A review of shear zone geometry

Abstract

Shear zones are divided into three types: brittle, brittle-ductile, and ductile. These zones’ geometry and displacement boundary conditions are determined. The directions and values of major finite strains, rotation, and deformation aspects of pre-existing planar and linear structures are characterized as geometric properties of ductile shear zones important to geological investigations. The fabric associated with the finite strain state may be seen in ductile shear zones. The techniques for calculating stresses and displacements from field investigations are discussed. Shear zones are frequent in conjugate sets, but the two oppositely oriented sets do not seem to be able to function in lockstep. Conjugate ductile shear zones have different angular correlations than brittle shear zones. Termination of all kinds of shear zones presents complicated compatibility issues, for which various solutions are proposed. A synthesis of shear zone geometry in crustal contraction and extension areas is presented, as well as suggestions for how deep level ductile shear zones connect to high level brittle shears and gliding nappes.