Multistage Variscan magmatism in the central Tauern Window (Austria) unveiled by U/Pb SHRIMP zircon data   总被引：2，自引：0，他引：2  

Roland Eichhorn  Georg Loth  Rudolf Höll  Fritz Finger  Andreas Schermaier  Allen Kennedy 《Contributions to Mineralogy and Petrology》2000,139(4):418-435

U/Pb SHRIMP ages of nine Variscan leucocratic orthogneisses from the central Tauern Window (Austria) reveal three distinct pulses of magmatism in Early Carboniferous (Visean), Late Carboniferous (Stephanian) and Early Permian, each involving granitoid intrusions and a contemporaneous opening of volcano-sedimentary basins. A similar relationship has been reported for the Carboniferous parts of the basement of the Alps further to the west, e.g. the “External massifs” in Switzerland. After the intrusion of subduction-related, volcanic-arc granitoids (374?±?10?Ma; Zwölferkogel gneiss), collisional intrusive-granitic, anatectic and extrusive-rhyolitic/dacitic rocks were produced over a short interval at ca. 340?Ma (Augengneiss of Felbertauern: 340?±?4?Ma, Hochweißenfeld gneiss: 342?± 5?Ma, Falkenbachlappen gneiss: 343?±?6?Ma). This Early Carboniferous magmatism, which produced relatively small volumes of melt, can be attributed to the amalgamation of the Gondwana-derived “Tauern Window” terrane with Laurussia–Avalonia. Probably due to the oblique nature of the collision, transtensional phenomena (i.e. volcano-sedimentary troughs and high-level intrusives) and transpressional regimes (i.e. regional metamorphism and stacked nappes with anatexis next to thrust planes) evolved contemporaneously. The magmas are mainly of the high-K I-type and may have been generated during a short phase of decompressional melting of lithospheric mantle and lower crustal sources. In the Late Carboniferous, a second pulse of magmatism occurred, producing batholiths of calc-alkaline I-type granitoids (e.g. Venediger tonalite: 296?±?4?Ma) and minor coeval bodies of felsic and intermediate volcanics (Heuschartenkopf gneiss: 299?±?4?Ma, Peitingalm gneiss: 300?±?5?Ma). Prior to this magmatism, several kilometres of upper crust must have been eroded, because volcano-sedimentary sequences hosting the Heu- schartenkopf and Peitingalm gneisses rest unconformably on 340-Ma-old granitoids. The youngest (Permian) period of magma generation contains the intrusion of the S-type Granatspitz Central Gneiss at 271?±?4?Ma and the extrusion of the rhyolitic Schönbachwald gneiss protolith at 279?±?9?Ma. These magmatic rocks may have been associated with local extension along continental wrench zones through the Variscan orogenic crust or with a Permian rifting event. The Permian and the above-mentioned Late Carboniferous volcano-sedimentary sequences were probably deposited in intra-continental graben structures, which survived post-Variscan uplift and Alpine compressional tectonics.  相似文献   

Durbachites–Vaugnerites – a geodynamic marker in the central European Variscan orogen     

Jürgen F. von Raumer  Fritz Finger  Petra Veselá  Gérard M. Stampfli 《地学学报》2014,26(2):85-95

Durbachites–Vaugnerites are K–Mg‐rich magmatic rocks derived from an enriched mantle source. Observed throughout the European Variscan basement, their present‐day geographical distribution does not reveal any obvious plate‐tectonic context. Published geochronological data show that most durbachites–vaugnerites formed around 335–340 Ma. Plotted in a Visean plate‐tectonic reconstruction, the occurrences of durbachites–vaugnerites are concentrated in a hotspot like cluster in the Galatian superterrane, featuring a distinctive regional magmatic province. Reviewing the existing local studies on Variscan durbachite–vaugnerite rocks, we interpret their extensive appearance in the Visean in terms of two factors: (i) long‐term mantle enrichment above early Variscan subduction systems; and (ii) melting of this enriched subcontinental mantle source during the Variscan collision stage due to thermal anomalies below the Galatian superterrane, possibly created by slab windows and and/or the sinking of the subducted Rheic slab into the mantle. The tectonic reorganization of Europe in the Late Palaeozoic and during the Alpine orogeny has torn apart and blurred this marked domain of durbachites–vaugnerites.  相似文献   

Timing and mechanisms of Central Himalayan exhumation: discriminating between tectonic and erosion processes     

Ana-Voica Bojar  Harald Fritz  Stefan Nicolescu  Martin Bregar  Ravi P. Gupta 《地学学报》2005,17(5):427-433

The ability to deduce exhumation mechanisms from thermochronological data is hampered by the fact that assumptions on the thermal state of the lithosphere have to be made. Additional argumentation is generally required to discriminate between erosion-controlled and tectonically induced exhumation. This problem can be overcome by studying the spatial distribution of zircon and apatite (U-Th)/He and fission track data. In this work the variation of four different low temperature isotopic systems generating age trends along a sampling line is used to infer mechanisms of Quaternary exhumation in the Central High Himalayan Metamorphic Belt. Observed zircon age trends with southwards increasing cooling ages (from 0.5 to 1.7 Ma) are attributed to tectonically induced exhumation. The uniform apatite cooling ages clustered c. 0.5 Ma are attributed to erosion.  相似文献   

A proposal for modelling physical correlations of GPS phase observations   总被引：2，自引：1，他引：1  

Steffen Schön  Fritz K. Brunner 《Journal of Geodesy》2008,82(10):601-612

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Box fractal dimension as a measure of statistical homogeneity of jointed rock masses   总被引：2，自引：0，他引：2  

Pinnaduwa H. S. W. Kulatilake  Reno Fiedler  Bibhuti B. Panda 《Engineering Geology》1997,48(3-4):217-229

A written computer programme to estimate the box fractal dimension (D_B) is verified by estimating D_B of the triadic Koch curve for which the theoretical D is known. The influence of a number of input parameters of the box-counting method on the accuracy of estimated D_B is evaluated using the same Koch curve. The employed size range of the applied box networks was found to be the parameter which has the strongest influence on the accuracy of estimated D_B. This indicated the importance of finding the range of self-similarity or self-affinity for the object considered to select the proper range for the box sizes and, in turn, to obtain accurate estimates of D_B. By calculating D_B for different block sizes sampled from three generated two-dimensional joint patterns, it is shown that D_B can capture the combined effect of joint-size distribution and joint density on the statistical homogeneity of rock masses. The spatial variation of D_B along a 350 m stretch of a tunnel in the shiplock area of the Three Gorges dam site is computed using the joint data mapped on the walls and the roof of the tunnel. This spatial variation of D_B is used, along with the visual geological evaluation of the joint trace maps of the tunnel, in making decisions about statistical homogeneity of the rock mass around the tunnel. The results obtained on statistically homogeneous regions were found to be quite similar to the results obtained from a previous statistical homogeneity investigation which incorporated the effect of number of joint sets and their orientation distributions, but not the spatial variation of D_B. It is recommended that the spatial variation of D_B is used, along with the results of other methods such as contingency table analysis and equal area plots, which incorporate the effect of joint orientation distribution, in addition to the geology of the site, in determining the statistically homogeneous regions of jointed rock masses.  相似文献   

On the variation of the energy-balance components with orography in the Upper Rhine Valley     

A. Wenzel  N. Kalthoff  F. Fiedler 《Theoretical and Applied Climatology》1997,57(1-2):1-9

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Organic carbon isotope geochemistry of clayey deposits and their associated porewaters, southern Alberta     

L. I. Wassenaar  M. J. Hendry  R. Aravena  P. Fritz 《Journal of Hydrology》1990,120(1-4):251-270

The organic carbon cycle of slowly permeable, clayey glacial till deposits in the Western Interior Great Plains, southern Alberta, was investigated by examining the relationship between solid organic matter (SOM) in the till sediments and dissolved organic carbon (DOC) in the till porewaters. Geochemically, the tills can be divided into two distinct zones: an upper oxidized (low SOM) till zone, and a lower unoxidized (high SOM) till zone. Till porewaters in both zones are characterized by high DOC contents. Radiocarbon dating and comparison of SOM and DOC fractions suggest DOC in the deep unoxidized zone originated during deglaciation, and is probably representative of groundwater ages in this till zone. In the oxidized zone, DOC originates from variable mixtures of soluble organic matter emplaced during deglaciation, and Cretaceous age coal fragments in this till zone. SOM in the upper till zone was mainly oxidized to CO₂ gas during lowered water table conditions of the Altithermal climatic period. The subsurface production of fossil CO₂ gas has serious implications for using the conventional dissolved inorganic carbon (DIC) ¹⁴C groundwater dating method in these clayey till porewaters.  相似文献   

A process-based evaluation of dust-emitting winds in the CMIP5 simulation of HadGEM2-ES     

Stephanie Fiedler  Peter Knippertz  Stephanie Woodward  Gill M. Martin  Nicolas Bellouin  Andrew N. Ross  Bernd Heinold  Kerstin Schepanski  Cathryn E. Birch  Ina Tegen 《Climate Dynamics》2016,46(3-4):1107-1130

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Paleolimnological records of regime shifts in lakes in response to climate change and anthropogenic activities     

Linda Randsalu-Wendrup  Daniel J. Conley  Jacob Carstensen  Sherilyn C. Fritz 《Journal of Paleolimnology》2016,55(1):1-16

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Satellite pictures of the snow-covered alps during April 1960     

Sigmund Fritz 《Meteorology and Atmospheric Physics》1962,13(2):186-198

Summary From April 2 to 7, 1960, the meteorological satellite Tiros I televised the Alps and the surrounding area. The Alpine mountains were snow covered but the river valleys and lakes were readily discernible in the pictures under clear sky conditions. The pictures show marked differences when the area was overcast as compared to times when the area was clear or partly cloudy. These differences are discussed with the aid of satellite pictures and surface cloud cover maps.

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Zusammenfassung Vom 2. bis 7. April 1960 hat der meteorologische Satellit Tiros I Fernsehaufnahmen der Alpen und der umliegenden Gebiete gemacht. Die Alpenberge waren damals schneebedeckt, dagegen waren die Flußtäler und Seen bei Schönwetter in den Bildern deutlich zu erkennen. Die Bilder zeigen markante Unterschiede, wenn das Gebiet von Wolken bedeckt war, im Vergleich zu den Bildern bei wolkenlosem oder nur teilweise wolkigem Wetter. Diese Unterschiede werden an Hand von Satellitenaufnahmen und von nach Bodenbeobachtungen entworfenen Bewölkungskarten diskutiert.

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Résumé Le satellite météorologique Tiros I a effectué du 2 au 7 avril 1960 des prises de vue télévisées des Alpes et des régions avoisinantes. Les montagnes étaient alors recouvertes de neige, mais les vallées et les lacs sont, par ciel serein, nettement visibles sur les images. Ces images montrent des différences sensibles si les diverses régions ont un ciel couvert ou, au contraire, serein ou peu nuageux. On discute alors ces différences tant au moyen des images produites par le satellite que par des cartes de la nébulosité basées sur des observations au sol.

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With 6 Figures

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Dedicated toDr. W. Mörikofer on the occasion of his 70th birthday.  相似文献