Ductile shear zones in rocks commonly develop in three-dimensional arrays involving non-plane strains and possibly volume loss. The purpose of this project is to establish the pattern of strain and fabric development in ductile shear zones that form an anastomosing network in three dimensions, to understand the kinematics of deformation, and to test models of shear zone development. The shear zone to be studied developed in high-grade metagabbros of the Seve-koli nappes of the northern Swedish Caledonides. Preliminary strain analysis according to the planar band model of shear zone development indicates volume loss with increasing strain, yet available geochemical data indicate that deformation occurred under isochemical conditions. The three-dimensional strain analysis will be applied to the resolution of the volume loss paradox, and a successful result will be broadly applicable.
