CATACLASTIC FLOW: A MEANS FOR ENSURING DUCTILITY WITHIN THE ELASTICO-FRICTIONAL REGIME

Cataclastic flow accommodates ductile deformation by satisfying the von Mises criterion within the upper crust (i.e. elastico-frictional regime). Although cataclastic flow is a critical process in upper crustal deformation, it continues to be largely ignored and/or misunderstood. Recent work, from portions of the Sevier fold-thrust belt that have deformed primarily within the elastico-frictional regime, reveals that cataclastic flow can be sub-divided into two types: matrix- and block controlled. Both types may operate simultaneously within the same deforming material, but their activity can vary spatially, temporally and across scales. Established concepts and definitions for cataclastic flow, however, are chiefly based on matrix-controlled cataclastic flow. Here, cataclastic flow is re-examined in terms of first principles in order to develop a more inclusive definition. To clarify the kinematics of the process, a mechanical analog model for cataclastic flow is presented. In addition, stress Mohr diagrams for ductile materials, such as those deforming by cataclastic flow, are re-evaluated. These models and revised definitions are tested against natural data from cataclasized rocks within the Sevier fold-thrust belt in terms of: (1) energy budget calculations, (2) fracture development forward modeling, and (3) by applying Schmid's law.