Cryogenic vitrification and 3D serial sectioning using high resolution cryo-FIB SEM technology for brine-filled grain boundaries in halite: first results

• Published in: Geofluids Vol. 8; no. 1; pp. 60 - 72
• Main Authors: DESBOIS, G, URAI, J.L, BURKHARDT, C, DRURY, M.R, HAYLES, M, HUMBEL, B
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01.02.2008; Blackwell Publishing Ltd
• Subjects: brine; cryo-SEM; FIB; grain boundary; halite; serial sectioning; vitrification
• ISSN: 1468-8115; 1468-8123
• DOI: 10.1111/j.1468-8123.2007.00205.x

The structure of brine films in grain boundaries of halite has been the subject of much controversy over the past 20 years; although a number of innovative methods have been developed to study these structures, much is still unknown and fundamental information is missing. In this study, we investigated different methods of plunge-freezing to vitrify the brine fill of grain boundaries for natural salt polycrystal. This was followed by a preliminary study of the 3D morphology of a vitrified grain boundary in a natural rock salt sample with a focused ion beam (FIB) excavation system. We have shown that brine-filled grain boundaries in rock salt can be efficiently well frozen when dimensions are less than about 1 mm. Coupled with an ion beam tool, cryo-SEM allows 3D observation of the well-frozen grain boundaries in large volumes and high resolution. Initial results of brine-filled natural halite grain boundaries show non-faceted crystal-brine interfaces and unexpectedly low dihedral angles at room temperature and pressure.