Detection of the Askja AD 1875 cryptotephra in Latvia,Eastern Europe          下载免费PDF全文

Normunds Stivrins  Sabine Wulf  Stefan Wastegård  Ewa M. Lind  Tiiu Alliksaar  Mariusz Gałka  Thorbjørn Joest Andersen  Atko Heinsalu  Heikki Seppä  Siim Veski 《第四纪科学杂志》2016,31(5):437-441

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Isotopic age determinations of crystalline rocks of the Upper Harz Mountains,Germany     

Dr. Albrecht Baumann  Prof. Dr. Borwin Grauert  Dr. Sabine Mecklenburg  Dr. Roland Vinx 《International Journal of Earth Sciences》1991,80(3):669-690

Dating of crystalline rocks occurring in the Upper Harz Mountains was carried out by means of U-Pb isotope investigations on zircons and sphene as well as by Rb-Sr isotope measurements on whole-rock samples and biotites.U-Pb data of euhedral and rounded, detrital zircons of the allochthonous block of the Ecker gneiss point to an age (upper intercept) of the source area of the predominantly metasedimentary rocks of about 1.6 Ga or older. The lower intercept indicates a possible metamorphic event at ca. 560 Ma in the Ecker gneiss or in the source rock of the zircons of this complex. The concordant data point of a sphene fraction from a metavolcanic sample documents contact metamorphic influence on the Ecker gneiss by the Variscan intrusions of the Upper Harz Mountains.Emplacement of the intrusions of the Harzburg gabbronorite and the Brocken and Oker granites occurred contemporaneously 293–297 Ma ago within the analytical error limits. This points to a common geotectonic cause of the ascent of the magmas. Uplift of the Ecker gneiss block, now squeezed in between Harzburg gabbronorite and Brocken granite, was connected to these processes.The mineral ages of the plutonites are close to the intrusion ages indicating fast cooling processes in shallow crustal levels.

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Zusammenfassung Eine altersmäßige Einstufung der im Oberharz vorkommenden kristallinen Gesteine wurde durch U-Pb-Isotopenuntersuchungen an Zirkonen und Titanit sowie Rb-Sr-Isotopenmessungen an Gesamtgesteinsproben und Biotiten durchgeführt.U-Pb-Daten von idiomorphen und runden, detritischen Zirkonen der allochthonen Eckergneis-Scholle deuten auf ein Alter des Ursprungsgebietes der weitgehend metasedimentären Gesteine von etwa 1. 6 Ga oder älter hin und sie weisen ferner auf ein mögliches Metamorphose-Ereignis vor rund 560 Ma im Eckergneis oder im Liefergestein der Zirkone des Eckergneises hin. Der konkordante Datenpunkt bei ca. 295 Ma einer Titanit-Fraktion aus einer Metavulkanit-Probe dokumentiert die kontaktmetamorphe Beeinflussung des Eckergneises durch die variskischen Intrusionen des Oberharzes.Die Platznahme der Intrusionen der Gesteine des Harzburger Gabbronorit-Massivs sowie des Brokken- und Oker-Granits erfolgten innerhalb der analytischen Fehlergrenzen zeitgleich vor 293–295 Ma. Dies deutet auf eine gemeinsame geotektonische Ursache des Aufdringens der Magmen. Damit verbunden war der Aufstieg der Eckergneis-Scholle, die jetzt zwischen Harzburger Gabbronorit und Brockengranit »eingeklemmt« ist.Mineralalter der Plutonite liegen nahe bei den Intrusionsaltern und weisen auf rasche Abkühlungsvorgänge in seichtem Krustenniveau hin.

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Résumé Des mesures d'âge ont été effectuées sur des roches cristallines de l'Oberharz par les méthodes de l'U-Pb sur zircon et sphène et du Rb-Sr sur roches totales et sur biotites. La méthode U-Pb, appliquée aux zircons idiomorphes et détritiques arrondis de l'écaille allochtone des gneiss d'Ecker, fournit un âge (intersection supérieure) d'environ 1,6 Ga au moins pour la source des matériaux surtout métasédimentaires. L'intersection inférieure indique la possibilité d'un événement métamorphique à ± 560 Ma soit dans les gneiss d'Ecker, soit dans les roches-sources de leurs zircons. Un résultat concordant à ± 295 Ma fourni par le sphène d'une métavolcanite enregistre l'action du métamorphisme de contact engendré dans les gneiss d'Ecker par les intrusions varisques.La mise en place des intrusions du massif gabbronoritique du Harzburg et celle des granite de Brocken et d'Ocker ont été contemporaines: âges de 293 à 297 Ma, compris dans l'intervalle d'approximation des mesures. Ce résultat est en faveur d'une même cause géotectonique pour l'ascension de ces magmas. C'est en relation avec ce processus que s'est produit le soulèvement de l'écaillé des gneiss d'Ecker, actuellement coincée entre le gabbro du Harzburg et le granite de Brocken.Les âges minéraux des plutons sont voisins des âges d'intrusion, ce qui indique un refroidissement rapide dans un niveau crustal peu profond.

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The role of ternary projections in colour displays for geochemical maps and in economic mineralogy and petrology     

P. A. Sabine  R. J. Howarth   《Journal of Geochemical Exploration》1998,63(2)

Ternary (triangular) diagrams show the compositional variation of three end-members, recalculated to 100%, and represent the projection into two dimensions of three or more components (since an end-member may represent the sum of more than one original component), and hence multiple space. During the present century they have been of particular importance in chemistry, the earth sciences, colour-mixing and the studies of colour that underlie the development of geochemical colour maps. Such concepts can be traced back to Newton's Opticks although he did not use an explicit ternary theory of colour mixing. Development of the trichromatic theory of colour deficiency began with Mariotte in the 17th century and was definitively established by Maxwell in the 1850s. These colour theorems underlie the development in recent years of the colour maps now in widespread use in geochemistry. The progress of regional geochemical mapping in the British Isles has gone hand-in-hand with the development of computer software and hardware. The use of multi-element colour-combined geochemical maps can be traced from early work at Imperial College by Webb and his co-workers (1964–79) to its later application in the British Geological Survey's Geochemical Atlas series (from 1983 onwards). Between 1955 and 1975 the use of ternary diagrams came to be commonly used in studies of mineralogical composition, including economic minerals, petrology, classification, and phase relationships. In igneous petrology, the quartz–alkali-feldspar–plagioclase-feldspathoid double-triangle has achieved increasing international acceptance. We illustrate these applications with examples pertinent to the Northern Highland Caledonides, with particular emphasis on the lamprophyres and associated rocks. Two distinct multivariate trends of variation are shown to be present which may warrant further investigation to elucidate their bearing on Caledonian mineralisation.  相似文献   

The role of ternary projections in colour displays for geochemical maps and in economic mineralogy and petrology     

P.A. Sabine  R.J. Howarth 《Journal of Geochemical Exploration》1998,63(2):123-144

Ternary (triangular) diagrams show the compositional variation of three end-members, recalculated to 100%, and represent the projection into two dimensions of three or more components (since an end-member may represent the sum of more than one original component), and hence multiple space. During the present century they have been of particular importance in chemistry, the earth sciences, colour-mixing and the studies of colour that underlie the development of geochemical colour maps. Such concepts can be traced back to Newton's Opticks although he did not use an explicit ternary theory of colour mixing. Development of the trichromatic theory of colour deficiency began with Mariotte in the 17th century and was definitively established by Maxwell in the 1850s. These colour theorems underlie the development in recent years of the colour maps now in widespread use in geochemistry. The progress of regional geochemical mapping in the British Isles has gone hand-in-hand with the development of computer software and hardware. The use of multi-element colour-combined geochemical maps can be traced from early work at Imperial College by Webb and his co-workers (1964–79) to its later application in the British Geological Survey's Geochemical Atlas series (from 1983 onwards). Between 1955 and 1975 the use of ternary diagrams came to be commonly used in studies of mineralogical composition, including economic minerals, petrology, classification, and phase relationships. In igneous petrology, the quartz–alkali-feldspar–plagioclase-feldspathoid double-triangle has achieved increasing international acceptance. We illustrate these applications with examples pertinent to the Northern Highland Caledonides, with particular emphasis on the lamprophyres and associated rocks. Two distinct multivariate trends of variation are shown to be present which may warrant further investigation to elucidate their bearing on Caledonian mineralisation.  相似文献   

Detection of the historical Askja ad 1875 and modern Icelandic cryptotephras in varved lake sediments – results from a first systematic search in northern Poland     

MaŁgorzata Kinder  Sabine Wulf  Oona Appelt 《第四纪科学杂志》2021,36(1):1-7

Volcanic ash can disperse thousands of kilometres from the source volcano and provide valuable chronostratigraphic markers for palaeoclimate studies. We present new cryptotephra findings of historical and modern Icelandic eruptions in annually laminated lacustrine sediment records from several sites within a 570 km SW–NE transect across northern Poland. Sediments from the two lakes Wąsoskie and Szurpiły contain glass shards originating from the Plinian Askja ad 1875 eruption and showing bimodal, rhyolitic and dacitic affinities. A further cryptotephra finding in Lake Lubińskie suggests a potential origin from the Hekla ad 1845 eruption. These new findings extend the tephra dispersal map towards the south-east and provide valuable isochrons for the synchronisation of palaeoclimate proxy data at the termination of the Little Ice Age in central eastern Europe. Very low glass concentrations of modern cryptotephra in Lake Wąsoskie were potentially correlated with the Eyjafjallajökull ad 2010 eruption. Further findings in the uppermost sediments of lakes Szurpiły and Żabińskie in north-eastern Poland tentatively suggest other sources from either the Hekla and/or Kamchatkan volcanoes.  相似文献   

Digital elevation model with the ground-based SAR IBIS-L as basis for volcanic deformation monitoring     

Sabine Rödelsperger  Matthias Becker  Carl Gerstenecker  Gwendolyn Läufer  Kathrin Schilling  Dieter Steineck 《Journal of Geodynamics》2010,49(3-4):241-246

Within the project Exupéry, a hybrid deformation observation system is developed, which is part of a Volcano Fast Response System (VFRS). The VFRS shall be a mobile, robust, real-time, easy to use early warning system, which, in case of a volcanic crisis, will support the locale authorities in their decisions about hazard mitigation provisions, especially about the evacuation of people.The hybrid deformation observation system combines a ground-based Synthetic Aperture Radar named IBIS-L with a network of GPS receivers and will allow the continuous, weather independent determination of areal 3D displacements.In this paper we present the results of first tests with IBIS-L in an active quarry near Dieburg, Germany. A Digital Elevation Model (DEM) was determined with IBIS-L and compared with a DEM derived by terrestrial laser scanning and photogrammetry. The ability to determine accurate DEMs with IBIS-L is the basis for the combination of different observation techniques, as without a DEM the displacements observed with IBIS-L cannot be georeferenced.The standard deviation of the differences between the DEM by IBIS-L and the DEM by laser scanning and photogrammetry depends on the surface characteristics. We found a standard deviation of 0.8 m at a slope of rocks and debris, 2.0 m at mining terraces with low vegetation and 3.0 m in a vegetation covered area.  相似文献   

Gas hydrates in shallow deposits of the Amsterdam mud volcano, Anaximander Mountains, Northeastern Mediterranean Sea   总被引：2，自引：2，他引：0  

Thomas Pape  Sabine Kasten  Matthias Zabel  André Bahr  Friedrich Abegg  Hans-Jürgen Hohnberg  Gerhard Bohrmann 《Geo-Marine Letters》2010,30(3-4):187-206

We investigated gas hydrate in situ inventories as well as the composition and principal transport mechanisms of fluids expelled at the Amsterdam mud volcano (AMV; 2,025 m water depth) in the Eastern Mediterranean Sea. Pressure coring (the only technique preventing hydrates from decomposition during recovery) was used for the quantification of light hydrocarbons in near-surface deposits. The cores (up to 2.5 m in length) were retrieved with an autoclave piston corer, and served for analyses of gas quantities and compositions, and pore-water chemistry. For comparison, gravity cores from sites at the summit and beyond the AMV were analyzed. A prevalence of thermogenic light hydrocarbons was inferred from average C₁/C₂₊ ratios <35 and δ¹³C-CH₄ values of ?50.6‰. Gas venting from the seafloor indicated methane oversaturation, and volumetric gas–sediment ratios of up to 17.0 in pressure cores taken from the center demonstrated hydrate presence at the time of sampling. Relative enrichments in ethane, propane, and iso-butane in gas released from pressure cores, and from an intact hydrate piece compared to venting gas suggest incipient crystallization of hydrate structure II (sII). Nonetheless, the co-existence of sI hydrate can not be excluded from our dataset. Hydrates fill up to 16.7% of pore volume within the sediment interval between the base of the sulfate zone and the maximum sampling depth at the summit. The concave-down shapes of pore-water concentration profiles recorded in the center indicate the influence of upward-directed advection of low-salinity fluids/fluidized mud. Furthermore, the SO ₄ ^2? and Ba²⁺ pore-water profiles in the central part of the AMV demonstrate that sulfate reduction driven by the anaerobic oxidation of methane is complete at depths between 30 cm and 70 cm below seafloor. Our results indicate that methane oversaturation, high hydrostatic pressure, and elevated pore-water activity caused by low salinity promote fixing of considerable proportions of light hydrocarbons in shallow hydrates even at the summit of the AMV, and possibly also of other MVs in the region. Depending on their crystallographic structure, however, hydrates will already decompose and release hydrocarbon masses if sediment temperatures exceed ca. 19.3°C and 21.0°C, respectively. Based on observations from other mud volcanoes, the common occurrence of such temperatures induced by heat flux from below into the immediate subsurface appears likely for the AMV.  相似文献   

The effect of different second-phase particle regimes on grain growth in two-phase aggregates: insights from in situ rock analogue experiments     

Sabine Helene Brodhag  Marco Herwegh 《Contributions to Mineralogy and Petrology》2010,160(2):219-238

The aim of the study was to investigate the effect of rigid second phases on grain growth of a matrix phase. For this purpose, variable mixtures of norcamphor as the matrix phase, with glass beads (0.08–0.51 volume fraction) as second phase, were used to perform see-through rock-analogue experiments under static conditions at constant temperatures (50°C). Irrespective of the second-phase content, grain-size evolution of all mixtures can be subdivided into a stage of continuous grain growth, a transient stage and a stage of a finally stabilized grain size. On the grain-scale, the second phases affect the migrating grain boundaries either by pinning by single particles, by multiple particles or even by particle clusters. Summed up over the entire aggregate, these pinning regimes affect the average bulk grain size of the matrix grains, such that the changes in matrix grain size directly correlate with the amount of second phases, their dispersion and their degree of clustering. In this way, the matrix grain size decreases with increasing second-phase content, which can be expressed as a Zener relationship. Originating from the modification of an ordinary grain growth law, a new mathematical expression is defined, which allows the calculation of changes in the matrix grain size as a function of different second-phase volume fractions and particle sizes. Such models will be helpful in the future to predict microstructural changes in polymineralic rocks at depth.  相似文献   

Gas in Groups and Clusters of Galaxies     

Sabine Schindler 《Astrophysics and Space Science》2004,289(3-4):419-428

Groups and clusters contain a large fraction of hot gas which emitsX-ray radiation. This gas yields information on the dynamical stateand on the total mass of these systems. X-ray spectra show that heavyelements are present in the gas. As these metals must have beenproduced in the cluster/group galaxies and later transported into thegas, the metallicity is a good tracer for the transport processes. Severalpossible processes, that transport gas from the small potential wellsof the galaxies into the clusters and groups, are discussed.  相似文献   

Long‐Term Sediment Export Estimates from Northern Jordan using Roman Cisterns as Sediment Traps     

Sabine Kraushaar  Gregor Ollesch  Christian Siebert  Hans‐Joerg Vogel  Markus Fuchs 《Geoarchaeology》2015,30(4):369-378

Roman cisterns served as rainwater storage devices for centuries and are densely distributed in parts of northern Jordan. A major earthquake hit the region ca. A.D. 750 and in a short time many settlements were abandoned. As a consequence, most cisterns were not maintained, and they filled with sediments that today provide a postabandonment depositional record. In two field surveys, we mapped the locations of more than 100 cisterns in the Wadi Al‐Arab basin and selected two for detailed stratigraphic analysis that included ¹⁴C and optically stimulated luminescence dating. Catchment basin area for each cistern was determined by differential GPS. Both cisterns filled with sediments after the great earthquake and consequent abandonment of the region. Calculated sediment volumes are translated to long‐term average sediment export rates of 2.6–6.6 t ha⁻¹a⁻¹, which are comparable to erosion and sediment yield rates from other studies within the Mediterranean region. Our pilot study suggests that this approach can be applied elsewhere to calculate long‐term sediment export rates on hill slopes containing relict cisterns.  相似文献