D/H exchange in pure and Cr-doped enstatite: implications for hydrogen diffusivity

The kinetics of hydrogen diffusion in enstatite was studied by hydrogen–deuterium exchange experiments in the range of 1–5,000 bar and 700–850°C using synthetic single crystals of pure and Cr-doped enstatites. The OH- and OD-content in the samples was quantified after each thermal treatment with Fourier transformed infrared spectroscopy. H–D-exchange rates were measured parallel to the three crystallographic axes. In addition, in order to visualize diffusion profiles, OH and OD were mapped for some samples, utilizing synchrotron IR micro-spectroscopy. Hydrogen self-diffusivities derived from D/H exchange experiments at one atmosphere are very similar to the chemical diffusivity of hydrogen in natural Fe-bearing orthopyroxene, which was reported previously (Stalder and Skogby 2003) to exhibit a small, but significant anisotropy (D[001] > D[100] > D[010]). Activation energies are estimated to be 211 (±31) kJ/mol for diffusion parallel [100] and 185 (±28) kJ/mol for diffusion parallel [010]. Lattice diffusion of hydrogen is decelerated by more than one order of magnitude when Cr is dissolved in enstatite. In comparison to the chemical composition, pressure seems to have only a minor influence on hydrogen diffusion. Compared to other minerals in the Earth’s upper mantle, enstatite exhibits the highest activation energy for hydrogen diffusion, suggesting faster diffusion than in other mafic minerals at mantle temperatures, but slower diffusion at crustal conditions. Thus under upper mantle conditions, physical properties that are expected to be influenced by hydrogen mobility, such as electrical conductivity, may in enstatite be more intensely affected by the presence of hydrogen than in other upper mantle minerals.     

The combination of sampling and kriging in the regional estimation of coal resources

Two-dimensional systematic sampling of small plots followed by the kriging of those plots may be employed to obtain regional estimates of coal resources and measures of the accuracy of the estimates. The use of sampling makes large savings in computation possible. Two case studies involving the estimation of coal tonnage are discussed.     

Versuche zur Messung der Schallgeschwindigkeit und Schalldämpfung im Sediment in situ

Zusammenfassung Ein neues Gerät mit einer verbesserten Konstruktion zur Messung der Schallgeschwindigkeit und Schalldämpfung im Sediment in situ läßt Eindringtiefen bis 3 m zu. Die Einsatzmöglichkeit ist durch höhere Schallsendepegel und höhere Empfindlichkeit erweitert worden. Zusätzlich wurde das Gerät umgerüstet zur Messung der Schalldämpfung im Sediment in situ. Als Schalldämpfungssignal dient die Regelspannung eines Empfangsverstärkers. Die Dämpfungswerte im Sediment werden auf die Dämpfungswerte im Seewasser bezogen. Vier Tabellen mit Meßwerten der Schallgeschwindigkeit und Schalldämpfung aus Nord- und Ostsee sind beigefügt.

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Experiments for measuring in situ the velocity and attenuation of sound in sediments

Summary A new device of an improved design for measuring in situ the velocity and attenuation of sound in sediments now covers depths of penetration up to 3 m. The range of application has been enlarged by a higher source level of sound and by a greater sensitivity. In addition, the device has been adapted to in situ measurements of sound attenuation in sediments. The control voltage of a ceiving amplifier serves as sound attenuation signal. The attenuation values in sediments are referred to those in sea water. Four tables providing the velocity and attenuation of sound in the North and Baltic Seas are attached.

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Expériences de mesures de la vitesse du son et de son amortissement dans le sédiment in situ

Résumé Un appareil nouveau, de construction améliorée pour mesurer la vitesse du son et de son amortissement dans le sédiment in situ permet une pénétration jusqu' à 3 m. De plus larges possibilités d'utilisation ont été obtenues en élevant le niveau d'émission du son et par plus de sensibilité. De plus l'équipement a été modifié en vue de la mesure de l'amortissement du son dans le sédiment in situ. Les valeurs d'amortissement dans le sédiment sont rapportées aux valeurs d'amortissement dans l'eau de mer. En annexe figurent quatre tableaux donnant les mesures de la vitesse du son et de son amortissement obtenues en mer du Nord et Baltique.

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Die Arbeiten wurden ermöglicht durch einen Gutachterauftrag des Bundesministers der Verteidigung.     

Untersuchungen an fränkischen Verwerfungen

Zusammenfassung An vier feldgeologisch untersuchten Beispielen, dem Gräfenthaler Horst im Frankenwald, der Fränkischen Linie bei Kronach, der Kulmbacher Verwerfung bei Kirchleus und an Verwerfungszonen im Steigerwald wird gezeigt, daß die fränkischen Verwerfungen als Flächen eines zusammenhängenden Strukturfeldes angesehen werden können, das trotz seiner verschiedenartigen Erscheinungsformen im Grund- und Deckgebirge auf eine gemeinsame Ursache zurückgehen dürfte.

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Four areas in Northern Bavaria, the Gräfenthaler Horst in the Frankenwald, the Franconian Line near Kronach, the Kulmbach Fault near Kirchleus and fault zones in the Steigerwald, were investigated by different field methods. The authors are in the opinion that these Franconian faults are elements of a connecting structural region though different tectonic phenomena may be observed on the surface.

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Résumé Dans le nord de la Bavière des grands accidents tectoniques de direction NW/ SE, dont quelques-uns traversent le socle hercynien, d'autres la couverture mésozoique avoisinante, ont été étudiés par des methodes diverses. Quoique leurs caractères changent selon l'étage affectée, ces accidents sont des élements d'un seul domaine structural et ont apparement une origine commune.

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Herrn Professor Dr.Roland Brinkmann zum 70. Geburtstag gewidmet.     

Sedimentationsabläufe im Atlas-Golf (Kreide Küstenbecken Marokko)

The Geological Institute of Bonn University since 1975 investigates in connection with DSDP/IPOD the Cretaceous of the Atlantic coastal basin in south-western Morocco. 30 main stratigraphic sections and numerous auxiliary ones were taken along several traverses, running along distances of 150 to 200 km in west-east direction. The recognized epicontinental facies-pattern along the traverse of the southern High Atlas mountain range depicts clearly, that we cut here the critical region of intertonguing marine, fine-clastic-carbonaceous sediments and continental detritic deposits. The littoral zone successively progrades with three major transgressions (Neocomian, Upper Aptian, Turonian) towards the African Continent. Sedimentation processes, stratigraphy, paleomagnetics, geochemistry, sedimentology and paleogeography are investigated, taking selected horizons on one hand and complete stratigraphic columns on the other. A new sedimentation model reflecting transgression and regression events in the Cretaceous “Atlas Gulf” show some probabilities of eustatic sea-level changes. There are similarities between the Atlas Gulf and other coastal basins on both sides of the Atlantic Ocean. There are certain relations between the sedimentary record of the proand regrading littoral zone on the continent and in the nearby deep sea deposits. There is an exciting coincidence between the stratigraphie succession of the downwarping Atlas Gulf and the sedimentary cover of the interior of Africa, especially the Mesozoic Sahara Basin.     

Modellseismische Untersuchungen an 2- und 3-dimensionalen Testmodellen,Teil 1

Summary Following the recommendation of the European Seismological Commission (Copenhagen 1966) to carry out comparative measurements on simple seismic models with a prescribed velocity-depth distribution (test models), an attempt was made to compare results obtained with different model techniques. In the present paper, model investigations with the first two proposed test models carried out by 2- and 3-dimensional model techniques are described. Seismogrammes, travel-time curves and amplitude-distance curves of the models investigated are given. A quantitative comparison of the results shows a satisfactory agreement.