RECONSTRUCTION OF DEFORMATION AND FLOW PARAMETERS FROM DEFORMED VEIN SETS

In any homogeneously deformed material, sets of material lines with a similar stretch history occupy sectors with a scale and orientation that depend on finite strain, area change rate and vorticity of the parent flow. If the size and shape of these "material line sectors" are known, they can be used to determine the sense of shear and to calculate deformation and flow parameters, even if actual stretches along material lines are unknown. In rocks which have undergone near-homogeneous deformation on a large scale, the orientation of sets of boudinaged folded and folded-boudinaged or boudinaged-folded veins can be used for such calculations. A general theoretical background to the problem is presented and a Mohr circle construction to carry out the deformation and flow analysis is introduced. Among other statements, the theory predicts that shortened or folded boudins must develop in non-coaxial monophase deformation, with considerable area change in the plane of observation, or in polyphase deformation. © 1990.