Divergent and convergent non-isochoric deformation

Plane strain flow with zero elongation parallel to, but widening, or shortening perpendicular to the flow plane results in either divergent or convergent non-isochoric deformation. During this special type of flow the kinematic dilatancy number, a measure of the rate at which a surface changes area with time, is directly dependent on the kinematic vorticity number, a measure of the rotational quality of a flow type, and vice versa. Thus, the velocity gradients' tensor can be simplified being only defined by the vorticity and the instantaneous area change. If these numbers can be deduced from natural deformed rocks with the help of quantitative kinematic indicators, the finite deformation can be calculated if the volume change is known from independent criteria. We quantitatively examine a marble mylonite from the Tauern Window, which deformed by stress-induced solution mass transfer that exhibits convergent non-isochoric deformation.