Classic models predicting a depth that separates brittle deformation in the upper crust from a region below in which deformation is dominated by ductile processes have long been outdated. In fact, the deformation behavior of Earth’s lithosphere is more complex and brittle and ductile processes may interact throughout the lithosphere. In the rock record, brittle deformation may be expressed as features ranging from micro-fracturing of mineral grains up to seismic ruptures (e.g., pseudotachylytes) or large-scale faults, and ductile deformation is typically expressed as shear zones ranging from millimeter to kilometer scales. Factors known to determine whether strain is accommodated by brittle and/or ductile processes include, but are not limited to: material properties (e.g., grain size, composition), strain rate, strain incompatibilities, pressure-temperature conditions, the availability of fluids, and rock modification by metamorphic reactions.
The multitude of possible factors determining the deformation style in the lithosphere make a comprehensive understanding of the deformation behavior of Earth’s lithosphere challenging. In this session we aim to tackle the complex topic of lithospheric deformation by combining observations from natural rocks with those from experimental and numerical studies.