. It seems that the only option to combine environmental and economic objectives is reducing the dependence of our economies on growth. Finding strategies in line with this requires a fundamental change of focus in both economic research and policy. 相似文献
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