High-temperature viscosity measurements of hydrous albite liquid using in-situ falling-sphere viscometry at 2.5 GPa

Brent T. Poe, Claudia Romano, Christian Liebske, David C. Rubie, Hidenori Terasaki, Akio Suzuki, Kenichi Funakoshi

Research output: Contribution to journalArticle

20 Citations (Scopus)

Abstract

In-situ falling-sphere viscometry using shadow radiography in a multianvil apparatus was conducted on a series of samples along the NaAlSi3O8-H2O join up to 2.8 wt.% H2O at the Spring-8 synchrotron radiation facility (Hyogo, Japan). This allowed us to determine viscosities normally too low to be measured at ambient pressure for hydrous silicate melts at high temperatures due to rapid devolatilization. Pressure was fixed at 2.5 GPa for all experiments allowing us to gauge the effect of chemical composition on viscosity. In particular, the series of samples allowed us to vary the melt's degree of polymerization while maintaining a constant Al to Si ratio. Our results show that, for all samples, viscosity decreases as a function of pressure between 1 atm and 2.5 GPa at 1550 °C, indicating that the pressure anomaly can still be observed as depolymerization of the melt increases from nominally 0 (dry albite liquid) to NBO/T = 0.8 (assuming water speciation entirely as hydroxyl groups at experimental conditions). We also find that the magnitude of the decrease in viscosity over this pressure interval does not appear to be dependent on the amount of water in the melt (i.e., NBO/T). An explanation for this behavior might be that the molar volume, at least over this limited compositional range, is nearly constant and the effects of compression of these melts, though different in degree of polymerization, are similar.

Original languageEnglish
Pages (from-to)2-9
Number of pages8
JournalChemical Geology
Volume229
Issue number1-3
DOIs
Publication statusPublished - 2006 May 16
Externally publishedYes

Keywords

  • High pressure
  • Silicate melts
  • Viscosity

ASJC Scopus subject areas

  • Geology
  • Geochemistry and Petrology

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