Structure and properties of loaded silica contacts during pressure solution: impedance spectroscopy measurements under hydrothermal conditions

• Published in: Physics and chemistry of minerals Vol. 38; no. 7; pp. 501 - 516
• Main Authors: van Noort, R., Spiers, C. J., Peach, C. J.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.07.2011; Springer Nature B.V
• Subjects: Contact pressure; Crystallography and Scattering Methods; Diffusion rate; Dissolution; Earth and Environmental Science; Earth Sciences; Electric contacts; Electrical impedance; Film thickness; Geochemistry; Glass; Grain boundaries; Grain boundary diffusion; Impedance; Impedance spectroscopy; In situ measurement; Mineral Resources; Mineralogy; Original Paper; Properties (attributes); Quartz; Silica; Silicon dioxide; Spectroscopic analysis; Spectroscopy; Spectrum analysis; Pressure solution; Grain boundary diffusion; Impedance spectroscopy; Quartz; Silica; Hydrothermal
• ISSN: 0342-1791; 1432-2021
• DOI: 10.1007/s00269-011-0423-6

In order to investigate directly the structure and properties of grain boundaries in silicate materials undergoing pressure solution, in situ measurements of these properties are required. We report electrical impedance spectroscopy measurements, performed, under hydrothermal conditions, on individual glass–glass and glass-quartz contacts undergoing pressure solution. Resulting estimates of the average grain boundary diffusivity product ( ) for silica transport and of the average grain boundary fluid film thickness ( ) fall in the ranges 6.3 ± 1.4 × 10 −18  m 3  s −1 and 350 ± 210 nm, respectively. However, the average values for Z and obtained were likely influenced by cracking and irregular dissolution of the dissolving contact surfaces, rather than representing uniformly wetted grain boundary properties. Post-mortem SEM observations indicate that the contact surfaces were internally rough. Taken together, our data support the notion that during pressure solution of quartz, grain boundary diffusion is rapid, and interface processes (dissolution and precipitation) are more likely to be rate-limiting than diffusion.