1st July 2026 - New publication in Tectonophysics

Amorphous silica revealed at grain boundaries in naturally deformed quartz

Quartz-rich shear zones often contain abundant microscopic pores, yet the origin of this porosity has remained a long-standing question in structural geology. In this new study, Gina McGill and co-workers combine SEM, EBSD, FIB serial sectioning and high-resolution TEM to investigate naturally deformed quartz from the Ikaria granite (Greece).

The electron microscopy observations reveal that pores are not isolated defects but are systematically associated with nanometre-thick films of amorphous silica wetting grain boundaries and deformation-induced subgrain boundaries. High-resolution TEM imaging and diffraction provide direct evidence for these amorphous layers, while FIB cross-sections demonstrate that faceted pores are embedded within them.

These observations support the idea that stress-induced mechanical amorphization accompanies crystal plastic deformation in quartz and plays a key role in the formation of syn-kinematic micro-porosity.

This work also highlights the unique contribution of advanced transmission electron microscopy to the study of geological materials. By combining site-specific FIB sample preparation, high-resolution TEM imaging and electron diffraction, the authors were able to directly identify amorphous silica at the nanometre scale—evidence that would have remained inaccessible using conventional microstructural techniques alone.

To learn more:

G. McGill, J. Précigout, C. Prigent, P. Cordier, A. Addad, L. Airaghi & L. Arbaret (2026) Micro-porosity in quartz-rich shear bands of the Ikaria granite. Tectonophysics, 935, 231298. https://doi.org/10.1016/j.tecto.2026.231298