The brittle-ductile deformation of rocks forms the foundation of structural geology, engineering geology and petroleum geology. Although brittle-ductile deformation structures and their evolutionary processes have been extensively investigated at macroscopic and microscopic scales, a reliable discrimination model remains elusive at the nanoscale. To establish distinctive nanostructural models for brittle-ductile deformations, this study combines the scanning electron microscopy analysis of thin shells within brittle-ductile shear zones with high-temperature and high-pressure experimental simulations. The brittle and ductile thin shell models exhibit markedly different structures. The models reveal a tripartite architecture in brittle thin shells: a vice-surface on top layer; a middle layer comprising individual spherical nanoparticles, nanoparticle aggregates and multi-aggregate nanoparticles; a basal substrate layer. In contrast, the ductile thin shell does not have a vice-surface on top layer or a basal substrate layer and its nanostructures are characterized by fibrous, chain-ball and schistose nanoparticles with their associated aggregate structures. Applying the space-for-time assumption, the evolution of thin shells in the shear zone was reconstructed, demonstrating that the brittle-ductile-viscous transition drives nanoparticle transformations through granularization - alienation - reuniting - reproduction sequences. This work extends the discrimination model of brittle-ductile deformation from the microscopic scale to the nanoscale.
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Advances in Geo-Energy Research 2025, 17(1): 56-67
Published: 01 July 2025
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