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31.
Polymetamorphic relations in iron ores from the Iron Quadrangle,Brazil: The correlation of oxygen isotope variations with deformation history 总被引:2,自引:0,他引:2
Joachim Hoefs Georg Müller Alfred K. Schuster 《Contributions to Mineralogy and Petrology》1982,79(3):241-251
This study deals with the oxygen isotope composition of hematite-rich ore bodies in the Iron Quadrangle, Brazil. The area studied can be divided into two different regions: a western (W) zone of greenschist facies assemblages and an eastern (E) zone of amphibolite facies with transitions into granulite facies assemblages.The
18O values of 136 quartz-iron oxide pairs have been determined and temperatures of formation have been calculated. The
18O values of quartz vary between +6 and 20 except one value near +23, whereas the iron oxides fall between –4 and +10, with nearly 80% of the iron oxide values between –0.5 and 4.0. The regional distribution of the
18O values is as follows: in the W-region 85% of the quartz are >12, whereas in the E-region only 46% fall in this range, In contrast to quartz the iron oxides do not show any regional differences.The variation of oxygen isotope fractionations between quartz and iron oxides is obviously related to the complex deformation history of the iron ores. Samples with a primary schistosity (S1) only represent peak metamorphic conditions. In the E-region the (S1) high temperatures >700° C seem to correspond to orogenic events in the Archaen basement 2,700 m.y. ago. In the W-region S1-temperatures between 460° and 560° C seem to represent peak metamorphic conditions of the Proterozoic Minas metamorphism 2,000 m.y. ago. Iron ores which have been overprinted by later deformation events are selectively reset to lower isotopic temperatures. The more closely spaced the schistosity planes the larger the extent of a temperature lowering.The genetic processes associated with these hematite-rich ore bodies appear to be sedimentary-metamorphic rather than metasomatic processes. Furthermore, there is no evidence for secondary leaching by weathering solutions. 相似文献
32.
Sven-Ulf Weber Michael Grodzicki Werner Lottermoser Günther J. Redhammer Gerold Tippelt Johann Ponahlo Georg Amthauer 《Physics and Chemistry of Minerals》2007,34(7):507-515
Natural alexandrite Al2BeO4:Cr from Malyshevo near Terem Tschanka, Sverdlovsk, Ural, Russia, has been characterized by 57Fe Mössbauer spectroscopy, electron microprobe, X-ray single-crystal diffractometry and by electronic structure calculations in order to determine oxidation state and location of iron. The sample contains 0.3 wt% of total iron oxide. The 57Fe Mössbauer spectrum can be resolved into three doublets. Two of them with hyperfine parameters typical for octahedrally coordinated high-spin Fe3+ and Fe2+, respectively, are assigned to iron substituting for Al in the octahedral M2-site. The third doublet is attributed to Fe3+ in hematite. Electronic structure calculations in the local spin density approximation are in reasonable agreement with experimental data provided that expansion and/or distortion of the coordination octahedra are presumed upon iron substitution. The calculated hyperfine parameters of Fe3+ are almost identical for the M1 and M2 positions, but the calculated ligand-field splitting is by far too large for high-spin Fe3+ on M1. 相似文献
33.
Roland Eichhorn Georg Loth Allen Kennedy 《Contributions to Mineralogy and Petrology》2001,142(2):147-162
The U-Pb SHRIMP age determinations of zircons from the Habach terrane (Tauern Window, Austria) reveal a complex evolution of this basement unit, which is exposed in the Penninic domain of the Alpine orogen. The oldest components are found in zircons of a metamorphosed granitoid clast, of a migmatitic leucosome, and of a meta-rhyolitic (Variscan) tuff which bear cores of Archean age. The U-Pb ages of discordant zircon cores of the same rocks range between 540 and 520 Ma. It is assumed that the latter zircons were originally also of Archean origin and suffered severe lead loss, whilst being incorporated into Early-Cambrian volcanic arc magmas. The provenance region of the Archean (2.64-2.06 Ga) zircons is assumed to be a terrane of Gondwana affinity: i.e., the West African craton (Hoggar Shield, Reguibat Shield). The Caledonian metamorphism left a pervasive structural imprint in amphibolite facies on rocks of the Habach terrane; it is postdated by discordant zircons of a migmatitic leucosome at <440 Ma (presumably ca. 420 Ma). Alpine and Variscan upper greenschist- to amphibolite-facies conditions caused partial lead loss in zircons of a muscovite gneiss ('white schist') only, where extensive fluid flow and brittle deformation due to its position near a nappe-sole thrust enhanced the grains' susceptibility to isotopic disturbance. The Habach terrane - an active continental margin with ensialic back-arc development - showed subduction-induced magmatic activity approx. between 550 and 507 Ma. Back-arc diorites and arc basalts were intruded by ultramafic sills and subsequently by small patches of mantle-dominated unaltered and (in the vicinity of a major tungsten deposit) altered granitoids. Fore-arc (shales) and back-arc (greywackes, cherts) basin sediments as well as arc and back-arc magmatites were not only nappe-stacked by the Caledonian compressional regime closing the presumably narrow oceanic back-arc basin and squeezing mafic to ultramafic cumulates out of high-level magma chambers (496-482 Ma). It also induced uplift and erosion of deeply rooted crystalline complexes and triggered the development of a successor basin filled with predominantly clastic greywacke-arkosic sediments. The study demonstrates that the basement rocks exposed in the Habach terrane might be the 'missing link' between similar units of the more westerly positioned External domain (i.e., Aar, Aiguilles Rouges, Mont Blanc) and the Austroalpine domain to the east (Oetztal, Silvretta). 相似文献
34.
Georg Koopmann 《Ocean Dynamics》1962,15(5):181-198
Zusammenfassung Nach den Erfahrungen im Windstau- und Sturmflutwarndienst des Deutschen Hydrographischen Instituts müssen bei Wasserstands- oder Sturmflutvorausberechnungen, außer einer statistisch ermittelten Beziehung Windfeld-Windstau, der statische Luftdruck, die Böigkeit des Windes sowie die Inhomogenität des Windfeldes berücksichtigt werden. Der noch verbleibende Reststau wird untersucht, soweit er dem Betrage nach größer als 30 cm ist.Es lassen sich nachweisen: 1. Fortschreitende Wellen, die mit Luftdruckschwankungen in Resonanz stehen, 2. Querschwingungen der Nordsee, 3. Schwallerscheinungen in der Deutschen Bucht, die mit den an der englischen Küste bekannten external surges in Beziehung gesetzt werden. Es wird dargestellt, wie diese wellenförmigen Wasserstandserhöhungen bei der Vorhersage berücksichtigt werden können. Zum Schluß wird eine Aufgliederung der bei der Sturmflut vom 16./17. Februar 1962 gemessenen Wasserstandserhöhungen auf die oben dargelegte Weise gegeben.
Ein Vortrag wurde am 11. Oktober 1962 auf der Meteorologentagung in Hamburg gehalten. 相似文献
Elevations of water level in the German Bight due to oscillations and surges and their importance to the storm surge of 16/17th February 1962
Summary According to the experiences made by the Storm Surge Warning Service of Deutsches Hydrographisches Institut in predicting water level and storm surges, it is necessary to consider not only the relation wind field — wind effect, calculated by statistical means, but also the squally character of the wind, the static atmospheric pressure, and the inhomogeneity of the wind field. The still remaining residual wind effect is analysed, as far as its value exceeds 30 cm.The following phenomena have been verified: 1. Progressive waves caused by atmospheric pressure variations (resonance case), 2. Transverse oscillations of the North Sea, 3. Surges in the German Bight that may be related to the external surges, a well known phenomenon on the British coasts. It is discussed how these wave-shaped elevations of the water level can be considered in predicting storm surges. Finally, the different elevations of the water level, measured during the storm surge of 16th to 17th February, 1962, are analysed with the aid of the afore mentioned method.
Elévations du niveau de la mer dues aux oscillations et aux ondes de tempêtes et leur importance à l'inondation du 16e et du 17e février 1962 dans la Deutsche Bucht
Résumé Suivant les expériences que le Service d'Avertissement des Marées de Tempêtes au Deutsches Hydrographisches Institut a faites à l'occasion de la prévision des ondes de tempêtes, il s'est montré nécessaire de tenir compte non seulement de la relation entre le champ du vent et l'effet du vent calculée à l'aide des moyens statistiques mais qu' il faut aussi bien considérer le vent à rafales, la pression atmosphérique statique et l'inhomogénéité du champ du vent. L'effet résiduel du vent qui pourtant reste, est analysé en tant que sa valeur s'élève à plus de 30 centimètres.Les phénomènes suivants ont été vérifiés: 10 «Ondes progressives» causées par des variations de la pression atmosphérique (cas de résonance), 20 «Oscillations transversales» de la mer du Nord, 30 «Houles» dans la Deutsche Bucht qui peuvent être associées aux houles externes (external surges), phénomènes bien connus sur les côtes britanniques. On discute de quelle manière on pourrait tenir compte de ces élévations ondulatoires du niveau de la mer dans la prévision des ondes de tempêtes. Enfin, les élévations diverses du niveau de la mer, mesurées à l'occasion de l'inondation du 16e et du 17e février 1962, sont analysées à l'aide de la méthode décrite ci-dessus.
Ein Vortrag wurde am 11. Oktober 1962 auf der Meteorologentagung in Hamburg gehalten. 相似文献
35.
Georg Wüst 《Ocean Dynamics》1961,14(3):81-92
Zusammenfassung Der Beitrag stellt eine Fortsetzung der 1960 in dieser Zeitschrift Jahrgang 13, Heft 3 erschienenen Abhandlung (Wüst [1960]) dar und führt die Studien über die mittelmeerische Tiefenzirkulation in bezug auf die Ausbreitungs- und Vermischungsvorgänge im Bodenwasser (bei Wassertiefen von mehr als 1500 m) fort. Nach einem detaillierten Nachweis über das Quellenmaterial, das 234 Stationen (von 11 Forschungsschiffen) umfaßt, wedden weitere Belege zur Frage der Formung des Nordbalearischen und des Adriatischen Bodenwassers gebracht und die Verbreitung dieser beiden Wasserarten auf Grund neuer Karten der potentiellen Bodentemperatur und des Bodensalzgehaltes in den beiden mittelmeerischen Großbecken verfolgt. Durch ein schematisches dreigeteiltes Blockdiagramm (Tafel 5) wird die Vertikalzirkulation und Salzgehaltsverteilung des Mittelmeeres im Winter in ihrem Zusammenwirken zonaler und meridionaler Komponenten veranschaulicht. In einem Nachtrag (zum 1. Beitrag 1960) wird eine weitere Kernschichtkarte des Levantinischen Zwischenwassers auf grund der Armauer Hansen-Stationen Mai–Juni 1931 vorgelegt.
Hierzu Tafeln 2–5 im Anhang
Herrn Professor Dr. Günter Dietrich zum 50. Geburtstag gewidmet. 相似文献
The bottom water and the vertical circulation of the Mediterranean Sea
Summary The present paper is a continuation of the first article published in vol. 13, page 105 of this journal (Wüst [1960]). It continues the studies of the deep circulation in the Mediterranean Sea with regard to distribution and mixing in the bottom water (at depths of 1500 m and more). A detailed verification of the observational material comprising 234 stations (of 11 research vessels) is presented and some further proofs concerning the formation of the North-balearic and the Adriatic bottom water are given. Besides, basing on new charts of the potential bottom temperature and bottom salinity, the distribution of the aforementioned two water types in the two large mediterranean basins is discussed. A schematical diagram consisting of three four-edged columns (Tafel 5), shows clearly the vertical circulation and salinity distribution in the Mediterranean Sea and the combined action of their zonal and meridional components during the winter months. As a supplement to the 1960-paper in this journal, another chart is added showing the core layers of the Levantine intermediate water based on the Armauer Hansen-stations from May and June 1931.
Les eaux du fond et la circulation verticale de la mer Méditerranée
Résumé L'article actuel fait suite au premier travail, paru dans le volume13, page 105 de ce journal (Wüst [1960]). Il continue les recherches de la circulation mediterranéenne par rapport aux processus de distribution et de mélange des eaux du fond (à 1500 mètres de profondeur et plus). Le matériel d'observation comprenant 234 stations (exécutées par 11 bâtiments de recherche) est soumis à une vérification détaillée; d'autres preuves sont apportées concernant la formation des eaux du fond dans la région septentrionale du bassin baléarique et dans la mer Adriatique. Partant de nouvelles cartes de la température potentielle et de la salinité des eaux du fond on poursuit, en même temps, les études de la distribution des deux types d'eaux rencontrés dans les deux grands bassins de la Méditerranée mentionnés ci-dessus. Un diagramme schématique se composant de trois colonnes quadrangulaires (Tafel 5) montre nettement la circulation verticale et la distribution de la salinité méditerranéenne ainsi que l'action combinée de leurs composantes régionales et méridionales pendant les mois d'hiver. Dans un supplément au premier travail (Wüst [1960]) une autre carte est ajoutée représentant les couches de noyaux des eaux intermédiaires levantines basant sur les stations de l'«Armauer Hansen» en mois de mai et de juin 1931.
Hierzu Tafeln 2–5 im Anhang
Herrn Professor Dr. Günter Dietrich zum 50. Geburtstag gewidmet. 相似文献
36.
37.
Kaledonische Intrusivgesteine des Stavanger-Gebietes 总被引:3,自引:0,他引:3
Prof. Dr. Georg Müller 《Contributions to Mineralogy and Petrology》1970,25(1):52-65
An empirical approach has been taken to develop a geothermometer based on plagioclase-magmatic liquid equilibrium. Compositions of coexisting plagioclase and liquid (glass) obtained by electron microprobe analysis of quenched samples from equilibrium melting experiments of natural granitic rocks at water pressures of 0.5 and 1.0 kilobars have been used along with data from the equilibrium experiments of Bowen (1913, 1915), Prince (1943) and Yoder et al. (1957) to calibrate this geothermometer. Applications of this geothermometer to natural occurrences demonstrate that it can provide useful information on temperature of equilibration of coexisting plagioclase and liquid in rocks ranging in composition from basalt to rhyolite. The plagioclase geothermometer is in good general agreement with other geothermometers wherever these are applicable. Where temperatures are known from other sources it can be used to predict the equilibrium compositions of plagioclase in magmas as well as to provide a rough estimate of water pressure. 相似文献
38.
39.
Georg Knetsch 《International Journal of Earth Sciences》1955,43(1):227-232
Zusammenfassung Im folgenden werden einige Beobachtungen und Schlüsse über die nach W fortschreitende orogenetische Verformung der Iraniden mitgeteilt. Diese Faltung zeigt eine deutliche Wanderung und macht sich in den östlichen Bereichen Mesopotamiens noch in den letzten 1700 Jahren bemerkbar. 相似文献
40.
Martin Sudmanns Dirk Tiede Stefan Lang Helena Bergstedt Georg Trost Hannah Augustin 《International Journal of Digital Earth》2020,13(7):832-850
ABSTRACT Turning Earth observation (EO) data consistently and systematically into valuable global information layers is an ongoing challenge for the EO community. Recently, the term ‘big Earth data’ emerged to describe massive EO datasets that confronts analysts and their traditional workflows with a range of challenges. We argue that the altered circumstances must be actively intercepted by an evolution of EO to revolutionise their application in various domains. The disruptive element is that analysts and end-users increasingly rely on Web-based workflows. In this contribution we study selected systems and portals, put them in the context of challenges and opportunities and highlight selected shortcomings and possible future developments that we consider relevant for the imminent uptake of big Earth data. 相似文献