Flow and strain patterns at the terminations of tapered shear zones

Abstract

With the help of corner flow theory, this paper numerically analyzes the deformation pattern at the terminations of tapered shear zones, the walls of which are rigid and move parallel to each other in opposite directions. The overall flow pattern is characterized by curvilinear particle paths that show convexity towards and opposite to the tapering direction respectively for low (< 5°) and high (> 10°) inclinations of the wall verging opposite to the sense of wall movement. In tapered shear zones there are two distinct fields of instantaneous shortening and extension parallel to the direction of wall movement. Numerical models reveal that the finite strain distributions are generally asymmetrical with larger strain concentration occurring near the wall verging opposite to sense of wall movement. The S-foliation trajectories show a curvilinear pattern, convexing against the tapering direction. The analysis of rotationality (vorticity) indicates that the sense of vorticity near the synthetically verging wall is reverse to the sense of wall movement; however W_k is one everywhere within the shear zone.