Low-temperature opal-CT precipitation in Antarctic deep-sea sediments: evidence from oxygen isotopes     

Reiner Botz  Gerhard Bohrmann   《Earth and Planetary Science Letters》1991,107(3-4)

Porcellanite has been found in Antarctic deep-sea sediments of shallow burial depth at four different sites in host sediments younger than 4 Ma. Oxygen isotope analysis shows that the opal-CT samples are extremely rich in¹⁸O (δ¹⁸O= 41.2to44.7‰ rel. SMOW). According to the quartz/water fractionation the calculated isotopic opal-CT formation temperature is in the range of 0 to 4°C. This agrees well with sediment temperature measurements. The low opal-CT precipitation temperature contrasts with current ideas about later diagenetic formation of opal-CT at higher temperatures of 18 to 56°C.  相似文献   

The professional image: Student,professor, practitioner     

Lee C. Gerhard 《Environmental Geology》1991,17(2):63-66

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Der Eiswinter 1989/90 im deutschen Küstengebiet zwischen Ems und Trave     

Dr. Gerhard Koslowski 《Ocean Dynamics》1990,43(2):89-90

Ohne Zusammenfassung  相似文献   

Reconstruction of the ice winter severity since 1701 in the Western Baltic     

Gerhard Koslowski  Rüdiger Glaser 《Climatic change》1995,31(1):79-98

This reconstruction of the ice winter severity in the Western Baltic is based for the period 1878-1993 on the accumulated areal ice volume along the German Baltic coast with observations from 13 coastal stations; for the period 1701-1877 it is based on the accumulated areal ice volume divided into 7 classes (ice winter severity types). The various types of data consulted in the latter case provided ice data of good spatial and temporal resolution.Speerschneider's compilation of data relating to ice conditions in Danish Baltic waters was found to be a valuable source of information. Using a classification table for the periods 1907-1943 and 1947-1992, five of the seven ice winter types have been derived with certainty as they are characterized by typical stages of maximum ice cover throughout the Western Baltic.The Gaussian lowpass-filtered time series of the ice winter index numerals with a 20 year cutoff period shows four periods of varying ice winter severity over a secular range: 1701-1720: slightly increased ice winter severity with regard to the mean of the 1701-1993 time series; this period can be assigned to the end of a cooling phase during Little Ice Age which in central Europe peaked in the second half of the 17th c. 1721-1760: ice winter severity is clearly reduced in this period. 1761-1860: ice winter severity is clearly increased (maximum occurs around 1800) towards the end of the Little Ice Age, associated with increased variability of ice production. 1861-1993: the present-day ice winter regime when three short intervals with increased ice winter severity (the 1890s, 1940s and 1980s) and a period of greatly reduced ice winter severity (between 1900 and the mid-1920s) stand out.  相似文献   

Experimental Na-K distribution between amphiboles and aqueous chloride solutions, and a mixing model along the richterite – K-richterite join     

Rolf Zimmermann  M. Gottschalk  Wilhelm Heinrich  Gerhard Franz 《Contributions to Mineralogy and Petrology》1997,126(3):252-264

The cation exchange equilibrium has been investigated by hydrothermal experiments at 700 and 800°C at 200 MPa. To avoid equilibration problems of conventional exchange experiments, we synthesized amphiboles with an excess fluid allowing exchange between solid and fluid during the experiment. The exchangeable cations Na and K were provided as excess 1 to 2n chloridic solution. These exchange syntheses can be described by the reaction equation with ^(aq) for hydroxides and chlorides in aqueous solutions and _{( s )} and _{( p )}?=?start and product fluid. The amphiboles grew in presence of the exchange fluid and adjusted their stoichiometry in equilibrium with the fluid phase. The solid products consist of more than 99% amphibole (Na,K-richterite_ss) with traces of diopside and quartz. The amphiboles are up to 1?mm long and often ≈ 40 μm thick. Detailed EMP- and HRTEM-observations show that they are chemically homogeneous and structurally wellordered. The experimental results give consistent phase relations in the reciprocal ternary system Na-richterite–K-richterite–NaCl–KCl. We analysed the product fluid with AAS- and ICP-methods. The Na-K distribution coefficients between fluid and amphiboles of the richterite–K-richterite join are close to unity at 700°C and 800°C at 200 MPa. Small systematic deviations are explained by a symmetric solution model for the A-position of the amphiboles. Using ideal mixing for H₂O-NaCl-KCl fluids, a mixing model for the system richterite–K-richterite is presented. We suggest that the composition of richterite solid solutions can be used as a sensor for NaCl/KCl-ratios in metamorphic fluids.  相似文献   

Copper isotope behavior during extreme magma differentiation and degassing: a case study on Laacher See phonolite tephra (East Eifel,Germany)     

Jian Huang  Sheng-Ao Liu  Gerhard Wörner  Huimin Yu  Yilin Xiao 《Contributions to Mineralogy and Petrology》2016,171(8-9):76

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Common human identity and the path to global climate justice     

Gerhard Reese 《Climatic change》2016,134(4):521-531

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Zur Berechnung der latenten und fürhlbaren Wärmeströme von der Meeresoberfläche an die Luft     

Gerhard Manier 《Pure and Applied Geophysics》1962,52(1):189-213

Zusammenfassung Ausgehend von der Temperaturänderung eines Einheitsvolumens einer inkompressiblen Strömung werden die Gleichungen für den Transport von Bewegungsgröße und von fühlbarer und latenter Wärme bestimmt. Mit der Annahme, daß die Temperaturschichtung in den untersten 10 cm vernachlässigbar ist, kann man aus den vorhandenen Messungen der Schubspannung bei adiabatischer Schichtung die Schubspannung bei nichtadiabatischer Schichtung berechnen, wenn man voraussetzt, daß die Windgeschwindigkeit einem Potenzgesetz der Höhe gehorcht und die Schubspannung höhenkonstant ist. Aus diesen Schubspannungswerten kann man den turbulenten Diffusionskoeffizienten für den Transport von Bewegungsgröße bestimmen. Nimmt man weiter an, daß sich die turbulenten Diffusionskoeffizienten für die drei Transporte nicht unterscheiden und daß auch die Temperatur und Feuchte einem Potenzgesetz der Höhe gehorchen, dann kann man aus den Temperatur-und Feuchtemessungen in zwei Höhen und einer Windgeschwindigkeitsmessung den fühlbaren und latenten Wärmestrom berechnen. Ein Vergleich mit denJacobs'schen Formeln für die Verdunstung und den Transport von fühlbarer Wärme zeigt, daß die Ergebnisse nur für mittlere Windgeschwindigkeiten gut übereinstimmen. Für höhere Windstärken liefern dieJacobs'schen Formeln viel zu kleine Werte.

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Summary From the change of potential temperature of unit volume of an incompressible fluid, the transport equation for sensible and latent heat and for momentum have been determined. Neglecting the influence of temperature stratification on the lowest 10 cm and assuming the wind speed to follow a power law of height and the shearing stress to be independent of height, it is possible to determine the shearing stress for nonadiabatic conditions from the measurements of the shearing stress for adiabatic stratification. From the shearing stress one may determine the eddy diffusivityK(z). Assuming the three coefficients for turbulent diffusion to be identical and the temperature and humidity to follow a power law of height, one can determine the latent and sensible heat transfer from temperature and humidity measurements at two heights and one wind speed measurement. Comparison withJacobs's formulas for the evaporation and sensible heat transfer shows that the results agree only for medium wind speed. For larger wind velocitiesJacobs's formulas yield much too low values.

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Zur Feinstruktur der geomagnetischen Pulsationenpc 3     

Gerhard Fanselau 《Pure and Applied Geophysics》1966,65(1):73-94

Zusammenfassung Nach Beobachtungen in Wingst und Niemegk zeigen Perioden und Amplituden von Pulsationszügen statistische Verteilungen um den Mittelwert. Die Periodendifferenzen zwischen beiden Observatorien schwanken statistisch, zeigen nur im Mittel eine ausgeprägte Abhängigkeit von der Periodenlänge selbst. Die Abhängigkeit der Perioden und Amplituden von derA _K -Zahl is klar ausgeprägt. Die statistischen Schwankungen an beiden Observatorien verlaufen lange Zeit hindurch absolut gleichmässig, wenn auch nicht zeitlich simultan.

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Summary The fine structure of pulsations typepc 3 was studied under quiet conditions at Niemegk and Wingst. A clear Gaussian distribution could be found for periods as well as amplitudes. This statistical noise is superimposed upon some regular features nearly identic at the both observatories. The connection between periods at the two observatories is not linear but parabolic. A physically significant difference of the periods at the two observatories cannot easily be defined.

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Mitteilung aus dem Geomagnetischen Institut der DAW, Potsdam, Nr. 230.  相似文献   

Statistische Bearbeitung der Parameter des geomagnetischen Feldes und der Säkularvariation     

Gerhard Fanselau  Wolfgang Mundt 《Pure and Applied Geophysics》1965,61(1):69-88

Zusammenfassung Es werden Möglichkeiten zur statistischen Bearbeitung der Parameter geomagnetischer Potentialberechnungen dargestellt und bezüglich der Potsdamer Potentialberechnung zur Epoche 1945.0 praktisch erprobt. Die Ergebnisse werden in zusammengefasster Form vorgelegt und diskutiert.

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Summary The possibilities of a statistical analysis of the parameters of geomagnetic field are presented, and with reference to the spherical harmonical analysis of the Geomagnetic Institute in Potsdam practical tested. The results are presented and discussed in a summarized manner.

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Mitteilung aus dem Geomagnetischen Institut der DAW, Potsdam, Nr. 199.  相似文献