Superposition of burial and hydrothermal events: post‐Variscan thermal evolution of the Erzgebirge,Germany          下载免费PDF全文

Reinhard Wolff  István Dunkl  Jan‐Michael Lange  Christian Tonk  Thomas Voigt  Hilmar von Eynatten 《地学学报》2015,27(4):292-299

The post‐Variscan thermal history of the Erzgebirge (Germany) is the result of periods of sedimentary burial, exhumation and superimposed hydrothermal activity. The timing and degree of thermal overprint have been analysed by zircon and apatite (U–Th)/He and apatite fission track thermochronology. The present‐day surface of the Erzgebirge was exhumed to a near‐surface position after the Variscan orogeny. Thermal modelling reveals Permo‐Mesozoic burial to temperatures of up to 80–100 °C, although the sedimentary cover thins out towards the north resulting in maximum burial temperatures of less than 40 °C. This thermal pattern was locally modified by Cretaceous hydrothermal activity that reset the zircon (U–Th)/He thermochronometer along ore veins. The thermal models show no significant regional exhumation during Cenozoic times, indicating that the peneplain‐like morphology of the basement is a Late Cretaceous feature.  相似文献   

Discrimination of TiO<Subscript>2</Subscript> polymorphs in sedimentary and metamorphic rocks     

Silke Triebold  George Luiz Luvizotto  Raimon Tolosana-Delgado  Thomas Zack  Hilmar von Eynatten 《Contributions to Mineralogy and Petrology》2011,161(4):581-596

Investigation by Raman spectroscopy of samples from different geological settings shows that the occurrence of TiO₂ polymorphs other than rutile can hardly be predicted, and furthermore, the occurrence of anatase is more widespread than previously thought. Metamorphic pressure and temperature, together with whole rock chemistry, control the occurrence of anatase, whereas variation of mineral assemblage characteristics and/or fluid occurrence or composition takes influence on anatase trace element characteristics and re-equilibration of relict rutiles. Evaluation of trace element contents obtained by electron microprobe in anatase, brookite, and rutile shows that these vary significantly between the three TiO₂ phases. Therefore, on the one hand, an appropriation to source rock type according to Nb and Cr contents, but as well application of thermometry on the basis of Zr contents, would lead to erroneous results if no phase specification is done beforehand. For the elements Cr, V, Fe, and Nb, variation between the polymorphs is systematic and can be used for discrimination on the basis of a linear discriminant analysis. Using phase group means and coefficients of linear discriminants obtained from a compilation of analyses from samples with well-defined phase information together with prior probabilities of groupings from a natural sample compilation, one is able to calculate phase grouping probabilities of any TiO₂ analysis containing at least the critical elements Cr, V, Fe, and Nb. An application of this calculation shows that for the appropriation to the phase rutile, a correct-classification rate of 99.5% is obtained. Hence, phase specification by trace elements proves to be a valuable tool besides Raman spectroscopy.  相似文献   

Provenance of Palaeo‐Rhine sediments from zircon thermochronology,geochemistry, U/Pb dating and heavy mineral assemblages          下载免费PDF全文

Michael Tatzel  István Dunkl  Hilmar von Eynatten 《Basin Research》2017,29(Z1):396-417

Sediments deposited in the Late Cenozoic basins of the Central European Rift System, including the Upper Rhine Graben (URG) and the Lower Rhine Embayment (LRE), document the drastic extension of the Rhine's catchment towards the Central Alps in the Late Pliocene by distinct heavy mineral assemblages. This outstanding change in principal sediment sources should be accompanied by a change towards distinctly younger (i.e. Tertiary) detrital mineral cooling ages. Therefore, it provides a particularly well‐suited framework to explore the thermochronological provenance record in relation to heavy mineral assemblages. In this multi‐proxy approach we (i) exploit and elaborate detrital zircon (U–Th)/He thermochronology (ZHe) for sediment provenance surveys, (ii) document shortcomings if only a single geochronological method is employed, and (iii) obtain tighter constraints on the sources of Paleo‐Rhine sediments. Our results are based on Pliocene and Pleistocene sediment samples from the northern URG (drill core Ludwigshafen P36) and the LRE (lignite mine Hambach). In a Late Pliocene URG sample, Variscan and Permo‐Triassic cooling ages dominate the age spectra of the ZHe and Zircon fission track (ZFT) thermochronometers. The youngest ages are Late Cretaceous and these zircons show rare earth element signatures that suggest derivation from hydrothermally affected basement rocks of the URG margins. In contrast, a Lower Pleistocene URG sample contains significant Tertiary age components that unequivocally indicate Alpine sources. This cardinal difference coincides well with a significant change in the heavy mineral assemblage. The extension of the catchment of the Rhine towards the Central Alps is considered to occur no earlier than the latest Pliocene (i.e. after ~3.0 Ma). Despite strongly contrasting heavy mineral compositions, the Pliocene and Pleistocene samples from the LRE show largely similar ZHe and ZFT age distributions dominated by Permo‐Triassic and Variscan ages. Admixture of zircon‐dominated, but overall heavy mineral‐poor sediment derived from local drainages of the Rhenish Massif likely explains this apparent contradiction in sediment provenance proxies. Tertiary cooling ages occur in both Pliocene and Pleistocene LRE samples. Zircon Th/U ratios and U/Pb ages reveal that the young age component in Late Pliocene sediments from the LRE is not derived from the Alps but from Oligocene trachytic members of the Central European volcanic centres of the Vogelsberg, Westerwald, and/or Siebengebirge. The integration of ZHe and ZFT techniques with zircon geochemistry and U/Pb geochronology adds the respective advantages of each method and allows for a very detailed picture of detrital zircon provenance.  相似文献   

Optical photometry of V4334 Sgr (Sakurai's Object)     

Hilmar W. Duerbeck 《Astrophysics and Space Science》2002,279(1-2):5-14

The optical photometric evolution of the final helium flash object V4334 Sgr from 1994 to 2001 is described. The rise to optical maximum (1994–1996) is characterized by a continuous increase of colour indices, indicating a slowly expanding, cooling pseudo-photosphere. This photosphere became stationary in 1997. In the following years, the object underwent brightnessdeclines of increasing strength, which are similar in character to the `reddeclines' of RCB stars. The fading of V4334 Sgr is more dramatic than anybrightness decline of an RCB star: at present, only 10^-5 of the visual light reaches the observer. Most short-wavelength radiation is absorbed by a dust envelopethat completely surrounds the star, and is re-radiated in the infrared. The sparse optical data of 2000–2001 show that the obscuration has not increased in strength any more. The light curve of V4334 Sgr is similar to that of the final helium flash object V605 Aql which erupted in 1919.  相似文献   

Initial Discrimination Results from the Norwegian Seismic Array     

John Filson  Hilmar Bungum 《Geophysical Journal International》1972,31(1-3):315-328

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A microearthquake survey of Bouvet Island, South Atlantic     

Y. Kristoffersen  H. Bungum   《Tectonophysics》1982,81(1-2)

A microearthquake survey carried out during the 1978–1979 Norwegian Antarctic Research Expedition indicates that only minor seismic activity is associated with the Bouvet volcano.  相似文献   

Evaluation of habitat use by adult plaice (Pleuronectes platessa L.) using underwater video survey techniques   总被引：1，自引：0，他引：1  

Richard Shucksmith  Hilmar Hinz  Melanie Bergmann  Michel J. Kaiser 《Journal of Sea Research》2006,56(4):317-328

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IV. Stratigraphie Die fazielle Einstufung fossilführender Sedimente     

Hermann Schmidt  Karl Hoffmann  Erich Brand  Wolfgang Schott  Otto Seitz  Johannes Wolburg  Franz Bettenstaedt  F. E. Hecht  Hilmar Schumann  F. Heidorn 《International Journal of Earth Sciences》1948,35(2):175-178

Ohne Zusammenfassung  相似文献   

Modelling Compositional Change: The Example of Chemical Weathering of Granitoid Rocks     

Hilmar von Eynatten  Carles Barceló-Vidal  Vera Pawlowsky-Glahn 《Mathematical Geology》2003,35(3):231-251

Perturbation on the simplex is an operation which can be used to numerically describe changes in the composition of, for example, soils, sediments, or rocks. The combination of perturbation and power transformation provides a strong tool for analyzing compositional linear processes in the simplex. When the process is constrained in the sense of a well-known starting (or final) composition, noncentred principal component analysis can be used to estimate the leading perturbation vector of the process. Applying these mathematical tools to chemical major element data from a weathering profile developed on granitoid rocks allows us to model the compositional changes associated with the process of chemical weathering. The comparison of these results with the compositional linear trend defined by erosional products of several of the world's major drainage systems yields close similarities. The latter observation allows for a mathematical formulation of a global mean weathering trend within the system Al₂O₃–CaO– Na₂O– K₂O. We further demonstrate the usefulness of the approach for validating processes behind individual trends and for combining the effects of different processes which modify the composition of soils, sediments, and rocks. Alternatives to the Chemical Index of Alteration (CIA) are discussed to obtain a translation-invariant scale for the process of chemical weathering.  相似文献   

Seismicity of the Norwegian Sea: The Jan Mayen Fracture Zone     

H. Bungum  E.S. Husebye 《Tectonophysics》1977,40(3-4):351-360

The seismicity of the Jan Mayen Island region is re-examined, and a new and improved seismicity map is presented. These data, together with four previously published and one new and very precise fault-plane solution, have been interpreted in the light of other geophysical information bearing on the area. The data support the hypothesis that the transform portion of the Jan Mayen Fracture Zone consists of a system of en-échelon faults. A separate seismicity area immediately northeast of the Jan Mayen Island itself is quite pronounced on the new seismicity map. Moreover, from the available earthquake data the suggested Iceland—Jan Mayen ridge offset is located at 70.75°N.  相似文献