Miocene tectonics of the Maramures area (Northern Romania): implications for the Mid-Hungarian fault zone

The interplay between the emplacement of crustal blocks (e.g. “ALCAPA”, “Tisza”, “Dacia”) and subduction retreat is a key issue for understanding the Miocene tectonic history of the Carpathians. Coeval thrusting and basin formation is linked by transfer zones, such as the Mid-Hungarian fault zone, which seperates ALCAPA from Tisza-Dacia. The presented study provides new kinematic data from this transfer zone. Early Burdigalian (20.5 to ∼18.5 Ma) SE-directed thrusting of the easternmost tip of ALCAPA (Pienides), over Tisza-Dacia is linked to movements along the Mid-Hungarian fault zone and the Periadriatic line, accommodating the lateral extrusion of ALCAPA. Minor Late Burdigalian (∼18.5 to 16 Ma) NE-SW extension is interpreted as related to back-arc extension. Post Burdigalian (post-16 Ma) NE–SW shortening and NW–SE extension correlate with “soft collision” of Tisza-Dacia with the European foreland coupled with southward migration of active subduction. During this stage the Bogdan-Voda and Dragos-Voda faults were kinematically linked to the Mid-Hungarian fault zone. Sinistral transpression (16 to 12 Ma) at the Bogdan-Voda fault was followed by sinistral transtension (12–10 Ma) along the coupled Bogdan-Dragos-Voda fault system. During the transtensional stage left-lateral offset was reduced eastwards by SW trending normal faults, the fault system finally terminating in an extensional horse-tail splay.     

Greigite: a true intermediate on the polysulfide pathway to pyrite

The formation of pyrite (FeS₂) from iron monosulfide precursors in anoxic sediments has been suggested to proceed via mackinawite (FeS) and greigite (Fe₃S₄). Despite decades of research, the mechanisms of pyrite formation are not sufficiently understood because solid and dissolved intermediates are oxygen-sensitive and poorly crystalline and therefore notoriously difficult to characterize and quantify.     

Meteorological singularities in the Czech Republic in the period 1961–2002

Summary Based on the mean daily values of air temperature, air pressure, and precipitation totals at 13 climatological stations within the territory of the Czech Republic in the period 1961–2002, a statistical analysis of “meteorological singularities” (i.e., calendar-dependent deviations from the mean annual variation for selected meteorological elements) was performed. At the 13 stations analysed, a total of 45 meteorological singularities (37 singularities in air temperature, 35 in air pressure, and 30 in precipitation) were found. The singularities detected correlate well with cases traditionally recognised in the Czech Republic as well as with the results of analyses performed for Germany. Despite the considerable variability of singularities in time and space, most of them are found across the entire territory of the Czech Republic and can be observed for the most part in all three elements processed. The majority of the singularities detected may be explained on the basis of circulation mechanisms, by relating them to a significantly higher occurrence of certain groups of synoptic situations characterised by anomalous temperature or precipitation effects. Cases of “competition” between singularities, when different singularities may occur on the same calendar day, were found.     

ENSO influence on Europe during the last centuries

El Niño/Southern Oscillation (ENSO) affects climate not only in the Pacific region and the tropics, but also in the North Atlantic-European area. Studies based on twentieth-century data have found that El Niño events tend to be accompanied in late winter by a negative North Atlantic Oscillation index, low temperatures in northeastern Europe and a change in precipitation patterns. However, many questions are open, for example, concerning the stationarity of this relation. Here we study the relation between ENSO and European climate during the past 500 years based on statistically reconstructed ENSO indices, early instrumental station series, and reconstructed fields of surface air temperature, sea-level pressure, precipitation, and 500 hPa geopotential height. After removing years following tropical volcanic eruptions (which systematically mask the ENSO signal), we find a consistent and statistically significant ENSO signal in late winter and spring. The responses to El Niño and La Niña are close to symmetric. In agreement with studies using twentieth-century data only, the ENSO signal in precipitation is different in fall than in late winter. Moving correlation analyses confirm a stationary relationship between ENSO and late winter climate in Europe during the past 300 years. However, the ENSO signal is modulated significantly by the North Pacific climate. A multi-field cluster analysis for strong ENSO events during the past 300 years yields a dominant pair of clusters that is symmetric and represents the ‘classical’ ENSO effects on Europe.     

GCM-based regional temperature and precipitation change estimates for Europe under four SRES scenarios applying a super-ensemble pattern-scaling method

Seasonal GCM-based temperature and precipitation projections for the end of the 21st century are presented for five European regions; projections are compared with corresponding estimates given by the PRUDENCE RCMs. For most of the six global GCMs studied, only responses to the SRES A2 and B2 forcing scenarios are available. To formulate projections for the A1FI and B1 forcing scenarios, a super-ensemble pattern-scaling technique has been developed. This method uses linear regression to represent the relationship between the local GCM-simulated response and the global mean temperature change simulated by a simple climate model. The method has several advantages: e.g., the noise caused by internal variability is reduced, and the information provided by GCM runs performed with various forcing scenarios is utilized effectively. The super-ensemble method proved especially useful when only one A2 and one B2 simulation is available for an individual GCM. Next, 95% probability intervals were constructed for regional temperature and precipitation change, separately for the four forcing scenarios, by fitting a normal distribution to the set of projections calculated by the GCMs. For the high-end of the A1FI uncertainty interval, temperature increases close to 10°C could be expected in the southern European summer and northern European winter. Conversely, the low-end warming estimates for the B1 scenario are ~ 1°C. The uncertainty intervals of precipitation change are quite broad, but the mean estimate is one of a marked increase in the north in winter and a drastic reduction in the south in summer. In the RCM simulations driven by a single global model, the spread of the temperature and precipitation projections tends to be smaller than that in the GCM simulations, but it is possible to reduce this disparity by employing several driving models for all RCMs. In the present suite of simulations, the difference between the mean GCM and RCM projections is fairly small, regardless of the number or driving models applied.     

Gradient in the climate change signal of European discharge predicted by a multi-model ensemble

In order to perform hydrological studies on the PRUDENCE regional climate model (RCM) simulations, a special focus was put on the discharge from large river catchments located in northern and central Europe. The discharge was simulated with a simplified land surface (SL) scheme and the Hydrological Discharge (HD) model. The daily fields of precipitation, 2 m temperature and evapotranspiration from the RCM simulations were used as forcing. Therefore the total catchment water balances are constrained by the hydrological cycle of the different RCMs. The validation of the simulated hydrological cycle from the control simulations shows that the multi-model ensemble mean is closer to the observations than each of the models, especially if different catchments and hydrological variables are considered. Therefore, the multi-model ensemble mean can be used to largely reduce the uncertainty that is introduced by a single RCM. This also provides more confidence in the future projections for the multi-model ensemble means. The scenario simulations predict a gradient in the climate change signal over Northern and Central Europe. Common features are the overall warming and the general increase of evapotranspiration. But while in the northern parts the warming will enhance the hydrological cycle leading to an increased discharge, the large warming, especially in the summer, will slow down the hydrological cycle caused by a drying in the central parts of Europe which is accompanied by a reduction of discharge. The comparison of the changes predicted by the multi-model ensemble mean to the changes predicted by the driving GCM indicates that the RCMs can compensate problems that a driving GCM may have with local scale processes or parameterizations.     

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

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.     

Trace element partitioning between apatite and silicate melts

We present new experimental apatite/melt trace element partition coefficients for a large number of trace elements (Cs, Rb, Ba, La, Ce, Pr, Sm, Gd, Lu, Y, Sr, Zr, Hf, Nb, Ta, U, Pb, and Th). The experiments were conducted at pressures of 1.0 GPa and temperatures of 1250 °C. The rare earth elements (La, Ce, Pr, Sm, Gd, and Lu), Y, and Sr are compatible in apatite, whereas the larger lithophile elements (Cs, Rb, and Ba) are strongly incompatible. Other trace elements such as U, Th, and Pb have partition coefficients close to unity. In all experiments we found D_Hf > D_Zr, D_Ta ≈ D_Nb, and D_Ba > D_Rb > D_Cs. The experiments reveal a strong influence of melt composition on REE partition coefficients. With increasing polymerisation of the melt, apatite/melt partition coefficients for the rare earth elements increase for about an order of magnitude. We also present some results in fluorine-rich and water-rich systems, respectively, but no significant influence of either H₂O or F on the partitioning was found. Furthermore, we also present experimentally determined partition coefficients in close-to natural compositions which should be directly applicable to magmatic processes.     

Chemo-dynamical Evolution of the ISM in Galaxies

Chemo-dynamical models have been introduced in the late eighties andare a generally accepted tool for understanding galaxy evolution. Theyhave been successfully applied to one-dimensional problems, e.g. theevolution of non-rotating galaxies, and two-dimensional problems,e.g. the evolution of disk galaxies. Recently, also three-dimensionalchemo-dynamical models have become available. In these models thedynamics of different components, i.e. dark matter, stars and amulti-phase interstellar medium, are treated in a self-consistent wayand several processes allow for an exchange of matter, energy andmomentum between the components or different gas phases. Some resultsof chemo-dynamical models and their comparison with observations ofchemical abundances or star formation histories will be reviewed.