Age, geodynamic setting, and mantle enrichment processes of a K-rich intrusion from the Meissen massif (northern Bohemian massif) and implications for related occurrences from the mid-European Hercynian     

T. Wenzel  D. F. Mertz  R. Oberhänsli  T. Becker  P. R. Renne 《International Journal of Earth Sciences》1997,86(3):556-570

The plutonic complex of the Meissen massif (northern margin of the Bohemian massif) comprises dioritic to mainly monzonitic and granitic rocks. The diorite to monzonite intrusions show major and trace element patterns typical for shoshonitic series. The chemical signatures of less crustally contaminated diorites are similar to arc-related shoshonitic rocks derived from continental lithospheric mantle (CLM) sources previously enriched by subduction of altered oceanic crust. Laser step heating ⁴⁰Ar/³⁹Ar analyses on actinolitic to edenitic amphiboles from geographically different occurrences of the monzonitic intrusion yielded concordant plateau ages as well as total gas ages ranging from 329.1±1.4 to 330.4±1.4?Ma and from 330.4±2.1 to 330.6±1.8?Ma, respectively. These cooling ages are indistinguishable from sensitive highresolution ion microprobe (SHRIMP) ²³⁸U/²⁰⁶Pb intrusion ages measured on magmatic zircon rims from the monzonite (Nasdala et al., submitted). This shows that the monzonite intrusion is probably not related temporally to active subduction because it postdates eclogites of the adjacent Saxonian Erzgebirge by approximately 20?Ma. The shoshonitic magmas intruded during strike-slip tectonism along the Elbe valley zone. The enrichment of their mantle sources may be of Upper Devonian/Lower Carboniferous age or older. Intrusions of shoshonitic to ultra-potassic (K-rich) rocks during the Upper Visean/Namurian are widespread in the Moldanubian zone. Based on similar ages and structural relationships a similar post-collisional setting to the Meissen shoshonitic rocks can be demonstrated. Most of these occurrences cut high-grade nappe units which were subducted during the Upper Devonian/Lower Carboniferous. In contrast to the Meissen massif, at least the ultra-potassic members of the Central and the South Bohemian batholiths were derived from CLM sources enriched by fluids or melts released from subducted oceanic crust and by greater portions of crustal material. Despite the similar post-collisional geodynamic setting of the K-rich intrusions, different enrichment processes generated mid-European Hercynian CLM sources with heterogeneous major and trace element and isotopic signatures.  相似文献   

Hydrothermal gases offshore Milos Island, Greece   总被引：3，自引：0，他引：3  

Reiner Botz  Doris Stüben  Gisela Winckler  Reinhold Bayer  Manfred Schmitt  Eckhard Faber 《Chemical Geology》1996,130(3-4):161-173

Hydrothermal fluids emerge from the seafloor of Paleohori Bay on Milos. The gases in these fluids contain mostly CO₂ but CH₄ concentrations up to 2% are present. The stable carbon isotopic composition of the CO₂ (near 0%) indicates an inorganic carbon source (dissociation of underlying marine carbonates). The carbon and hydrogen isotopes of most CH₄ samples are enriched in the heavy species (δ¹³C = −9.4 to −17.8‰; δD = −102 to −189‰) which is believed to be characteristic for an abiogenic production of CH₄ by CO₂-reduction (Fischer-Tropsch reactions). Depletions in the deuterium content of three CH₄ samples (to −377%) are probably caused by unknown subsurface rock alteration processes. Secondary hydrogen isotope exchange processes between methane, hydrogen and water are most likely responsible for calculated unrealistic methane formation temperatures.

We show that excess helium, slightly enriched in ³He, is present in the hydrothermal fluids emerging the seafloor of Paleohori Bay. When the isotopic ratio of the excess component is calculated a ³He/⁴He_excess of 3.6 · 10⁻⁶ is obtained: This indicates that the excess component consists of about one third of mantle helium and two thirds of radiogenic helium. We infer that the mantle-derived component has been strongly diluted by radiogenic helium during the ascent of the fluids to the surface.  相似文献   

Tectonic style and pressure distribution at the northern margin of the Alps between Lake Constance and the River Inn     

Manfred Müller Dipl.-Geol. Dr.  Franz Nieberding Dipl.-Geol. Dr.  Anton Wanninger Dipl.-Geophys. 《International Journal of Earth Sciences》1988,77(3):787-796

Hydrocarbon exploration in the Molasse basin and the Alpine thrust belt has provided new information on the tectonic structure of the foreland margin of the overthrust belt. Two N-S cross-sections show the front of the Folded Molasse as a so-called Triangle Zone in the area north of the Hindelang 1 well (Bavaria) and the Sulzberg 1 well (Vorarlberg). The Triangle Zone was described and defined byJones (1982) for the Alberta Foothills in Canada.Oil and gas wells commonly encountered overpressured zones with pressure gradients up to 2.5 bar/10 m. The pressure profiles from the Sulzberg1, Hindelang1, Staffelsee1, Miesbach 1 and Bromberg 1 wells were analysed stratigraphically and lithologically with respect to the tectonics of the region. It can be concluded that the overpressures in the Foreland Molasse were caused by compaction, where those within the thrust belt were caused by tectonics.

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Zusammenfassung Die von der Erdöl- und Erdgasindustrie im Bereich des Alpennordrandes durchgeführten Untersuchungsarbeiten brachten neue Ergebnisse zum tektonischen Bau. So stellt sich in zwei N-S-Profilen nördlich von Hindelang (Bayern) und über die Tiefbohrung Sulzberg 1 (Vorarlberg) die Stirn der Faltenmolasse als Triangelzone dar, wie sie von Jones (1982) aus den Foothills der Rocky Mountains beschrieben wird.Tiefbohrungen auf Erdöl und Erdgas haben verbreitet überhydrostatische Porendrücke mit Gradienten bis 2,5 bar/10 m angetroffen. Es wurden Druckprofile aus den Bohrungen Sulzberg 1, Hindelang 1, Staffelsee 1, Miesbach 1 und Bromberg 1 nach stratigraphisch-lithologischen Gesichtspunkten analysiert, regionaltektonisch zugeordnet und interpretiert. Es zeigt sich, daß die Überdrücke in der Vorlandmolasse durch Kompaktion entstanden sind, während diejenigen unter den Decken tektonische Ursachen haben.

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Résumé Les travaux d'exploration entrepris par l'industrie du pétrole dans le bassin molassique et dans la bordure septentrionale des Alpes ont conduit à de nouveaux résultats en ce qui concerne les structures tectoniques de cette région. Dans deux profils nord — sud établis dans la région, respectivement au nord de Hindelang (Bavière) et au nord de Sulzberg (Vorarlberg), le front de la molasse plissée se présente comme une »zone triangulaire« du type défini parJones (1982) dans les Foothills d'Alberta au Canada.Des forages pétroliers profonds ont fréquemment recontré des pressions interstitielles hyperhydrostatiques avec des gradients pouvant atteindre 2,5 bars / 10 m.Les profils de pression relevés dans les sondages de Sulzberg 1, Hindelang 1, Staffelsee 1, Miesbach 1 et Bromberg 1 ont été analysés au point de vue stratigraphique et lithologique et placés dans le cadre tectonique de la région. Il en résulte que les surpressions dans la molasse d'avant-pays (Vorlandmolasse) sont dues à la compaction et que celles des formations recouvertes par les nappes sont d'origine tectonique.

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, - , . , Hindelang / /, Sulzberg 1 / Vorarlberg / , Jones' 1982 Foothills . 2.5 /10 . , . , , - .

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Local geoid determination and comparison with GPS results     

H. Denker  H. -G. Wenzel 《Journal of Geodesy》1987,61(4):349-366

Ellipsoidal heights have been determined for a test network in Lower Saxony withGPS. TheGPS results, with a relative precision of a few centimeters, have been used to compute quasigeoid heights by substracting leveling heights. This data set is compared to mainly gravimetrically determined quasigeoid heights using least squares collocation techniques. The discrepancies between the two data sets amount to about ±2cm, the maximum interstation distance is about50 km. This agreement shows, thatGPS can be used in combination with gravity information to obtain normal heights withcm-precision.  相似文献   

Medium-scale maps after survey from space—The “Metric-Camera”—Experiment     

Fezer Fritz Prof. Dr.  Reichenbach Bernhard  Witschel Christian MA  Hell Günter Prof. Dr.-Ing.  Duster Manfred Dipl.-Ing  Heidrich Brigitte 《GeoJournal》1987,14(4):467-478

Airphotos have been used for topographic survey since the Twenties. The “European Space Agency” (ESA), the “Deutsche Forschungs- und Versuchsanstalt für Luft- und Raumfahrt” (DFVLR) and “Carl Zeiss” have modified this successful technique for spacecraft and recently have tested the system over four continents. Each of these satellite photos covers a region of 189×189 km to the scale of 1∶800000 and may be enlarged to 1∶250000 or 1∶100000. Between the altitudes of 200 and 300 km, mapmaking or-revision seems to be economic in zones or in countries, where existing maps are of minor quality or outdated. In this paper, examples from deserts and semideserts in the Sudan are presented.  相似文献   

Subsurface countercurrent in the Bosporus already known to 6th century A. D. Byzantine fishermen     

Prof. Dr. Manfred Korfmann  Prof. Dr. Jehuda Neumann 《Ocean Dynamics》1985,38(4):189-190

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Shock effects on hydrous minerals and implications for carbonaceous meteorites     

Manfred A. Lange  Philippe Lambert  Thomas J. Ahrens 《Geochimica et cosmochimica acta》1985,49(8):1715-1726

New infrared absorption spectra, thermo-gravimetric analyses and optical-and scanning electron microscopy of shock-recovered specimens of antigorite serpentine (Mg₃Si₂O₅(OH)₄) from the pressure range between 25 to 59 GPa are reported. The infrared spectra show systematic changes in absorption peaks related to structural and molecular surface absorbed water. H₂O absorption peaks increase at the expense of OH peaks with increasing shock pressure. Changes in SiO bond vibrational modes with increasing shock pressure parallel those seen for other, non-hydrous minerals. Thermogravimetric analyses of shock-recovered samples determine the amount of shock-induced water loss. For samples shocked in vented assemblies, the data define a relation between shock-induced water loss versus shock pressure. Results for samples shocked in sealed assemblies demonstrate a dependence of water loss on shock pressure and target confinement. For the vented assembly samples, a linear relation between shock pressure and both the length of dehydration interval and the effective activation energy for releasing post-shock structural water in antigorite is found. Optical and scanning electron miscroscopy of shocked antigorite reveal a number of textures thought to be unique to shock loading of volatile-bearing minerals. Gas bubbles, which probably are the result of shock-released H₂O appear to be injected into zones of partial melting. This process may produce the vesicular dark veins which are distributed throughout heavily shocked samples. The present observations suggest several criteria which may constrain possible shock histories of the hydrous matrix phases of carbonaceous condrites. A model is proposed for explaining hydrous alteration processes occurring on carbonaceous chondrite parent bodies in the course of their accretion. We speculate that shock loading of hydrous minerals would release and redistribute free water in the regoliths of carbonaceous chondrite parent bodies giving rise to the observed hydrous alterations.  相似文献   

Melting and subsolidus reactions in the system K2O-CaO-Al2O3-SiO2-H2O: corrections and additional experimental data   总被引：2，自引：0，他引：2  

Manfred Schliestedt  Wilhelm Johannes 《Contributions to Mineralogy and Petrology》1984,88(4):403-405

Melting relationships in the system K₂O-CaO-Al₂O₃-SiO₂-H₂O have been reinvestigated using Schreinemakers analysis and hydrothermal experiments. The reaction sanidine+muscovite+zoisite+quartz+vapor =melt has been bracketed at 10, 15, and 20 kbars and 670–680, 680–690, and 690–700° C, respectively and it marks the lowest solidus temperatures in the system investigated.Below 10 kbars, experimental data on the beginning of melting in zoisite- or muscovite-bearing anorthite+sanidine assemblages have been obtained, which are not showing any differences and therefore point to melt compositions close to the feldspar-quartz join.  相似文献   

Accounting for site effect in probabilistic assessment of seismic hazard for Romania and Bucharest: a case of deep seismicity in Vrancea zone     

Vladimir Sokolov  Klaus-Peter Bonjer  Friedemann Wenzel 《Soil Dynamics and Earthquake Engineering》2004,24(12):929-947

The paper presents recent achievements in evaluations of site-dependent seismic hazard in Romania and the capital city of Bucharest caused by the Vrancea focal zone (SE-Carpathians). The zone is characterized by a high rate of occurrence of large earthquakes in a narrow focal volume at depths 60–170 km. The database that was used for the hazard evaluation includes parameters of seismicity, ground-motion source scaling and attenuation models (Fourier amplitude spectra), and site-dependent spectral amplification functions. Ground-motion characteristics were evaluated on the basis of several hundred records from more than 120 small magnitude (M 3.5–5) earthquakes occurred in 1996–2001 and a few tens of acceleration records obtained during four large (M 7.4, 7.2, 6.9 and 6.3) earthquakes. The data provide a basis for probabilistic seismic hazard assessment in terms of peak ground acceleration, peak spectral acceleration and MSK intensity using Fourier amplitude spectra for various exceedance probabilities or average return periods. It has been shown that the influence of geological factors plays very important role in distribution of earthquake ground-motion parameters along the territory of Romania.  相似文献   

Interferometric studies of the twilight and nightglow sodium D-line profiles     

Dwight P. Sipler  Manfred A. Biondi 《Planetary and Space Science》1978,26(1):65-73

A 150 mm aperture, pressure scanned Fabry-Perot interferometer has been used to study the midlatitude twilight and nightglow sodium D-line profiles. The line width measurements during evening and morning twilight indicate that the sodium layer temperature rises to a midwinter maximum (～230 K) and then falls to a midsummer minimum (～150 K), in qualitative agreement with the CIRA 1972 model predictions. Nightglow intensity measurements obtained with the interferometer indicate a highly variable behaviour, ranging from near-constant intensities, to monotonically falling, and to rising and falling intensities during the night. Broadening of the nightglow line profiles yields a sodium atom dissociation kinetic energy of (46 ± 4) meV. This suggests that the Chapman NaO + O chemiexcitation process, rather than dissociative recombination of “corkscrewing” ions and electrons, gives rise to the nightglow.  相似文献