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  • Explosive volcanism  (2)
  • Polymer and Materials Science  (2)
  • 1
    ISSN: 1432-0819
    Schlagwort(e): Mount St Helens ; Experimental petrology ; Explosive volcanism ; Magmatic water contents ; Magmatic storage region
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie
    Notizen: Abstract Compositionally diverse dacitic magmas have erupted from Mount St Helens over the last 4000 years. Phase assemblages and their compositions in these dacites provide information about the composition of the pre-eruptive melt, the phases in equilibrium with that melt and the magmatic temperature. From this information pre-eruptive pressures and water fugacities of many of the dacites have been inferred. This was done by conducting hydrothermal experiments at 850°C and a range of pressures and water fugacities and combining the results with those from experiments at temperatures of 780 and 920°C, to cover the likely range in equilibration conditions of the dacites. Natural phase assemblages and compositions were compared with the experimental results to infer the most likely conditions for the magmas prior to eruption. Water contents disolved in the melts of the dacites were then estimated from the inferred conditions. Water contents in the dacites have varied greatly, from 3.7 to 6.5 wt.%, in the last 4000 years. Between 4000 and about 3000 years ago the dacites tended to be water saturated and contained 5.5 to 6.5 wt.% water. Since then, however, the dacites have been significantly water-undersaturated and contained less than 5.0 wt.% water. These dacites have tended to be hotter and more mafic, and andesitic and basaltic magmas have erupted. These changes can be explained by variable amounts of mixing between felsic dacite and basalt, to produce hotter, drier and more mafic dacites and andesites. The magma storage region of the dacitic magmas has also varied significantly during the 4000 years, with shifts to shallower levels in the crust occurring within very short time periods, possibly even two years. These shifts may be related to fracturing of overlying roof rock as a result of magma with-drawal during larger volume eruptions.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    ISSN: 1432-0819
    Schlagwort(e): Key words Mount St Helens ; Experimental petrology ; Explosive volcanism ; Magmatic water contents ; Magmatic storage region
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie
    Notizen: Abstract  Compositionally diverse dacitic magmas have erupted from Mount St Helens over the last 4000 years. Phase assemblages and their compositions in these dacites provide information about the composition of the pre-eruptive melt, the phases in equilibrium with that melt and the magmatic temperature. From this information pre-eruptive pressures and water fugacities of many of the dacites have been inferred. This was done by conducting hydrothermal experiments at 850°  C and a range of pressures and water fugacities and combining the results with those from experiments at temperatures of 780 and 920°  C, to cover the likely range in equilibration conditions of the dacites. Natural phase assemblages and compositions were compared with the experimental results to infer the most likely conditions for the magmas prior to eruption. Water contents dissolved in the melts of the dacites were then estimated from the inferred conditions. Water contents in the dacites have varied greatly, from 3.7 to 6.5 wt.%, in the last 4000 years. Between 4000 and about 3000 years ago the dacites tended to be water saturated and contained 5.5 to 6.5 wt.% water. Since then, however, the dacites have been significantly water-undersaturated and contained less than 5.0 wt.% water. These dacites have tended to be hotter and more mafic, and andesitic and basaltic magmas have erupted. These changes can be explained by variable amounts of mixing between felsic dacite and basalt, to produce hotter, drier and more mafic dacites and andesites. The magma storage region of the dacitic magmas has also varied significantly during the 4000 years, with shifts to shallower levels in the crust occurring within very short time periods, possibly even two years. These shifts may be related to fracturing of overlying roof rock as a result of magma withdrawal during larger volume eruptions.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 26 (1975), S. 629-633 
    ISSN: 0947-5117
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Beschreibung / Inhaltsverzeichnis: Einfluß der Chloridkonzentration auf die Kinetik der Anfangsperiode des Lochfraßes von AluminiumVersuche wurden durchgeführt, um den Einfluß von angelegten Potentialen und der Chloridkonzentration auf die Kinetik des Lochfraßes von unlegiertem Aluminium zu untersuchen. Für den in entlüfteten Natriumchloridlösungen bei 30°C durchgeführten Versuch wurde eine potentiostatische Methode verwendet. Das Lochfraßpotential wird nach der von Broli, Holtan und Midjo stammenden Extrapolationsmethode ermittelt, wobei sich eine Beziehung zwischen dem Lochfraßpotential und der Chloridkonzentration ergibt. Die Verfasser legen eine kinetische Deutung des Einflusses des angelegten Potentials und der Chloridkonzentration auf die Induktionsperiode vor.
    Notizen: Experiments are performed to study the influence of applied potential and chloride concentration on the kinetic behaviour of pitting corrosion initiation for unalloyed aluminium. A potentiostatic method is used at 30°C in deaerated solutions of sodium chloride. The pitting potential, Ep, is determined by the extrapolation method described by Broli, Holtan and Midjo, and a relation between Ep and chloride concentration is found. Kinetic interpretations such as the influence of applied potential and chloride concentration on the induction time are given.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 28 (1977), S. 475-477 
    ISSN: 0947-5117
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Beschreibung / Inhaltsverzeichnis: Lochkorrosionspotentiale von AluminumlegierungenDas Lochkorrosionspotential der folgenden Aluminiumlegierungen wurde in 3%iger NaCl-Lösung potentiodynamisch und potentiostatisch bestimmt: Al-2,7 Mg-(0-,94) Mn; Al-2,7 Mg-0,43 Mn-(d0-0.3) Cr; Al-4,7 Mg-0,13 Cr-0,78 Mn; Al-5,1 Mg-0,1 Sb; al-5,1 Mg-0,3 Sb; Al-2S-1/2H (handelsübliches Aluminum) und hochreines Aluminum (99,99 Al). Die Ergebbisse zeigen, daß die Legierungszusätze das Lochfraßpotential nicht sehr stark beeinflussen. Mit zunehmendem Magnesiumgehalt nimmt das Lochfraßpotential ab, während es mit zunehmendem Mangangehalt bis zu einem bestimmten Punkt zunimmt. Die Art und die Menge der Sekundärphasen scheinen das Lockkorrosionspotential nicht merklich zu beeinflussen.
    Notizen: The pitting potential of the following aluminum alloys in 3% sodium chloride solution was measured using potentiodynamic and potentionstatic methods: Al-2.7 Mg with 0-0.47% Cr, Al-2.7 Mg with 0-0.94% Mn, Al-2.7 Mg-0.43 Mn with 0-0.31% Cr, Al-4.7 Mg-0.13 Cr-0.78 Mn, Al-51 Mg with 0.1 and 0.3% Sb, Al 2S-1/2H (commercial aluminum) super pure Al (99,99% Al). The results show that the pitting potential is not much affected by the alloying elements. The pitting potetial decreases with increasing content of magnesium and increases slightly with increasing content of manganese up to a certain point. The nature and amount of secondary phases do not seem to have any marked influence upon the pitting potential.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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