Under lithospheric temperature and pressure, deformation occurs by cataclastic, semi-brittle and viscous flow, involving a number of processes such as fracturing, comminution, pressure solution, dislocation creep, diffusion creep, and others. The 'end members', i.e., the predominantly pressure dependent brittle processes and the pre-dominantly temperature dependent viscous processes are reasonably well understood through field observation, rock deformation and friction experiments, and through theoretical or modeling works. At the same time, the interaction of these 'end member' processes is complex, resulting in a transitional regime which is characterized by localization (temporal and spatial), heterogeneity, and transient behavior. The study of this regime still present numerous challenges: observational, technical and conceptual ones. In this session we therefore invite contributions that are concerned with the deformation mechanisms and processes of the intermediate pressure-temperature regime, the brittle-viscous and the brittle-ductile transition. We welcome field and laboratory observations, as well as numerical modeling and theoretical analyses that may advance our understanding of this transitional regime.

Invited speaker: Brian Evans, MIT, USA